Composite substrate

Abstract

This invention provides a technology that facilitates optical coupling and electrical connection in the mounting of functional devices onto a composite substrate including a conductor pattern and an optical waveguide. [Solution] The composite substrate 10A includes a wiring substrate 11A and a substrate with optical waveguides 12A. The wiring substrate 11A includes an insulating layer and a conductor pattern. The substrate with optical waveguides 12A includes a substrate 121 and an optical waveguide layer 122, the optical waveguide layer 122 includes a first cladding layer 122A, a second cladding layer 122C, and a core 122B provided between them. The upper surface of the optical waveguide layer 122 of the substrate with optical waveguides 12A includes a third region R3 where the second cladding layer 122C is provided and a fourth region R4 where the second cladding layer 122C is not provided, the fourth region R4 has a groove GR extending along the boundary between the third region R3 and the fourth region R4, and the core 122B has an end face adjacent to the upper space of the groove GR.

Description

Technical Field

[0001] The present invention relates to a composite substrate.

Background Art

[0002] In recent years, in order to achieve high-speed and high-capacity communication with low power consumption, introducing photonics-based technology into all components from the network to the terminal has attracted attention.

[0003] In particular, the optoelectronic integration technology that replaces part of the electric circuit in a terminal with a circuit that handles optical signals is one of the important technologies. In the optoelectronic integration technology, for example, an optical waveguide is provided on a circuit board, and a device that performs optoelectronic conversion and a device that processes electrical signals are mounted thereon. The optical waveguide and the former device are optically coupled, and an optoelectronic integration device in which these devices are electrically connected by a circuit provided on the circuit board is used (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a technology that can facilitate optical coupling and electrical connection in mounting a functional device on a composite substrate including a conductor pattern and an optical waveguide.

Means for Solving the Problems

[0006] According to one aspect of the present invention, a wiring substrate comprising one or more insulating layers and one or more first conductor patterns, having a first surface and a second surface which is its back surface, wherein the first surface comprises one or more first regions and one or more second regions which are recessed from the one or more first regions, one of the one or more first conductor patterns is located in the one or more first regions, and the height of the one or more second regions is lower than the lower surface of one of the one or more first conductor patterns located in the one or more first regions, and each of the optical waveguide layers comprises a first cladding layer provided on the substrate, a second cladding layer provided on the first cladding layer, and the first cladding layer A composite substrate is provided comprising one or more optical waveguide substrates including one or more cores provided between the optical waveguide layer and the second cladding layer, wherein the optical waveguide layer is provided above the substrate and the one or more second regions are each placed on the one or more second regions, and the height of the lower surface of the one or more cores is higher than that of the one or more first regions, wherein at least one of the one or more optical waveguide substrates has a surface on which the optical waveguide layer is provided that includes a third region on which the second cladding layer is provided and a fourth region on which the second cladding layer is not provided, the fourth region has a groove extending along the boundary between the third region and the fourth region, and the one or more cores have an end face adjacent to the space above the groove.

[0007] According to another aspect of the present invention, a composite substrate relating to the above aspect is provided, wherein the depth of the groove is in the range of 20 μm or more and 50 μm or less.

[0008] According to yet another aspect of the present invention, a composite substrate relating to any of the above aspects is provided, wherein the width of the groove is within the range of 20 μm to 200 μm.

[0009] According to yet another aspect of the present invention, a composite substrate is provided in which the upper surface of the substrate is recessed at the position of the groove, corresponding to any of the above-mentioned sides.

[0010] According to yet another aspect of the present invention, a composite substrate is provided relating to any of the above aspects, wherein in at least one of the one or more optical waveguide substrates, the first cladding layer includes a first portion provided at the location of the third region and a second portion provided at the location of the fourth region.

[0011] According to yet another aspect of the present invention, a composite substrate is provided in which the bottom surface of the groove is part of the upper surface of the second portion.

[0012] According to yet another aspect of the present invention, a composite substrate is provided in which the bottom surface of the groove is part of the top surface of the substrate.

[0013] According to yet another aspect of the present invention, a composite substrate is provided in which the height of the upper surface of the substrate is lower than any of the above aspects.

[0014] According to yet another aspect of the present invention, a composite substrate is provided in which the lower surface of the one or more cores relates to any of the above-mentioned sides, wherein the height of the one or more first regions is 100 μm or less.

[0015] According to yet another aspect of the present invention, a composite substrate according to any of the above aspects is provided, further comprising one or more stress-relaxing layers interposed between the one or more optical waveguide substrates and the one or more second regions.

[0016] According to yet another aspect of the present invention, a composite substrate is provided in which each of the one or more stress relaxation layers has an elastic modulus in the range of 0.1 MPa to 3 GPa.

