CN120821155B - Exposure structure and exposure equipment - Google Patents
Exposure structure and exposure equipmentInfo
- Publication number
- CN120821155B CN120821155B CN202410442323.XA CN202410442323A CN120821155B CN 120821155 B CN120821155 B CN 120821155B CN 202410442323 A CN202410442323 A CN 202410442323A CN 120821155 B CN120821155 B CN 120821155B
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- transparent mask
- mask substrate
- substrate
- exposure
- immersion liquid
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/20—Exposure; Apparatus therefor
- G03F7/2041—Exposure; Apparatus therefor in the presence of a fluid, e.g. immersion; using fluid cooling means
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70058—Mask illumination systems
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
- G03F7/70341—Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
Abstract
The invention relates to the technical field of holographic lithography, in particular to an exposure structure and exposure equipment. When the exposure light beam passes through the transparent mask substrate and is completely imaged in the immersion liquid in the exposure structure, the imaging theoretical distance is larger than the thickness of the transparent mask substrate and smaller than the sum of the maximum thickness of the immersion liquid drops and the thickness of the transparent mask substrate, so that the exposure light beam can be ensured to completely image the inside of the immersion liquid drops after passing through the immersion liquid drops, further, the exposure light beam can be ensured to be completely imaged on the wafer substrate after passing through the immersion liquid drops, and the photoetching quality can be greatly improved. Meanwhile, a smaller imaging distance is set through calculation, and the immersion liquid drops are formed by using surface tension without completely immersing the transparent mask substrate or the wafer substrate in the immersion liquid, so that smaller imaging structure size and smaller immersion liquid consumption are realized, and the wafer substrate and the transparent mask substrate can be cleaned conveniently after photoetching is finished.
Description
Technical Field
The invention relates to the technical field of holographic lithography, in particular to an exposure structure and exposure equipment.
Background
Laser holographic lithography is a very potential lithography technique whose basic principle is diffraction imaging, where a beam irradiates a holographic mask, diffracts on a microstructure arranged according to a certain rule, and these diffracts are finally superimposed on a silicon wafer to obtain the desired pattern.
In order to solve the problem of smaller and smaller feature size requirements in the conventional photolithography technology, in addition to reducing the wavelength of laser, the resolution of photolithography is generally improved by immersion lithography. The immersion lithography replaces the air medium between the projection objective lens and the silicon wafer in the traditional lithography technology with water with a larger refractive index, so that the numerical aperture is increased, and the resolution of the lithography machine is further improved. In holographic lithography, when the lithographic resolution reaches a limit, the resolution of the lithography can be increased by means of immersion liquid.
In order to realize smaller photoetching feature sizes, the holographic photoetching device in the prior art generally submerges an optical path for generating a holographic image at a set distance by an optical diffraction element in water, and simultaneously submerges an amplitude diffraction element, a phase diffraction element and a substrate to be etched with photoresist in the device in water to carry out holographic photoetching in the water. However, because the micro-nano structure gap on the mask is smaller, when the mask is immersed in water, due to the existence of air pressure and surface tension, a small gap exists between the water and the micro-nano structure, so that the projection quality of laser passing through the mask is poor, and the photoetching quality is affected. And because the distance of the light path is larger, the whole light path is immersed in water, and the problem of larger water consumption can occur, so that the imaging structure of the whole system has larger size, and when the substrate is taken out after photoetching is finished, the water treatment between the mask and the substrate is difficult.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defect that the photoetching quality is affected because the photoetching structure on the mask cannot be completely immersed by water in the holographic photoetching system in the prior art, thereby providing an exposure structure and an exposure device.
