CN101853866A - Solid-state image pickup device, manufacturing method thereof, image pickup device, and electronic device - Google Patents

Abstract

The present invention relates to solid-state image pickup apparatus and manufacture method thereof, image pick-up device and electronic installation.Solid-state image pickup apparatus comprises pixel portion, and described pixel portion is limited by the unit pixel of arranging along the row and column direction at the semiconductor-based end.Each unit pixel comprises: be formed at semiconductor-based the end and with incident ray be converted to signal charge optical-electrical converter, be formed on the optical-electrical converter top and incident ray be directed to the waveguide of optical-electrical converter, and be formed on the waveguide top and incident ray be directed to the lenticule of light light incident side one end of waveguide.Waveguide has from light light incident side one end and has the cylindrical bodies of constant cross section to beam projecting side one end, and is arranged so that the ray center of the incident ray of the lenticule incident from light light incident side one end of waveguide aligns with the central shaft of waveguide.

Description

Solid-state image pickup device, manufacturing method thereof, image pickup device, and electronic device

technical field

The present invention relates to a solid-state image pickup device and a method of manufacturing the solid-state image pickup device, the image pickup device, and electronic devices such as video cameras including the solid-state image pickup device therein.

Background technique

The solid-state image pickup device includes, for example, an amplifying solid-state image pickup device typified by a metal oxide semiconductor (MOS) such as a complementary metal oxide semiconductor (CMOS) image sensor. Also, the solid-state image pickup device includes a charge-transfer solid-state image pickup device typified by a charge-coupled device (CCD) image sensor. These types of solid-state image pickup devices are widely used in digital still cameras and digital video cameras. MOS solid-state image pickup devices are commonly used in mobile devices such as camera-equipped mobile phones and personal digital assistants (PDAs) due to their low power supply voltage and low power consumption.

A typical MOS solid-state image pickup device includes a plurality of arrays of unit pixels each having a photodiode serving as a photoelectric converter and a plurality of pixel transistors as a set. In recent years, the miniaturization of the pixel size has progressed. In order to reduce the number of pixel transistors of a unit pixel and increase the area of a photodiode, a MOS solid-state image pickup device has been developed in which unit pixel groups each having a pixel transistor shared by a plurality of pixels are made into an array ( See Japanese Unexamined Patent Application Publication Nos. 2006-54276 and 2009-135319).

Also, a solid-state image pickup device is proposed in which waveguides guide incident light to corresponding photodiodes to improve sensitivity characteristics (see Japanese Unexamined Patent Application Publication No. 2008-166677). Furthermore, a solid-state image pickup device is proposed in which pupil correction is performed for an on-chip lens to correct shading (Japanese Patent No. 2600250).

A solid-state image pickup device includes a waveguide disposed above a photodiode that photoelectrically converts incident light and an on-chip lens that guides the incident light to the waveguide. In addition, a color filter layer is formed between the on-chip lens and the waveguide. The color filter layer splits incident light into, for example, colored light including red (R) light, green (G) light, and blue (B) light. In order to reduce the effect of color aberration, the radius of curvature of the on-chip lens for RGB colors is adjusted. In addition, the pupil correction amount at high image height positions for on-chip lenses and color filters is determined to become smaller than the lens chief ray angle (CRA) to reduce the influence of chromatic aberration.

For example, when using an on-chip lens with a high chief ray angle (eg, 25°), color aberrations at high image height positions may produce shadowing (differences between image focus positions (depth)) and color mixing.

When a method of adjusting the radius of curvature of an on-chip lens according to color is used as in the related art, it is possible to increase the number of processing steps for the on-chip lens. As pixels are further miniaturized, the radius of curvature of the on-chip lens increases. It is difficult to adjust the radius of curvature according to the color.

In the high incident angle portion, the center of image formation (including the F ray) deviates from the center of the photodiode toward the optical center (for example, toward the center of the pixel portion). From this, shading and color mixing are produced. In the related art, if the curvature radius of the on-chip lens is not adjusted according to the color, the spot diameter of the incident light at the light incident side end of the waveguide may change according to the color due to color aberration. As pixels are further miniaturized, it becomes more difficult to perform correction to obtain balanced positions for all colors. If the pupil correction amounts for the on-chip lenses and color filter layers vary by color, gaps or overlapping portions may occur. Thus, shading and color mixing can be produced. For this reason, pupil correction is performed for on-chip lenses and color filter layers to effectively converge and even oblique light rays. However, such a structure may still cause luminance shading, in which the sensitivity of the periphery of the image angle is reduced, and color shading, which is caused by a difference in the shape of the shading between colors.

A technology of a waveguide is disclosed for guiding incident light to a photodiode even when the incident light has a large incident angle. According to this technique, the image angle is divided into four quadrants, and the tapered position of the waveguide is changed according to its position in the four quadrants, so that the waveguide guides incident light rays at different incident angles (see, for example, Japanese Unexamined Patent Application Publication No.2005-175234).

However, even though a portion of the waveguide is tapered, the inventors have found that light entering the waveguide perpendicularly is reflected by the chamfer in the tapered waveguide, reducing sensitivity. Therefore, even a portion of the waveguide should not be tapered, as the tapered shape reduces sensitivity. Furthermore, to form a waveguide with a tapered portion, the number of processes and masks is increased compared to the case of forming a standard waveguide. Furthermore, since this technique only divides the image angle into four quadrants and changes the shape of the waveguide, this technique does not reduce the shadowing characteristics.

FIG. 1 shows an example of a two-pixel sharing type MOS solid-state image pickup device 1 in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor according to the related art. The solid-state image pickup device 1 includes two pixel-sharing type unit pixel groups 2 in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor. The unit pixel group 2 includes two photodiodes PD1 and PD2, two transfer transistors Tr11 and Tr12, a floating diffusion FD, a reset transistor Tr2, and an amplification transistor Tr3. In this example, color filters with a Bayer pattern are used. The two pixel sharing type unit pixel groups 2 are arranged such that the first green pixel Gb is arranged adjacent to the blue pixel B and the second green pixel Gr is arranged adjacent to the red pixel R. In FIG. 1, two pixel-sharing type unit pixel groups 2 including a red pixel R and a first green pixel Gb and two pixel-sharing type unit pixel groups 2 including a blue pixel B and a second green pixel Gr are repeatedly repeated. Form the array.

The transfer transistors Tr11 and Tr12 include respective transfer gate electrodes 3 made of polysilicon, respective photodiodes PD ( PD1 , PD2 ), and floating diffusion regions FD. The reset transistor Tr2 includes a reset gate electrode 4 made of polysilicon, a floating diffusion region FD, and a source region 5 . The amplification transistor Tr3 includes an amplification gate electrode 6, a source region 7, and a drain region 8 made of polysilicon. The floating diffusion FD and the amplification gate electrode 6 are connected to each other through the wiring portion 9 . The source region 7 of the amplification transistor Tr3 is connected to a vertical signal line (not shown).

In the solid-state image pickup device 1, the layout of the transfer gate electrode 3 of the first green pixel Gb is asymmetrical to the layout of the transfer gate electrode 3 of the second green pixel Gr. The layout causes a difference in sensitivity produced between the first and second green pixels Gb and Gr. For example, a difference between the incident light quantities on both the green pixels Gb and Gr is caused by a difference between the layout of the base layer of the transfer gate electrode 3, because part of the obliquely incident light is absorbed by the transfer gate electrode of one of the green pixels. shaded. In a MOS solid-state image pickup device, as miniaturization of pixels progresses, a difference in sensitivity between pixels becomes conspicuous. The difference in sensitivity is a bottleneck for miniaturization.

And, referring to FIG. 2 , there is proposed a solid-state image pickup device 10 in which two pixel-sharing type unit pixel groups 2 in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor are arranged in a staggered form. Since the two pixel-sharing type unit pixel groups 2 are arranged in a staggered form in the solid-state image pickup device 10, the layouts of the transfer gate electrodes of the first and second green pixels Gb and Gr are symmetrical to each other. Thus, the difference in sensitivity between the green pixels Gb and Gr is reduced.

The difference in sensitivity between the first and second green pixels Gb and Gr may cause noise, such as harsh noise, and may also cause color shading. It is desirable to eliminate differences in sensitivity.

Contents of the invention

Meanwhile, in the solid-state image pickup device 10 shown in FIG. 2, the layout of the pixel transistors and the layout of the floating diffusion FD are limited to maintain the symmetrical layout of the transfer gate electrodes of the first and second green pixels Gb and Gr. This limitation can be a bottleneck for miniaturization. For example, unit pixel group 2 only gets two-pixel sharing, so that the number of pixel transistors and floating diffusions is twice that of a four-pixel-sharing layout. Therefore, the area of the photodiode PD used for photoelectric conversion is reduced. A reduction in the area of the photodiode PD results in a loss of sensitivity. Furthermore, in the solid-state image pickup device 10, the layout of the transfer gate electrodes 3 of the green pixels Gb and Gr is asymmetrical to the layout of the transfer gate electrodes 3 of the red pixels R and blue pixels B. Thus, it is difficult to prevent occurrence of color shading.

As described above, since the base layer has an asymmetrical arrangement with respect to predetermined boundaries between adjacent pixels, optical asymmetry is generated between pixels.

In view of such circumstances, it is desirable to provide a solid-state image pickup device and an electronic device such as a video camera including the solid-state image pickup device, which improve optical asymmetry between pixels due to an asymmetrical arrangement of a base layer including electrodes and wiring portions therein .

A solid-state image pickup device according to an embodiment of the present invention includes: a pixel portion in which a plurality of pixels are arranged; a base layer formed in a multi-pixel group at a position below the light incident surface of the group, and having an electrode and a wiring. a layout that is asymmetrical with respect to a predetermined boundary between adjacent pixels; and an adjustment mechanism for making the optical asymmetry between the pixels brought about by the base layer into optical symmetry.

As a desirable embodiment of a solid-state image pickup device, the pixel portion includes a plurality of unit pixel groups each having a plurality of pixels sharing a predetermined transistor. The base layer may be a base layer including a gate electrode of a pixel transistor and a wiring portion.

According to the solid-state image pickup device of this embodiment, the influence of the base layer on incident light is reduced or eliminated in accordance with the adjustment direction and adjustment amount of the positional shift of the adjustment mechanism. The incident efficiency of the incident light on the photoelectric converter of each pixel can be equal.

According to a solid-state image pickup device of a desirable embodiment, the pixel portion may include a plurality of unit pixel groups of a pixel sharing type. Therefore, in a unit pixel group or in a plurality of adjacent unit pixel groups, the incident efficiency of light incident on photoelectric converters of at least common color pixels that output the same color signal can be equal.

An electronic device according to an embodiment of the present invention includes: a solid-state image pickup device; an optical system that guides incident light to a photoelectric converter of the solid-state image pickup device; and a signal processing circuit that processes output signal. The solid-state image pickup device is any of the solid-state image pickup devices described above.

According to the electronic device of this embodiment, since the solid-state image pickup device is used, the influence of the base layer on incident light is reduced or eliminated. The incident efficiency of the incident light on the photoelectric converter of each pixel can be equal.

As a drawback of the related art, it is difficult to perform correction to obtain a balanced position for all pixels as pixels are further miniaturized because the spot diameter of incident light at the light incident side end of the waveguide may vary by color due to chromatic aberration. Also, if the pupil correction amount for the on-chip lens and the color filter layer varies according to the color, a gap or an overlapping portion may be generated. From this, shadows and color mixing are possible.

Instead of performing pupil correction on the on-chip lens and the color filter layer based on the color of incident light passing through the color filter layer, the device performs pupil correction based on a reference color of the incident light. Thus, even when the spot diameter of the incident light varies according to the color due to chromatic aberration, the incident light can be efficiently incident on the light incident side end of the waveguide.

A solid-state image pickup device according to an embodiment of the present invention includes: a pixel portion defined by unit pixels arranged in row and column directions of a semiconductor substrate. Each of the unit pixels includes: a photoelectric converter formed on the semiconductor substrate and converting incident light into signal charges; a waveguide formed over the photoelectric converter and guiding the incident light to the photoelectric converter; and a microlens formed above the waveguide and guiding incident light to a light incident side end of the waveguide. The waveguide has a cylindrical body having a constant cross-section from one end on the light incident side to one end on the light exit side, and the waveguide is arranged such that all light incident on the waveguide from the microlens The ray center of the incident light at one end on the incident side of the light is aligned with the central axis of the waveguide.

According to the solid-state image pickup device of this embodiment, the waveguide has a cylindrical body with a constant cross section from the light incident side end to the light light exit side end. Light rays perpendicularly incident on the light-incident-side end of the waveguide are not reflected by the sidewalls of the waveguide but pass through the waveguide 16 . Sensitivity reduction is limited. Also, the ray center of the incident light incident on the light incident side end of the waveguide is aligned with the central axis of the waveguide. Thus, pupil correction is performed on the waveguide. Therefore, incident light rays from the microlenses are efficiently guided to the waveguide.

A method of manufacturing a solid-state image pickup device according to an embodiment of the present invention, the method including the step of forming a waveguide hole in a wiring layer, the waveguide hole guiding incident light to a photoelectric converter that converts the incident light into signal charges Above, the photoelectric converter is formed at a semiconductor substrate, the wiring layer formed at the semiconductor substrate and including an interlayer insulating film has a multilayered wiring portion; the waveguide hole is filled with a waveguide material film, the The refractive index of the waveguide material film is greater than the refractive index of the interlayer insulating film, and a waveguide is formed in the waveguide hole; by sandwiching a planarized insulating film, a color that separates incident light is formed on the waveguide material film a filter layer; and microlenses are formed on the color filter layer, and the microlenses guide incident light to the electro-optic converter. A plurality of unit pixels each having the photoelectric converter are arranged in row and column directions of the semiconductor substrate to define a pixel portion. The waveguide formed for the corresponding photoelectric converter has a cylindrical body having a constant cross section from one end on the light incident side to one end on the light exit side, and the waveguide is arranged such that from the micro A ray center of the incident light incident on the light incident side end of the waveguide by the lens is aligned with a central axis of the waveguide.

According to the method of manufacturing a solid-state image pickup device of this embodiment, the waveguide has a cylindrical body with a constant cross section from the light incident side end to the light light exit side end. Light rays perpendicularly incident on the light-incident-side end of the waveguide are not reflected by the sidewalls of the waveguide but pass through the waveguide 16 . Sensitivity reduction is limited. Also, the ray center of the incident light incident on the light incident side end of the waveguide is aligned with the central axis of the waveguide. Thus, pupil correction is performed on the waveguide. Therefore, incident light rays from the microlenses are efficiently guided to the waveguide.

An image pickup device according to an embodiment of the present invention includes: a light condensing optical unit that condenses incident light; an image pickup unit including a solid-state image pickup device that receives the light condensed by the light condensing optical unit, and performs photoelectricity on the light converting; and a signal processing unit processing a signal obtained by photoelectric conversion of the solid-state image pickup device. The solid-state image pickup device includes: a pixel portion defined by unit pixels arranged in row and column directions of a semiconductor substrate. Each of the unit pixels includes: a photoelectric converter formed on the semiconductor substrate and converting incident light into signal charges; a waveguide formed over the photoelectric converter and guiding the incident light to the photoelectric converter; and a microlens formed above the waveguide and guiding incident light to a light incident side end of the waveguide. The waveguide has a cylindrical body having a constant cross-section from one end on the light incident side to one end on the light exit side, and the waveguide is arranged such that all light incident on the waveguide from the microlens The ray center of the incident light at one end on the incident side of the light is aligned with the central axis of the waveguide.

According to the image pickup device of this embodiment, since the above-described solid-state image pickup device is used, reduction in sensitivity is limited, and incident light from the microlens can be efficiently guided to the waveguide.

Since pupil correction is performed even on the waveguide in the solid-state image pickup device, incident rays of each color are completely converged to the waveguide. Therefore, color unbalance due to shading (color shading) according to wavelength can be reduced. Sensitivity can be increased when limiting the sensitivity to the average of the output across the screen due to reduced shading. For example, exposure time can be reduced, and image capture in a dark environment can be performed.

According to the method of manufacturing the solid-state image pickup device, since pupil correction is performed even on the waveguide, incident rays of each color are completely converged to the waveguide. Therefore, color unbalance due to shading (color shading) according to wavelength can be reduced. Sensitivity can be increased when limiting the sensitivity to the average of the output across the screen due to reduced shading. For example, exposure time can be reduced, and image capture in a dark environment can be performed. Thus, the influence of chromatic aberration can be reduced without increasing the number of processes.

Also, in a miniaturized pixel, the light that does not enter the waveguide is reduced by adjusting the pupil correction amount for each color. Shading and color blending can be reduced.

Since the image pickup device according to this embodiment employs the above-described solid-state image pickup device, color unbalance due to shading (color shading) by wavelength can be reduced. Sensitivity can be increased to obtain high-quality images.

According to the solid-state image pickup device, the incident efficiency of incident light rays to the respective photoelectric converters can be equalized. Optical symmetry can be obtained for the photoelectric converters of individual pixels. For example, if the influence of the asymmetrical base layer is reduced or eliminated using a pixel sharing type solid-state image pickup device, the difference in sensitivity between common color pixels outputting the same color signal can be reduced. Also, color shading can be reduced.

According to the electronic device, optical symmetry can be provided in the photoelectric converters of the respective pixels in the solid-state image pickup device. The quality of the electronic device can be improved, and its image quality can be improved.