[0017] According to yet another aspect of the present invention, a composite substrate is provided in which each of the one or more stress relaxation layers has a thickness in the range of 5 μm to 50 μm, relating to any of the above aspects.

[0018] According to still another aspect of the present invention, at least one of the one or more substrates with optical waveguides further includes a second conductor pattern provided between the substrate and the optical waveguide layer, and in each of the at least one substrate with optical waveguides further including the second conductor pattern, the second cladding layer is provided such that a part of the upper surface of the first cladding layer has an exposed portion, and the exposed portion is provided with a plurality of through holes each extending to the second conductor pattern, and there is provided a composite substrate according to any one of the above aspects.

[0019] According to still another aspect of the present invention, there is provided a composite substrate according to any one of the above aspects, wherein the one or more insulating layers include an insulating resin layer, and the substrate includes a glass substrate.

[0020] According to still another aspect of the present invention, there is provided a composite substrate according to any one of the above aspects, which is an interposer.

[0021] According to still another aspect of the present invention, there is provided an optoelectronic fusion device including a composite substrate according to any one of the above aspects, a first functional device mounted on the composite substrate and optically coupled to at least one of the one or more substrates with optical waveguides by butt coupling, and a second functional device mounted on the composite substrate and electrically connected to the first functional device.

[0022] According to still another aspect of the present invention, there is provided an optoelectronic fusion device according to the above aspect, further including a refractive index adjusting layer having a portion interposed between the first functional device and at least one of the one or more substrates with optical waveguides.

Advantages of the Invention

[0023] According to the present invention, there is provided a technique capable of facilitating optical coupling and electrical connection in mounting a functional device on a composite substrate including a conductor pattern and an optical waveguide.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a top view of a composite substrate according to a first embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view taken along the line II-II of the composite substrate shown in Figure 1. [Figure 3] Figure 3 is a top view of the substrate with an optical waveguide included in the composite substrate shown in Figures 1 and 2. [Figure 4] Figure 4 is a cross-sectional view of the substrate with an optical waveguide shown in Figure 3. [Figure 5] Figure 5 is a top view of the optoelectronic fusion device including the composite substrate shown in Figures 1 and 2. [Figure 6] Figure 6 is a cross-sectional view taken along the line VI-VI of the optoelectronic fusion device shown in Figure 5. [Figure 7] Figure 7 is a partially enlarged view of the cross-sectional view of the optoelectronic fusion device shown in Figure 6. [Figure 8] Figure 8 is a cross-sectional view showing a modified example of the substrate with an optical waveguide shown in Figures 3 and 4. [Figure 9] Figure 9 is a cross-sectional view showing a modified example of the optoelectronic fusion device shown in Figures 5 and 6. [Figure 10] Figure 10 is a top view of the optoelectronic fusion device with a connector including the optoelectronic fusion device shown in Figures 5 and 6. [Figure 11] Figure 11 is a cross-sectional view showing a modified example of the optoelectronic fusion device shown in Figures 5 and 6. [Figure 12] Figure 12 is a top view of the composite substrate according to the second embodiment of the present invention. [Figure 13] Figure 13 is a top view of the optoelectronic fusion device with a connector including the composite substrate shown in Figure  12. [Figure 14] Figure 14 is a top view of the composite substrate according to the third embodiment of the present invention. [Figure 15] Figure 15 is a cross-sectional view taken along the line XV-XV of the composite substrate shown in Figure 14. [Figure 16] Figure 16 is a top view of the optoelectronic fusion device including the composite substrate shown in Figures 14 and 15. [Figure 17] Figure 17 is a cross-sectional view taken along the line XVII-XVII of the optoelectronic fusion device shown in Figure 16. [Figure 18]Figure 18 is a top view of a composite substrate according to a fourth embodiment of the present invention. [Figure 19] Figure 19 is a cross-sectional view of the composite substrate shown in Figure 18 along the line XIX-XIX. [Figure 20] Figure 20 is a top view of the optical waveguide substrate included in the composite substrate shown in Figures 18 and 19. [Figure 21] Figure 21 is a cross-sectional view of the substrate with an optical waveguide shown in Figure 20. [Figure 22] Figure 22 is a top view of the photoelectric fusion apparatus including the composite substrate shown in Figures 18 and 19. [Figure 23] Figure 23 is a cross-sectional view along the line XXIII-XXIII of the photoelectric fusion apparatus shown in Figure 22. [Figure 24] Figure 24 is a top view showing one modified example of the substrate with an optical waveguide shown in Figures 20 and 21. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are more specific to any of the above aspects. The matters described below can be incorporated into each of the above aspects, individually or in combination.