In order to solve the above technical problems, the present invention provides an exposure structure, including:
A wafer substrate, one surface of which is provided with a photoresist layer;
The transparent mask substrate is provided with a holographic pattern, the holographic pattern is arranged on one surface of the transparent mask substrate, which is away from the wafer substrate, and one surface of the wafer substrate, which is provided with the photoresist layer, is arranged towards the transparent mask substrate;
the immersion liquid drops are arranged between the transparent mask substrate and the wafer substrate, the immersion liquid drops are adsorbed between the transparent mask substrate and the wafer substrate through surface tension, and the transparent mask substrate and the wafer substrate are contacted with the immersion liquid drops;
when the exposure beam passes through the transparent mask substrate and is completely imaged in the immersion liquid, the theoretical imaging distance is larger than the thickness of the transparent mask substrate and smaller than the sum of the maximum thickness of the liquid drops and the thickness of the transparent mask substrate.
Alternatively, when the exposure beam is completely imaged in the immersion liquid through the transparent mask substrate, the imaged theoretical distance z is calculated as follows:
z=(z0－z1/n1)n2
Where z 0 is the full air imaging distance set by the transparent mask substrate, n 1 is the refractive index of the transparent mask substrate, and n 2 is the refractive index of the immersion liquid droplets.
Optionally, the photoresist layer surface is provided with a hydrophilic layer.
Optionally, a hydrophobic structure layer is disposed on the transparent mask substrate, and the hydrophobic structure layer and the holographic pattern are respectively disposed on two opposite sides of the transparent mask substrate.
Optionally, a limiting groove is arranged on one surface of the transparent mask substrate, which faces away from the holographic pattern, and the limiting groove is arranged corresponding to the holographic pattern.
Optionally, a drainage runner is further arranged on the transparent mask substrate, one end of the drainage runner is communicated with the limit groove, the other end of the drainage runner extends to the edge of the transparent mask substrate to be communicated with the outside, and a fluid driving pump is communicated with the drainage runner.
Optionally, the volume of the immersion liquid droplet is the product of the bottom area of the limiting groove and the theoretical distance.
Optionally, a photonic crystal layer is arranged on the bottom surface of the limiting groove.
The present invention also provides another exposure structure, comprising:
A wafer substrate, one surface of which is provided with a photoresist layer;
The transparent mask substrate is provided with a holographic pattern, the holographic pattern is arranged on one surface of the transparent mask substrate, which is away from the wafer substrate, and one surface of the wafer substrate, which is provided with the photoresist layer, is arranged towards the transparent mask substrate;
the immersion liquid drops are arranged between the transparent mask substrate and the wafer substrate, the immersion liquid drops are adsorbed on the surface of the wafer substrate through surface tension, and the immersion liquid drops are arranged separately from the transparent mask substrate.
The invention also provides exposure equipment, which has the exposure structure, and further comprises an exposure light source, an illumination light path, a reflecting mirror and a mask loading table, wherein the transparent mask substrate is arranged on the mask loading table, and the light path adjustment and the reflection of the reflecting mirror are sequentially carried out on the light beam emitted by the exposure light source through the illumination light path, and then the light beam is irradiated on the transparent mask substrate.
The technical scheme of the invention has the following advantages:
1. When the exposure structure is used for patterning a wafer substrate, an exposure light beam path firstly passes through a holographic pattern on a transparent mask substrate to form optical information with the pattern, then enters into immersion liquid drops through the transparent mask substrate, is contracted through the immersion liquid drops, and then irradiates a photoresist layer of the wafer substrate to finish photoetching of the wafer substrate. By arranging immersion liquid drops between the transparent mask substrate and the wafer substrate and arranging the holographic pattern on one surface of the transparent mask substrate, which is away from the wafer substrate, exposure light beams are formed by imaging after the holographic pattern is reduced by the immersion liquid drops, and the immersion liquid drops can completely immerse the surface of the transparent mask substrate or the wafer substrate. However, due to different imaging parameters of different transparent mask substrates, the imaging position of the exposure beam after passing through the transparent mask substrate may be in the transparent mask substrate or located at the back of the wafer body, so that the photoresist layer of the wafer substrate cannot be etched, and immersion lithography cannot be performed on the wafer substrate. When the light passes through the transparent mask substrate and is completely imaged in the immersion liquid, the theoretical imaging distance is larger than the thickness of the transparent mask substrate and smaller than the sum of the maximum thickness of the immersion liquid drops and the thickness of the transparent mask substrate, so that the exposure light beam can be ensured to completely image the inside of the immersion liquid drops after passing through the immersion liquid drops, and the exposure light beam can be ensured to completely image on the wafer substrate after passing through the immersion liquid drops by adjusting the position of the wafer substrate, so that the photoetching quality can be greatly improved. Meanwhile, a smaller imaging distance is set through calculation, and the immersion liquid drops are formed by using surface tension without completely immersing the transparent mask substrate or the wafer substrate in the immersion liquid, so that smaller imaging structure size and smaller immersion liquid consumption are realized, and the wafer substrate and the transparent mask substrate can be cleaned conveniently after photoetching is finished.