Description of drawings

1 is a schematic configuration diagram showing a main part of an exemplary solid-state image pickup device of a two-pixel sharing type in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor according to the related art;

2 is a schematic configuration diagram showing a main part of another example solid-state image pickup device of a two-pixel sharing type in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor according to the related art;

3A to 3C are cross-sectional schematic diagrams and plan layout schematic diagrams showing a first example structure of a solid-state image pickup device according to a first embodiment of the present invention;

4A and 4B are schematic cross-sectional views illustrating an example method of calculating a pupil correction amount according to an embodiment of the present invention;

5A and 5B are schematic cross-sectional views showing an example structure of a solid-state image pickup device according to the related art;

6A and 6B are schematic cross-sectional views illustrating an example method of calculating a pupil correction amount according to the related art;

7A to 7C are schematic cross-sectional views showing pupil correction amounts for waveguides of various colors;

8 is a schematic plan layout showing a second example structure of the solid-state image pickup device according to the first embodiment of the present invention;

9A to 9C are schematic cross-sectional views showing a second example structure of the solid-state image pickup device according to the first embodiment of the present invention;

10A to 10D are schematic cross-sectional views showing a third example structure of the solid-state image pickup device according to the first embodiment of the present invention;

11 is a schematic cross-sectional view showing a third example structure of the solid-state image pickup device according to the first embodiment of the present invention;

12 is a sectional view showing manufacturing steps in a first exemplary method of manufacturing a solid-state image pickup device according to a second embodiment of the present invention;

13 is a sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

14 is a sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

15 is a sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

16 is a sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

17 is a cross-sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

18 is a cross-sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

19 is a sectional view showing manufacturing steps in a first example method of manufacturing a solid-state image pickup device;

20 is a sectional view showing manufacturing steps in the first exemplary method of manufacturing the solid-state image pickup device;

21 is a sectional view showing manufacturing steps in the first example method of manufacturing the solid-state image pickup device;

22 is a sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device according to a second embodiment of the present invention;

23 is a cross-sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device;

24 is a sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device;

25 is a sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device;

26 is a cross-sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device;

27 is a sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device;

28 is a cross-sectional view showing manufacturing steps in a second exemplary method of manufacturing a solid-state image pickup device;

29 is a block diagram showing an exemplary image pickup device according to a third embodiment of the present invention;

30 is a schematic diagram showing the structure of a pixel portion in a solid-state image pickup device according to a fourth embodiment of the present invention;

31A and 31B are schematic configuration diagrams showing main parts of a solid-state image pickup device according to a fourth embodiment of the present invention;

Figure 32 is a cross-sectional view taken along XXXII-XXXII in Figure 31A;

33 is a graph plotting wavelength and output of green pixels Gb and Gr according to the fourth embodiment shown in FIGS. 31A and 31B;

34A and 34B are schematic configuration diagrams showing main parts of a solid-state image pickup device according to a fifth embodiment of the present invention;

35 is a schematic configuration diagram showing a main part of a solid-state image pickup device in a final state according to a sixth embodiment of the present invention;

36A and 36B are structural views showing a main part of a solid-state image pickup device according to a sixth embodiment to explain movement of a waveguide;

37 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to a seventh embodiment of the present invention;

38 is a structural view showing a main part of a solid-state image pickup device according to a comparative example for explaining the seventh embodiment;

39A and 39B are schematic configuration diagrams showing main parts of a solid-state image pickup device according to an eighth embodiment of the present invention;

40A and 40B are schematic cross-sectional views showing main parts of a solid-state image pickup device for describing pupil correction of a waveguide according to an eighth embodiment;

41A to 41C are cross-sectional views showing main parts of a solid-state image pickup device for describing pupil correction of a waveguide according to an eighth embodiment;

42A and 42B are plan views showing main parts of a solid-state image pickup device for describing pupil correction of a waveguide according to an eighth embodiment;

43 is a plan view showing a pixel portion of a solid-state image pickup device for describing pupil correction of a waveguide according to an eighth embodiment;

44 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to a ninth embodiment of the present invention;

45 is a structural view showing a main part of a solid-state image pickup device according to a comparative example for explaining the ninth embodiment;

46 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to a tenth embodiment of the present invention;

Fig. 47A and Fig. 47B are respectively the schematic cross-sectional views taken along XLVIIA-XLVIIA and line XLVIIB-XLVIIB in Fig. 46;

48 is a structural view showing a main part of a solid-state image pickup device according to a comparative example for explaining the tenth embodiment;

Fig. 49A and Fig. 49B are the cross-sectional diagrams taken along XLIXA-XLIXA and line XLIXB-XLIXB in Fig. 48 respectively;

FIG. 50 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to an eleventh embodiment of the present invention;

51A and FIG. 51B are schematic cross-sectional views taken along LIA-LIA and line LIB-LIB in FIG. 50, respectively;

52 is a structural view showing a main part of a solid-state image pickup device according to a comparative example for explaining the eleventh embodiment;

53A and 53B are schematic cross-sectional views taken along line LIIIA-LIIIA and line LIIIB-LIIIB in FIG. 52, respectively;

54 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to a twelfth embodiment of the present invention;

55A and 55B are schematic cross-sectional views taken along LVA-LVA and line LVB-LVB in FIG. 54, respectively;

56 is a structural view showing a main part of a solid-state image pickup device according to a comparative example for explaining the twelfth embodiment;

Fig. 57A and Fig. 57B are respectively the cross-sectional diagrams taken along LVIIA-LVIIA and line LVIIB-LVIIB in Fig. 56;

58 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to a thirteenth embodiment of the present invention;

Fig. 59A and Fig. 59B are respectively the cross-sectional diagrams taken along LIXA-LIXA and line LIXB-LIXB in Fig. 58;

60 is a schematic configuration diagram showing a Bayer-type color filter as an example color filter of a solid-state image pickup device according to a fourteenth embodiment of the present invention;

61 is a schematic configuration diagram showing a honeycomb-type color filter as another example of a color filter of a solid-state image pickup device according to a fourteenth embodiment of the present invention;

62 is a schematic configuration diagram showing a main part of a solid-state image pickup device according to a comparative example;

Figure 63 is a schematic cross-sectional view taken along LXIII-LXIII in Figure 62;

FIG. 64 is a graph plotting wavelengths and outputs of the green pixels Gb and Gr according to the comparative example shown in FIG. 62;

65A and 65B are schematic configuration diagrams showing main parts of a solid-state image pickup device according to a comparative example; and

FIG. 66 is a schematic diagram showing the structure of an electronic device according to a fifteenth embodiment of the present invention.

Detailed ways

Embodiments of the present invention will be described below.

1. The first embodiment

First example structure of solid-state image pickup device

A first example structure of the solid-state image pickup device according to the first embodiment of the present invention will be described with reference to schematic cross-sectional views and schematic plan layouts of FIGS. 3A to 3C . FIG. 3A shows a unit pixel at the center of an image corner, FIG. 3B shows a unit pixel at an edge of an image corner, and FIG. 3C shows a pixel portion including a plurality of unit pixels.

Hereinafter, reference numeral 1 denotes a solid-state image pickup device, 11 denotes a semiconductor substrate, 12 denotes a photoelectric converter, 14 denotes an interlayer insulating film, 16 denotes a waveguide, 17 denotes a color filter layer, 18 denotes a microlens, and 19 denotes a waveguide hole, 20 denotes a pixel portion, 21 denotes a unit pixel, 53 denotes a waveguide material film, 200 denotes an image pickup device, 201 denotes an image pickup unit, 202 denotes a light condensing optical unit, 203 denotes a signal processing unit, and 210(1) denotes a solid state Image pickup device.

Referring to FIGS. 3A to 3C , a photoelectric converter 12 is formed on the surface (light incident side) of a semiconductor substrate 11 . The photoelectric converter 12 converts incident light into signal charges. A silicon substrate is used for the semiconductor substrate 11 . Alternatively, the semiconductor substrate 11 may use a silicon-on-insulator (SOI) substrate. In this case, the photoelectric converter 12 is formed on the silicon layer of the SOI substrate. The wiring layer 13 is formed over the photoelectric converter 12 . For example, the wiring layer 13 is formed such that a plurality of layers including the wiring portion 15 are formed in the interlayer insulating film 14 . The wiring portion 15 is not formed in the region above the photoelectric converter 12 . The surface of the interlayer insulating film 14 is planarized.

Furthermore, a waveguide 16 is formed in the wiring layer 13 in a region above the photoelectric converter 12 . The waveguide 16 guides the incident light to the photoelectric converter 12 . The waveguide 16 is formed such that a waveguide hole is formed in the interlayer insulating film 14 in a region above the photoelectric converter 12 , and the waveguide hole is filled with a light-transmitting material having a higher refractive index than the interlayer insulating film 14 . The material is, for example, a silicon nitride film, a diamond film, or a resin film.

A microlens 18 (also referred to as an on-chip lens) is formed on the interlayer insulating film 14 in a region above the waveguide 16 with the color filter layer 17 interposed therebetween. The color filter layer 17 separates the incident light. The microlens 18 guides incident light emitted from the color filter layer 17 to one end of the waveguide 16 on the light incident side. The microlenses 18 and color filter layer 17 undergo pupil correction to efficiently converge and even oblique light rays. The pupil correction amount becomes larger from the center of the image angle (for example, the center of the pixel portion) toward the edge of the image angle. The color filter layer 17 divides the incident light into red light, green light and blue light, for example. Thus, color filters for various colors are provided. The microlens 18 is also called an on-chip lens. The microlens 18 has a shape of a convex lens and is provided in the top layer.

A photoelectric converter 12 , a waveguide 16 , a color filter layer 17 , a microlens 18 , a transmission grid (not shown), and the like define a unit pixel 21 . A plurality of such unit pixels 21 are arranged in the row and column directions of the semiconductor substrate 11 and define the pixel portion 20 . A pixel amplification unit (not shown, also referred to as a pixel transistor unit) is used for each unit pixel, every two unit pixels or every four unit pixels. The pixel amplification unit amplifies the signal charge read by the transfer gate and outputs the amplified signal charge.

Waveguides 16 are formed in the pixel portions 20 to correspond to the photoelectric converters 12, respectively. Each waveguide 16 has a cylindrical body with a constant cross section from the light incident side end to the light exit side end. For example, a cylindrical body of constant cross-section may be a cylinder or an elliptical cylinder (including elliptical cylinders). Alternatively, waveguide 16 may be a rounded prism. The ray center LC of the incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 .

In this case, in the unit pixel 21 (see FIG. 3A ) at the center of the image angle, incident light is incident on the microlens 18 in the central axis direction. The incident light condensed by the microlens 18 passes through and is separated by the color filter layer 17 , and is incident on the light incident side end of the waveguide 16 . The incident light is guided along the central axis C of the waveguide 16 and exits from the light exit side end of the waveguide 16 . The light hits the center of the photoelectric converter 12 . That is, incident light passing through the center of the microlens 18 passes along the center of the color filter layer 17 and the central axis C of the waveguide 16 , and is incident on the center of the photoelectric converter 12 . Thus, no pupil correction is performed on the waveguide 16 .

In the unit pixel 21 located at a position shifted from the center of the image angle (see FIG. 3B ), as described above, the microlens 18 and the color filter layer 17 undergo pupil correction to effectively converge and even oblique light rays. Also, the waveguide 16 is arranged such that the ray center LC of the incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 . That is, pupil correction has been performed for the waveguide 16 .

In the pixel portion 20, in the photoelectric converters 12 on which incident rays having equal wavelengths are incident, the center axis C of each waveguide 16 with respect to the center of the corresponding photoelectric converter 12 is shifted from that of the pixel portion 20 to The center becomes larger toward the outside. That is, the incident angle of the incident light condensed by the microlens 18 becomes larger from the center of the pixel portion 20 toward the outside. Pupil correction has been performed on the microlens 18, however the pupil correction amount is insufficient. In view of this, for incident rays having equal wavelengths, the offset of the central axis of the waveguide 16 relative to the center of the photoelectric converter 12 increases so that the ray center of the light from the microlens 18 is aligned with the central axis C of the waveguide 16 .

The diameter of the waveguide 16 allows incident light from the light exit side end of the waveguide 16 to impinge on an area within the surface of the photoelectric converter 12 . Thus, the size of the waveguide 16 is not equal to the size of the surface of the photoelectric converter 12, unlike the waveguide of the related art. The diameter of the waveguide 16 is desirably larger than the spot diameter of incident light passing through the color filter layer 17 on the light incident side end of the waveguide 16 . The spot diameter varies according to the wavelength of the incident light. For example, when the color filter layer 17 divides the incident light into red light, green light and blue light, the spot diameter of green light is smaller than that of red light, and the spot diameter of blue light is smaller than that of green light . If the diameter of the waveguide 16 is determined by color, the overall situation will become complicated. In some cases, the waveguide 16 may reach the wiring portion 15 of the wiring layer 13 . For example, the diameter of the waveguide 16 is determined based on green light having an intermediate wavelength range of the incident light rays. Alternatively, if an edge is provided between the waveguide 16 and the wiring portion 15 of the wiring layer 13, the diameter of the waveguide 16 can be determined based on red light.

As described above, by reducing the diameter of the waveguide 16 to be smaller than that of the related art waveguide, the margin for pupil correction can be increased. Furthermore, by reducing the width of the wiring portion 15 provided around the waveguide 16, the margin for pupil correction can be further increased. For example, the row width of the wiring portion 15 can be reduced within a range possible for the process that prevents clock delay from occurring due to an increase in the resistance of the wiring portion 15 (because the row width is reduced). For example, if the row width of the wiring portion 15 is reduced by 10 nm, the margin for pupil correction can be increased by 10 nm.

The solid-state image pickup device 1 ( 1A) is configured as described above.

Example Calculations for Pupil Correction

Next, an example method of calculating the pupil correction amount of the solid-state image pickup device 1 will be described with reference to schematic cross-sectional views in FIGS. 4A and 4B . Fig. 4A shows a unit pixel at the center of the image angle. Fig. 4B shows unit pixels at the corner edges.

Referring to FIG. 4A, in the unit pixel 21 at the center of the image angle, incident light is incident on the microlens 18 in the central axis direction. The incident light condensed by the microlens 18 passes through and is separated by the color filter layer 17 , and is incident on the light incident side end of the waveguide 16 . The incident light is guided along the central axis C of the waveguide 16 and exits from the light exit side end of the waveguide 16 . The light hits the center of the photoelectric converter 12 . That is, incident light passing through the center of the microlens 18 passes along the center of the color filter layer 17 and the central axis C of the waveguide 16 , and is incident on the center of the photoelectric converter 12 . Thus, no pupil correction is performed on the waveguide 16 .

In contrast, in the unit pixel 21 at the edge of the image angle, referring to FIG. 4B , the pupil correction amount is calculated at a position where the incident angle θ1 of the incident ray incident on the microlens 18 is, for example, θ1=25°.

The refractive index n of the microlens 18 is n=1.5.

If the refractive index n0 of the environment of the microlens 18 is n0=1, and the refractive index n1 of the microlens 18 is n1=1.6, then the following relationship is established:

sinθ2=(n0/n1)×sinθ1

If θ1=25°, then the result is:

θ2=sin ^-1 {(n0/n1)×sinθ1}

＝sin ^-1 {(1/1.6)×sin25}

=15.3°

For example, when one end of the light incident side of the waveguide 16 is used as the reference position (reference layer), the height h1 represents the height from the reference position to the formation plane of the microlens 18, and the height h2 represents the height from the reference position to the color filter layer 17. The height of the incident surface.

For example, assume that h1 = 2 μm, h2 = 1.5 μm. In this case, the deviation X_OCL' between the central axis C of the waveguide 16 and the central axis LC of the microlens 18 is as follows:

X_OCL'=h1×tanθ2+X_WG

=2×tan15.3°+X_WG

＝0.547μm+X_WG

Here, X_WG is the deviation between the center of the photoelectric converter 12 and the central axis C of the waveguide 16 .

And, the deviation X_CF' between the central axis C of the waveguide 16 and the central axis FC of the color filter layer 17 is as follows:

X_CF'=h2×tanθ2+X_WG

=1.5×tan15.3°+X_WG

=0.411μm+X_WG

If the diffraction angle θ3 at one end of the light exit side of the waveguide 16 is θ3=13.0°, then the diffraction width W to the surface of the photoelectric converter 12 is as follows:

W=h3×tanθ3.

If the distance h3 from the photoelectric converter 12 to the light exit side end of the waveguide 16 is, for example, h3=0.5 μm, the result is as follows:

W=h3×tanθ3=0.5×tan13.0°=0.115μm

For example, if the width PD of the photoelectric converter 12 is PD=1.1 μm, and the diameter WG' of the waveguide 16 is WG'=0.6 μm, then the The distance α of the projected position on the surface is expressed as follows: (PD-WG′)/2>W+α

According to this expression, the value becomes as follows:

(1.1-0.6)/2＞0.11+α

Pupil correction X_WG can be provided until the following conditions are met,

α＜0.25-0.115＝0.135μm

Next, a method of calculating the diffraction angle θ3 will be described.

Based on Young's implementation, if d is equal to the pixel pitch × 2, n is equal to 1 (first-order diffracted light), and λ is the wavelength of the incident light, the following expression is provided:

d×sinθ=nλ

Therefore, the result is as follows:

θ=sin ^-1 (nλ/d)

For example, if d=1.4 μm×2=2.80 μm and n=1, and if the wavelength λ of red light is λ=630 nm (red), then the diffraction angle θ of red light is as follows:

θ＝sin ^-1 (0.63/2.8)＝13.00°

As a reference, if the wavelength λblue of blue light is λblue=450nm (blue), then the diffraction angle of blue light is as follows:

θblue=sin ^-1 (0.45/2.8)=9.25°

And, if the wavelength λgreen of the green light is λgreen=550nm (green), the diffraction angle of the green light is as follows:

θgreen=sin ^-1 (0.55/2.8)=11.33°

Next, the structure of a solid-state image pickup device according to the related art as a comparative example will be described with reference to schematic cross-sectional views in FIGS. 5A and 5B . Fig. 5A shows a unit pixel at the center of the image angle. Fig. 5B shows unit pixels at the corner edges.