[0026] The embodiments described below illustrate examples that embody the technical concept of the present invention, and the technical concept of the present invention is not limited to the materials, shapes, structures, and arrangements of the components described below. Various modifications can be made to the technical concept of the present invention within the technical scope defined by the claims described in the patent claims.

[0027] In the drawings referenced in the following description, components with similar or identical functions are given the same reference numerals. It should be noted that the drawings are schematic, and the relationships between dimensions in the thickness direction and dimensions perpendicular to the thickness direction (i.e., in-plane direction), as well as the relationships between dimensions in the thickness direction of multiple layers, may differ from reality. Therefore, specific dimensions should be determined by referring to the following description. It should also be noted that the dimensional relationships between two or more components may differ across multiple drawings.

[0028] In this disclosure, "upper surface" and "lower surface" refer to the two main surfaces of the plate-like member or the layer contained therein, namely the surface perpendicular to the thickness direction and having the largest area, and the back surface thereof, which are shown at the top and bottom in the drawings, respectively. Furthermore, "end surface" refers to the surface of the plate-like member or the layer contained therein that is located on the outer periphery when viewed from a direction parallel to the thickness direction. And "side surface" refers to a surface that is perpendicular to or inclined with respect to the in-plane direction.

[0029] Furthermore, in this disclosure, the phrase "AA on BB" is used independently of the direction of gravity. The state specified by the phrase "AA on BB" includes the state in which AA is in contact with BB. The phrase "AA on BB" does not exclude the presence of one or more other components between AA and BB.

[0030] <1> First Embodiment <1.1> Composite substrate Figure 1 is a top view of a composite substrate according to a first embodiment of the present invention. Figure 2 is a cross-sectional view of the composite substrate shown in Figure 1 along the line II-II. Figure 3 is a top view of a substrate with an optical waveguide included in the composite substrates shown in Figures 1 and 2. Figure 4 is a cross-sectional view of the substrate with an optical waveguide shown in Figure 3.

[0031] In these and other figures, the X and Y directions are perpendicular to the thickness direction of the composite substrate and are also orthogonal to each other. In these figures, the Z direction is perpendicular to the X and Y directions, i.e., the thickness direction of the composite substrate.

[0032] The composite substrate 10A shown in Figures 1 and 2 is an interposer. The composite substrate 10A includes a wiring board 11A, a substrate with an optical waveguide 12A, and an adhesive layer 13 that bonds them together.

[0033] The wiring board 11A includes a core insulating layer 111, an insulating layer 112, a first conductor pattern 113, and an insulating layer 114. Hereafter, the first conductor pattern 113 will be referred to as "conductor pattern 113".

[0034] The core insulating layer 111 is, in this case, an insulating resin layer. For example, the core insulating layer 111 is a composite material containing glass fibers and a cured resin. The core insulating layer 111 may also be a glass plate. The core insulating layer 111 may have a single-layer structure or a multi-layer structure. The core insulating layer 111 is provided with a plurality of through holes, each extending in the thickness direction.

[0035] The insulating layer 112 is laminated on each of the main surfaces of the core insulating layer 111. The insulating layer 112 is, in this case, an insulating resin layer. The insulating layer 112 is made of, for example, a cured resin. Each of the insulating layers 112 may have a single-layer structure or a multi-layer structure. Each of the insulating layers 112 is provided with a plurality of through holes, each extending in the thickness direction.

[0036] Here, two insulating layers 112 are laminated on each main surface of the core insulating layer 111. The number of insulating layers 112 provided on each main surface of the core insulating layer 111 may be one or three or more. Also, an insulating layer 112 may not be provided on at least one main surface of the core insulating layer 111.

[0037] The conductor pattern 113 is a wiring layer that includes a lead layer. The conductor pattern 113 may have a single-layer structure or a multi-layer structure. Here, the "lead layer" is the thickest layer among the conductive layers included in the wiring layer. The lead layer is made of a metallic material such as copper. Each of the conductor patterns 113 may further include one or more other layers such as an adhesion layer and a seed layer.

[0038] The conductor pattern 113 includes an inner conductor pattern (not shown) that includes a portion interposed between the core insulating layer 111 and an adjacent insulating layer 112, an intermediate conductor pattern that includes a portion interposed between adjacent insulating layers 112, and an outer conductor pattern that includes a portion interposed between the insulating layer 112 and the insulating layer 114.

[0039] The portion of the inner conductor pattern interposed between the core insulating layer 111 and the adjacent insulating layer 112 includes land portions, pad portions, and wiring portions. Each of the wiring portions has one end connected to a land portion and the other end connected to a pad portion. The inner conductor pattern further includes through electrodes, which are portions that cover the side walls of through holes provided in the core insulating layer 111. Each of the through electrodes is connected to the land portions on both sides of the core insulating layer 111. The inner conductor pattern may also embed the through holes provided in the core insulating layer 111.