2. According to the exposure structure provided by the invention, the hydrophilic layer is arranged on the surface of the photoresist layer and is used for increasing the surface tension between the photoresist layer and the immersed liquid drops so as to improve the maximum thickness of the immersed liquid on the surface of the photoresist layer, thereby improving the imaging distance, increasing the imaging distance of the holographic pattern which can be received in the immersed liquid drops and reducing the required assembly precision of the device in normal operation.
3. According to the exposure structure provided by the invention, the hydrophobic structure layer is arranged on the transparent mask substrate, and the hydrophobic structure layer and the holographic pattern are respectively arranged on the two opposite sides of the transparent mask substrate. By providing a hydrophobic structural layer to increase the adhesion between the transparent mask body and the immersion liquid droplets, hydrophobic high adhesion and hydrophobic low adhesion surfaces can be achieved by altering the micro-nano structure of the surface. The high adhesiveness before infiltration can be realized to increase the thickness of the liquid, and the hydrophobicity after infiltration can be realized, so that the purpose of protecting the transparent mask substrate is achieved.
4. According to the exposure structure provided by the invention, the side, away from the holographic pattern, of the transparent mask substrate is provided with the limit groove, and the limit groove is correspondingly arranged with the holographic pattern. The position of the immersed liquid drop is limited by arranging the limiting groove corresponding to the holographic pattern, so that the immersed liquid drop can accurately flow to the area corresponding to the holographic pattern, the accuracy of the position of the immersed liquid drop is improved, and the photoetching quality of an exposure structure is improved.
5. According to the exposure structure provided by the invention, the transparent mask substrate is also provided with the drainage runner, one end of the drainage runner is communicated with the limit groove, the other end of the drainage runner extends to the edge of the transparent mask substrate to be communicated with the outside, and the drainage runner is communicated with the fluid driving pump. The purpose of drainage is achieved by etching the drainage flow channel, and then residual liquid is extracted in a fluid driving pump pumping mode, so that the purpose of cleaning the transparent mask body after photoetching is achieved.
6. According to the exposure structure provided by the invention, the bottom surface of the limiting groove is provided with the photonic crystal layer. The photon crystal layer is etched in the limit groove corresponding to the holographic pattern area, so that the light field limit area with specific wavelength is realized on the photon crystal structure, and the utilization rate of the energy of the exposure light beam can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural view of an exposure apparatus provided in a first embodiment of the present invention, wherein an arrow direction is a propagation direction of an exposure beam.
Fig. 2 is a schematic illustration of a droplet resting on a solid surface under surface tension as provided in an embodiment of the invention.
Fig. 3 is a schematic diagram showing the change of gradually increasing volume of a droplet when the droplet is stopped on a solid surface under the action of surface tension in an embodiment of the present invention.
Fig. 4 is a graph of the force analysis of a droplet provided in an embodiment of the present invention when resting on a solid surface under surface tension.
