WO2024262137A1 - Polymer optical waveguide substrate, optical module using same, and production methods therefor - Google Patents

Abstract

This polymer optical waveguide substrate (100) is provided with: a substrate (120); a polymer base cladding (111) which is formed on the substrate (120); an optical waveguide groove (114) which is formed in the base cladding (111); a polymer core (112) which is embedded so as to be in contact with the bottom surface and the side surface of the optical waveguide groove (114); a polymer upper cladding (113) which covers the core (112); and positioning parts (115, 116, 117) which are formed using the base cladding (111) and determine the positions of optical devices (130, 140) to be mounted.

Description

Polymer optical waveguide substrate, optical module using same, and manufacturing method thereof

This disclosure relates to a polymer optical waveguide substrate, an optical module using the same, and a method for manufacturing the same.

In recent years, there has been an increasing demand for polymer optical waveguides, which are easy to process and reduce costs, in order to replace quartz-based optical waveguides and simplify optical fiber wiring.

Methods for positioning optical input/output parts formed on conventional optical devices, including polymer optical waveguides, include an active alignment method in which one of the optical devices is aligned while emitting or receiving light, and a passive alignment method in which positioning is achieved solely by assembly precision.

As an example of the active alignment method, consider using a semiconductor laser as one optical device and an optical fiber as the other. At this time, the light emitted by the semiconductor laser is taken into the optical fiber, and the relative positions of the two devices are adjusted so that the output light from the optical fiber is maximized. While this method can reduce optical coupling loss, it takes a long time to align the cores and the equipment configuration is complex, making it difficult to keep costs down.

On the other hand, passive alignment methods include image recognition, solder self-alignment, fitting, and hybrid methods that combine these.

In the image recognition method, alignment marks on optical devices are identified by image recognition on a high-precision mounter, and the optical device is mounted using this as a reference. This method is easy to automate, but the accuracy depends on the accuracy of the equipment. To improve accuracy, it is necessary to optimize the recognition accuracy of the equipment itself, mounting accuracy, control of the mounting environment, adhesive materials, etc. Therefore, costs tend to increase as accuracy increases.

In the solder self-alignment method, an optical device is joined to an electrode land on a substrate via solder. At this time, the surface tension of the molten solder creates a self-alignment effect that adjusts the optical device to a specified position on the substrate. This method requires very simple equipment. The mounting accuracy depends heavily on the relative positional accuracy of the optical device, the optical input/output unit, and the electrode land on the substrate.

In the fitting method, for example, a highly accurate V-groove is formed on a silicon substrate by anisotropic wet etching that utilizes the crystal orientation of silicon, and an optical fiber is then butted into the V-groove for mounting. With this method, the equipment can be of a simple structure, similar to the solder self-alignment method. Mounting accuracy depends heavily on the relative accuracy between the fitting groove (V-groove) and the optical input/output part of the optical device.

Patent Document 1 discloses the positioning of a polymer optical waveguide and an optical device using an interlocking method. Specifically, as shown in FIG. 4 of Patent Document 1, a recess (core portion) in which a polymer optical waveguide (PWG) array is formed and a protrusion in which a silicon optical waveguide (SiWG) array is formed are self-aligned. Nanoimprinting is also used to form the polymer optical waveguide array.

JP 2014-081587 A

In the conventional polymer optical waveguide substrate, the core portion of the polymer optical waveguide array itself is imprinted. The bottom surface of the core and the bottom surface of the alignment protrusion are flush with each other. In a direction deeper than the core bottom surface, it is not possible to form an uneven structure with good relative accuracy with the polymer optical waveguide. Therefore, it is not possible to handle optical devices that have a protrusion higher than the optical input/output surface or a portion with a thickness on the side of the optical input/output surface of the optical device that is optically coupled to the polymer optical waveguide. This means, for example, that a specially designed optical device is required.

In response to the above, this disclosure provides a polymer optical waveguide that can be precisely positioned with the optical input/output parts of optical devices with various configurations.

The polymer optical waveguide substrate of the present disclosure comprises a substrate, a polymer base clad formed on the substrate, an optical waveguide groove formed in the base clad, a polymer core embedded so as to contact the bottom and side surfaces of the optical waveguide groove, a polymer upper clad covering the core, and a positioning portion formed using the base clad and used to determine the position of the mounted optical device. The positioning portion has a surface at a different height than the bottom surface of the optical waveguide groove.

The manufacturing method of the polymer optical waveguide substrate in this disclosure includes a coating process for coating a base clad material onto a substrate, and a transfer process for simultaneously forming the optical waveguide groove and the positioning portion by transferring the pattern corresponding to the optical waveguide groove and the positioning portion to the base clad material using a transfer mold having both the pattern corresponding to the optical waveguide groove and the pattern corresponding to the positioning portion in the same mold.

In the present disclosure, the manufacturing method of an optical module in which an optical device is mounted on the polymer optical waveguide substrate includes a fixing material supplying step of supplying a fixing material onto the polymer optical waveguide substrate, a rough mounting step of placing the optical device at a predetermined position on the polymer optical waveguide substrate to which the fixing material has been supplied, a self-alignment mounting step of positioning the optical device by self-alignment with higher accuracy than in the first mounting step using a positioning portion, and a fixing step of fixing the optical device by hardening the fixing material after the self-alignment mounting step.

The optical waveguide substrate disclosed herein is formed using a base clad and has a positioning portion that has a different height than the bottom surface of the optical waveguide groove, so that the positioning portion can be used to mount optical devices using a self-alignment method, enabling highly accurate mounting of optical devices of various configurations.