[0040] Each of the intermediate conductor pattern and the outer conductor pattern includes pad portions, wiring portions, and via portions. In each of the intermediate conductor pattern and the outer conductor pattern, the pad portions include those positioned to cover or surround one opening of a through-hole provided in the insulating layer 112 adjacent to the core insulating layer 111 side, and those positioned away from the through-hole. The wiring portions connect the former pad portions to the latter pad portions. The via portions fill the through-holes provided in the insulating layer 112 adjacent to the core insulating layer 111 side of the pad portions of the intermediate conductor pattern or outer conductor pattern, and connect the pad portions facing each other with the insulating layer 112 in between. The distance between pad portions is greater in the lower outer conductor pattern compared to the upper outer conductor pattern.

[0041] The insulating layer 114 is an organic insulating layer. The insulating layer 114 is made of, for example, solder resist. Each insulating layer 114 covers one of the insulating layers 112 and one of the conductor patterns 113. Each insulating layer 114 has through holes at the positions of the pads of the conductor pattern 113 that it covers.

[0042] The wiring board 11A has a first surface S1 and a second surface S2 which is its back surface. Here, the first surface S1 is the top surface of the wiring board 11A, and the second surface S2 is the bottom surface of the wiring board 11A.

[0043] The first surface S1 includes a first region R1 and a second region R2 that is recessed relative to the first region R1. That is, the first surface S1 has a recess at the location of the second region R2.

[0044] Here, the wiring board 11A has a shape that, when orthogonally projected onto a plane perpendicular to the Z direction, is a square or rectangle with sides parallel to the X direction and sides parallel to the Y direction. The dimensions of the wiring board 11A in the X and Y directions are, in one example, within the range of 30 mm to 150 mm, and in another example, within the range of 50 mm to 100 mm.

[0045] The shape of the second region R2 is, in this case, a rectangle extending from the edge of the first surface S1, which is parallel to the Y direction, in a direction parallel to the X direction. The dimensions of the second region R2 in the X direction, i.e., the length direction, are preferably within the range of 5 mm to 50 mm, and more preferably within the range of 10 mm to 30 mm. The dimensions of the second region R2 in the Y direction, i.e., the width direction, are preferably within the range of 1 mm to 10 mm, and more preferably within the range of 2 mm to 5 mm.

[0046] The uppermost conductor pattern 113 is located in the first region R1. A portion of the through-holes in the insulating layer 114 located above it is located near the second region R2.

[0047] The height of the second region R2 is lower than the lower surface of the conductor pattern 113 located in the first region R1, i.e., the uppermost conductor pattern 113. The difference between the height of the lower surface of the uppermost conductor pattern 113 and the height of the second region R2 is preferably in the range of 70 μm to 250 μm, and more preferably in the range of 100 μm to 200 μm.

[0048] The optical waveguide substrate 12A includes a substrate 121 and an optical waveguide layer 122 provided thereon.

[0049] The substrate 121 is made of, for example, glass, ceramic, plastic, metal, or a combination of two or more of these materials. The substrate 121 only needs to have a smooth surface. Here, as an example, the substrate 121 is assumed to be a glass plate.

[0050] The shape of the orthogonal projection of the substrate 121 onto a plane perpendicular to its thickness is approximately equal to the shape of the second region R2. Here, the shape of the orthogonal projection of the substrate 121 is a rectangle corresponding to the shape of the second region R2. Furthermore, the dimensions of the orthogonal projection of the substrate 121 are slightly smaller than those of the second region R2.

[0051] The difference between the lengthwise dimension of the second region R2 and the lengthwise dimension of the orthogonal projection of the substrate 121 is, in one example, within the range of 5 μm to 300 μm, and in another example, within the range of 10 μm to 200 μm. The difference between the widthwise dimension of the second region R2 and the widthwise dimension of the orthogonal projection of the substrate 121 is, in one example, within the range of 5 μm to 300 μm, and in another example, within the range of 10 μm to 200 μm.

[0052] The thickness of the substrate 121 is preferably in the range of 50 μm to 150 μm, and more preferably in the range of 80 μm to 100 μm.

[0053] The optical waveguide layer 122 includes a first cladding layer 122A, a core 122B, and a second cladding layer 122C.

[0054] The first cladding layer 122A is provided on one main surface of the substrate 121. The first cladding layer 122A is made of a first low refractive index material. For example, the first low refractive index material is a cured resin. The first low refractive index material preferably has a refractive index for light with a wavelength of 1300 nm in the range of 1.4 to 1.7, and more preferably in the range of 1.5 to 1.6.

[0055] As shown in Figure 4, the first cladding layer 122A includes a first portion P1 with greater thickness and a second portion P2 with less thickness. The first portion P1 and the second portion P2 are arranged in the longitudinal direction of the substrate 121. The second portion P2 includes a portion that forms a groove GR.