Fig. 5 is a schematic diagram showing the change of the hydrophobic structure layer from hydrophobic to immersed by a droplet provided in an embodiment of the present invention.
Fig. 6 is a schematic structural diagram of a limiting groove according to an embodiment of the present invention.
Fig. 7 is a schematic structural diagram of a photonic crystal layer provided in an embodiment of the present invention.
Fig. 8 is a schematic structural view of an exposure apparatus provided in another embodiment of the present invention, in which an arrow direction is a propagation direction of an exposure beam.
The reference numerals indicate that 1, an exposure light source, 2, an illumination light path, 3, a reflector, 4, a mask loading table, 5, a transparent mask substrate, 6, immersion liquid drops, 7, an exposure table, 8, a limit groove, 9, a drainage flow passage, 10, a fluid driving pump, 11, a hydrophobic structure layer, 12 and a photonic crystal layer.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected via an intervening medium, or in communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Fig. 1 shows an exposure apparatus provided in this embodiment, which includes an exposure structure composed of a wafer substrate, a transparent mask substrate 5, and immersion liquid droplets, and further includes a laser as an exposure light source 1, an illumination light path 2, a mirror 3, and a mask loading stage 4, the wafer substrate being fixedly mounted on an exposure stage 7. In some other embodiments, the exposure light source 1 may also be a laser light source, an extreme ultraviolet light source, an x-ray light source, or the like, which can expose the wafer.
The transparent mask substrate 5 is fixedly arranged on the mask loading table 4, the laser beam emitted by the laser device sequentially passes through the illumination light path 2 for light path adjustment and the reflector 3 for reflection and then irradiates on the transparent mask substrate 5, carries holographic pattern information and then irradiates on the wafer substrate through the immersion liquid drops 6 for photoetching on the wafer substrate.
A photoresist layer is arranged on one surface of the wafer substrate irradiated by the laser. A holographic pattern is arranged on the transparent mask substrate 5, the holographic pattern is arranged on one surface of the transparent mask substrate 5, which is away from the wafer substrate, and one surface of the wafer substrate, which is provided with the photoresist layer, is arranged towards the transparent mask substrate 5. The immersion liquid droplets 6 are disposed between the transparent mask substrate 5 and the wafer substrate, and the immersion liquid droplets 6 are adsorbed on the surface of the transparent mask substrate 5 and the surface of the wafer substrate by surface tension. In this embodiment, the exposure structure adopts a positive structure, the transparent mask substrate 5 is disposed below the wafer substrate, and both the transparent mask substrate 5 and the wafer substrate are in contact with the immersion liquid droplets 6. In this embodiment, the transparent mask substrate 5 is a quartz glass substrate, the transparent mask substrate 5 and the hologram pattern area are transparent, other positions are required to be shielded by a metal film, the metal film is arranged on one surface of the transparent mask substrate 5 provided with the hologram pattern, the metal film is used for shielding stray light, only the hologram pattern area transmits light, and the whole surface is a smooth quartz substrate surface on one surface of the transparent mask substrate 5 not provided with the hologram pattern.
In order to ensure that the laser beam path is capable of projecting an image of the holographic pattern onto the wafer substrate, the theoretical distance travelled by the laser light in the immersion liquid is not greater than the maximum thickness of the droplets on the surface of the transparent mask substrate 5 when the laser light is fully imaged in the immersion liquid through the transparent mask substrate 5 when the transparent mask substrate 5 is prepared.
The beam is emitted by a laser, the wave front and the beam radius are adjusted through an illumination light path 2, the beam is reflected and irradiated onto a transparent mask substrate 5 on a mask loading table through a reflecting mirror 3, an immersion liquid drop 6 is dripped on the transparent mask substrate 5, the pattern in the beam is reduced when the beam passes through the immersion liquid drop 6, and finally a designed integrated circuit pattern is obtained on a wafer substrate on an exposure table 7.