Referring to FIGS. 5A and 5B , in a unit pixel 21 , a photoelectric converter 12 is formed on the surface (light incident side) of a semiconductor substrate 11 . The photoelectric converter 12 converts incident light into signal charges. The wiring layer 13 is formed over the photoelectric converter 12 . For example, the wiring layer 13 is formed such that a plurality of layers including the wiring portion 15 are formed in the interlayer insulating film 14 . The wiring portion 15 is not formed in the region above the photoelectric converter 12 . The surface of the interlayer insulating film 14 is planarized.

Furthermore, a waveguide 16 is formed in the wiring layer 13 in a region above the photoelectric converter 12 . The waveguide 16 guides the incident light to the photoelectric converter 12 . A microlens 18 (also referred to as an on-chip lens) is formed on the interlayer insulating film 14 in a region above the waveguide 16 with the color filter layer 17 interposed therebetween. The color filter layer 17 separates the incident light. The microlens 18 guides incident light emitted from the color filter layer 17 to one end of the waveguide 16 on the light incident side. The color filter layer 17 divides the incident light into red light, green light and blue light, for example. Thus, color filters for various colors are provided. The microlens 18 is also called an on-chip lens. The microlens 18 has a shape of a convex lens and is provided in the top layer.

Referring to FIG. 5A, in the unit pixel 21 at the center of the image angle, incident light is incident on the microlens 18 in the central axis direction. The incident light condensed by the microlens 18 passes through and is separated by the color filter layer 17 , and is incident on the light incident side end of the waveguide 16 . The incident light is guided along the central axis C of the waveguide 16 and exits from the light exit side end of the waveguide 16 . The light hits the center of the photoelectric converter 12 . That is, incident light passing through the center of the microlens 18 passes along the center of the color filter layer 17 and the central axis C of the waveguide 16 , and is incident on the center of the photoelectric converter 12 . Thus, no pupil correction is performed on the microlenses 18 or the color filter layer 17 .

In contrast, referring to FIG. 5B , in the unit pixel 21 located at a position offset from the center of the image angle, the microlens 18 and the color filter layer 17 undergo pupil correction to effectively converge or even oblique light rays. The pupil correction amount increases from the center of the image angle toward the edges of the image angle.

Next, an example method of calculating a pupil correction amount according to a comparative example will be described with reference to schematic cross-sectional views in FIGS. 6A and 6B . Fig. 6A shows a unit pixel at the center of the image angle. Fig. 6B shows unit pixels at the corner edges.

Referring to FIG. 6A, in the unit pixel 21 at the center of the image angle, incident light is incident on the microlens 18 in the central axis direction. The incident light condensed by the microlens 18 passes through and is separated by the color filter layer 17 , and is incident on the light incident side end of the waveguide 16 . The incident light is guided along the central axis C of the waveguide 16 and exits from the light exit side end of the waveguide 16 . The light hits the center of the photoelectric converter 12 . That is, incident light passing through the center of the microlens 18 passes along the center of the color filter layer 17 and the central axis C of the waveguide 16 , and is incident on the center of the photoelectric converter 12 . Thus, no pupil correction is performed on the waveguide 16 .

In contrast, referring to FIG. 6B , in the solid-state image pickup device of the related art, pupil correction is not performed on the waveguide 16 even in the unit pixel 21 at the edge of the image angle. Here, the pupil correction amount for the microlens 18 and the color filter layer 17 is calculated at a position where the incident angle θ1 of the incident ray incident on the microlens 18 is, for example, θ1=25°.

For example, the F-number of the microlens 18 is F=2.8, and the refractive index n of the microlens 18 is n=1.5.

Also, the angle θ3 of the edge ray is θ3=6.8°.

If the refractive index n0 of the environment of the microlens 18 is n0=1, and the refractive index n1 of the microlens 18 is n1=1.6, the following relationship is established:

sinθ2=(n0/n1)×sinθ1

If θ1=25°, the result is as follows:

θ2=sin ^-1 {(n0/n1)×sinθ1}

＝sin ^-1 {(1/1.6)×sin25}

=15.3°

For example, when one end of the light incident side of the waveguide 16 is used as the reference position (reference layer), the height h1 represents the height from the reference position to the formation plane of the microlens 18, and the height h2 represents the height from the reference position to the color filter layer 17. The height of the incident surface.

For example, assume that h1 = 2 μm, h2 = 1.5 μm. In this case, the deviation X_OCL between the central axis C of the waveguide 16 (the center of the photoelectric converter) and the central axis LC of the microlens 18 is as follows:

X_OCL=h1×tanθ2=2×tan15.3°=0.547μm

And, the deviation X_CF between the central axis C of the waveguide 16 and the central axis FC of the color filter layer 17 is as follows:

X_CF=h2×tanθ2=1.5×tan15.3°=0.411μm

In this embodiment, no pupil correction is performed on the waveguide 16 . Thus, the problems described with reference to FIGS. 3A to 3C may occur.

In the solid-state image pickup device 1, the waveguide 16 has a cylindrical body with a constant cross section from the light incident side end to the light light exit side end. The light rays perpendicularly incident on the light incident side end of the waveguide 16 are not reflected by the side walls of the waveguide 16 but pass through the waveguide 16 . Since the light is not reflected by the side walls of the waveguide 16, the reduction in sensitivity is limited. Also, since the ray center of the incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis of the waveguide 16 , the incident light is efficiently guided to the waveguide 16 . That is, pupil correction is performed even on the waveguide 16 .

Since pupil correction is performed even on the waveguide 16 in the solid-state image pickup device 1 , incident rays of each color are completely converged to the waveguide 16 . Therefore, color unbalance due to shading (color shading) according to wavelength can be reduced.

In addition, the distance from the surface of the photoelectric converter 12 to the light exit side end of the waveguide 16 should be a predetermined distance in order to prevent the occurrence of white spots. For example, if interlayer insulating film 14 formed between photoelectric converter 12 and waveguide 16 is made of silicon oxide, the distance from photoelectric converter 12 to waveguide 16 may be, for example, about 500 nm.

The diameter of the waveguide 16 is determined such that incident light exiting from the light exit side end of the waveguide 16 and having a diffuse property due to diffraction strikes an area within the surface of the photoelectric converter 12 . Thus, since the diffused portion of the light emitted from the waveguide 16 also impinges on the photoelectric converter 12, the sensitivity is improved.

Sensitivity can be increased and exposure time can be reduced when limiting sensitivity to the average output across the screen due to reduced shading. As a practical result, the sensitivity increased by 4% for green light, 3% for red light and 2% for blue light.

In the related art, the size of the waveguide 16 is increased as much as possible within the range relative to the edge of the wiring portion 15 to improve sensitivity. The incident light rays emitted from the light emitting side end of the waveguide 16 are diffused due to diffraction and emitted. Thus, if the diameter of the waveguide 16 is substantially equal to the size of the surface of the photoelectric converter 12 , the diffuse portion of the exiting light rays does not impinge on the photoelectric converter 12 . This diffuse portion degrades sensitivity.

Next, reduction in the diameter of the waveguide 16 will be described. As described above, the diameter of the waveguide 16 is such that the incident light emitted from the light-emitting-side end of the waveguide 16 strikes an area within the surface of the photoelectric converter 12 . Thus, the size of the waveguide 16 is not equal to the size of the surface of the photoelectric converter 12, unlike waveguides in the related art. Furthermore, the diameter of the waveguide is reduced. For example, although the structure is similar to the related art in which the space between the wiring portion 15 and the waveguide 16 is substantially only the lamination edge, pupil correction can be performed on the waveguide 16 by reducing the diameter of the waveguide 16 . For example, assume that the diameter of the waveguide 16 of the related art is 1.5 μm. By reducing the diameter of the waveguide 16 to 1 μm, the diameter is reduced by 0.25 μm for each side. Pupil correction can be performed by 0.25 μm. As described above, the diameter of the waveguide 16 is desirably larger than the spot diameter of the incident light passing through the color filter layer 17 on the light incident side of the waveguide 16 . For example, the diameter of the waveguide 16 is determined based on green light having an intermediate wavelength range of incident light rays. Alternatively, if an edge is provided between the waveguide 16 and the wiring portion 15 of the wiring layer 13, the diameter of the waveguide 16 can be determined based on red light.

In the case of the miniaturized pixel described above, the pupil correction amount is determined in accordance with the distance from the waveguide 16 to the wiring portion 15 . For example, the diameter of the waveguide 16 is reduced to a desired value to be larger than the spot diameter of the incident light rays incident on the waveguide 16 . Determine the amount of reduction to obtain the desired amount of pupil correction. However, if the pupil correction amount is insufficient, as described above, reducing the row width of the wiring portion 15 increases the pupil correction amount at all. The pupil correction for the waveguide 16 in this embodiment of the present invention is not simply to perform pupil correction on the waveguide 16 having the structure of the related art, but for example by reducing the diameter of the waveguide 16 or by reducing the row of the wiring portion 15 width to provide pupil correction for the waveguide 16. Thus, a sufficient pupil correction amount can be provided. Color shading can be significantly reduced. The ratio of the pupil correction amount for the waveguide 16 relative to the pupil correction amount for the microlens 18 or color filter layer 17 is constant. For example, the pupil correction amount for waveguide 16 may be 0.2 times the pupil correction amount for microlens 18 .

In the solid-state image pickup device 1 described in the first exemplary embodiment, the idea of the waveguide 16 of the related art is significantly changed. Specifically, in the related art, the diameter of the waveguide 16 is increased as large as possible within the range relative to the edge of the wiring portion 15 in order to improve the sensitivity. In contrast, in the solid-state image pickup device 1 described above, as long as the diameter of the waveguide 16 is larger than the spot diameter of the incident light on the light incident side, the diameter of the waveguide 16 (diameter on the light incident side) is reduced as much as possible, All outgoing rays from the waveguide 16 thus impinge on the photoelectric converter 12 . This is a significant difference from the waveguide of the related art. Furthermore, as described above, performing pupil correction on the waveguide 16 is another point that is significantly different from the waveguide of the related art.

The solid-state image pickup device 1 may desirably have different pupil correction amounts for the waveguide 16 according to the color of incident light rays separated by the color filter layer 17 . This will be described with reference to the schematic cross-sectional views in FIGS. 7A to 7C . 7A to 7C show unit pixels located at equal distances from the center of the image angle (e.g., the center of the pixel portion) and having color filter layers 17 of different colors, and FIG. 7A shows a blue unit 7B shows a green unit pixel, and FIG. 7C shows a red unit pixel.

In the solid-state image pickup device 1, referring to FIGS. 7A to 7C , in the photoelectric converter 12 on which incident rays having equal wavelengths are incident in the pixel portion 20, the central axis C of each waveguide 16 is relative to the corresponding The shift amount of the central axis FC of the photoelectric converter 12 becomes larger from the photoelectric converter 12 at the center of the pixel portion 20 toward the outside. In other words, with respect to the photoelectric converters 12 located at equal distances from the center of the pixel portion 20, the shift amount of the central axis C of each waveguide 16 with respect to the central axis FC of the corresponding photoelectric converter 12 increases with the color-filtered The wavelength of light that separates the sheets 17 and is incident on the photoelectric converter 12 decreases as the wavelength increases.

More specifically, when the solid-state image pickup device 1 has photoelectric converters 12 at a pitch of about 1 to 3 μm and has a waveguide 16 having a diameter of about 0.5 to 2.5 μm, the pupil correction amount for the waveguide 16 satisfies the relationship “blue light (B )<green light (G)<red light (R)". It should be noted that the waveguide 16 is smaller than the photoelectric converter 12 for ease of illustrating the planar layout. For example, about 20 to 50 nm of pupil correction is performed for the waveguide 16 on which blue light is incident, about 50 to 80 nm is performed for the waveguide 16 on which green light is incident, and pupil correction is performed for the waveguide 16 on which red light is incident. Pupil correction around 80 to 110nm. Shading can thus be optimized by each waveguide 16 .

Typically, as the position shifts from the center of the pixel portion 20 toward the outside, the incident angle of the incident light condensed by the microlens 18 increases. Pupil correction is performed for the microlens 18, however, the pupil correction amount is insufficient. In view of this, as described above, for incident light rays having equal wavelengths, the offset of the central axis of each waveguide 16 relative to the center of the corresponding photoelectric converter 12 increases, so that the ray of light from the microlens 18 The center is aligned with the central axis of the waveguide 16 .

Typically, the microlenses 18 and the color filter layer 17 undergo pupil correction so that incident light rays are incident on the photoelectric converter 12 in the direction of the central axis. For example, pupil correction of incident light rays (for example, green light) having a reference wavelength is performed for the microlenses 18 and the color filter layer 17 . In this case, referring to FIG. 7A , since the blue light is easily bent by the microlens 18 , the incident angle of the blue light incident on the light incident side end of the waveguide 16 becomes large. Therefore, even when the microlens 18 and the color filter layer 17 are greatly shifted toward the center of the pixel portion with respect to the center axis FC of the photoelectric converter 12 by pupil correction, the light emitted from the color filter layer 17 is It is incident on the light incident side end of the waveguide 16 at a position close to the central axis FC of the photoelectric converter 12 . Therefore, almost all of the incident light rays incident on the light incident side end of the waveguide 16 are guided to the waveguide 16 . In this case, the position of the waveguide 16 is corrected so that the central axis LC of the ray of the incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 .

In contrast, referring to FIG. 7C , since red light is less bent by the microlens 18 than blue light, the incident angle of the red light incident on the light incident side end of the waveguide 16 becomes smaller than that of the blue light. And, since the microlens 18 and the color filter layer 17 are greatly shifted toward the center of the pixel portion with respect to the central axis FC of the photoelectric converter 12 by pupil correction, the light emitted from the color filter layer 17 is far away from the photoelectric converter. The position of the center axis FC of the converter 12 is incident on the light incident side end of the waveguide 16 . In some cases, the light is incident such that the main part of the light protrudes from the light incident side end of the waveguide 16 . However, in this embodiment of the invention, the position of the waveguide 16 is corrected so that the central axis LC of the ray of incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 . Thus, almost all of the incident light emitted from the color filter layer 17 is incident on the light incident side end of the waveguide 16 and guided into the waveguide 16 .

Also, referring to FIG. 7B , green light is less bent by the microlens 18 than blue light, and is easily bent by the microlens 18 than red light. The incident angle of the incident light rays incident on the light incident side end of the waveguide 16 is smaller than that of blue light and larger than that of red light. Since the microlens 18 and the color filter layer 17 are greatly shifted toward the center of the pixel portion with respect to the center axis FC of the photoelectric converter 12 by pupil correction, the light emitted from the color filter layer 17 is far away from the photoelectric converter. 12 is incident on the light incident side end of the waveguide 16 at the position of the central axis FC of the waveguide 16 . However, in this embodiment of the invention, the position of the waveguide 16 is corrected so that the central axis LC of the ray of incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 . Thus, almost all of the incident light emitted from the color filter layer 17 is incident on the light incident side end of the waveguide 16 and guided into the waveguide 16 .

As described above, as the wavelength of light separated by the color filter layer 17 decreases, the amount of offset of the central axis C of each waveguide 16 with respect to the center of the corresponding photoelectric converter 12 decreases. Therefore, even when the wavelengths of the incident light on the light incident side end of the waveguide 16 are different from each other, the waveguides 16 are also separately arranged according to the wavelength, the sensitivity of the unit pixel 21 is equal, and color shading does not occur.

Second example structure of solid-state image pickup device

A second example structure of the solid-state image pickup device according to the first embodiment of the present invention will be described with reference to the plan layout diagram in FIG. 8 and the cross-sectional diagrams in FIGS. 9A to 9C . In FIG. 8 and FIGS. 9A to 9C, for example, four unit pixels share one pixel transistor unit. Four unit pixels define a unit pixel group.

Referring to FIGS. 8 and 9A to 9C , the unit pixel group 22 includes, for example, two first unit pixels 21 ( 21G), one second unit pixel 21 ( 21B) and one third unit pixel 21 ( 21R). The first unit pixel 21G includes a photoelectric converter 12 ( 12G) on which light having a first wavelength (for example, green light, G) separated by a color filter layer 17 ( 17G) is incident. The second unit pixel 21B includes a photoelectric converter 12B on which light having a second wavelength (blue light, B) separated by the color filter layer 17B is incident. The second wavelength is less than the first wavelength. The third unit pixel 21R includes a photoelectric converter 12R on which light having a third wavelength (red light, R) separated by the color filter layer 17R is incident. The third wavelength is greater than the first wavelength.

Regarding the offset of the central axis C of each waveguide 16 in the unit pixel group 22 relative to the central axis FC of the corresponding photoelectric converter 12, the offset of the central axis C of the waveguide 16 relative to the center of the photoelectric converter 12 varies with decreases as the wavelength of light separated by the color filter layer 17 decreases. Also, the amount of shift of the central axis C of each waveguide 16 with respect to the central axis FC of the corresponding photoelectric converter 12 becomes smaller toward the center of the pixel portion 20 . In other words, the amount of offset becomes larger from the center of the image angle (for example, the center of the pixel portion) toward the edge of the image angle, and the offset direction from the center of the photoelectric converter 12 is toward the center of the image angle.

The solid-state image pickup device 1 ( 1B) is configured as described above. It should be noted that the first unit pixel 21G, the second unit pixel 21B, and the third unit pixel 21R each have a basic structure similar to that described in the first example structure of the solid-state image pickup device 1 .