[0056] The thickness of the first portion P1 is preferably in the range of 120 μm to 170 μm, and more preferably in the range of 130 μm to 160 μm. The difference between the thickness of the first portion P1 and the thickness of the second portion P2 is preferably in the range of 60 μm to 140 μm, and more preferably in the range of 80 μm to 120 μm. Here, the thickness of the second portion P2 refers to the thickness measured in the portion where the groove GR is not formed.

[0057] The second cladding layer 122C is provided on the first portion P1 of the first cladding layer 122A. The second cladding layer 122C covers the first portion P1 of the first cladding layer 122A without covering the second portion P2 of the first cladding layer 122A. That is, the second cladding layer 122C is provided such that a portion of the upper surface of the first cladding layer 122A is exposed.

[0058] The second cladding layer 122C consists of a second low refractive index material. For example, the second low refractive index material is a cured resin. Preferably, the second low refractive index material has the refractive index described above for the first low refractive index material. Preferably, the second low refractive index material is the same as the first low refractive index material.

[0059] Core 122B is provided between the first cladding layer 122A and the second cladding layer 122C. Here, the number of cores 122B included in the optical waveguide substrate 12A is 2, but the number of cores 122B included in the optical waveguide substrate 12A may be 1 or 3 or more.

[0060] Each of the cores 122B has a shape that extends in the longitudinal direction of the substrate 121. These cores 122B are arranged in the width direction. Each of the cores 122B preferably has a diameter in the range of 6 μm to 60 μm, and more preferably in the range of 8 μm to 50 μm.

[0061] Core 122B is made of a high refractive index material. For example, the high refractive index material is a cured resin. The high refractive index material preferably has a refractive index for light of the above wavelength in the range of 1.4 to 1.7, and more preferably in the range of 1.5 to 1.6.

[0062] The difference between the refractive index of the high refractive index material for the above wavelength and the refractive index of the first low refractive index material for the above wavelength is preferably within the range of 0.5% to 5.0%, and more preferably within the range of 1.0% to 3.0%, when the refractive index of the high refractive index material is set to 100%. The difference between the refractive index of the high refractive index material for the above wavelength and the refractive index of the second low refractive index material for the above wavelength is also preferably within these ranges.

[0063] As shown in Figure 4, the surface of the optical waveguide substrate 12A on which the optical waveguide layer 122 is provided (i.e., the upper surface of the optical waveguide layer 122) includes a third region R3 on which the second cladding layer 122C is provided, and a fourth region R4 on which the second cladding layer 122C is not provided. The fourth region R4 has a groove GR that extends along the boundary between the third region R3 and the fourth region R4. Details of the groove will be described later.

[0064] The optical waveguide substrate 12A is installed on the second region R2 such that the optical waveguide layer 122 is located above the substrate 121. As described above, the wiring board 11A has a recess at the location of the second region R2. The optical waveguide substrate 12A is installed within this recess.

[0065] The height of the lower surface of core 122B is higher than that of the first region R1. The height of the lower surface of core 122B relative to the first region R1, in this case, relative to the upper surface of the insulating layer 114 located above it, is preferably 100 μm or less, and more preferably 80 μm or less. Furthermore, the height of the lower surface of core 122B relative to the first region R1 is preferably 50 μm or more, and more preferably 60 μm or more.

[0066] The height of the upper surface of the substrate 121 is preferably lower than that of the first region R1. The difference between the height of the first region R1 and the height of the upper surface of the substrate 121 is preferably in the range of 10 μm to 30 μm, and more preferably in the range of 15 μm to 25 μm.

[0067] The adhesive layer 13 is interposed between the wiring board 11A and the optical waveguide substrate 12A. The adhesive layer 13 fixes the optical waveguide substrate 12A to the wiring board 11A. The adhesive layer 13 includes a layer made of adhesive. The adhesive layer 13 may have a single-layer structure or a multi-layer structure.

[0068] <1.2>Optoelectronic fusion device Figure 5 is a top view of the photoelectric fusion apparatus including the composite substrate shown in Figures 1 and 2. Figure 6 is a cross-sectional view of the photoelectric fusion apparatus shown in Figure 5 along the line VI-VI.

[0069] The photoelectric integration apparatus 1A shown in Figures 5 and 6 includes the composite substrate 10A, the bonding conductor 14, the first functional device 20, and the second functional device 30.

[0070] The joining conductor 14 covers the pad portion of the conductor pattern 113 covered by the insulating layer 114 at the location of the through-hole provided in the insulating layer 114. Each of the joining conductors 14 includes a portion located within the through-hole provided in the insulating layer 114 and a portion protruding from the insulating layer 114. The joining conductor 14 is, for example, a solder bump.