In the exposure structure, after laser beam shaping and collimation are carried out through an illumination light path 2 into plane waves, the plane waves are reflected to a vertical mask loading table through a reflecting mirror 3, a transparent mask substrate 5 is turned downwards to separate immersion liquid drops 6 from holographic patterns serving as mask micro-nano structures, then water is dripped on the back surface of the transparent mask substrate 5, immersion liquid is realized through the surface tension of water on a quartz substrate, finally the integrated circuit patterns formed by the transparent mask substrate 5 form holographic images in a set immersion area, and the wafer substrate coated with photoresist on an exposure table 7 is exposed to obtain the designed integrated circuit patterns.
In this embodiment, the transparent mask substrate 5 is turned over and immersed, so that the holographic pattern faces downwards, complete immersion is realized under the condition that the micro-nano structure of the holographic pattern is not damaged, and the liquid on the surface of the transparent mask substrate 5 is better cleaned by the back immersion mode. By computationally setting a smaller imaging distance, using the tension of the liquid on the surface of the transparent mask substrate 5, a smaller imaging structure size and less water usage is achieved.
The following describes advantages of the technical solution provided in this embodiment in combination with theoretical deduction and accompanying drawings:
Assuming such a situation, water is slowly injected onto an absolutely smooth substrate, assuming that as the volume increases, the water remains integral, i.e. a large droplet forms on the surface. The relationship between the thickness and volume of the droplets was analyzed as follows:
when the liquid volume is small, the liquid drop is on the solid surface as shown in fig. 2 below, and the height e of the liquid drop is:
in the formula (1), r is the radius of the droplet, and θ is the contact angle of the liquid with the solid surface.
The volume V of the droplet at this time is:
As the volume of the liquid increases, the variation of the liquid droplet on the solid surface is shown in fig. 3 below. When the volume of the liquid drop is small, the action of surface tension is dominant, and the gravity action is negligible, so that the liquid drop can keep a spherical crown shape. But gravity begins to dominate when the droplet size is greater than the capillary length (about 2.71 mm). The droplets are flat under the action of gravity. The relationship between the thickness e of the flat droplet and the solid surface contact angle θ E is obtained by mechanical analysis. And carrying out stress analysis on a part of the liquid drop, and establishing a stress balance equation of the liquid drop in the horizontal direction. The force diagram is shown in fig. 4, it can be seen from fig. 4 that the two forces applied to the liquid drop are respectively surface tension f 1 and static pressure P of the liquid, wherein the surface tension f 1 is:
f1＝γSO-(γ+γSL) (3)
In the formula (3), gamma SO is the outward diffusion tension of the edge of the liquid drop, gamma is the middle-top-to-middle gathering tension of the liquid drop, and gamma SL is the middle-bottom-to-middle gathering tension of the liquid drop.
The static pressure P of the liquid acts on the whole liquid film height. By integrating the entire liquid film thickness, it is possible to obtain:
in the formula (4), ρ is the density of the liquid drop, g is the constant of gravitational force, and z is the angle between any position of the surface of the liquid drop and the horizontal direction.
The force balance equation for a droplet per unit length is:
the above surface tension can be converted to the formula for contact angle expression according to young's equation:
γSO-(γcosθE+γSL)=0 (6)
the simultaneous formulas can be obtained:
The volume of the droplets at this time is:
In the formula (8), S is the bottom area of the droplet.