FIG. 1 is a plan view illustrating an exemplary optical module according to an embodiment of the present disclosure. FIG. 2 is an enlarged view of the A-A' cross section of FIG. 1 and a portion F thereof. FIG. 3 is a diagram showing a cross section taken along line B-B' of FIG. FIG. 4 is a diagram showing a cross section taken along the line C-C' of FIG. FIG. 5 is a diagram showing a cross section taken along line D-D' of FIG. FIG. 6 is a diagram showing a cross section taken along the line E-E' of FIG. FIG. 7 is a diagram showing a modified example corresponding to the portion F in FIG. 2 and the B-B' and E-E' cross sections in FIG. FIG. 8 is a flow diagram of the entire process showing the method for producing a polymer optical waveguide substrate according to the present disclosure. FIG. 9 is a plan view of the imposition board 124 and its cross section taken along line G-G'. FIG. 10 is a diagram showing the G-G' cross section illustrating the base clad coating process. FIG. 11 is a cross-sectional view in the transfer process and an enlarged view of the H portion. 12A to 12C are diagrams showing cross sections corresponding to lines A-A', B-B', C-C', and E-E' in FIG. 1 during the transfer process. FIG. 13 is a diagram showing cross sections corresponding to lines A-A', B-B', C-C', and E-E' in FIG. 1 during the demolding process. FIG. 14 is a diagram showing cross sections corresponding to lines A-A' and B-B' in FIG. 1 during the core formation process. FIG. 15 is a diagram showing cross sections corresponding to lines A-A' and B-B' in FIG. 1 during the upper cladding formation process. FIG. 16 is a cross-sectional view in a substrate dividing step. FIG. 17 is a flow diagram of the entire process showing a method for manufacturing the optical module 190. FIG. 18 is a diagram showing the planar configuration of the optical waveguide substrate to be prepared and its C-C' cross section. FIG. 19 is a diagram showing a planar configuration in the first fixing material supplying step and its C-C' cross section. FIG. 20 is a diagram showing the planar configuration in the first rough mounting process and its C-C' cross section. FIG. 21 is a diagram showing a planar configuration in the first self-alignment mounting process and its C-C' cross section. FIG. 22 is a diagram showing the planar configuration in the first fixing step and its C-C' cross section. FIG. 23 is a diagram showing a planar configuration in the second fixing material supplying step. 24 is a diagram showing the A-A' and D-D' cross sections of FIG. 23. FIG. FIG. 25 is a diagram showing a planar configuration in the second rough mounting process. 26 is a diagram showing the A-A' and D-D' cross sections of FIG. 25. FIG. FIG. 27 is a diagram showing a planar configuration in the second self-alignment mounting process. 28 is a diagram showing the A-A' and D-D' cross sections of FIG. 27. FIG.

Below, an embodiment will be described with reference to the drawings. The following description is an example, is not limiting, and can be modified as appropriate within the scope of the effect. Also, all of the following drawings are schematic diagrams, and dimensions, etc. may be exaggerated.

(Configuration of polymer optical waveguide substrate and optical module)
Fig. 1 is a plan view showing an optical module 190 according to the present disclosure. The optical module 190 has a configuration in which a silicon optical waveguide substrate 130 as a first optical device and an optical fiber 140 as a second optical device are mounted on a polymer optical waveguide substrate 100. In addition to the optical device, a semiconductor device 150 is also mounted on the polymer optical waveguide substrate 100. Note that in Fig. 1, the fitting groove 115, the fiber fixing groove 116, the pedestal 117, and the like are shown through the silicon optical waveguide substrate 130 and an optical connector 142 (described later).

Next, Figure 2 shows a cross section taken along line A-A' in Figure 1, and an enlarged view of part F (enclosed in a dashed rectangle). Figures 3, 4, 5, and 6 show cross sections taken along lines B-B', C-C', D-D', and E-E' in Figure 1, respectively.

As shown in FIG. 2, the polymer optical waveguide substrate 100 includes a wiring substrate 120 and a polymer optical waveguide layer 110 formed thereon. The wiring substrate 120 is, for example, a rigid printed wiring substrate, a flexible substrate, or a polymer substrate. The polymer optical waveguide layer 110 is composed of a base clad 111, a core 112, and an upper clad 113 formed on the wiring substrate 120.

As shown in FIG. 3, the core 112 is embedded in an optical waveguide groove 114 provided in the base clad 111, and is covered by the upper clad 113. The core 112 contacts the bottom and side surfaces of the optical waveguide groove 114.

The base clad 111 is provided with a positioning portion that enables highly accurate positioning when mounting the polymer optical waveguide substrate 100 and the optical fiber 140. Specifically, as a first positioning portion, a fitting groove 115 (FIGS. 1 and 4) is provided that is used for positioning the silicon optical waveguide substrate 130 in the horizontal direction (direction parallel to the surface of the base clad 111). As a second positioning portion, a fiber fixing groove 116 is provided that is used for positioning the optical fiber 140 (FIGS. 1, 2, and 5). Furthermore, as a third positioning portion, a pedestal 117 is provided that is used for positioning the silicon optical waveguide substrate 130 in the vertical direction (direction perpendicular to the surface of the base clad 111).

These positioning parts (fitting groove 115, fiber fixing groove 116, and base 117) are formed by transferring and molding them as a single unit into the material of base clad 111 using a single high-precision mold. As a result, their relative positions and dimensions have a high degree of precision of about several μm. In particular, the adjacent optical waveguide groove 114, fitting groove 115, and base 117, as well as the optical waveguide groove 114 and fiber fixing groove 116, are formed with extremely high positional precision, and it is possible to make the difference from the design dimensions 0.5 μm or less. This is the desired precision for sufficiently suppressing optical loss at each joint.