[0071] The first functional device 20 is a device that includes an optical integrated circuit and an optical waveguide. The optical integrated circuit includes a photoelectric conversion element and performs conversion of optical signals to electrical signals, conversion of electrical signals to optical signals, or both. Here, as an example, the optical integrated circuit is assumed to perform both conversion of optical signals to electrical signals and conversion of electrical signals to optical signals. Each optical waveguide has one end face exposed to the end face of the first functional device 20 and is optically coupled to the photoelectric conversion element at the other end. Here, the number of optical waveguides included in the first functional device 20 is 2. The number of optical waveguides included in the first functional device 20 may be 1 or 3 or more.

[0072] The first functional device 20 is flip-chip mounted on the wiring board 11A via a bonding conductor 14 in the vicinity of the optical waveguide substrate 12A. Furthermore, the first functional device 20 is positioned such that the end face EF2 of the core 21 of its optical waveguide faces the end face EF1 of the core 122B of the optical waveguide layer 122. In other words, the optical waveguide of the first functional device 20 is optically coupled to the optical waveguide layer 122 by butt coupling.

[0073] The second functional device 30 is, for example, a device that operates when at least one of power and / or an electrical signal is supplied, a device that outputs at least one of power and / or an electrical signal in response to an external stimulus, or a device that operates when at least one of power and / or an electrical signal is supplied and also outputs at least one of power and / or an electrical signal in response to an external stimulus. The second functional device 30 is in the form of a chip, for example, a semiconductor chip or a chip on which circuits and elements are formed on a substrate made of a material other than a semiconductor, such as a glass substrate. The second functional device 30 can include, for example, one or more of a large-scale integrated circuit (LSI), memory, image sensor, light-emitting element, and MEMS (Micro Electro Mechanical Systems). MEMS are, for example, one or more of a pressure sensor, acceleration sensor, gyroscope, tilt sensor, microphone, and acoustic sensor. In one example, the second functional device 30 is a semiconductor chip including an LSI.

[0074] The second functional device 30 is flip-chip mounted on the wiring board 11A via a bonding conductor 14. The second functional device 30 is electrically connected to the first functional device 20 via a conductor pattern 113 and a bonding conductor 14.

[0075] Here, the number of second functional devices 30 included in the photoelectric fusion device 1A is 1. The number of second functional devices 30 included in the photoelectric fusion device 1A may be 2 or more.

[0076] <1.3> Groove As described above, in the photoelectric fusion apparatus 1A, the surface of the optical waveguide substrate 12A on which the optical waveguide layer 122 is provided (i.e., the upper surface of the optical waveguide layer 122) includes a third region R3 on which the second cladding layer 122C is provided and a fourth region R4 on which the second cladding layer 122C is not provided, and the fourth region R4 has a groove GR that extends along the boundary between the third region R3 and the fourth region R4. Figure 7 is a partially enlarged view of the cross-sectional view of the photoelectric fusion apparatus shown in Figure 6, showing an enlarged view of the vicinity of the groove GR.

[0077] In Figure 7, the bottom surface of groove GR is covered by the first cladding layer 122A. That is, the bottom surface of groove GR is part of the upper surface of the second portion P2 of the first cladding layer 122A.

[0078] The upper surface of the substrate 121 is recessed at the location of groove GR, corresponding to groove GR. When a recess corresponding to groove GR is provided on the upper surface of the substrate 121 at the location of groove GR, the depth of groove GR, i.e., the depth represented by the symbol D in Figure 7, can be increased. Alternatively, a recess corresponding to groove GR does not need to be provided on the upper surface of the substrate 121 at the location of groove GR. In this case, the depth D of groove GR cannot be greater than the thickness of the second portion P2.

[0079] The core 122B of the optical waveguide layer 122 has an end face EF1 adjacent to the upper space of the groove GR. The core 21 of the optical waveguide of the first functional device 20 has an end face EF2 adjacent to the upper space of the groove GR.

[0080] The distance between the first functional device 20 and the substrate 12A with an optical waveguide, i.e., the distance represented by the symbol G in Figure 7, is preferably narrowed in order to reduce the loss of optical signals. This distance G is preferably in the range of 1 μm to 10 μm, and more preferably in the range of 2 μm to 8 μm.