The solid-state image pickup device 1B is a so-called multi-pixel sharing type (four-pixel sharing type) in which a plurality of (or four) pixels share one floating diffusion region, one amplification transistor, and one selection transistor. The shift amount of the central axis of each waveguide 16 relative to the center of the corresponding photoelectric converter 12 decreases as the wavelength of the incident light incident on the light incident side end of the waveguide 16 increases. In such a four-pixel sharing type, regarding the four pixels (unit pixels 21), the shift amount (pupil correction amount) of the waveguide 16 of the third unit pixel 21R is larger than that of the first unit pixel 21G, and the third unit pixel 21G The shift amount (pupil correction amount) of the waveguide 16 of the two-unit pixel 21B is smaller than that of the first-unit pixel 21G.

Typically, the microlenses 18 and the color filter layer 17 undergo pupil correction so that incident light rays are incident on the photoelectric converter 12 in the direction of the central axis. For example, pupil correction of incident light rays (for example, green light) having a reference wavelength is performed for the microlenses 18 and the color filter layer 17 . In this case, since the blue light is easily bent by the microlens 18 , the incident angle of the blue light when incident on the light incident side end of the waveguide 16 becomes large. Therefore, even when the microlens 18 and the color filter layer 17 are greatly deviated from the center axis FC of the photoelectric converter 12 to the center of the image angle (for example, the center of the pixel portion) by pupil correction, the color filter The light emitted from the optical sheet layer 17 is also incident on the light incident side end of the waveguide 16 at a position close to the central axis FC of the photoelectric converter 12 . Therefore, almost all of the incident light rays incident on the light incident side end of the waveguide 16 are guided to the waveguide 16 . In contrast, since red light is less bent by the microlens 18 than blue light, the incident angle of the red light when incident on the light incident side end of the waveguide 16 becomes smaller than that of the blue light. And, since the microlens 18 and the color filter layer 17 are shifted toward the center of the pixel portion with respect to the central axis FC of the photoelectric converter 12 by pupil correction, the light emitted from the color filter layer 17 is farther away from the photoelectric converter. 12 is incident on the light incident side end of the waveguide 16 at the position of the central axis FC of the waveguide 16 . In some cases, the light is incident such that the main part of the light protrudes from the light incident side end of the waveguide 16 . However, in this embodiment of the invention, the position of the waveguide 16 is corrected so that the central axis LC of the ray of incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 . Thus, the incident light emitted from the color filter layer 17 is incident on the light incident side end of the waveguide 16 and is guided into the waveguide 16 . Also, green light is less bent by the microlens 18 than blue light, and is more easily bent by the microlens 18 than red light. The incident angle of the incident light rays incident on the light incident side end of the waveguide 16 is smaller than that of blue light and larger than that of red light. Since the microlens 18 and the color filter layer 17 are shifted to the center of the pixel portion with respect to the central axis FC of the photoelectric converter 12 through pupil correction, the light emitted from the color filter layer 17 is far away from the photoelectric converter 12. The position of the central axis FC is incident on the light incident side end of the waveguide 16 . However, according to this embodiment, the position of the waveguide 16 is corrected so that the central axis LC of the ray of the incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis C of the waveguide 16 . The incident light emitted from the color filter layer 17 is incident on the light incident side end of the waveguide 16 and is guided into the waveguide 16 . As described above, with respect to the waveguide 16 in the unit pixel group 22, the shift amount of the central axis C of the waveguide 16 relative to the central axis FC of the corresponding photoelectric converter 12 decreases as the wavelength of the light separated by the color filter layer 17 decreases. Small and reduced. Therefore, that is, when the wavelengths of incident light on the light incident side end of the waveguide 16 are different from each other, the waveguides 16 are separately arranged according to the wavelength, the sensitivity of the unit pixel 21 is equal, and color shading does not occur.

Third example structure of solid-state image pickup device

A third example structure of the solid-state image pickup device according to the first embodiment of the present invention will be described with reference to the cross-sectional views of FIGS. 10A to 10D . Referring to FIGS. 10A to 10D , the solid-state image pickup device of this third example has a structure similar to that of the solid-state image pickup device 1 of the first example except for the structure of the waveguide 16 .

Referring to FIGS. 10A and 10B , a unit pixel 21 includes a waveguide 16 having a first waveguide 16A and a second waveguide 16B. The first waveguide 16A defines a peripheral portion of the waveguide 16 . The second waveguide 16B is formed inside the first waveguide 16A and has a smaller refractive index than the first waveguide 16A. The first waveguide 16A may also be formed at the bottom of the second waveguide 16B. FIG. 10A shows the unit pixel 21 at the central portion of the image angle. FIG. 10B shows the unit pixel 21 at a position away from the center of the image corner and near the edge of the image corner. Similar to the solid-state image pickup device 1 of the first example, pupil correction is performed on the waveguide 16 when the waveguide 16 is positioned closer to the edge of the image angle.

For example, referring to FIG. 11 , the structure may include a waveguide 16 having a diameter of 1 μm for a photoelectric converter 12 (eg, a photodiode) having a size of 2 μm. The structure may be designed such that pupil correction of 0.45 μm is performed for the portion closest to the edge of the image angle. The first waveguide 16A is formed by using a film having a refractive index n1 of about 1.8 (for example, a film made of a material selected from nitrides) to define a side wall portion of the waveguide 16 . The second waveguide 16B is formed of a film made of a material selected from resin and having a refractive index n2 of about 1.4. The side wall portion of the first waveguide 16A has a film thickness of about 100 nm. Therefore, both side wall portions of the first waveguide 16 have a thickness of 200 nm. The second waveguide 16B has a diameter of 800 nm. If the first waveguide 16A is formed with a film made of a material selected from nitrides (for example, a silicon nitride film), the film functions as a passivation film.

Next, the optical paths of incident rays will be described with reference to FIGS. 10C and 10D . FIG. 10C shows the unit pixel 21 at the central portion of the image angle. FIG. 10D shows the unit pixel 21 at a position away from the center of the image corner and closer to the edge of the image corner. Referring to Fig. 10C, the incident light passing through the microlens 18 and the color filter layer 17 mainly converges to the first waveguide 16A as the sidewall part, because in the waveguide 16 at the center of the image angle, the first waveguide 16A in the sidewall part One waveguide 16A has a higher refractive index than the second waveguide 16B in the central portion.

In contrast, referring to FIG. 10D , when the pupil correction is performed on the waveguide 16, although the waveguide 16 is located near the edge of the image angle, the ray of the incident light rays passing through the microlens 18 and the color filter layer 17 may have to the center of the photoelectric converter 12 (as shown, the refractive index satisfies n1>n2). Specifically, obliquely incident light rays incident on the waveguide 16 enter the first waveguide 16A from the second waveguide 16B, are reflected in the first waveguide 16A having a higher refractive index than the second waveguide 16B, are guided to the light exit side end, and are to the photoelectric converter 12. Since the light is guided through the waveguide 16, it is reasonable to determine that the refractive index of the material used for the waveguide 16 (first waveguide 16A) is greater than that of the material used for members around the waveguide 16 (first waveguide 16A). Specifically, pupil correction is performed for the waveguide 16 at the edge of the image angle so that the central axis C of the waveguide 16 is aligned with the central axis LC of the rays of the incident light rays on the light incident side end of the waveguide 16 . Thus, the central axis C of the waveguide 16 is offset toward the center of the image angle with respect to the center of the photoelectric converter 12 . Therefore, even if an incident ray of light incident on the light incident side end of the waveguide 16 is incident on the second waveguide 16B, the ray enters the first waveguide 16A having a higher refractive index than the second waveguide 16B. The light propagates within the first waveguide 16A and emerges from the emitting end toward the photoelectric converter 12 . And, since the oblique incident light is emitted from a position near the center of the image angle toward a position near the edge of the image angle, the incident light is incident on the second waveguide 16B toward the edge of the image angle in an oblique manner. Thus, light propagates through the portion near the edge of the image corner of the first waveguide 16A. That is, since the portion near the edge of the image angle of the first waveguide 16A is located near the center of the photoelectric converter 12 , the incident light incident on the second waveguide 16B passes through the first waveguide 16A and effectively hits the photoelectric converter 12 .

Since the waveguide 16 has a structure including the first waveguide 16A and the second waveguide 16B, the amount of light leakage of light from the bottom of the waveguide 16 all the way to the photoelectric converter 12 can be minimized. Even if the polysilicon electrode 61 and the like are provided near the photoelectric converter 12 , light is incident on the center of the photoelectric converter 12 or at a position near the center, and components shaded by the polysilicon electrode 61 can be reduced. If the waveguide 16 having the above structure is made of one material, by reducing the diameter of the waveguide 16, the amount of light shielded by the polysilicon electrode 61 can be reduced.

Also, pupil correction may be performed on the photoelectric converter 12 , the pixel transistor (not shown), and the wiring portion 15 (not shown) of the wiring layer 13 . Therefore, the amount of light shaded by the pixel transistor can be reduced, and color shading can be reduced.

2. The second embodiment

First example method of manufacturing solid-state image pickup device

Hereinafter, a first exemplary method of manufacturing a solid-state image pickup device according to a second embodiment of the present invention will be described with reference to FIGS. 12 to 21 .

Referring to FIG. 12 , a photoelectric converter 12 is formed on the surface (light incident side) of a semiconductor substrate 11 . The photoelectric converter 12 converts incident light into signal charges. Also, a transfer gate 31 is formed on the semiconductor substrate 11 . The transfer gate 31 reads signal charges that have undergone photoelectric conversion by the photoelectric converter 12 . In addition, although not shown, pixel transistors and peripheral circuit units are formed on the semiconductor substrate 11 . The pixel transistor amplifies and outputs signal charges that have undergone photoelectric conversion by the photoelectric converter 12 . A peripheral circuit unit processes the amplified output signal. The semiconductor substrate 11 uses, for example, a silicon substrate. Alternatively, the semiconductor substrate 11 may use a silicon-on-insulator (SOI) substrate. In this case, the photoelectric converter 12, the transfer gate 31, and the like are formed on the silicon layer of the SOI substrate.

A plurality of unit pixels 21 each having a photoelectric converter 12 are arranged in an array in the row and column directions of the semiconductor substrate 11 to define the pixel portion 20 .

An insulating film is formed on the semiconductor substrate 11 to cover the photoelectric converter 12 , the transfer gate 31 , pixel transistors, peripheral circuit units, and the like, thereby forming the five-principle wiring layer 13 . For example, the wiring layer 13 is formed such that a plurality of layers including the wiring portion 15 are formed in the interlayer insulating film 14 . The barrier metal layer 141 is formed around the wiring portion 15 . In interlayer insulating film 14 , for example, a silicon carbide (SiC) film is formed as diffusion prevention layer 142 that prevents diffusion of metal or the like from wiring portion 15 . The interlayer insulating film 14 may be formed of a silicon oxide (SiO ₂ ) film. The surface of the interlayer insulating film 14 is planarized. The wiring portion 15 is not formed in the region above the photoelectric converter 12 .

Next, referring to FIG. 13 , a resist film 51 is formed on the interlayer insulating film 14 positioned on top of the wiring layer 13 by a typical resist process. By photolithography, an opening 52 is formed in a region of the resist film 51 above the region where the waveguide is formed. When the layout of the openings 52 is obtained, pupil correction is performed for the waveguide as described with reference to FIGS. 3A to 3C , 4A and 4B and the like. Specifically, the opening 52 is formed such that the central axis of the waveguide formed below the opening 52 is aligned with the center of the ray of incident light rays incident on the light-ray-incident-side end of the waveguide.

Next, referring to FIG. 14 , dry etching is performed using the resist film 51 as an etching mask to form a waveguide hole 19 for forming a waveguide in the interlayer insulating film 14 in the wiring layer 13 . At this time, the waveguide hole 19 is formed such that the side walls of the waveguide hole 19 are vertical and the depth of the waveguide hole 19 is about 4 to 5 μm. Also, the waveguide hole 19 has a constant cross section from the opening toward the bottom. The shape of the opening may be circular, oval (including oval) and the like. Alternatively, the shape of the opening of the waveguide hole 19 may be a rectangle (such as a square) with rounded corners.

Next, referring to FIG. 15 , the resist film 51 (see FIG. 14 ) is removed to allow the surface of the interlayer insulating film 14 in the wiring layer 13 to be exposed.

Next, referring to FIG. 16 , the waveguide hole 19 is filled with a waveguide material film 53 .

For the waveguide material, a material having a higher refractive index than the material of the interlayer insulating film 14 in the wiring layer 13 is selected. For example, when the interlayer insulating film 14 is a film made of a material selected from silicon oxide and having a refractive index of 1.4, the waveguide material film 53 is a film having a refractive index greater than or equal to 1.4. The waveguide material film 53 uses a film made of a material selected from nitrides and having a refractive index of about 1.8. For example, a silicon nitride film can be used. A waveguide material film 53 is also formed on the interlayer insulating film 14 . The waveguide material film 53 is formed by coating, chemical vapor deposition, or the like. Thus, the waveguide 16 is formed such that the waveguide material film 53 is filled in the waveguide hole 19 .

Next, referring to FIG. 17 , a planarization insulating film 54 for planarizing the surface of the waveguide material film 53 is formed. The planarization insulating film 54 is formed of, for example, a resin layer.

Next, referring to FIG. 18 , the color filter layer 17 is formed on the planarizing insulating film 54 . The color filter layer 17 is formed by applying a color filter material and then patterning by exposure, development, or the like. The color filter layer 17 uses, for example, red filters, green filters, and blue filters to correspond to the colors detected by the corresponding photoelectric converters 12 . The layout of the color filter layer 17 is also subjected to pupil correction.

Next, referring to FIG. 19 , a lens forming film 55 is formed on the color filter layer 17 . The lens forming film 55 is a material for microlenses (also referred to as on-chip lenses). The lens forming film 55 is formed of, for example, a light-transmitting resin film.

Next, referring to FIG. 20 , a resist pattern 56 for microlenses is formed on the lens forming film 55 . The layout of the resist pattern 56 is subjected to pupil correction. Then, although not shown, the resist pattern 56 is molded to have a lens shape. Then, the shape of the resist pattern 56 molded to have a lens shape is transferred to the lens forming film 55 by back etching.

Thus, referring to FIG. 21 , the microlens 18 is formed in the lens forming film 55 .

In the manufacturing method described above, the waveguide 16 has a cylindrical body with a constant cross section from the light incident side end to the light light exit side end. The light rays perpendicularly incident on the light incident side end of the waveguide 16 are not reflected by the side walls of the waveguide 16 but pass through the waveguide 16 . Thus, reduction in sensitivity is limited. Also, since the ray center of the incident light incident on the light incident side end of the waveguide 16 is aligned with the central axis of the waveguide 16 , the incident light is efficiently guided to the waveguide 16 . Therefore, the solid-state image pickup device 1 ( 1A) that can be manufactured provides effects and advantages similar to those of the first example of the first embodiment.

Second example method of manufacturing solid-state image pickup device

Hereinafter, a second exemplary method of manufacturing a solid-state image pickup device according to a second embodiment of the present invention will be described with reference to FIGS. 22 to 28 .

Referring to FIG. 22 , waveguide holes 19 are formed in wiring layer 13 in a similar manner to the first example manufacturing method. Then, a first waveguide material film 57 for the first waveguide 16A is formed inside the waveguide hole 19 . The first waveguide material film 57 is also formed on the interlayer insulating film 14 . The first waveguide material film 57 is made of a material having a higher refractive index than the interlayer insulating film 14 . For example, the first waveguide material film 57 may be a film made of a material selected from nitrides. For example, such a film may be a silicon nitride (SiN) film or a silicon oxynitride film. Also, if the first waveguide material film 57 is formed of a silicon nitride film, this film functions as a passivation film. Although the material of the first waveguide material film 57 is not necessarily a film of a material selected from nitrides, a silicon nitride film having a high refractive index (for example, n=1.8) may be used. As for the film thickness, for example, the side wall portion may have a thickness of about 100 nm. The film thickness of the first waveguide material film 57 can be ideally determined as long as the second waveguide formed below can be formed inside the first waveguide 16A. The film forming method may be coating. Of course, the film forming method may be other methods such as chemical vapor deposition.

Next, referring to FIG. 23, the waveguide hole 19 in which the first waveguide material film 57 is formed is filled with the second waveguide material film 58, thereby forming the second waveguide 16B. The second waveguide material film 58 is a material having a lower refractive index than the first waveguide material film 57 . For example, a resin film having a refractive index of about 1.4 (for example, a resin film having good light transmission, such as PMMA) or a film made of a material selected from silicon oxide may be selected. A waveguide material film 53 is also formed on the interlayer insulating film 14 . Each waveguide material film described above can be formed by coating, chemical vapor deposition, or the like. Thus, the first waveguide 16A made of the first waveguide material film 57 is formed inside the waveguide hole 19 , and the second waveguide 16B made of the second waveguide material film 58 is formed inside the first waveguide 16A.

Next, referring to FIG. 24 , a planarization insulating film 54 for planarizing the surface of the second waveguide material film 58 is formed. The planarization insulating film 54 is formed of, for example, a resin layer.

Next, referring to FIG. 25 , the color filter layer 17 is formed on the planarization insulating film 54 . The color filter layer 17 is formed by applying a color filter material and then patterning by exposure, development, or the like. The color filter layer 17 uses, for example, red filters, green filters, and blue filters to correspond to the colors detected by the corresponding photoelectric converters 12 . The layout of the color filter layer 17 is also subjected to pupil correction.

Next, referring to FIG. 26 , a lens forming film 55 is formed on the color filter layer 17 . The lens forming film 55 is a material for microlenses (also referred to as on-chip lenses). The lens forming film 55 is formed of, for example, a light-transmitting resin film.

Next, referring to FIG. 27 , a resist pattern 56 for microlenses is formed on the lens forming film 55 . The layout of the resist pattern 56 is subjected to pupil correction. Then, although not shown, the resist pattern 56 is molded to have a lens shape. Then, the shape of the resist pattern 56 molded to have a lens shape is transferred to the lens forming film 55 by back etching.