In addition, since the core 112 is formed by filling the optical waveguide groove 114, the relative positional accuracy with the fitting groove 115, the base 117, and the fiber fixing groove 116 is the same as that of the optical waveguide groove 114.

By mounting an optical device (silicon optical waveguide substrate 130 and optical fiber 140) on the polymer optical waveguide substrate 100 using such a positioning portion, highly accurate mounting can be achieved using relatively simple equipment. Furthermore, it is not necessary for the positioning portion to be flush with the bottom surface of the core 112, and it can be configured three-dimensionally. Therefore, it can be used with a variety of optical devices.

The positioning unit and its use will be explained in more detail below. First, the alignment of the silicon optical waveguide substrate 130 will be explained.

The silicon optical waveguide substrate 130 is mounted using the fitting groove 115 and the base 117 as positioning parts. As shown in FIG. 4, the fitting groove 115 is formed so as to open the base clad 111 and expose the wiring substrate 120. The sidewall of the fitting groove 115 is provided with an inclined surface 115a inclined with respect to the surface of the wiring substrate 120. The silicon optical waveguide substrate 130 is also provided with an inclined surface 132 on its lower periphery. By fitting the inclined surface 115a on the fitting groove 115 side with the inclined surface 132 on the silicon optical waveguide substrate 130 side, the silicon optical waveguide substrate 130 can be aligned in the horizontal direction. Although only one side of the silicon optical waveguide substrate 130 is shown in FIG. 4, similar alignment can be performed on the other sides.

In addition, at a position inside the silicon optical waveguide substrate 130, the base clad 111 forms a pedestal 117, which is a positioning portion in the height direction. By butting the bottom surface of the silicon optical waveguide substrate 130 against the pedestal 117, it is possible to easily and highly accurately align the height direction.

The core 112 extends from the base 117, and a first optical input/output section 112a (polymer optical waveguide end array) is provided near its end (Figs. 2 and 4). A silicon optical waveguide 131 is provided on the underside of the silicon optical waveguide substrate 130, and a silicon optical waveguide array 131a (optical input/output section) is provided near its end. Through the high-precision alignment described above, the first optical input/output section 112a and the silicon optical waveguide array 131a overlap with high precision, achieving low-loss adiabatic coupling.

The fitting groove 115 also functions as an opening that exposes the land electrode 121 provided on the wiring substrate 120 (FIG. 4). In this opening, the land electrode 121 and the pad electrode 133 of the silicon optical waveguide substrate 130 are bonded via solder 160.

In this embodiment, as an example of the configuration of the positioning portion, an inclined surface 115a is provided in the fitting groove 115. However, this is not limited to this, and it is sufficient to provide a combination of three-dimensional structures that can assist in alignment on the base clad 111 side and the optical device (silicon optical waveguide substrate 130) side. For example, a combination of a line-shaped protrusion and a slit, a combination of a pin-shaped protrusion and an insertion hole, etc.

Next, we will explain how to align the optical fiber 140.

The optical fibers 140 are connected to the polymer optical waveguide substrate 100 using an optical connector 142. The optical fibers 140 are aligned in a row, and are fixed one by one using the fiber fixing grooves 116 provided in the base clad 111 as positioning sections (Figures 1 and 5).

As shown in FIG. 5, the fiber fixing groove 116 has a sidewall that is an inclined surface 116a, and is shaped so that it narrows on the wiring board 120 side. Therefore, by pressing the optical fiber 140 from above, the optical fiber 140 can be aligned in the horizontal direction (the lateral direction in FIG. 5). The positioned optical fiber 140 is fixed with, for example, a UV-curable adhesive 170.

The optical input/output section 141 (Figure 5) of the optical fiber 140 fixed in the fiber fixing groove 116 and the second optical input/output section 112b formed at one end of the core 112 are butt-coupled with high precision.

A part of the base clad 111 and adhesive 170 are interposed between the tip of the core 112 and the tip of the optical waveguide groove 114 (part F in Figure 2). The tip surface 116b of the fiber fixing groove 116 and the tip surface 114a of the optical waveguide groove 114 are both molded by transfer using a high-precision mold, so they can be made to be very smooth surfaces. Therefore, optical connection loss can be suppressed at the interface between the core 112 embedded in the optical waveguide groove 114 and the base clad 111, and at the interface between the adhesive 170 and the base clad 111.

Also, as shown in Figures 1 and 6, a waveguide alignment mark 118 is formed near the corner of the base clad 111 so as to penetrate the base clad 111. The waveguide alignment mark 118 is used as a mark for camera recognition when mounting an optical device, for example. To improve the recognition of the waveguide alignment mark 118, it is desirable to provide it on the wiring layer 122 of the wiring board 120, for example.

As described above, the optical waveguide groove 114, the fitting groove 115, the fiber fixing groove 116, and the pedestal 117 formed in the base clad 111 are formed by a high-precision mold, and therefore have extremely high relative positional accuracy. Therefore, the diabatic coupling accuracy between the first optical input/output section 112a (polymer optical waveguide array) in the core 112 in the optical waveguide groove 114 and the silicon optical waveguide array 131a of the silicon optical waveguide substrate 130 aligned by the fitting groove 115 and the pedestal 117 is very good. Similarly, the direct coupling between the second optical input/output section 112b in the core 112 in the optical waveguide groove 114 and the optical input/output section 141 of the optical fiber 140 aligned by the fiber fixing groove 116 is also very high precision. Such high precision can be achieved without using high-precision equipment or an active alignment method.