[0081] Furthermore, in order to reduce the loss of optical signals, it is preferable to flow a cleaning solution into the narrow gap between the first functional device 20 and the optical waveguide substrate 12A to clean the end faces of the optical waveguide, that is, the end face EF1 of the core 122B of the optical waveguide layer 122 of the optical waveguide substrate 12A and the end face EF2 of the core 21 of the optical waveguide of the first functional device 20. As described above, the surface of the optical waveguide substrate 12A on which the optical waveguide layer 122 is provided has a groove GR. When a cleaning solution is flowed into the narrow gap between the first functional device 20 and the optical waveguide substrate 12A from above the photoelectric fusion apparatus 1A, the cleaning solution flows more easily, improving the cleanability of the end faces of the optical waveguide. In particular, it is possible to improve the difficulty of cleaning the end faces of the optical waveguide when the above-mentioned gap G is narrowed. Improving the cleanability of the end faces of the optical waveguide enhances the effect of reducing the loss of optical signals. For example, it is possible to improve the flux cleaning performance when a flux cleaning solution is applied after reflow.

[0082] The depth of the groove GR, represented by the symbol D in Figure 7, is preferably within the range of 20 μm to 50 μm, and more preferably within the range of 30 μm to 45 μm. The width of the groove GR, represented by the symbol W in Figure 7, is preferably within the range of 20 μm to 200 μm, and more preferably within the range of 50 μm to 180 μm. When the depth D and width W of the groove GR are within the above ranges, the cleaning solution can be easily flowed into the narrow gap between the first functional device 20 and the optical waveguide substrate 12A from above the photoelectric fusion apparatus 1A. If the depth D and width W of the groove GR are too large, deformation of the optical waveguide substrate 12A is more likely to occur.

[0083] <1.4> Method for manufacturing a photoelectric fusion device The above-described photoelectric fusion apparatus 1A can be manufactured, for example, by the following method. <1.4.1> Manufacturing method of a wiring board The wiring board 11A is manufactured, for example, by the following method. Specifically, first, a composite material is prepared that includes a core insulating layer 111 and first conductor layers provided on both sides thereof. Here, as will be described later, a composite substrate is first manufactured, and this composite substrate is then divided into multiple wiring boards 11A. Therefore, the dimensions of the composite material prepared here are slightly larger than the dimensions of the assembly formed by arranging multiple wiring boards 11A. The first conductor layer is, for example, copper foil attached to the core insulating layer 111.

[0084] Next, through-holes are formed in this composite material to electrically connect its front and back surfaces. These through-holes are formed, for example, using a drill.

[0085] Next, a second conductor layer is formed on the side walls of the through-holes and on the surface of the first conductor layer. The second conductor layer may be formed so that the through-holes in the core insulating layer 111 are not completely filled, or it may be formed so that these through-holes are completely filled.

[0086] The second conductive layer can be obtained, for example, by forming a seed layer by electroless plating and then forming a plating layer by electroplating, in that order. For the seed layer, metallic materials such as Cu, Pd, Al, Sn, Ni, and Cr can be used. For the plating layer, metallic materials such as Cu, Cu alloys, Ag, Ag alloys, Sn, Pd, Au, Ni, Cr, Pt, Fe, and combinations of two or more of these can be used.

[0087] Next, the through-holes in the core insulating layer 111 are filled with a hole-filling resin. For example, the through-holes are filled with resin, allowed to harden, and then any excess hardened resin that has protruded from the through-holes is removed by buffing or the like. If the through-holes in the core insulating layer 111 are completely filled with the conductive layer, this step and the following step can be omitted.

[0088] Next, a third conductive layer is formed on both sides of the composite material obtained as described above. The third conductive layer is, for example, a laminate of a seed layer and a plating layer provided thereon. These seed layer and plating layer can be formed, for example, using the method and materials described above for the second conductive layer.

[0089] The seed layer of the third conductive layer can also be formed by sputtering. When forming the seed layer by sputtering, the material can be, for example, Cu, Ni, Al, Ti, Cr, Mo, W, Ta, Au, Ir, Ru, Pd, Pt, AlSi, AlSiCu, AlCu, NiFe, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), ZnO, PZT (Lead Zirconate Titanate), TiN, Cu3N4, Cu alloy, or a combination of two or more of these.

[0090] Next, a resist resin is applied to both sides of the composite material obtained as described above, or a dry film resist is laminated onto it. Then, pattern exposure and development are sequentially performed on these resist layers to obtain a resist pattern.

[0091] Next, etching is performed using the resist pattern as an etching mask to remove portions of the first to third conductor layers corresponding to the openings in the resist pattern. In this way, a conductor pattern including the portion covering the upper surface of the core insulating layer 111 and a conductor pattern including the portion covering the lower surface of the core insulating layer 111 are obtained.

[0092] Next, an insulating layer 112 having through holes is formed on both sides of the composite material obtained as described above. The insulating layer 112 is formed using, for example, a thermosetting resin or a photosensitive resin. When using a thermosetting resin, a coating film made of the thermosetting resin is cured, and the cured film is subjected to laser processing such as CO2 laser processing and UV laser processing to obtain an insulating layer 112 having through holes. When using a photosensitive resin, a coating film made of the photosensitive resin is subjected to pattern exposure and development to obtain an insulating layer 112 having through holes. These through holes are formed at the positions of the pad portions of the conductor pattern covered by the insulating layer 112.