Thus, referring to FIG. 28 , microlenses 18 are formed in lens forming film 55 . The height h1 from the surface of the second waveguide material film 58 to the base of the microlens 18 is, for example, 1 to 3 μm. Also, the height h2 from the surface of the second waveguide material film 58 to the bottom surface of the color filter layer 17 is, for example, 0.5 to 2.5 μm. In addition, the height h3 from the surface of the photoelectric converter 12 to the light exit side end of the waveguide 16 is, for example, 0.3 to 2 μm.

According to the second manufacturing method, the waveguide 16 is formed such that the second waveguide 16B is formed inside so that the first waveguide 16A having a relatively high refractive index is formed around the second waveguide 16B. Light entering the first waveguide 16A from the second waveguide 16B propagates through the first waveguide 16A and exits therefrom.

Therefore, the solid-state image pickup device 1 ( 1B) provides similar effects and advantages to the solid-state image pickup device described in the first example of the first embodiment.

3. The third embodiment

Example structure of image pickup device

Next, an example structure of an image pickup apparatus according to a third embodiment of the present invention will be described with reference to FIG. 29 . This image pickup device uses a solid-state image pickup device according to an embodiment of the present invention.

Referring to FIG. 29 , an image pickup device image pickup device 200 includes an image pickup unit and a solid-state image pickup device 210 . A light condensing optical unit 202 for forming an image is provided on the light condensing side of the image pickup unit 201 . The image pickup unit 201 is connected to a signal processing unit 203 . The signal processing unit 203 includes a signal processing circuit that drives the drive circuit of the image pickup unit 201 to process a signal that is photoelectrically converted into an image by the solid-state image pickup device 210 . The image signal processed by the signal processing unit 203 may be stored in an image storage unit (not shown). In such an image pickup device 200, the solid-state image pickup device 210 can use the solid-state image pickup device 1 described according to the above-mentioned embodiments.

Since the image pickup device 200 according to this embodiment uses the solid-state image pickup device 1 according to the above-described embodiments, color unbalance (color shading) caused by shading by wavelength in the solid-state image pickup device 1 can be reduced. Sensitivity can be improved, and thus images with high quality can be obtained.

The image pickup device 200 may be formed as one chip or module in which an image pickup unit and a signal processing unit or an optical system are integrated, thereby having an image pickup function. The image pickup device 200 is, for example, a video camera or a mobile device having an image pickup function. And, "image pickup" includes not only capturing an image during normal shooting with a video camera, but also detecting fingerprints and the like in a broad sense.

4. The fourth embodiment

Example structure of solid-state image pickup device

30 to 32 each show a solid-state image pickup device according to a fourth embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. 30 is a plan view showing a pixel portion in which a plurality of four-pixel sharing type unit pixel groups are two-dimensionally arranged. 31A and 31B are views showing a unit pixel group at an image corner center and a unit pixel group at an image corner edge of a pixel portion. Fig. 32 is a cross-sectional view taken along XXXII-XXXII in Fig. 31A.

Hereinafter, reference numeral 40 denotes a pixel portion, 38 denotes a solid-state image pickup device, 42 denotes a unit pixel group, PD (PD1 to PD4) denotes a photoelectric converter, Tr11 to Tr14, Tr2, Tr3, and Tr4 denotes a pixel transistor, 43 denotes a transmission Gate electrode, 48 denotes a reset gate electrode, 49 denotes an amplifying gate electrode, 151 denotes a selection gate electrode, 152 denotes a waveguide, 154 denotes an interlayer insulating film, 155 denotes a wiring part, 155a denotes a protruding part, 150 denotes a wiring layer, and 157 denotes a color The filter layer, 158, represents microlenses, and L represents incident light.

First, to facilitate understanding of the fourth embodiment, a comparative example before improvement will be described with reference to FIGS. 62 and 63 . This comparative example is a four-pixel sharing type MOS solid-state image pickup device in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. The solid-state image pickup device 113 of this comparative example includes a pixel portion in which a plurality of unit pixel groups are arranged. In each unit pixel group, a plurality of pixels share one pixel transistor. Specifically, the solid-state image pickup device 113 includes a four-pixel sharing type unit pixel group 114 in which four photodiodes PD serving as photoelectric converters share one pixel transistor unit. More specifically, the unit pixel group 114 includes four photodiodes PD ( PD1 to PD4 ), four transfer transistors Tr ( Tr11 to Tr14 ), and one floating diffusion region FD. In addition, the unit pixel group 114 includes a reset transistor Tr2, an amplification transistor Tr3, and a selection transistor Tr4. The transfer gate electrode 115 made of polysilicon is disposed between the floating diffusion region FD located at the center of the unit pixel group 114 and the photodiodes PD1 to PD4 . Thus, four transfer transistors Tr11 to Tr14 for the four photodiodes PD are formed.

The reset transistor Tr2 , the amplification transistor Tr3 , and the selection transistor Tr4 are horizontally and continuously arranged below the photodiodes PD1 to PD4 . The reset transistor Tr2 includes a diffusion region 116 , a diffusion region 117 and a reset gate electrode 120 . The amplification transistor Tr3 includes a diffusion region 117 , a diffusion region 118 and an amplification gate electrode 121 . The selection transistor Tr4 includes a diffusion region 118 , a diffusion region 119 and a selection gate electrode 122 . In the unit pixel group 114, the base layer including the gate electrode made of polysilicon has an asymmetric arrangement with respect to the boundary of adjacent pixels. Pixel transistor units including the reset transistor Tr2 , the amplification transistor Tr3 , and the selection transistor Tr4 are arranged asymmetrically with respect to the boundaries between the pixels Gb and R and between the pixels Gr and B. Also, the transfer gate electrodes 115 of the pixels Gr, R, Gb, and B are arranged asymmetrically with respect to the respective boundaries of the pixels Gr, R, Gb, and B. Referring to FIG.

Waveguides 23 for the photodiodes PD1 to PD4 are formed respectively. In this example, a color filter layer with a Bayer type is used. In this layer, a plurality of unit pixel groups 114 of a four-pixel sharing type in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor are repeatedly arranged. Each unit pixel group 114 includes a red pixel R, a first green pixel Gb, a blue pixel B, and a second green pixel Gr.

FIG. 63 is a cross-sectional view taken along line LXIII-LXIII passing through the second green pixel Gr in FIG. 62 . Referring to FIG. 64 , photodiode PD4 as a photoelectric converter is formed on the surface of semiconductor substrate 24 , and a plurality of layers including wiring portion 26 is formed over semiconductor substrate 24 with interlayer insulating film 25 interposed therebetween. The waveguide 23 is formed over the photodiode PD4 so that the waveguide 23 is embedded in the interlayer insulating film 25 . A color filter layer 28 is formed over the waveguide 23 . Microlenses 29 (also called on-chip lenses) are formed on the color filter layer 28 . Also, the amplification gate electrode 121 is formed near the photodiode PD4. The gate insulating film 27 is arranged between the amplification gate electrode 121 and the photodiode PD4.

In the solid-state image pickup device 113 of the comparative example, incident light rays L pass through the microlens 29 and the waveguide 23, and are incident on the photodiode PD of each pixel. At this time, in the second green pixel Gr, part of the incident light L passing through the waveguide 23 is shielded by the amplifying gate electrode 121 disposed near the second green pixel Gr and having a large gate length, as circled in FIGS. 62 and 63 . as shown in c. In the first green pixel Gb, the incident light L passing through the waveguide 23 is incident on the photodiode PD1 without being affected by the reset gate electrode 120 or the amplification gate electrode 121 . In view of this, as shown in a graph plotting wavelength and output in FIG. 64 , the sensitivity of the second green pixel Gr (see curve r1 ) is smaller than that of the first green pixel Gb (see curve b1 ). Thus, a difference in sensitivity occurs between the green pixels Gb and Gr.

In contrast, the solid-state image pickup device according to the fourth embodiment can control the sensitivity so that the sensitivities of the first and second green pixels Gb and Gr share one floating diffusion region, one amplification transistor, and one selection transistor in four pixels The four-pixel sharing type unit is equal within the pixel group.

Referring to FIG. 31 , a solid-state image pickup device 38 of this fourth embodiment includes a pixel portion in which a plurality of unit pixel groups 41 are arranged. In each unit pixel group 42, a plurality of pixels share one pixel transistor. Specifically, the solid-state image pickup device 38 includes a four-pixel sharing type unit pixel group 42 that shares one floating diffusion region, one amplification transistor, and one selection transistor, in which four photodiodes PD serving as photoelectric converters share one pixel transistor unit . More specifically, the unit pixel group 42 includes four photodiodes PD ( PD1 to PD4 ), four transfer transistors Tr ( Tr11 to Tr14 ), and one floating diffusion region FD. In addition, the unit pixel group 42 includes a reset transistor Tr2, an amplification transistor Tr3, and a selection transistor Tr4. The floating diffusion FD is arranged at the center of the four photodiodes PD1 to PD4 in a 2×2 array. A transfer gate electrode 43 made of polysilicon is arranged between the floating diffusion FD and the photodiodes PD1 to PD4 . Thus, four transfer transistors Tr11 to Tr14 for the four photodiodes PD are formed.

The reset transistor Tr2 , the amplification transistor Tr3 , and the selection transistor Tr4 are horizontally and continuously arranged below the four photodiodes PD1 to PD4 . The reset transistor Tr2 includes a diffusion region 44 , a diffusion region 45 and a reset gate electrode 48 . The amplification transistor Tr3 includes a diffusion region 45 , a diffusion region 46 and an amplification gate electrode 49 . The selection transistor Tr4 includes a diffusion region 46 , a diffusion region 47 and a selection gate electrode 151 .

Waveguides 152 for the photodiodes PD1 to PD4 are formed respectively. In this embodiment, the color filter layer 157 uses the Bayer type color filter 101 shown in FIG. 60 . Therefore, in this embodiment, referring to FIG. 30, a plurality of unit pixel groups 42 of a four-pixel sharing type in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor are repeatedly arranged, thereby forming a pixel portion. 40. Each unit pixel group 42 includes a red pixel R, a first green pixel Gb, a blue pixel B, and a second green pixel Gr.

Pixels R, Gb, B, and Gr have a basic structure similar to that shown in FIG. 32 . Specifically, the pixels R, Gb, B, and Gr each have a photodiode PD as a photoelectric converter on the surface of the semiconductor substrate 153 . The wiring layer 150 is formed over the semiconductor substrate 153 . In the wiring layer 150 , a plurality of layers including the wiring portion 155 are provided in regions other than the region above the photodiode PD with the interlayer insulating film 154 interposed therebetween. The waveguide 152 is formed over the photodiode PD such that the waveguide 152 is embedded in the interlayer insulating film 154 . The waveguide 152 guides the incident light to the photodiode PD. The surface of the interlayer insulating film 154 is planarized. A color filter layer 157 that splits incident light rays to correspond to the waveguides 152 is formed on the planarized surface. Microlenses 158 (also referred to as on-chip lenses) are formed on the color filter layer 157 . The gate electrodes 43, 48, 49, and 151 made of polysilicon of the pixel transistor are formed with the gate insulating film 131 interposed therebetween. Referring to the cross-sectional view in FIG. 32 , an amplification gate electrode 49 is formed near the photodiode PD4. The gate insulating film 131 is provided between the amplification gate electrode 121 and the photodiode PD4.

The waveguide 152 formed corresponding to the photodiode PD has a cylindrical body with a constant cross-section from the light incident side end to the light light exit side end. For example, a cylindrical body may be a cylinder or an elliptical cylinder (including an elliptical cylinder). The diameter (width) of the waveguide 152 is smaller than the width of the photodiode PD and the opening width of the wiring portion 155 for the photodiode PD so that the waveguide 152 can be adjusted by offset, which will be described below. The waveguide 152 may be a tapered cylinder whose cross-section decreases from the light incident side end to the light exit side end.

In the unit pixel group 42, the base layer disposed under the light incident surface has an asymmetric arrangement. In this embodiment, the base layer including the transfer gate electrode 43 (the base layer formed under the waveguide 152 ) has an asymmetric arrangement with respect to the boundaries of the adjacent pixels Gr, R, Gb, and B. That is, the transfer gate electrodes 43 of the pixels Gr, R, Gb, and B are asymmetrically arranged in the unit pixel group 42 . Also, in the unit pixel group 42 , pixel transistor units including the reset transistor Tr2 , the amplification transistor Tr3 , and the selection transistor Tr4 are arranged asymmetrically with respect to the boundaries between the pixels Gb and R and between the pixels Gr and B.

In the state before the waveguide 152 of a predetermined pixel is adjusted by offset adjustment (corresponding to the state of the comparative example in FIG. The positional relationship between the PD and the waveguide 152 is equivalent throughout the pixel portion 40 . For example, there are cases where the center of the photodiode PD is slightly offset from the center axis of the waveguide 152 , and there are cases where the center of the photodiode PD is aligned with the center axis of the waveguide 152 . In any case, the positional relationship between the center of the photodiode PD and the waveguide 152 is equivalent in the entire pixel portion 40 .

The color filter layer 157 and microlens 158 of each color may undergo pupil correction, or may not undergo pupil correction. If the pupil correction is performed for the color filter layer 157 and the microlens 158, the pupil correction is performed so that the offset amount of the center of the color filter layer 157 or the microlens 158 with respect to the center of the photodiode PD is removed from the pixel portion The center of 40 becomes larger towards the periphery.

In this embodiment, the waveguide 152 is used as an adjustment mechanism for obtaining optical symmetry in the unit pixel group 42 for the photodiode PD. In this embodiment, the waveguides 152 of the second green pixels Gr are shifted away from the amplification gate electrode 49 from the reference position where the waveguides 152 of the pixels are arranged at regular intervals in the entire area of the pixel portion 40 . In this case, the adjustment direction and adjustment amount of the positional shift are determined such that the sensitivity of the second green pixel Gr is equal to the sensitivity of the first green pixel Gb. In this embodiment, the waveguide 152 of the second green pixel Gr is shifted obliquely upward and leftward, as shown by the arrow B in FIGS. 31A and 31B , so that the distance d1 (see Comparative example) becomes the distance d2 greater than the distance d1. The adjustment direction (offset direction) and adjustment amount (offset amount) of the positional offset of the waveguide 152 of the second green pixel Gr are equal in the entire pixel portion including the waveguide 152 at the edge of the image corner. The positions of the waveguides 152 of the other red pixels R, blue pixels B and the first green pixel Gb are not changed from the original state.

Therefore, the waveguide 152 of the second green pixel Gr in the unit pixel group 42 of the four-pixel sharing type of the four-pixel sharing type that shares one floating diffusion region, one amplification transistor, and one selection transistor with respect to the second green pixel Gr The boundaries between the other red pixel R, the blue pixel B, and the first green pixel Gb are arranged asymmetrically with the other red pixel R, blue pixel B, and first green pixel Gb.

The entire layout of the waveguides 152 in the unit pixel group 42 is preset in the exposure mask used to form the waveguides 152, indicating the shifted position of the waveguides 152 of the second green pixel Gr. Thus, only the waveguide 152 of the second green pixel Gr in the formed waveguide layout is intentionally shifted by a predetermined distance in a predetermined direction in the unit pixel group 42 compared to the other pixels Gb, R, and B by using the exposure mask.

With the solid-state image pickup device 38 of the fourth embodiment, only the waveguide 152 of the second green pixel Gr is intentionally shifted from the amplification gate electrode 49 made of polysilicon in the base layer. Therefore, it is possible to prevent the incident light L from being shielded by the amplifying grid electrode 49 . Thereby, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced or eliminated, and thus, optical symmetry for the green pixels Gb and Gr can be obtained. Referring to curves r2 and b2 in a graph plotting wavelength and output in FIG. 33 , sensitivities of the first and second green pixels Gb and Gr may be equal to each other. Therefore, by reducing the difference in sensitivity between the first and second green pixels Gb and Gr, noise such as harsh noise can be reduced, and a solid-state image pickup device with high image quality can be provided.

5. Fifth Embodiment

Example structure of solid-state image pickup device

34A and 34B each show a solid-state image pickup device according to a fifth embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. 34A and 34B are plan views showing a unit pixel group at the corner center and a unit pixel group at the corner edge in the pixel portion.

Based on the edge of the opening width of the wiring portion 155 corresponding to the photodiode PD, an offset amount that is an adjustment amount of the waveguide 152 is determined. Thus, the offset is limited. With this limitation, even if only the waveguide 152 of the second green pixel Gr is shifted, the difference in sensitivity between the first and second green pixels Gb and Gr may not be reduced. The fifth embodiment improves on this.

In the solid-state image pickup device 161 according to the fifth embodiment, similarly to the fourth embodiment, as shown by the arrow B in FIGS. 34A and 34B , the waveguide 152 of the second green pixel Gr is directed obliquely upward and rightward from the amplification gate electrode. 49 offset by a predetermined distance. Meanwhile, as shown by arrow C in FIGS. 34A and 34B , the waveguide 152 of the first green pixel Gb is shifted obliquely upward and rightward by a predetermined distance d3 to be close to the reset gate electrode 48 . The layout of the waveguides 152 in the unit pixel group 42 is equivalent over the entire pixel portion 40 . In this embodiment, the offset direction of the waveguide 152 of the first green pixel Gb is the same as the offset direction of the second green pixel Gr indicated by arrow C. Referring to FIG. The shift direction of the first and second green pixels Gb and Gr is not limited thereto. The optimum direction can be determined according to the layout of the pixel transistors Tr11 to Tr14.

Other structures are similar to those described according to the fourth embodiment. Like reference numerals in FIGS. 31A and 31B refer to like components.