The base clad 111, the core 112, and the upper clad 113 are all made of an optically transparent material that transmits light of a specific wavelength used in optical communications. The specific light is typically light with a wavelength of 850 nm when the waveguide mode is multimode, and light with a wavelength of 1300 nm to 1500 nm when the waveguide mode is single mode. Examples of materials include epoxy-based polymers, polyimide-based polymers, silicone-based polymers, and acrylic-based polymers.

Furthermore, the base clad 111 and upper clad 113 are set to have a lower refractive index than the core 112. For example, for an optical waveguide for light with a wavelength of 850 nm, the refractive index of the core 112 is set to about 1.58, and the refractive index of the base clad 111 and upper clad 113 is set to about 1.54.

There are no particular limitations on the width and height of the core 112, but from the perspective of optical waveguiding properties, it is preferable to set it to 20 to 80 μm for a multimode wavelength of 850 nm, and to about 2 to 20 μm for a single mode wavelength of 1300 to 1500 nm.

(Modification)
Modified examples of each part of the optical module 190 of this embodiment will be described below. Fig. 7 shows modified examples of the part F in Fig. 2, the BB' cross section corresponding to Fig. 3, and the EE' cross section corresponding to Fig. 6.

2, the bottom surface of the optical waveguide groove 114 has a constant depth. In contrast, in the example shown in FIG. 7, the depth becomes deeper toward the tip surface 112b near the tip that is directly coupled to the optical fiber 140. This makes it easy to form a flat surface perpendicular to the surface of the wiring board 120 at the tip surface 112b. In this regard, in a design in which the depth of the optical waveguide groove 114 is constant as in FIG. 2, it is difficult to process the lower end of the tip surface 112b into an accurately perpendicular shape, and it is prone to becoming rounded. As a result, the lower part of the tip surface 112b does not become a flat surface. In contrast, with the shape of FIG. 7, even if it cannot be processed exactly as designed, it is possible to flatten the tip surface 112b in the range involved in the transmission of light.

In the example of FIG. 4, the upper cladding 113 is formed to cover the core 112 only in each optical waveguide groove 114. In contrast, as shown in FIG. 8, the upper cladding 113 may be formed to cover the core 112 including the base cladding 111.

In addition, although the waveguide alignment mark 118 shown in FIG. 6 is simply a through hole, this is not limited to this. As shown in FIG. 7, a large-diameter recess 118a that does not expose the wiring board 120 (or the wiring layer 122) may be provided, and the waveguide alignment mark 118 may be provided so as to expose the wiring board 120 in a predetermined planar shape within the recess 118a.

In the above, the silicon optical waveguide substrate 130 including the silicon optical waveguide array 131a and the optical fiber 140 are taken as examples of the first and second optical devices mounted on the polymer optical waveguide substrate 100. However, various optical devices can be used, such as laser diodes which are side-emitting devices, VCSELs (Vertical Cavity Surface Emitting Lasers) which are surface-emitting devices, photodiodes which are light-receiving devices, silicon photonics in which optical and electronic integrated circuits are formed on silicon microchips, optical connectors, PLCs (Planar Lightwave Circuits), etc. In addition, although solder connection and UV-curing adhesives have been described for fixing the optical device to the polymer optical waveguide substrate 100, other methods such as screwing and crimping may also be used.

(Method of Manufacturing Polymer Optical Waveguide Substrate)
Next, a method for manufacturing the polymer optical waveguide substrate 100 will be described.

FIG. 8 is a flow diagram of the entire process showing the manufacturing method of the polymer optical waveguide substrate 100. Also, FIGS. 9 to 16 are diagrams showing each step of FIG. 8. In FIGS. 9 to 16, the same components as those described above are given the same reference numerals.

As shown in FIG. 8, the manufacturing method for the polymer optical waveguide substrate 100 includes a substrate preparation process, a base clad application process, a mold transfer process, a curing process, a demolding process, a core formation process, an upper clad formation process, and a substrate division process.

First, the substrate preparation process will be described with reference to Figure 9. Figure 9 shows a plan view of the imposition substrate 124 and its cross section taken along line G-G'.

The imposition board 124 has wiring boards 120 arranged in a 3 x 3 pattern, and after each component is formed, it is divided into nine polymer optical waveguide boards 100. The imposition board 124 is, for example, a rigid wiring board, and on its surface, land electrodes 121 for mounting semiconductor devices, optical devices having electrodes, etc., and board alignment marks 123, etc. are formed. In the board preparation process, such an imposition board 124 is prepared.

Next, the base clad application process will be described with reference to FIG. 10. Here, a layer of base clad material 111a is formed in a predetermined area on mounting substrate 124. This can be done using inkjet printing, screen printing, transfer printing, or the like. Alternatively, a layer of base clad material 111a may be formed over the entire surface of mounting substrate 124. In this case, a method of laminating a film-like base clad material 111a, a method of applying by spin coating, or the like can be used.

Next, the transfer process and the curing process will be described with reference to Figures 11 and 12. Figure 11 shows a cross section of the process of transferring the transfer mold 180 to the base clad material 111a, and an enlarged view of part H. Figure 12 shows the A-A', B-B', C-C', and E-E' cross sections in this state, respectively.

In the transfer process, as shown in FIG. 11, the transfer mold 180 is placed on the mounting substrate 124, and the pattern of the transfer mold 180 is transferred to the base clad material 111a.

As a result, the optical waveguide groove 114, the fitting groove 115 and its inclined surface 115a, the base 117, the opening 183a which becomes the waveguide alignment mark 118, etc. are formed (FIGS. 1 and 12). One end of the optical waveguide groove 114 (the side where the optical fiber 140 is mounted) is formed into a shape including the tip surface 114a.