As can be seen from the above mechanical analysis, the thickness and volume of the large droplets are independent and only related to the wettability of the solid surface. According to formula (7), under the condition of constant surface tension and contact angle, the maximum thickness of the liquid drop on the surface of the substrate can be obtained
The imaging position of the holographic pattern irradiated by the laser beam after passing through the transparent mask substrate 5 and the immersion liquid droplets 6 is calculated by theory:
parallel light vertically enters the transparent mask body, the holographic pattern micro-nano structure on the transparent mask body is of a small hole structure, and the complex amplitude field of single hole diffraction is considered:
In the formula (9), U represents the diffraction complex amplitude of a single square hole, the center is positioned at the origin of coordinates, L represents the size of the square hole, lambda represents the wavelength of light,
Behind the holographic pattern is a transparent mask body medium with refractive index n, then the complex amplitude U g at z g is
The complex amplitude U a of propagation z a distance in the immersion liquid droplet 6 is then:
It can be seen that if z a is defined as Then U a and U g differ only by a phase factor(In the sense that r expands to 2 nd order, y/r and x/r expand to 1 st order).
Thus, assuming that the original beam is imaged in air by a propagation distance z after diffraction by the holographic pattern, the final imaging distance is around z 1+z－z1/n, assuming that the original beam propagates first by a distance z 1 in the transparent mask substrate 5.
Assuming that the full air imaging distance set by the transparent mask substrate 5 is z 0, and the thickness of the transparent mask substrate 5 is z 1, the final laser beam is imaged in the immersion liquid droplets 6 through the transparent mask substrate 5 after passing through the holographic pattern on the transparent mask substrate 5, and the theoretical distance of laser beam imaging is z= (z 0－z1/n1)n2, where n 1 is the refractive index of the transparent mask substrate 5, and n 2 is the refractive index of the immersion liquid droplets 6.
In the preparation of the transparent mask substrate 5, it should be ensured that the laser beam, after diffraction by the holographic pattern and passing through the transparent mask substrate 5, is imaged in the immersion liquid droplets 6. The theoretical distance that the laser beam passes through the transparent mask substrate 5 to be completely imaged in the immersion liquid is the distance between the surface of the transparent mask substrate 5 on which the holographic pattern is located and the imaged surface in the immersion liquid. In order to ensure that the imaged position of the laser beam is within the immersion liquid droplet 6 and not within the transparent mask substrate 5 or behind the location of the wafer substrate, the theoretical distance z of laser beam imaging should be greater than the thickness of the transparent mask substrate 5 and less than the sum of the maximum thickness e of the immersion liquid droplet 6 achievable on the surface of the transparent mask substrate 5 and the thickness of the transparent mask substrate 5 to ensure that the laser beam can image the photoresist layer of the wafer substrate.
In order to fully utilize the surface tension of the immersion liquid droplets 6, a hydrophobic structure layer 11 is arranged on the transparent mask substrate 5, and the hydrophobic structure layer 11 and the holographic pattern are respectively arranged on two opposite sides of the transparent mask substrate 5. The adhesion between the transparent mask substrate 5 and the immersion liquid droplets 6 is increased by etching some micro-nano structures of the hydrophobic structure layer 11 on the back side of the transparent mask substrate 5, and hydrophobic high adhesion and hydrophobic low adhesion surfaces are achieved by changing the position of the micro-nano structures within the hydrophobic structure layer 11 on the surface of the transparent mask substrate 5, as shown in fig. 5. Specifically, the spherical micro-nano array structure can be etched on the back of the transparent mask substrate 5 to serve as the hydrophobic structure layer 11, so that high adhesiveness can be achieved to increase the thickness of the immersed liquid drops 6, hydrophobicity can be achieved, and the purpose of protecting the transparent mask substrate 5 is achieved.