With the solid-state image pickup device 161 of the fifth embodiment, the sensitivity of the second green pixel Gr is improved by offsetting the waveguide 152 of the second green pixel Gr from the amplification gate electrode 49 in the base layer; The waveguide 152 of Gb is offset from the reset gate electrode 48 in the base layer, intentionally reducing the sensitivity of the second green pixel Gr. Therefore, optical symmetry for the first and second green pixels Gb and Gr can be obtained. That is, the difference in sensitivity between the first and second green pixels Gb and Gr can be further reduced or eliminated. The sensitivity of both green pixels Gb and Gr may be equal. Therefore, by reducing the difference in sensitivity between the first and second green pixels Gb and Gr, noise such as harsh noise can be reduced, and a solid-state image pickup device with high image quality can be provided.

6. The sixth embodiment

Example structure of solid-state image pickup device

35, 36A and 36B each show a solid-state image pickup device according to a sixth embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. Fig. 35 is a schematic configuration diagram showing a unit pixel group in a final state according to the sixth embodiment. 36A and 36B are schematic plan views showing unit pixel groups at the angular center and at the angular edges for providing improved pixel portions for oblique incident rays.

The solid-state image pickup device according to the sixth embodiment can provide control over color shading in addition to controlling the difference in sensitivity between the green pixels Gb and Gr.

First, to facilitate understanding of the sixth embodiment, a comparative example before improvement will be described with reference to FIGS. 65A and 65B . The comparative example in FIGS. 65A and 65B is similar to the comparative example in FIG. 62 described above. Like reference numerals refer to like parts. As shown in FIG. 65A, at the center of the image angle, the incident ray L is incident in a direction perpendicular to the paper (in the figure, for convenience of illustration, the incident ray L enters the lower side from the upper side). The waveguides 23 for the pixels R, Gr, Gb and B are arranged near the respective transfer gate electrodes 115 . Thus, as indicated by circle f, part of the incident light L passing through the waveguide 23 may be shielded by the transmission grid electrode 115 . In contrast, as shown in FIG. 65B, at the edge of the image angle (in the drawing, for example, the left pixel portion is shown), the incident ray L obliquely enters the left side from the right side. Since the photodiodes PD1 and PD2 are shielded by the transfer gate electrode 115 , as indicated by circle g, part of the incident light L incident on the first green pixel Gb and the red pixel R is shielded by the transfer gate electrode 115 . As indicated by the circle f, part of the incident light L incident on the second green pixel Gr and the blue pixel B may also be shielded by the transfer gate electrode 115 . Also, the waveguides 23 of the second green pixel Gr and blue pixel B are located near the amplification gate electrode 121 at the center and edge of the image angle. As indicated by circle e, part of the incident light L is shielded by the amplifying grid electrode 121 . Therefore, a difference in sensitivity between the first and second green pixels Gb and Gr occurs, and color shading occurs.

With the solid-state image pickup device 63 of the sixth embodiment, at the center of the image angle shown in FIG. 36A and at the edge of the image angle shown in FIG. 36B, the waveguides of the pixels R, Gr, Gb, and B in the unit pixel group 42 152 is offset from the corresponding transfer gate electrode 43 in the horizontal direction, as indicated by arrow X. Therefore, in the pixels R, Gr, Gb, and B, the portions of the vertically incident rays L and the obliquely incident rays L at the center of the image angle are hardly shielded by the transfer gate electrode 43 . Therefore, the shielding of the incident light L by the transmission grid electrode 43 is reduced or eliminated.

And, similar to the description according to the fourth embodiment, the waveguide 152 of the second green pixel Gr is offset from the amplification gate electrode 49 , and the waveguide 152 of the blue pixel B is offset from the amplification gate electrode 159 .

Therefore, referring to FIG. 35 , the solid-state image pickup device 63 according to the sixth embodiment is shifted by a predetermined shift amount in the direction indicated by the arrow. Specifically, the waveguide 152 of the second green pixel Gr is offset away from the transfer gate electrode 43 and the amplification gate electrode 49 to the obliquely upper right (arrow Y). The waveguide 152 of the blue pixel B is shifted obliquely downward and rightward (arrow Z) to be symmetrical with the waveguide 152 of the second green pixel Gr. The waveguide 152 of the first green pixel Gb and the red pixel R are offset horizontally to the left from the transfer gate electrode 43 . The layout of the waveguides 152 in the unit pixel group 42 is identical in the entire pixel portion 40 .

Other structures are similar to those described according to the fourth embodiment. In Figures 35, 36A and 36B, like reference numerals refer to like parts in Figures 31A and 31B.

With the solid-state image pickup device 63 of the sixth embodiment, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced or eliminated. Noise (such as harsh noise) can be reduced. In addition, the sensitivity of the red pixel R and the blue pixel B can be controlled. Variations in sensitivity of the pixel portion 40 can be reduced, and color shading can be reduced. Since variations in sensitivity of the pixel portion 40 can be reduced, correction circuits can be reduced, and the circuit size can be reduced.

7. The seventh embodiment

Example structure of solid-state image pickup device

Fig. 37 shows a solid-state image pickup device according to a seventh embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. FIG. 37 is a cross-sectional view showing the second green pixel Gr in the unit pixel group.

A symmetrical arrangement in the base layer can be performed not only for gate electrodes made of polysilicon, but also for wiring patterns. The solid-state image pickup device according to the seventh embodiment can obtain optical symmetry in the base layer with respect to the wiring portion 155 .

First, to facilitate understanding of the seventh embodiment, a comparative example before improvement will be described with reference to FIG. 38 . 38 is a cross-sectional view of the second green pixel Gr in a four-pixel sharing type unit pixel group in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. In the solid-state image pickup device 33 of the comparative example, referring to FIG. formed over the semiconductor substrate 24 . The waveguide 23 is formed over the photodiode PD4 so that the waveguide 23 is embedded in the interlayer insulating film 25 . A color filter layer 28 is formed over the waveguide 23 . Microlenses 29 (also called on-chip lenses) are formed on the color filter layer 28 . In this example, the waveguide 23 is disposed over the wiring portion 26 in the bottom layer. A part of the wiring portion 26 in the bottom layer protrudes to a region above the photodiode PD4, and the base layer including the wiring portion 26 has an asymmetric arrangement in the unit pixel group. Although not shown, in other pixels including the red pixel R, the blue pixel B, and the first green pixel Gb, the wiring portion 26 in the bottom layer below the waveguide 23 does not protrude beyond the photodiodes PD1, PD2, and PD3. area.

In the solid-state image pickup device 33 of the comparative example, referring to FIG. 38 , part of the incident light L incident on the second green pixel Gr is shielded by the wiring portion 26 in the bottom layer, reducing the sensitivity of the second green pixel Gr. Therefore, a difference in sensitivity between the first and second green pixels Gb and Gr occurs. Color shading occurs if a part of the wiring portion 26 in the bottom layer extends to an area above the electrophotodiode of another pixel, and if the layout of the base layer including the wiring portion 26 is asymmetric.

In the solid-state image pickup device 65 according to the seventh embodiment, a photodiode PD4 as a photoelectric converter is formed on the surface of a semiconductor substrate 153, and a plurality of layers including a wiring portion 155 are formed with an interlayer insulating film 154 interposed therebetween. above the semiconductor substrate 153 . The wiring portion 155 is substantially opened in a region corresponding to the photodiode PD4. The waveguide 152 is formed over the photodiode PD4 so that the waveguide 152 is embedded in the interlayer insulating film 154 . The waveguide 152 guides the incident light to the photodiode PD. The surface of the interlayer insulating film 154 is planarized. The color filter layer 157 is formed on the surface of the interlayer insulating film 154 . Microlenses 158 (also referred to as on-chip lenses) are formed on the color filter layer 157 . In this example, the waveguide 152 is provided over the wiring portion 155 in the bottom layer, and a part of the wiring portion 155 in the bottom layer protrudes to a region above the photodiode PD4. Although not shown, in other pixels including the red pixel R, the blue pixel B, and the first green pixel Gb, the wiring portion 155 in the bottom layer below the waveguide 152 does not protrude to the area above the photodiodes PD1, PD2, and PD3. area. Thus, the layout of the base layer including the wiring portion 155 has an asymmetrical arrangement in the unit pixel group 42 .

In this embodiment, the waveguide 152 of the second green pixel Gr is offset from a wiring portion 155 protruding to a region above the photodiode PD4. The waveguides 152 of the pixels R, Gb and B of the other colors are arranged at equivalent positions relative to the corresponding photodiodes. Since only the waveguide 152 of the second green pixel Gr is shifted from the initial position, the waveguide 152 of the second green pixel Gr in the unit pixel group 42 is relative to the distance between the second green pixel Gr and the pixels Gb, R, and B of other colors. Borders are arranged asymmetrically with pixels Gb, R, and B of other colors. The layout of the waveguides 152 in the unit pixel group 42 is the same in the entire pixel portion 40 .

Other structures of the four-pixel sharing type in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor are similar to those described according to the fourth embodiment. Duplicate descriptions will be omitted.

According to the solid-state image pickup device 65 of the seventh embodiment, the waveguide 152 of the second green pixel Gr is offset from the wiring portion 155 protruding to the region above the photodiode PD4. Accordingly, the incident light L is not shielded by the wiring portion 155 and is incident on the photodiode PD4, so that the sensitivity of the second green pixel Gr is improved. Thereby, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced or eliminated. The sensitivity of both green pixels Gb and Gr may be equal. Therefore, by reducing the difference in sensitivity between the first and second green pixels Gb and Gr, noise such as harsh noise can be reduced, and a solid-state image pickup device with high image quality can be provided.

If a part of the wiring portion 155 in the bottom layer protrudes to an area above the photodiode PD of another color pixel, the waveguide of the pixel is shifted. According to this structure, the incident light L is not shielded by the wiring portion 155, and color shading can be reduced.

8. Eighth embodiment

Example structure of solid-state image pickup device

39A and 39B each show a solid-state image pickup device according to an eighth embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. 39A and 39B are schematic configuration diagrams showing unit pixel groups at the center of the image corner and at the edge of the image corner in the final state according to the eighth embodiment.

The solid-state image pickup device according to this embodiment reduces the difference in sensitivity between the green pixels Gb and Gr by combining the shifting of the waveguide according to any of the fourth to seventh embodiments described with pupil correction for the waveguide , and lower the color shadows.

First, pupil correction for a waveguide will be described with reference to FIGS. 40A to 43 . In the cross-sectional views of FIGS. 40A to 43 , pixel transistors are not shown for convenience of description. Figure 40A shows the pixel at the center of the image angle. Fig. 40B shows pixels at the corner ends. Referring to FIGS. 40A and 40B, in a pixel of a solid-state image pickup device, a photodiode PD as a photoelectric converter is formed on the surface of a semiconductor substrate 153, and a plurality of layers including a wiring portion 155 are sandwiched by an interlayer insulating film. 154 is formed in a region above the semiconductor substrate 153 other than the region above the photodiode PD. The waveguide 152 is formed over the photodiode PD such that the waveguide 152 is embedded in the interlayer insulating film 154 . The waveguide 152 guides the incident light to the photodiode PD. The surface of the interlayer insulating film 154 is planarized. A color filter layer 157 for the corresponding waveguide 152 is formed on the planarized surface. Microlenses 158 (also referred to as on-chip lenses) are formed on the color filter layer 157 .

The waveguide 152 is formed such that a waveguide hole is formed in the interlayer insulating film 154 in a region above the photodiode PD, and the waveguide hole is filled with a light-transmitting material having a higher refractive index than the interlayer insulating film 154 . The material is, for example, a silicon nitride film, a diamond film, or a resin film. Microlenses 158 and color filter layer 157 undergo pupil correction to efficiently converge and even oblique light rays. The pupil correction amount increases from the center of the image angle (ie, the center of the pixel portion) toward the edge of the image angle.

As described above, the waveguide 152 formed corresponding to the photodiode PD in the pixel portion 40 has a cylindrical body with a constant cross section from the light incident side end to the light light exit side end. For example, a cylindrical body of constant cross-section may be a cylinder or an elliptical cylinder (including elliptical cylinders). The ray center LC of the incident light incident on the light incident side end of the waveguide 152 is aligned with the central axis C of the waveguide 152 .

In this case, in the pixel at the center of the image angle in FIG. 40A, incident light rays are incident on the microlens 158 in the central axis direction. The incident light condensed by the microlens 158 passes through and is separated by the color filter layer 157 , and is incident on the light incident side end of the waveguide 152 . The incident light is guided along the central axis C of the waveguide 152 and emerges from the light exit side end of the waveguide 16 . Light strikes the center of the photodiode PD. That is, incident light passing through the center of the microlens 158 passes along the center of the color filter layer 157 and the central axis C of the waveguide 152, and is incident on the center of the photodiode PD. Thus, no pupil correction is performed on the waveguide 152 .

In pixels located at positions offset from the center of the image angle, or in pixels at the edges of the image angle in the figure, as described above, the microlens 158 and the color filter layer 157 undergo pupil correction to effectively converging or even oblique rays, as described above. Furthermore, the ray center LC of the incident light incident on the light incident side end of the waveguide 152 is aligned with the central axis C of the waveguide 152 . That is, pupil correction has been performed for the waveguide 152 .

In the pixel portion 40, among the photodiodes PD on which incident rays having equal wavelengths are incident, the center axis C of each waveguide 152 is shifted from the center of the pixel portion 40 toward the center axis C of the corresponding photodiode PD. The outside becomes larger. The pupil correction is performed on the microlens 158 from the center of the pixel portion 40 toward the outside, however the pupil correction amount is insufficient. In view of this, for incident rays of equal wavelength, the offset of the central axis of the waveguide 152 relative to the center of the photodiode PD increases so that the ray center of the light from the microlens 158 is aligned with the central axis C of the waveguide 152 .

The diameter of the waveguide 152 allows incident light from the light exit side end of the waveguide 152 to impinge on an area within the surface of the photodiode PD. Thus, the size of the waveguide 152 is not equal to the size of the surface of the photodiode PD, unlike the waveguide of the related art. The diameter of the waveguide 152 is desirably larger than the spot diameter of incident light passing through the color filter layer 157 on the light incident side end of the waveguide 152 . The spot diameter varies according to the wavelength of the incident light. For example, when the color filter layer 157 divides the incident light into red light, green light and blue light, the spot diameter of the red light is the largest, the spot diameter of the green light is smaller than that of the red light, and the spot diameter of the blue light is smaller than that of the red light. The spot diameter is smaller than that of green light. If the diameter of the waveguide 152 is determined by color, the overall situation will become complicated. For example, the diameter of the waveguide 152 is determined based on green light having an intermediate wavelength range of the incident light rays. Alternatively, if an edge is provided between the waveguide 152 and the wiring portion 155 of the wiring layer 150, the diameter of the waveguide 152 may be determined based on red light.

By reducing the diameter of the waveguide 152 to be smaller than that of the related art waveguide, the margin for pupil correction can be increased. Furthermore, by reducing the width of the wiring portion 155 provided around the waveguide 152, the edge of the waveguide 152 for pupil correction can be further enlarged.

Referring to FIGS. 41A to 41C , in the pixel portion 40, in the photodiodes PD on which incident rays having equal wavelengths are incident, the amount of shift of the central axis C of each waveguide 152 with respect to the center of the corresponding photodiode PD It becomes larger from the center of the pixel portion 40 toward the outside. In other words, with respect to the photodiodes PD positioned at equal distances from the center of the pixel portion 40, the shift amount of the central axis C of each waveguide 152 relative to the central axis FC of the corresponding photodiode PD increases with increases with the increase of the wavelength of the light. The pupil correction amount for the waveguide 152 satisfies the relationship "blue light (B)<green light (G)<red light (R)". For ease of illustrating the floor plan, the waveguide 152 is smaller than the photodiode PD. Thus, shading can be optimized by each waveguide 152 .

Typically, the incident angle of the incident light condensed by the microlens 158 increases as the position shifts from the center of the pixel portion 20 toward the outside. Pupil correction is performed for the microlens 158, however, the pupil correction amount is insufficient. In view of this, as described above, for incident rays having equal wavelengths, the offset of the central axis of each waveguide 16 relative to the center of the photodiode increases so that the center of the ray from the microlens 158 is aligned with the center of the waveguide 16. aligned with the central axis.

Typically, microlenses 158 and color filter layer 157 undergo pupil correction so that incident light is incident on photodiode PD in the direction of the central axis. For example, pupil correction of incident light rays (for example, green light) having a reference wavelength is performed for the microlens 158 and the color filter layer 157 . In this case, referring to FIG. 41A , since the blue light is easily bent by the microlens 158 , the incident angle of the blue light incident on the light incident side end of the waveguide 152 becomes large. Therefore, the microlens 158 and the color filter layer 157 are greatly shifted toward the center of the pixel portion with respect to the central axis FC of the photodiode PD by pupil correction. However, even when the microlens 158 and the color filter layer 157 are greatly shifted, the light emitted from the color filter layer 157 is incident on the waveguide 152 at a position close to the central axis FC of the photodiode PD. side on one end. Therefore, almost all of the incident light rays incident on the light incident side end of the waveguide 152 are guided to the waveguide 152 . In this case, the position of the waveguide 152 is corrected so that the central axis LC of the ray of the incident light incident on the light incident side end of the waveguide 152 is aligned with the central axis C of the waveguide 152 .