Here, the transfer mold 180 may be composed of a rough mold 181 and a high-precision mold 182. The rough mold 181 is a mold in which a transfer pattern is formed in areas where the precision requirement is relatively low, for example, over the entire surface mounting substrate 124. The precision of the rough mold 181 in the planar direction is, for example, several μm to several tens of μm. In contrast, the high-precision mold 182 is a mold that includes at least a pattern for transferring and forming the optical waveguide groove 114 and a pattern for forming positioning parts (fitting groove 115, fiber fixing groove 116, and pedestal 117), and has a relative precision of 1 μm or less. In order to suppress optical loss in the joint, it is preferable that the relative precision be 0.5 μm or less for the adjacent optical waveguide groove 114, fitting groove 115, and pedestal 117, and for the optical waveguide groove 114 and fiber fixing groove 116.

In this way, by using a one-piece high-precision mold 182 for parts that require particularly high precision, and using a rough mold 181 with sufficient precision for other parts, it is possible to achieve the required precision while suppressing the difficulty of manufacturing the mold, and therefore the cost. However, it is possible to make the entire mold into a one-piece high-precision mold.

When transferring the transfer mold 180, a portion of the pattern of the transfer mold 180 is butted against the mounting substrate 124, thereby making it possible to maintain a constant distance between the mounting substrate 124 and the transfer mold 180. Such butting is performed, for example, in the area where the semiconductor device is mounted, on the land electrode 121, on the wiring layer 122, etc. This forms an opening 183b in the land electrode 121 and an opening 183a on the wiring layer 122, which can be used as a land for mounting the optical device and a waveguide alignment mark 118, respectively.

The abutting portion that forms the opening 183a and/or the opening 183b may be configured as the rough mold 181 and configured to be movable independently of the high precision mold 182. For example, when forming the shape shown in the E-E' cross section of FIG. 7, the transfer mold 180 is configured so that the portion corresponding to the waveguide alignment mark 118 that exposes the wiring layer 122 can be moved independently of the surrounding area (the portion corresponding to the recess 118a). In this way, in the subsequent demolding process, the portion in contact with the wiring layer 122 and the portion in contact with the base clad 111 can be moved separately, making it easier to demold the transfer mold 180.

The precision required to place the transfer mold 180 on the imposition board 124 is on the order of several μm to several tens of μm. This is equivalent to the precision required to form solder resist for typical board wiring, and there is no need to use expensive high-precision equipment.

Then, the base clad material 111a is cured to form the base clad 111. The curing is performed, for example, by irradiating UV light through the transfer mold 180. In this case, the transfer mold 180 is made of glass, transparent resin, or the like.

The transfer mold 180 can be made by using a master mold formed directly on quartz glass or the like using electron beam drawing, or by using a replica mold that is transferred and replicated from a master mold formed by etching, machining, or the like. An example of a method for producing a replica mold is a method in which a master mold is transferred to a glass substrate coated with sol-gel glass or PDMS (Polydimethylsiloxane) to produce a replica mold.

The curing method may be a method in which the resin is cured by heat, or a method in which the resin is partially cured by heat and then released from the mold, and then completely cured by UV light.

Next, the demolding process will be described with reference to Figure 13. Figure 13 shows the A-A' cross section, the B-B' cross section, the C-C' cross section, and the E-E' cross section.

In the demolding process, the transfer mold 180 is demolded to obtain the base clad 111 on which the optical waveguide groove 114, the fitting groove 115, the fiber fixing groove 116, the pedestal 117, etc. are formed.

In addition, to improve releasability, a release agent or the like may be applied to the transfer mold 180 in advance (by application, immersion, steam, etc.). For the same purpose, it is desirable to provide a taper on the side of a relatively large pattern (E-E' cross section).

Next, the core formation process will be described with reference to Figure 14. Figure 14 shows the A-A' and B-B' cross sections.

In the core formation process, the core 112 is formed in the optical waveguide groove 114. For example, this method involves dropping an appropriate amount of liquid core material into the optical waveguide groove 114 using an inkjet method, and then curing it with UV light. This forms the core 112 along the shape of the optical waveguide groove 114. At this time, the formation of the tip surface 114a of the optical waveguide groove 114, which is the end of the optical waveguide groove 114, prevents the supplied core material from flowing out toward the fiber fixing groove 116. It is also possible not to form the tip surface 114a, in which case it may be formed using a transfer mold in the same way as the formation of the base clad 111.

Next, the upper cladding formation process will be described with reference to Figure 15. Figure 14 shows the A-A' and B-B' cross sections following Figure 15.

As shown in FIG. 15, in the upper cladding formation process, the upper cladding 113 is formed on the core 112. For example, similar to the formation of the core 112, a method is used in which the material is applied by inkjet and cured by UV light. Also, here too, formation may be performed using a transfer mold.

Although not shown in the figures, after the demolding process, the core formation process, and the upper cladding formation process, an etching process using oxygen plasma may be performed to remove unnecessary resin residue.

Next, the substrate division process shown in Figure 16 will be explained.

In the substrate division process, the imposition substrate 124 on which the base clad 111, the core 112, and the upper clad 113 are formed is divided into individual polymer optical waveguide substrates 100. This is performed using methods such as division using a router, blade dicing, and laser processing.

The above steps result in the formation of the polymer optical waveguide substrate 100.

Note that the above has been described as a method of transferring all over the surface at once using a transfer mold 180 of a size corresponding to the mounting substrate 124. Alternatively, a transfer mold 180 of a size corresponding to the wiring substrate 120 can be used to repeatedly transfer to the entire surface of the mounting substrate 124 in a step-and-repeat manner.