As shown in fig. 6, a limiting groove 8 is arranged on one surface of the transparent mask substrate 5 facing away from the holographic pattern, and the limiting groove 8 is arranged corresponding to the holographic pattern. The transparent mask substrate 5 is also provided with a drainage runner 9, one end of the drainage runner 9 is communicated with the limit groove 8, the other end of the drainage runner 9 extends to the edge of the transparent mask substrate 5 to be communicated with the outside, and the drainage runner 9 is communicated with a fluid driving pump 10. In the exposure light path of the front-mounted structure, the purpose of drainage is realized by etching the drainage flow channel 9, so that the immersed liquid drops 6 can accurately flow to the corresponding areas of the holographic patterns, and the required water quantity can be accurately obtained through the area size of the holographic pattern areas and the etching depth of the limit grooves 8. The immersed liquid drops 6 are led into the limit groove 8 from the flow guide channel 9 at one side of the transparent mask substrate 5, and the limit groove 8 has a certain size. After the imaging theoretical distance of the transparent mask substrate 5 is obtained through algorithm calculation, the area size of the limiting groove 8 is determined to be S, the volume of the immersed liquid drops 6 is the product of the bottom area of the limiting groove 8 and the theoretical distance, the volume of the liquid drops which are dripped into the limiting groove 8 is accurately controlled to just cover the limiting groove 8, and the purpose of complete immersion can be achieved. After the photoetching is finished, the waste liquid flows out from the drainage flow channel 9 on the right side in a drainage way, and the residual liquid is extracted in a fluid driving pump 10 extraction way so as to achieve the purpose of cleaning the transparent mask substrate 5.
In the forward exposure light path, on the basis of the drainage structure, the micro-nano structure of the photonic crystal layer 12 can be continuously etched on the bottom surface of the limit groove 8, so that the energy utilization rate of the transparent mask substrate 5 at the limit groove 8 is improved. Specifically, as shown in fig. 7, the micro-nano structure of the photonic crystal layer 12 is a series of photonic crystal structures which are periodically arranged, and an optical field limit of a specific wavelength is realized on the photonic crystal structure to improve the energy utilization rate.
The exposure structure provided in this embodiment achieves separation of the immersion liquid droplets 6 and the holographic pattern mask structure on the transparent mask substrate 5 by turning over the transparent mask substrate 5, can achieve complete immersion of the immersion liquid droplets 6 and the surface of the transparent mask substrate 5, achieves the purpose of protecting the transparent mask substrate 5, and can clean the liquid droplets on the back surface of the transparent mask substrate 5 better after photolithography is completed. By computationally setting a smaller imaging distance, using the tension of the drops on the surface of the transparent mask substrate 5, a smaller imaging structure size is achieved, as well as less water usage. By providing the hydrophobic structure layer 11 on the surface of the transparent mask substrate 5, the maximum thickness of the immersion liquid droplets 6 on the surface of the transparent mask substrate 5 is increased, thereby increasing the imaging distance. Through the spacing groove 8 and the drainage runner 9 on the surface of the transparent mask substrate 5, the immersion liquid drops 6 are accurately drained to the spacing groove 8, and the immersion of the spacing groove 8 is accurately realized. The energy utilization rate of the limit groove 8 region is improved by combining the drainage structure with the photonic crystal layer 12 micro-nano structure. After the size and the imaging distance of the limiting groove 8 are determined, the volume of liquid dripped in the limiting groove 8 can be quantitatively controlled, and the liquid consumption can be saved while complete immersion can be realized.