Referring to FIG. 41C , since red light is less bent by the microlens 158 than blue light, the incident angle of red light incident on the light-incident side end of waveguide 152 becomes smaller than that of blue light. Also, the microlens 158 and the color filter layer 157 are greatly shifted toward the center of the pixel portion with respect to the central axis FC of the photodiode PD by pupil correction. Due to this, the light emitted from the color filter layer 157 is incident on the light incident side end of the waveguide 152 at a position away from the central axis FC of the photodiode PD. In some cases, the light is incident such that a major part of the light protrudes from the light incident side end of the waveguide 152 . However, in this embodiment of the invention, the position of the waveguide 152 is corrected so that the central axis LC of the ray of the incident light incident on the light incident side end of the waveguide 152 is aligned with the central axis C of the waveguide 152 . Thus, almost all of the incident light emitted from the color filter layer 157 is incident on the light incident side end of the waveguide 152 and guided into the waveguide 152 .

Also, referring to FIG. 41B , green light is less bent by the microlens 158 than blue light, and is easily bent by the microlens 158 than red light. The incident angle of the incident light rays incident on the light incident side end of the waveguide 152 is smaller than that of blue light and larger than that of red light. Since the microlens 158 and the color filter layer 157 are greatly shifted toward the center of the pixel portion with respect to the central axis FC of the photodiode PD by pupil correction, the light emitted from the color filter layer 157 is far away from the photodiode PD. The light is incident on the light incident side end of the waveguide 152 at the position of the center axis FC of the waveguide 152 . However, in this embodiment of the invention, the position of the waveguide 152 is corrected so that the central axis LC of the ray of the incident light incident on the light incident side end of the waveguide 152 is aligned with the central axis C of the waveguide 152 . Thus, almost all of the incident light emitted from the color filter layer 157 is incident on the light incident side end of the waveguide 152 and guided into the waveguide 152 .

As described above, as the wavelength of light separated by the color filter layer 157 decreases, the amount of offset of the central axis C of each waveguide 152 with respect to the center of the corresponding photodiode PD decreases. Therefore, even when the wavelengths of incident light rays on the light incident side end of the waveguides 152 are different from each other, the waveguides 152 are also arranged separately according to the wavelengths, the sensitivity of the pixels is equal, and color shading does not occur.

42A, 42B, and 43 each show a four-pixel sharing type MOS solid-state image pickup device that shares one floating diffusion region, one amplification transistor, and one selection transistor, in which pupil correction is performed for the waveguide described above. FIG. 42A shows that at the center of the image angle of the pixel portion 40 shown in FIG. 43, four pixels share one floating diffusion region, one amplification transistor, and one selection transistor of the waveguide 152 in the four-pixel sharing type unit pixel group 42. layout. FIG. 42B shows that at the upper right edge of the image angle of the pixel portion 40 shown in FIG. 43 , four pixels share a floating diffusion region, an amplification transistor, and a selection transistor in a four-pixel sharing type unit pixel group 42 waveguide 152 Layout. At the lower right, upper left, and lower left edges of the image corner of the pixel portion 40, the layout of the waveguides 152 in the four-pixel sharing type unit pixel group 42 is symmetrical to the layout of the waveguides 152 shown in FIG. 42B with respect to the center of the image corner.

By adding the layout of the waveguide 152 in which only the second green pixel Gr is added according to the fourth embodiment to the layout of the waveguide 152 in which the pupil correction shown in FIGS. 40A to 43 is performed, the solid state according to the eighth embodiment is constructed. Image pickup device 67 .

Since pupil correction is performed on the waveguide 152 in the structure of the solid-state image pickup device 67 according to the eighth embodiment, color shading can be reduced. Also, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced, and a solid-state image pickup device with high image quality can be provided.

Alternatively, the structure of the eighth embodiment may be a combination of any of the fifth to seventh embodiments and the pupil correction for the waveguide described with reference to FIGS. 40A to 43 .

9. Ninth Embodiment

Example structure of solid-state image pickup device

Fig. 44 shows a solid-state image pickup device according to a ninth embodiment of the present invention. The solid-state image pickup device of this embodiment is a two-pixel sharing type MOS solid-state image pickup device that two pixels share one floating diffusion region, one amplification transistor, and one selection transistor.

First, in order to facilitate understanding of the ninth embodiment, a comparative example in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor two-pixel sharing type solid-state image pickup device 34 before improvement will be described with reference to FIG. 45 . The solid-state image pickup device 34 has an example structure in which the waveguide 111 is included. The solid-state image pickup device 34 is constituted by adding the waveguide 111 to each pixel in the above-described solid-state image pickup device 1 shown in FIG. 1 . Other structures are similar to those described with reference to FIG. 1 . In FIG. 45 , like reference numerals refer to like components in FIG. 1 . In the solid-state image pickup device 34, in the two-pixel sharing type unit pixel group 2 where two pixels share one floating diffusion region, one amplification transistor, and one selection transistor, the transfer gate electrode 3 is indistinguishable from each other with respect to the boundary between adjacent pixels. symmetry. Specifically, the transfer gate electrodes 3 of the pixels B and Gr are asymmetrical to each other with respect to the boundary between the pixels B and Gr, and the transfer gate electrodes 3 of the pixels Gb and R are asymmetrical to each other with respect to the boundary between the pixels Gb and R. Assuming that the group of four pixels including the red pixel R, the first and second green pixels Gb and Gr, and the blue pixel B has a Bayer type, green pixels appear because the layouts of the transfer gate electrodes 3 in the base layer are asymmetrical to each other. The difference in sensitivity between Gb and Gr, and color shading occurs.

Referring to FIG. 44 , the solid-state image pickup device 69 according to the ninth embodiment has a pixel portion in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor two-pixel sharing type unit pixel group 71 two-dimensionally repeatedly arrangement. The two-pixel sharing type unit pixel groups 71 each include two photodiodes PD1 and PD2 (or PD3 and PD4 ), two transfer transistors Tr11 and Tr12 , one floating diffusion FD, a reset transistor Tr2 and an amplification transistor Tr3 . Waveguides 78 are formed for photodiodes PD1 and PD2 (or PD3 and PD4 ), respectively. In this embodiment, since a color filter having a Bayer type is used, a two-pixel sharing type unit pixel group 71 including a red pixel R and a first green pixel Gb and a unit pixel group 71 including a blue pixel B and a second green pixel Gr Two-pixel sharing type unit pixel groups 71 are repeatedly arranged. Adjacent two two-pixel sharing type unit pixel groups 71 define a set of four pixels Gr, R, Gb, and B.

The transfer transistors Tr11 and Tr12 include respective transfer gate electrodes 70 made of polysilicon, respective photodiodes PD ( PD1 , PD2 , PD3 , PD4 ), and floating diffusion regions FD. The reset transistor Tr2 includes a reset gate electrode 72 made of polysilicon, a floating diffusion FD, and a source region 73 . The amplification transistor Tr3 includes an amplification gate electrode 74 made of polysilicon, a source region 75 and a drain region 76 . The floating diffusion FD and the amplification gate electrode 74 are connected to each other through a wiring portion 77 . The source region 7 of the amplification transistor Tr3 is connected to a vertical signal line (not shown).

In this embodiment, the waveguides 78 in the respective pixels Gr, R, Gb and B are offset along the direction in which the substrate layer has an asymmetrical layout, i.e. in this embodiment, a transfer gate electrode 70 made of polysilicon is included therein. The base layer hardly affects the waveguide 78. In this embodiment, the waveguides 78 of the first green pixel Gb and blue pixel B are offset horizontally to the right, and the waveguides 78 of the second green pixel Gr and red pixel R are offset vertically downward. The offset direction in this embodiment is just an example. Any offset direction can be chosen according to the asymmetric arrangement of the substrate layer. A structure according to any of the fourth to eighth embodiments may also be selected. When four pixels Gr, R, Gb, and B define a group, the layout of the waveguides 78 in each group is identical in the entire pixel portion.

According to the solid-state image pickup device 69 of the ninth embodiment, since the waveguide 78 of each pixel is far away from the transfer gate electrode 70 which affects the waveguide 78 . Thus, the difference in sensitivity and color shading between the green pixels Gb and Gr can be reduced. Optical symmetry can be provided for individual pixels, and a solid-state image pickup device with high image quality can be provided.

10. Tenth embodiment

Example structure of solid-state image pickup device

46, 47A and 47B each show a solid-state image pickup device according to a tenth embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. FIG. 47A is a cross-sectional view taken along XLVIIA-XLVIIA in FIG. 46 . FIG. 47B is a cross-sectional view taken along XLVIIB-XLVIIB in FIG. 46 .

This embodiment does not use a waveguide as an adjustment mechanism, but uses a wiring portion to adjust the amount of light and thereby obtain optical symmetry.

First, in order to facilitate the understanding of the tenth embodiment, a comparative example before improvement, which is a four-pixel sharing example in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor, will be described with reference to FIGS. 48 , 49A, and 49B. Type solid-state image pickup device 35. The unit pixel group 114 of the solid-state image pickup device 35 of the comparative example is similar to the structure shown in FIG. 62 except that the solid-state image pickup device 35 does not include a waveguide in the region above the photodiodes PD ( PD1 to PD4 ). In the plan view in FIG. 48, a wiring portion 26 is added. The wiring portion 26 is arranged not to be located above the photodiode PD. Referring to FIGS. 48 , 49A, and 49B , like reference numerals refer to like components in referring to FIGS. 62 , 63A, and 63B , and repeated descriptions thereof are omitted.

In the unit pixel group 114 of the solid-state image pickup device 35 of the comparative example, referring to the cross-sectional view in FIG. 49A taken along the line XLIXA-XLIXA in FIG. The amplification gate electrode 121 in the base layer and disposed near the photodiode PD4 is shielded. In contrast, referring to the cross-sectional view taken along the line XLIXB-XLIXB in FIG. 48 in FIG. 49B, the incident light incident on the first green pixel Gb is not shielded by the gate electrode in the base layer, and is incident on the on photodiode PD1. Incident light incident on the blue pixel B is shielded by the amplifying gate electrode 121 . The incident light incident on the first green pixel Gb is not shielded by the amplifying gate electrode 121 . Therefore, the amount of light incident on the green pixel Gr is different from the amount of light incident on the green pixel Gb. Thus, a difference in sensitivity occurs. And a difference in the amount of incident light appears between the pixels Gr and B and between the pixels Gb and R. Optical asymmetry occurs.

According to the solid-state image pickup device 81 of the tenth embodiment, referring to FIGS. 46 , 47A, and 47B, the structure of a four-pixel sharing type unit pixel group 42 in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor is the same as that of FIG. 31A , 31B and 32, the structure of the fourth embodiment is similar except for the waveguide and wiring parts. Specifically, referring to FIG. 46 , a solid-state image pickup device 81 according to the tenth embodiment includes a four-pixel sharing type unit pixel group 42 in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor, which are used as photoelectric conversion The four photodiodes PD of the device share one pixel transistor unit. More specifically, the unit pixel group 42 includes four photodiodes PD ( PD1 to PD4 ), four transfer transistors Tr ( Tr11 to Tr14 ), and one floating diffusion region FD. In addition, the unit pixel group 42 includes a reset transistor Tr2, an amplification transistor Tr3, and a selection transistor Tr4. A waveguide is not formed over the photodiode PD of each pixel.

The floating diffusion FD is arranged at the center of the four photodiodes PD1 to PD4 in a 2×2 array. A transfer gate electrode 43 made of polysilicon is arranged between the floating diffusion FD and the photodiodes PD1 to PD4 . Thus, four transfer transistors Tr11 to Tr14 for the four photodiodes PD are formed. The reset transistor Tr2 , the amplification transistor Tr3 , and the selection transistor Tr4 are horizontally and continuously arranged below the four photodiodes PD1 to PD4 .

As shown in FIGS. 47A and 47B, in each of the pixels R, Gb, B, and Gr, a photodiode PD as a photoelectric converter is formed on the surface of a semiconductor substrate 153, and the wiring layer 150 passes through an interlayer insulating film. 154 is formed on the semiconductor substrate 153 . The wiring layer 150 includes a multilayer wiring portion 155 . Also, a color filter layer 157 and a microlens 158 (also referred to as an on-chip lens) are laminated on the wiring layer 150 .

This embodiment uses the wiring portion 155 as an adjustment mechanism for obtaining optical symmetry. In this embodiment, the protruding portion 155a protrudes from the wiring portion 155 in the upper layer. The protruding portion 155a shields light from the portion of the photodiodes PD1 and PD2 of the first green pixel Gb and red pixel R that are not affected by the amplification gate electrode in the base layer. The amount of adjustment of the amount of incident light passing through the protruding portion 155a, that is, the amount of protrusion by which the protruding portion 155a overlaps with each of the photodiodes PD1 and PD2, is determined so that the amount of light incident on each of the photodiodes PD1 and PD2 is the same as that for the other. The photodiodes PD3 and PD4 are equal. The layout of the protruding portion 155 a of the wiring portion 155 is the same for the unit pixel group 42 in the entire pixel portion 40 .

Other structures are similar to those described with reference to FIGS. 31A , 31B and 32 . Referring to FIGS. 46 , 47A, and 47B , like reference numerals designate like components in FIGS. 31A , 31B, and 32 , and repeated descriptions thereof are omitted.

According to the solid-state image pickup device 81 of the tenth embodiment, the protrusion amount of the protrusion portion 155a of the wiring portion 155 is adjusted for pixels not affected by the amplification gate electrode 49, the first green pixel Gb and the red pixel R in this embodiment, The amount of emitted light is thereby adjusted. Therefore, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced or eliminated. Also, the incident light amounts to the respective pixels Gr, Gb, R, and B can be made equal. Also, color shading can be reduced. Thereby, optical symmetry can be obtained, and a solid-state image pickup device with high image quality can be provided.

11. Eleventh embodiment

Example structure of solid-state image pickup device

50, 51A and 51B each show a solid-state image pickup device according to an eleventh embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. This embodiment does not use a waveguide but a dummy electrode made of polysilicon as an adjustment mechanism to obtain optical symmetry.

First, in order to facilitate understanding of the eleventh embodiment, a comparative example before improvement in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor and does not have A waveguide four-pixel sharing type solid-state image pickup device 36 . The unit pixel group 114 of the solid-state image pickup device 36 of the comparative example is similar to the structures shown in FIGS. The layout of the waveguide and wiring sections is omitted. In the solid-state image pickup device 36, the layout of the wiring portion 26 is asymmetrical. In this example, in the unit pixel group 114 , the wiring portion 26 is formed to overlap with portions of the blue pixel B and the second green pixel Gr. Referring to FIGS. 52 , 53A, and 53B , like reference numerals refer to like components in referring to FIGS. 48 , 49A, and 49B , and repeated descriptions thereof are omitted.

As described about the solid-state image pickup device 36 of the comparative example, if the wiring portion 26 is unavoidably asymmetric, part of the incident light rays incident on the blue pixel B and the second green pixel Gr are shielded by the wiring portion 26 . The amount of incident light may vary from pixel to pixel, thereby providing no optical symmetry.

The solid-state image pickup device 83 according to the eleventh embodiment has the pixel section 40 in which four pixels sharing type unit pixel of one floating diffusion region, one amplification transistor, and one selection transistor are shared by four pixels having no waveguide above the photodiode PD The group 42 is arranged in the same manner as the structure described in the tenth embodiment. The layout of the wiring portion 155 is asymmetrical in a similar manner to the comparative example in FIGS. 52 , 53A, and 53B. Specifically, the wiring portion 155 is formed to overlap with portions of the blue pixel B and the second green pixel Gr.

This embodiment achieves optical symmetry using a dummy electrode 84 made of polysilicon and used as an adjustment mechanism. The dummy electrode 84 is formed simultaneously with the gate electrode of the pixel transistor. That is, in this embodiment, the dummy electrode 84 is formed near the photodiodes PD1 and PD2 of the first green pixel Gb and red pixel R that are not affected by the wiring portion 155 . At the position where each dummy electrode 84 is formed, part of the incident light is shielded by the dummy electrode 84 . The adjustment amount of the dummy electrode 84 to the amount of incident light, ie, along the length of the photodiodes PD1 and PD2, is determined such that the amount of light incident to each of the photodiodes PD1 and PD2 is equal to that of the other photodiodes PD3 and PD4. The layout of the dummy electrodes 84 is identical for the unit pixel group 42 in the entire pixel portion 40 .

Other structures are similar to those described with reference to Figs. 46, 47A and 47B. Referring to FIGS. 50 , 51A, and 51B , like reference numerals designate like components in FIGS. 46 , 47A, and 47B , and repeated descriptions thereof are omitted.

According to the solid-state image pickup device 83 of the eleventh embodiment, referring to FIG. 51 , part of the incident light L incident on the second green pixel Gr is shielded by the protruding wiring portion 155, and thereby the incident light to the second green pixel Gr is reduced. amount of light. Similarly, part of the incident light L incident on the blue pixel B is shielded by the protruding portion 155 a of the wiring portion 155 , and thus the amount of incident light to the blue pixel B is reduced. In contrast, referring to FIG. 51B , for the first green pixel Gb that is not affected by the wiring portion 155, part of the incident light L incident on the first green pixel Gb is shielded by the dummy electrode 84, thereby reducing the effect on the first green pixel Gb. Amount of incident light for pixel Gb. By controlling the size of the dummy electrodes 84, the amount of reduction in the amount of incident light to the pixels can be equalized.

According to the solid-state image pickup device 83 of the eleventh embodiment, if the wiring portion 155 is unavoidably asymmetrical in the unit pixel group 42, the dummy electrode 84 may be provided in the base layer near the pixels not affected by the wiring portion 155. Location. Thus, optical symmetry can be obtained. That is, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced or eliminated. Also, the incident light amounts to the respective pixels Gr, Gb, R, and B can be made equal. Also, color shading can be reduced.

12. Twelfth Embodiment

Example structure of solid-state image pickup device

54, 55A and 55B each show a solid-state image pickup device according to a twelfth embodiment of the present invention. The solid-state image pickup device of the present embodiment is a four-pixel sharing type MOS solid-state image pickup device, and the four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. This embodiment does not use a waveguide but a microlens as the adjustment mechanism to achieve optical symmetry.