(Method of manufacturing optical module)
Next, a method for manufacturing the optical module 190 using the polymer optical waveguide substrate 100 will be described.

FIG. 17 is a flow diagram of the entire process showing the manufacturing method of the optical module 190. Also, FIGS. 18 to 28 are diagrams showing each process of FIG. 17. In FIGS. 18 to 28, the same components as those explained so far are given the same reference numerals.

As shown in FIG. 17, the method for manufacturing the optical module 190 includes a polymer optical waveguide substrate preparation process, a first fixing material supply process, a first rough mounting process, a first self-alignment mounting process, a first fixing process, a second fixing material supply process, a second rough mounting process, a second self-alignment mounting process, and a second fixing process.

First, the polymer optical waveguide substrate preparation process will be described with reference to Figure 18. Figure 18 shows the planar structure of the polymer optical waveguide substrate 100 to be prepared and its C-C' cross section.

The polymer optical waveguide substrate 100 prepared in this process comprises a wiring substrate 120 and a polymer optical waveguide layer 110 consisting of a base clad 111, a core 112 and an upper clad 113 formed on a predetermined region of the wiring substrate 120. In addition, in the region where the polymer optical waveguide layer 110 is not present, a substrate alignment mark 123 formed of a wiring layer or solder resist, a land electrode 121, etc. are formed on the wiring substrate 120. An opening is provided in the polymer optical waveguide layer 110, thereby forming a waveguide alignment mark 118.

In addition, in FIG. 18, the base clad 111 is not formed on the substrate alignment mark 123. However, if the substrate alignment mark 123 can be recognized by a camera, the base clad 111 may be formed on it.

After this, the silicon optical waveguide substrate 130 and the semiconductor device 150 are placed through the steps from the first fixing material supply step to the first fixing step.

The first fixing material supplying process will be described with reference to Figure 19. Figure 19 shows a plan view and a C-C' cross section of this process, following Figure 18.

As shown in FIG. 19, in the first fixing material supplying process, solder paste 161, which is the first fixing material, is supplied onto the land electrode 121 in the fitting groove 115. This can be done by an inkjet method, or by applying with a dispenser. It is preferable to use the substrate alignment mark 123 for positioning when supplying the solder paste 161. The substrate alignment mark 123 and the land electrode 121 are formed on the same layer. In other words, the substrate alignment mark 123 and the land electrode 121 are layers formed in the same patterning process including lithography and etching. Therefore, the relative accuracy is high, and by using the substrate alignment mark 123 for recognition, it is possible to reduce the positional deviation of the solder paste 161 relative to the land electrode 121.

Next, the first rough mounting process will be described with reference to Figure 20. Figure 22 shows a plan view and a C-C' cross section of this process.

As shown in FIG. 20, in the first rough mounting process, a silicon optical waveguide substrate 130, which is the first optical device, and a semiconductor device 150 are placed on a polymer optical waveguide substrate 100. At this time, the positioning accuracy can be lower than the final positioning accuracy required for the optical module 190.

The silicon optical waveguide substrate 130 is provided with a silicon optical waveguide array 131a, which is the optical input/output section of the silicon optical waveguide 131, pad electrodes 133, and solder bumps 134, and further has an inclined surface 132 on the lower outer periphery. Here, the inclined surface 132 and the silicon optical waveguide array 131a have extremely high relative positional accuracy by being formed using a general semiconductor process.

The silicon optical waveguide array 131a is precisely overlapped with the first optical input/output section 112a (polymer optical waveguide array) of the polymer optical waveguide substrate 100, and is thus adjacently coupled. However, at this stage of the process, it is sufficient for the silicon optical waveguide 131 to fit within the fitting groove 115, and it does not matter if a horizontal misalignment (Δy) occurs. Furthermore, if a misalignment Δy occurs, a vertical misalignment (Δz) also occurs at the same time.

As an alignment mark when mounting the semiconductor device 150, the substrate alignment mark 123 can be used, as in the case of supplying the solder paste 161. As mentioned above, high precision is not required in this process, but it is necessary to fit the silicon optical waveguide substrate 130 into the fitting groove 115. Therefore, if the position of the fitting groove 115 formed by the base clad 111 is significantly misaligned with respect to the wiring substrate 120, it is preferable to use the waveguide alignment mark 118 to position the silicon optical waveguide substrate 130.

Next, the first self-alignment mounting process will be described with reference to Figure 21. Figure 23 shows a plan view and a C-C' cross section of this process.

In the first self-alignment mounting process, the silicon optical waveguide array 131a and the polymer optical waveguide array (first optical input/output unit 112a) are aligned with high precision. To achieve this, the inclined surface 115a of the fitting groove 115 is butted against the inclined surface 132 of the silicon optical waveguide substrate 130 to align the horizontal position. The base 117 is butted against the bottom surface of the silicon optical waveguide substrate 130 to align the vertical position. This eliminates both the horizontal positional deviation Δy and the vertical positional deviation Δz. As a specific operation, for example, the first rough mounting process is performed while the silicon optical waveguide substrate 130 is being sucked by the collet, and then the suction is temporarily released. Next, a load is applied from above to the silicon optical waveguide substrate 130, and it is pushed toward the wiring substrate 120. This allows the inclined surface 132 on the silicon optical waveguide substrate 130 side to slide over the inclined surface 115a on the base clad 111 side and be moved to the appropriate position.

Although not shown, a transparent adhesive or matching oil may be applied in advance between the silicon optical waveguide array 131a and the base 117, and then the two may be pressed together to temporarily secure them in place.

Next, the first fixing step will be described with reference to Figure 22. Figure 22 shows a plan view and a C-C' cross section of this step.