When the imaging quality of the exposure equipment is tested, the transparent mask body is fixed, the angle of the transparent mask body is adjusted to be perpendicular to the light incoming direction of the laser beam, and then water with the volume the same as that of the limiting groove is injected into the limiting groove on the surface of the transparent mask body to serve as immersion liquid drops. The wafer substrate is moved to the imaging zone to find the appropriate focal plane, and then the laser is activated for immersion exposure. In this embodiment, the laser wavelength is 354.776nm, the size of the projection pattern on the transparent mask body is 1.5mm×1.5mm, the aperture size on the projection pattern is 300nm, and the minimum line width of the exposure pattern finally obtained on the wafer substrate is 350nm. If no immersion liquid drop is arranged, imaging is directly carried out in air, and the minimum linewidth of the finally obtained exposure pattern on the wafer substrate is 450nm. It can be seen that the minimum linewidth of the laser imaged after passing through the immersion liquid droplet is reduced. As an alternative embodiment, the exposure structure in this embodiment adopts an inverted structure, and the entire structure of the exposure apparatus is as shown in fig. 8, with the transparent mask substrate 5 disposed over the wafer substrate. The positions of the exposure stage 7 and the mask loading stage can be adjusted at will by using the surface tension of the immersion liquid droplets 6 at the surface of the photoresist layer. The surface tension of a liquid is essentially an intermolecular force. Intermolecular forces, i.e., van der Waals forces, include induced forces, dispersive forces, and orientation forces, which are of course related to the polarity of the molecule. In this embodiment, the photoresist layer is provided with a hydrophilic layer on the surface. The adhesion of a droplet to the surface of a solid is related to the surface energy of the solid. On a solid surface with a flat surface, the greater the surface energy of the solid, the more hydrophilic it exhibits, i.e. the greater the adhesion to water. The smaller the surface energy of the solid, the more hydrophobic it exhibits, the less the adhesion to water will be. The hydrophilic surface is generally hydroxyl, carboxyl, amino, etc., and the hydrophobic surface is fluorine, chlorine, carbon branched chain, etc. In the exposure light path with the inverted structure, in order to better utilize the surface tension of the liquid on the surface of the photoresist layer in the inverted light path, the surface tension between the liquid drop and the photoresist layer is increased by carrying out some treatments on the surface of the photoresist layer, and as the photoetching precision of the surface of the photoresist layer is required, etching of some micro-nano structures can not be carried out, some hydrophilic treatments can be carried out on the surface of the photoresist layer on the premise of not influencing the photoetching process before the surface of the photoresist layer is exposed, so that the surface of the photoresist layer has hydroxyl groups, carboxyl groups, amino groups and the like.
As an alternative implementation manner, the exposure structure in this embodiment adopts an inverted structure, the transparent mask substrate 5 is disposed above the wafer substrate, the immersion liquid droplets 6 are disposed between the transparent mask substrate 5 and the wafer substrate, the immersion liquid droplets 6 are adsorbed on the surface of the wafer substrate by surface tension, and the immersion liquid droplets are disposed separately from the transparent mask substrate 5, so that a space exists between the immersion liquid droplets and the transparent mask substrate. At this time, the imaging parameters of the transparent mask substrate 5 are not limited, and when the exposure apparatus is in operation, the position of the wafer substrate is fixed by adjusting the position of the wafer substrate to a position where the exposure beam can present a clear image on the photoresist layer of the wafer substrate. Because the immersion liquid drops are directly contacted with the wafer substrate, the exposure light beam is necessarily imaged on the wafer substrate after carrying holographic pattern information through the transparent mask substrate.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
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| CN101859072A (en) * | 2009-04-10 | 2010-10-13 | Asml荷兰有限公司 | Fluid processing device, immersion lithography apparatus, and device manufacturing method |
| CN104678712A (en) * | 2013-12-03 | 2015-06-03 | 上海微电子装备有限公司 | Immersion type exposure equipment |
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| US7532309B2 (en) * | 2006-06-06 | 2009-05-12 | Nikon Corporation | Immersion lithography system and method having an immersion fluid containment plate for submerging the substrate to be imaged in immersion fluid |
| TWI643027B (en) * | 2009-11-09 | 2018-12-01 | 尼康股份有限公司 | Exposure apparatus, exposure method, maintenance method of exposure apparatus, adjustment method of exposure apparatus, and component manufacturing method |
| NL2005666A (en) * | 2009-12-18 | 2011-06-21 | Asml Netherlands Bv | A lithographic apparatus and a device manufacturing method. |
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| CN101859072A (en) * | 2009-04-10 | 2010-10-13 | Asml荷兰有限公司 | Fluid processing device, immersion lithography apparatus, and device manufacturing method |
| CN104678712A (en) * | 2013-12-03 | 2015-06-03 | 上海微电子装备有限公司 | Immersion type exposure equipment |
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