First, in order to facilitate the understanding of the twelfth embodiment, a comparative example before improvement in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor and does not have A waveguide four-pixel sharing type solid-state image pickup device 37 . The unit pixel group 114 of the solid-state image pickup device 37 of the comparative example is similar to the structures shown in FIGS. 48 , 49A and 49B except that the solid-state image pickup device 35 does not include a waveguide in the region above the photodiodes PD ( PD1 to PD4 ). Referring to FIGS. 56 , 57A, and 57B , like reference numerals refer to like components in referring to FIGS. 48 , 49A, and 49B , and repeated descriptions thereof are omitted.

In the unit pixel group 114 of the solid-state image pickup device 37 of the comparative example, referring to the cross-sectional view in FIG. 57A taken along the line LVIIA-LVIIA in FIG. The amplification gate electrode 121 in the base layer and disposed near the photodiode PD4 is shielded. In contrast, referring to the cross-sectional view taken along the line LVIIB-LVIIB in FIG. 56 in FIG. 57B, the incident light incident on the first green pixel Gb is not shielded by the gate electrode in the base layer, and is incident on the first green pixel Gb. on photodiode PD1. Incident light incident on the blue pixel B is shielded by the amplifying gate electrode 121 . The incident light incident on the first green pixel Gb is not shielded by the amplifying gate electrode 121 . Therefore, the amount of light incident on the green pixel Gr is different from the amount of light incident on the green pixel Gb. Thus, a difference in sensitivity occurs. And a difference in the amount of incident light appears between the pixels Gr and B and between the pixels Gb and R. Optical asymmetry occurs.

Referring to FIGS. 54 , 55A, and 55B, a solid-state image pickup device 85 according to the twelfth embodiment includes four pixels sharing one floating diffusion region, one amplification transistor, and one selection transistor with four pixels having no waveguide above the photodiode PD. type unit pixel group 42 . A plurality of four-pixel sharing type unit pixel groups 42 are arranged to define the pixel portion 40 . As described above, the unit pixel group 42 includes four photodiodes PD ( PD1 to PD4 ), four transfer transistors Tr ( Tr11 to Tr14 ), and one floating diffusion region FD. In addition, the unit pixel group 42 includes a reset transistor Tr2, an amplification transistor Tr3, and a selection transistor Tr4.

As shown in FIGS. 55A and 55B, in each of the pixels R, Gb, B, and Gr, a photodiode PD as a photoelectric converter is formed on the surface of a semiconductor substrate 153, and the wiring layer 150 passes through an interlayer insulating film. 154 is formed on the semiconductor substrate 153 . The wiring layer 150 includes a multilayer wiring portion 155 . Also, a color filter layer 157 and a microlens 158 (also referred to as an on-chip lens) are laminated on the wiring layer 150 .

The solid-state image pickup device 85 in this embodiment uses the microlens 158 as an adjustment mechanism for obtaining optical symmetry. In this embodiment, only the microlenses 158 of the second green pixel Gr and blue pixel B, which are affected by the enlarged gate electrode 49 as the base layer, are shifted to the point where the incident light passing through the microlens 158 is not shielded by the gate electrode. Location. Specifically, the focal points of the microlenses 158 of the second green pixel Gr and blue pixel B are shifted away from the magnifying gate electrode 49 . The layout of the microlenses 158 in the unit pixel group 42 is the same for the unit pixel group 42 in the entire pixel portion 40 .

In the twelfth embodiment, as shown in FIG. 55A, the microlens 158 of the second green pixel Gr is shifted away from the magnifying gate electrode. Thus, the radiated light L for the second green pixel Gr is not shielded by the amplification gate electrode 49 and is incident on the photodiode PD4. Also, the microlens 158 of the blue pixel B is shifted in a similar manner to the second green pixel Gr. In contrast, the microlens 158 of the first green pixel Gb is not shifted, and incident light is incident on the photodiode PD1 without being affected by the gate electrode as the base layer. Also, in a similar manner to the first green pixel Gb, incident light is incident on the red pixel R without being affected by the gate electrode as the base layer.

According to the solid-state image pickup device 85 of the twelfth embodiment, the amount of light can be adjusted by shifting the microlenses 158 of the pixels Gr and B. Thus, the difference in sensitivity between the first and second green pixels Gb and Gr can be made equal. Also, the incident light amounts to the respective pixels Gr, Gb, R, and B can be made equal. Also, color shading can be reduced. Thus, optical symmetry can be obtained.

13. Thirteenth embodiment

Example structure of solid-state image pickup device

58, 59A and 59B each show a solid-state image pickup device according to a thirteenth embodiment of the present invention. The solid-state image pickup device of this embodiment is a four-pixel sharing type MOS solid-state image pickup device. If the adjustment of the difference in sensitivity is not sufficient even by light amount adjustment according to the twelfth embodiment, this embodiment provides an improvement.

The solid-state image pickup device 87 according to the thirteenth embodiment includes a four-pixel sharing type unit pixel group 42 in which four pixels share one floating diffusion region, one amplification transistor, and one selection transistor, in which the second green pixel Gr and the blue pixel B The microlenses 158 are offset away from the magnifying gate electrode 49 in the base layer. Also, the microlenses 158 of the first green pixel Gb and the red pixel R are shifted toward the wiring portion 155 in the base layer.

According to the solid-state image pickup device 87 of the thirteenth embodiment, the microlenses 158 of the second green pixel Gr and blue pixel B are shifted away from the magnifying gate electrode 49 in the base layer to move the focal point. Thus, the loss of the amount of incident light is limited, and the sensitivity is improved. In contrast, the microlenses 158 of the first green pixel Gb and red pixel R are shifted toward the wiring portion 155 in the base layer so that adjustment is performed through the wiring portion 155 to reduce the amount of incident light. Therefore the sensitivity is reduced. Thereby, the difference in sensitivity between the first and second green pixels Gb and Gr can be reduced. Also, the incident light amounts to the respective pixels Gr, Gb, R, and B can be made equal. Also, color shading can be reduced. Thus, optical symmetry can be obtained.

14. Fourteenth Embodiment

Example structure of solid-state image pickup device

Although not shown, a solid-state image pickup device having a structure for obtaining optical symmetry as described in any of the fourth to thirteenth embodiments may be used for a CCD solid-state image pickup device. Even when this structure is used in a CCD solid-state image pickup device, light amount adjustment similar to the above can be performed, and optical symmetry can be obtained for each pixel.

In the above-described embodiments, this structure is used for a two-pixel sharing type solid-state image pickup device in which two pixels share one floating diffusion region, one amplification transistor, and one selection transistor, or four pixels share one floating diffusion region, one amplification transistor, and one selection transistor. A four-pixel sharing type solid-state image pickup device that selects transistors. However, this structure can be used for other numbers of pixel-sharing type solid-state image pickup devices in which other numbers of pixels share one floating diffusion region, one amplification transistor, and one selection transistor.

In the above-described embodiments, this structure is used for the solid-state image pickup device having the color filter 101 of the Bayer type. However, this structure can be used for a solid-state image pickup device having a honeycomb-type color filter 102 in an inclined array as shown in FIG. 61 .

In the above-described embodiments, this structure is used for a color solid-state image pickup device. However, this structure can be used for a monochrome (for example, black and white) solid-state image pickup device. In this case, a waveguide, a wiring portion, a dummy electrode, an on-chip lens, or the like can be used as adjustment means.

15. Fifteenth embodiment

Example structure of electronic device

The solid-state image pickup device according to any of the embodiments described above may be used in a camera system such as a digital camera or a video camera, a mobile phone with an image pickup function, or another device with an image pickup function.

FIG. 66 shows a fifteenth embodiment in which a solid-state image pickup device is used for a video camera as an example of an electronic device. The camera of this embodiment is, for example, a video camera that captures still images or movies. The video camera 91 in this embodiment includes a solid-state image pickup device 92 , an optical system 93 that guides incident light to a photosensor of the solid-state image pickup device 92 , and a shutter device 94 . Also, the camera 91 includes a drive circuit 95 and a signal processing circuit 96 that processes a signal output from the solid-state image pickup device 92 .

The solid-state image pickup device 92 may be any solid-state image pickup device according to the above-described embodiments. The optical system (optical lens) 93 focuses image rays (incident rays) from an object on the image pickup surface of the solid-state image pickup device 92 . Accordingly, signal charges are accumulated in the solid-state image pickup device 92 for a predetermined period. The optical system 93 may be an optical lens system including a plurality of optical lenses. The shutter device 94 controls a light irradiation period and a light shielding period for the solid-state image pickup device 92 . The drive circuit 95 supplies drive signals for controlling the transfer operation of the solid-state image pickup device 92 and the shutter operation of the shutter device 94 . A signal from the solid-state image pickup device is transmitted in response to a drive signal (timing signal) supplied from the drive circuit 95 . The signal processing circuit 96 performs various signal processing. The signal-processed video signal is stored in a storage medium such as a memory or output to a monitor.

According to the electronic device such as a video camera of the fifteenth embodiment, for example, optical symmetry can be obtained so that the sensitivity between the green pixels Gb and Gr in the solid-state image pickup device 92 can be equalized, and thus the image quality can be improved. Thus, a reliable electronic device can be provided.

Any of the embodiments described above may be implemented with another embodiment. Optical symmetry is obtained accordingly.

The present invention incorporates matters related to the subject matter disclosed in Japanese Priority Patent Application JP2009-081100 filed with Japan Patent Office on March 30, 2009 and Japanese Priority Patent Application JP2009-240774 filed with Japan Patent Office on October 19, 2009 subject, the entire contents of which are hereby incorporated by reference.

Those skilled in the art should understand that as long as they are within the scope of the appended claims or their equivalents, various changes, combinations, subcombinations and substitutions can be made according to design requirements and other factors.

Claims (20)

1. A solid-state image pickup device, comprising: a pixel portion defined by unit pixels arranged in row and column directions of the semiconductor substrate, Wherein, each described unit pixel comprises: a photoelectric converter formed on the semiconductor substrate and converts incident light into signal charges, a waveguide formed over the photoelectric converter and guiding incident light to the photoelectric converter, and a microlens formed over the waveguide and guiding incident light to a light incident side end of the waveguide, and Wherein, the waveguide has a cylindrical body, and the cylindrical body has a constant cross-section from one end on the light incident side to one end on the light exit side, and the waveguide is arranged such that the microlens is incident on the waveguide. The ray center of the incident light on one end of the incident side of the light is aligned with the central axis of the waveguide. 2. The solid-state image pickup device according to claim 1, further comprising: a color filter layer formed between the waveguide and the microlens and splitting incident light rays, Wherein, pupil correction is performed on the microlens and the color filter layer based on the reference color of the incident light. 3. The solid-state image pickup device according to claim 1, wherein, in the pixel portion, with respect to the photoelectric converters on which incident light rays having equal wavelengths are incident, the central axes of each of the waveguides are opposite to each other. The amount of shift from the center of the corresponding photoelectric converter becomes larger from the center of the pixel portion toward the outside. 4. The solid-state image pickup device according to claim 1, wherein, for the photoelectric converters located at equal distances from the center of the pixel portion, the central axis of each of the waveguides is relative to the corresponding The amount of offset of the center of the photoelectric converter decreases as the wavelength of the light separated by the color filter layer and incident on the photoelectric converter increases. 5. The solid-state image pickup device according to claim 1, wherein the diameter of the waveguide allows incident light from the light exit side end of the waveguide to impinge on a region within the surface of the photoelectric converter. 6. The solid-state image pickup device according to claim 1, further comprising: unit pixel group, Wherein, the unit pixel group includes: The first unit pixel includes incident light with a first wavelength separated by the color filter layer on the photoelectric converter, The second unit pixel includes light having a second wavelength separated by the color filter layer incident on the photoelectric converter, the second wavelength being smaller than the first wavelength, a third unit pixel comprising incident light rays having a third wavelength separated by the color filter layer on the photoelectric converter, the third wavelength being greater than the first wavelength, and Wherein, for the photoelectric converters in the unit pixel group, the offset of the central axis of each of the waveguides relative to the center of the corresponding photoelectric converter increases with the separation by the color filter layer The wavelength of the light decreases. 7. The solid-state image pickup device according to claim 1, Wherein, the waveguide includes: a first waveguide defining a peripheral portion of the waveguide, and a second waveguide formed inside the first waveguide and having a smaller refractive index than the first waveguide. 8. A method of manufacturing a solid-state image pickup device, the method comprising the steps of: A waveguide hole is formed in the wiring layer, the waveguide hole guides incident light to a photoelectric converter that converts the incident light into signal charges, the photoelectric converter is formed at a semiconductor substrate, is formed at the semiconductor substrate and includes The wiring layer of the interlayer insulating film has a multilayer wiring portion; filling the waveguide hole with a waveguide material film having a refractive index greater than that of the interlayer insulating film and forming a waveguide in the waveguide hole; forming a color filter layer separating incident light rays on said waveguide material film by sandwiching a planarizing insulating film; and forming microlenses on the color filter layer, the microlenses guiding incident light to the electro-optic converter, wherein a plurality of unit pixels each having said photoelectric converter are arranged in a row and column direction of said semiconductor substrate to define a pixel portion, and Wherein, the waveguide formed for the corresponding photoelectric converter has a cylindrical body having a constant cross section from one end on the light incident side to one end on the light exit side, and the waveguide is arranged such that at the The ray center of the incident light incident on the light incident side end of the waveguide is aligned with the central axis of the waveguide. 9. The method of manufacturing a solid-state image pickup device according to claim 8, Wherein, the formation of the waveguide includes: forming a first waveguide on the inner surface of the waveguide hole, and The waveguide hole in which the first waveguide is formed is filled with a material having a lower refractive index than the first waveguide, and a second waveguide is formed. 10. An image pickup device, comprising: The light converging optical unit converges the incident light; including an image pickup unit of a solid-state image pickup device, receiving light condensed by the light condensing optical unit, and performing photoelectric conversion on the light; and a signal processing unit processing a signal obtained by photoelectric conversion of said solid-state image pickup device, Wherein, the solid-state image pickup device includes: a pixel portion defined by unit pixels arranged in row and column directions of the semiconductor substrate, Wherein, each described unit pixel comprises: a photoelectric converter formed on the semiconductor substrate and converts incident light into signal charges, a waveguide formed over the photoelectric converter and guiding incident light to the photoelectric converter, and a microlens formed over the waveguide and guiding incident light to a light incident side end of the waveguide, and Wherein, the waveguide has a cylindrical body, and the cylindrical body has a constant cross-section from one end on the light incident side to one end on the light exit side, and the waveguide is arranged such that the microlens is incident on the waveguide. The ray center of the incident light on one end of the incident side of the light is aligned with the central axis of the waveguide. 11. A solid-state image pickup device comprising: pixel section in which multiple pixels are arranged, a base layer formed in a multi-pixel group at a position below a light incident surface of the group, and has a layout including electrodes and wiring, the layout being asymmetrical with respect to a predetermined boundary between adjacent pixels; and The adjustment mechanism is used to make the optical asymmetry between the pixels brought about by the base layer become optical symmetry. 12. The solid-state image pickup device according to claim 11, wherein an adjustment direction and an adjustment amount of the positional shift of the adjustment mechanism are the same throughout the pixel portion. 13. The solid-state image pickup device according to claim 12, further comprising: a color filter layer formed over the photoelectric converters of the pixels and splitting the incoming light, an on-chip lens on the color filter layer; and A base layer is formed under the color filter layer. 14. The solid-state image pickup device according to claim 13, wherein the pixel portion includes a plurality of unit pixel groups each having a plurality of pixels sharing a predetermined transistor, and Wherein, the asymmetric base layer is a base layer including a gate electrode and a wiring portion of a pixel transistor. 15. The solid-state image pickup device according to claim 14, wherein the adjustment mechanism is a waveguide for each pixel, wherein the color filter layer is formed above the waveguide, wherein the base layer is a base layer located below the waveguide and including the gate electrode and the wiring portion, and Wherein, in the state in which the waveguides are arranged at regular intervals throughout the pixel portion as a reference state, in the unit pixel group or in a plurality of adjacent unit pixel groups, at least a specific The position of the pixel waveguide offset away from the reference state. 16. The solid-state image pickup device according to claim 15, wherein, among the waveguides of the common color pixels outputting the same color signal, at least the waveguide of the first common color pixel is shifted away from the shared pixel transistor located close to the waveguide The gate electrode, so that the difference in sensitivity between the common color pixels in the unit pixel group or in a plurality of adjacent unit pixel groups becomes equal. 17. The solid-state image pickup device according to claim 16, wherein, among the waveguides of the common color pixels, at least the waveguides of the second common color pixels are offset from the gate electrodes of the shared pixel transistors, so that in the unit pixel group or Differences in sensitivity between the common color pixels in a plurality of adjacent unit pixel groups become equal. 18. The solid-state image pickup device according to claim 14 , wherein, for the photoelectric converters located at equal distances from the center of the pixel portion, waveguide pupil correction is performed such that central axes of the waveguides are opposite to each other. The amount of offset from the center of the photoelectric converter increases as the wavelength of light separated by the color filter layer and incident on the photoelectric converter increases. 19. The solid-state image pickup device according to claim 12, wherein the adjustment mechanism is a protruding part of the wiring part, and Wherein, in the unit pixel group or in a plurality of adjacent unit pixel groups, the protruding portion of the wiring portion protrudes to a region above the photoelectric converter that does not affect the base layer. 20. An electronic device comprising: Solid-state image pickup device; an optical system that guides incident light to a photoelectric converter of the solid-state image pickup device; and a signal processing circuit for processing an output signal of said solid-state image pickup device, Wherein, the solid-state image pickup device is the solid-state image pickup device according to any one of claims 1 to 4.

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