In the first fixing step, the solder paste 161 and the solder bumps 134 are melted and integrated into solder 160 by a reflow process or the like. This causes the silicon optical waveguide substrate 130 to be fixed to the polymer optical waveguide substrate 100. Similarly, the semiconductor device 150 is also fixed by solder.

In the steps of Figures 20 to 22, the silicon optical waveguide substrate 130 that has been roughly mounted (first rough mounting step) is then repositioned with high precision by a pushing operation (first self-alignment mounting step). However, for example, when the solder is melted in the first fixing step, the silicon optical waveguide substrate 130 may be allowed to sink under its own weight, thereby achieving high-precision positioning. In this case, there is no need to push it in with a load, and the first self-alignment mounting step is performed when the solder is melted.

Then, the optical fiber 140 is mounted as the second optical device through the steps from the second fixing material supplying step to the second fixing step.

The second fixing material supplying process will be described with reference to Figures 23 and 24. Figure 23 is a plan view of this process, and Figure 24 is a diagram showing the A-A' and D-D' cross sections of Figure 23.

23 and 24, in the second fixing material supplying process, adhesive 170, which is the second fixing material, is supplied into fiber fixing groove 116, which is the second positioning portion. The supplying method may be inkjet printing, application by a dispenser, or the like. In the figure, adhesive 170 is supplied to connect multiple fiber fixing grooves 116, but it may be supplied to each individual fiber fixing groove 116. The adhesive 170, which is solidified by UV irradiation, is a light-transmitting resin, and preferably has a refractive index equivalent to that of base clad 111 and upper clad 113. As a result, even if adhesive 170 is interposed between light input/output portion 141 and core 112 of optical fiber 140 (FIGS. 2, 5, etc.), optical loss at the joint is suppressed.

Next, the second rough mounting process will be described with reference to Figures 25 and 26. Figure 25 is a plan view of this process, and Figure 26 is a diagram showing the A-A' and D-D' cross sections of Figure 25.

In the second rough mounting process, the optical fiber 140, which is the second optical device, is placed in the fiber fixing groove 116. It is preferable to use the waveguide alignment mark 118 for recognition at this time.

Multiple optical fibers 140 (seven in the illustrated example) are aligned to match the pitch of the fiber fixing grooves 116 and are fixed by an optical connector 142. The optical connector 142 includes a glass lid.

In this process, it is sufficient that each optical fiber 140 fits within the fiber fixing groove 116. In Figure 26, the optical fiber 140 is shown tilted in its length direction relative to the surface of the wiring board 120 (A-A' cross section) and offset from the center of the fiber fixing groove 116 in the width direction (D-D' cross section).

Next, the second self-alignment mounting process and the second fixing process will be described with reference to Figures 27 and 28. Figure 27 is a plan view of these processes, and Figure 28 is a diagram showing the A-A' and D-D' cross sections of Figure 27.

In the second self-alignment mounting process, a load is applied via the optical connector 142 so as to push the optical fiber 140 towards the wiring board 120. This positions the optical fiber 140 with high precision. In other words, the optical fiber 140 abuts against the inclined surfaces 116a on both sides of the fiber fixing groove 116, and fits accurately in the horizontal direction on the wiring board 120. In addition, the inclination in the length direction of the optical fiber 140 is eliminated, and the optical fiber 140 is extended parallel to the surface of the wiring board 120.

Then, UV light is irradiated through the optical connector 142 (glass lid) to harden the adhesive 170, thereby fixing the optical connector 142 and the optical fiber 140.

The optical module 190 is now complete.

In the above, the fixing material supply process, rough mounting process, self-alignment mounting process, and fixing process are performed as a series of processes for the first optical device (silicon optical waveguide substrate 130) and the second optical device (optical fiber 140). Therefore, the series of processes is performed twice, but this is not limited to this. Depending on the optical device to be mounted, the series of processes may be performed only once, or three or more times.

Furthermore, with regard to the mounting of the semiconductor device 150 and the silicon optical waveguide substrate 130, solder mounting has been used as an example of the method of electrical connection, but this is not limiting. For example, a method of mounting face-up and then electrically connecting by wire bonding is also acceptable. Furthermore, the semiconductor device 150 may be connected by inserting a PGA (Pin Grid Array) package into a PGA socket.

The above manufacturing method makes it possible to obtain a low-loss optical module that is inexpensive and can be mass-produced without the need for expensive active alignment devices or highly accurate mounting equipment.

The polymer optical waveguide substrate disclosed herein has a structure that allows optical devices to be mounted with high precision using a self-alignment method, making it useful as an optoelectronic fusion substrate for use in high-speed communication equipment, server platforms, etc.

100: Polymer optical waveguide substrate 110: Polymer optical waveguide layer 111: Base clad 111a: Base clad material 112: Core 112a: First optical input/output section 112b: Second optical input/output section (front end surface)
113 Upper cladding 114 Optical waveguide groove 114a Tip surface 115 Fitting groove 115a Inclined surface 116 Fiber fixing groove 116a Inclined surface 116b Tip surface 117 Pedestal 118 Waveguide alignment mark 118a Recess 120 Wiring substrate 121 Land electrode 122 Wiring layer 123 Substrate alignment mark 124 Substrate 130 Silicon optical waveguide substrate 131 Silicon optical waveguide 131a Silicon optical waveguide array 132 Inclined surface 133 Pad electrode 134 Solder bump 140 Optical fiber 141 Optical input/output section 142 Optical connector 150 Semiconductor device 160 Solder 161 Solder paste 170 Adhesive 180 Transfer mold 181 Rough mold 182 High-precision mold 183a Opening 183b Opening 190 Optical module

Claims (21)

A substrate;
a polymeric base clad formed on the substrate;
an optical waveguide groove formed in the base clad;
a polymer core embedded in the optical waveguide groove so as to contact the bottom and side surfaces;
a polymeric upper cladding covering the core;
a positioning portion formed using the base clad and for determining a position of an optical device to be mounted;
13. A polymer optical waveguide substrate, comprising: a positioning portion having a surface at a different height from a bottom surface of the optical waveguide groove; In claim 1,
A polymer optical waveguide substrate, characterized in that the relative positional accuracy between the positioning portion and one of the ends of the optical waveguide groove is 0.5 μm or less. In claim 1,
A polymer optical waveguide substrate, characterized in that at least a fitting groove is provided as the positioning portion. In claim 3,
13. A polymer optical waveguide substrate, comprising: a substrate having a surface inclined relative to a surface of the substrate; In claim 1,
A polymer optical waveguide substrate, comprising, as the positioning portion, at least a base for supporting an optical device. In claim 1,
A polymer optical waveguide substrate, characterized in that an opening is provided in the base clad, the opening reaching the substrate. In claim 6,
A polymer optical waveguide substrate, wherein the opening includes at least an alignment mark for positioning. In claim 6 or 7,
the substrate is a wiring substrate including electrical wiring and electrode pads;
A polymer optical waveguide substrate, wherein at least a portion of the opening is located above the electrode pad. In claim 1,
A polymer optical waveguide substrate, wherein a terminal face of the polymer optical waveguide faces an end wall face of the optical waveguide groove. The polymer optical waveguide substrate of claim 1;
and an optical device mounted on the polymer optical waveguide substrate. A method for manufacturing a polymer optical waveguide substrate, comprising the steps of:
The polymer optical waveguide substrate comprises:
A substrate;
a polymeric base clad formed on the substrate;
an optical waveguide groove formed in the base clad;
a polymer core embedded in the optical waveguide groove so as to contact the bottom and side surfaces;
a polymeric upper cladding covering the core;
a positioning portion formed by using the base clad, having a surface at a different height from a bottom surface of the optical waveguide groove, for determining a position of an optical device to be mounted;
The manufacturing method includes:
a coating step of coating the base clad material onto the substrate;
a transfer step of simultaneously forming the optical waveguide groove and the positioning portion by using a transfer mold having both a pattern corresponding to the optical waveguide groove and a pattern corresponding to the positioning portion within the same mold and transferring the pattern to the material of the base clad. In claim 11,
A method for manufacturing a polymer optical waveguide substrate, characterized in that in the transfer mold pattern, the relative positional accuracy between a pattern corresponding to the positioning portion and a pattern corresponding to one of the ends of the optical waveguide groove is 0.5 μm or less. In claim 11,
the transfer mold includes an abutment portion that is abutted against the substrate,
A method for producing a polymer optical waveguide substrate, comprising the step of abutting the abutting portion against the substrate in the transfer step. In claim 13,
A method for producing a polymer optical waveguide substrate, wherein a part of the abutting portion forms an alignment mark. In claim 13 or 14,
the substrate is a wiring substrate including electrical wiring and electrode pads;
A method for producing a polymer optical waveguide substrate, wherein in the transfer step, at least a part of the abutting portion is abutted against the electrode pad. In claim 11,
A method for manufacturing a polymer optical waveguide substrate, characterized in that the transfer mold includes a precision mold having a high-precision pattern portion including at least both a pattern corresponding to the optical waveguide groove and a pattern corresponding to the positioning portion, and a rough mold corresponding to other portions. In claim 11,
the transfer mold includes an abutment portion that is abutted against the substrate,
the transfer mold includes a precision mold having a high-precision pattern portion including at least both a pattern corresponding to the optical waveguide groove and a pattern corresponding to the positioning portion, and a rough mold corresponding to other portions;
A method for manufacturing a polymer optical waveguide substrate, characterized in that a part of the abutment portion is constituted by the rough mold and is configured so as to be able to move independently of the precision mold. A method for manufacturing an optical module in which an optical device is mounted on a polymer optical waveguide substrate, comprising the steps of:
The polymer optical waveguide substrate comprises:
A substrate;
a polymeric base clad formed on the substrate;
an optical waveguide groove formed in the base clad;
a polymer core embedded in the optical waveguide groove so as to contact the bottom and side surfaces;
a polymeric upper cladding covering the core;
a positioning portion formed by using the base clad, having a surface at a different height from a bottom surface of the optical waveguide groove, for determining a position of an optical device to be mounted;
The manufacturing method includes:
a fixing material supplying step of supplying a fixing material onto the polymer optical waveguide substrate;
a rough mounting step of placing the optical device at a predetermined position on the polymer optical waveguide substrate to which the fixing material has been applied;
a self-alignment mounting process in which the optical device is positioned by self-alignment using the positioning unit with higher accuracy than in the first mounting process;
a fixing step of fixing the optical device by hardening the fixing material after the self-alignment mounting step;
A method for manufacturing an optical module, comprising: In claim 18,
The fixing material includes at least solder,
4. A method for manufacturing an optical module, wherein in the fixing step, the optical device is fixed by melting and solidifying the solder. In claim 18,
A method for manufacturing an optical module, comprising the steps of: mounting a semiconductor device different from the optical device simultaneously through the fixing material supplying step, the rough mounting step, and the fixing step. In claim 18,
The fixing material includes at least a UV adhesive,
In the self-alignment mounting step, the optical device is held while being abutted against the positioning portion;
A method for manufacturing an optical module, wherein in the fixing step, the UV adhesive is cured by irradiating it with UV light.

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