[0093] Next, the seed layer is formed to cover the main surface of the insulating layer 112, the side walls of the through holes in the insulating layer 112, and the area of ​​the pad portion of the conductor pattern covered by the insulating layer 112 that is adjacent to the internal space of the through holes in the insulating layer 112. The seed layer can be formed for the seed layers of the second and third conductor layers using the method and materials described above.

[0094] Next, a resist resin is applied to both sides of the composite material obtained as described above, or a dry film resist is laminated onto it. Then, pattern exposure and development are sequentially performed on these resist layers to obtain a resist pattern.

[0095] Next, a plating layer is formed by an electroplating method using the seed layer as a power supply layer. The metal materials mentioned above can be used for these plating layers.

[0096] Next, the resist pattern is removed, and then the portion of the seed layer not covered by the plating layer is removed by etching. This yields a conductive pattern 113 consisting of the seed layer and the plating layer, respectively.

[0097] Subsequently, an insulating layer 112 and a conductor pattern 113 are formed on the upper and lower surfaces of the composite material obtained as described above.

[0098] Next, insulating layers are provided as continuous films on both sides of the composite material obtained as described above. These insulating layers are solder resist layers. The solder resist layers can be provided on the composite material by applying liquid solder resist or by laminating a dry film type solder resist. The solder resist is, for example, a photosensitive epoxy resin or a non-photosensitive thermosetting resin. The solder resist may further contain inorganic fillers.

[0099] Next, through-holes are formed in the solder resist layer to obtain an insulating layer 114. These through-holes are formed at the positions of the pads of the conductor pattern 113 covered by the solder resist layer. When using a solder resist containing a photosensitive resin, through-holes can be formed by pattern exposure and development of the solder resist layer. When using a solder resist containing a thermosetting resin, through-holes can be formed by laser processing such as CO2 laser processing and UV laser processing of the solder resist layer.

[0100] Next, a surface treatment layer is formed on the surface of the pad portion of the conductor pattern 113 so as to cover the area adjacent to the internal space of the through-hole of the insulating layer 114. The surface treatment layer is provided for the purpose of preventing oxidation of the surface of the conductor pattern 113 and improving its wettability to solder.

[0101] The surface treatment layer is, for example, an electroless Ni / Pd / Au plating layer. Alternatively, an OSP (Organic Solderability Preservative) film, i.e., a surface treatment layer using a water-soluble preflux, may be formed as the surface treatment layer. Alternatively, an electroless tin plating or electroless Ni / Au plating layer may be formed as the surface treatment layer.

[0102] Next, a bonding conductor 14 is formed on the surface treatment layer. The bonding conductor 14 is, for example, a metal bump such as a solder bump. The bonding conductor 14 can be formed, for example, by printing a metal paste such as solder paste onto the surface treatment layer using a screen printing method. Alternatively, the bonding conductor 14 can be formed by printing flux onto the surface treatment layer using a screen printing method, placing metal balls such as solder balls into the through-holes of the insulating layer 114 using a ball-filling method or the like, melting them, and then cooling them.

[0103] Subsequently, a recess corresponding to the second region R2 is formed on one surface of the composite material obtained as described above to obtain a composite substrate. These recesses are formed, for example, by cutting or laser ablation. When recesses are formed by laser ablation, it is preferable that the composite material includes a stopper film that defines the position of the bottom of the recess. The stopper film is preferably a metal layer that exhibits high reflectivity at the wavelength of the laser beam. This metal layer may also be part of the conductor pattern described above.

[0104] Next, the assembled substrate is divided into multiple individual wiring boards. Specifically, dicing is performed along the dicing lines. In this way, wiring board 11A is obtained.

[0105] <1.4.2> Method for manufacturing a substrate with optical waveguides The optical waveguide substrate 12A is manufactured, for example, by the following method. Specifically, first, a substrate 121 is prepared. Here, as will be described later, a composite substrate is first manufactured, and this composite substrate is then divided into multiple optical waveguide substrates 12A. Therefore, the dimensions of the substrate 121 prepared here are slightly larger than the dimensions of the composite formed by arranging multiple optical waveguide substrates 12A. To facilitate handling, the substrate 121 may be supported by a support that can be removed from the substrate 121.

[0106] If necessary, a recess corresponding to the groove GR is provided on the upper surface of the substrate 121 at the location of the groove GR. For example, if the depth D of the groove GR is greater than the thickness of the second portion P2 of the first cladding layer 122A, a recess corresponding to the groove GR is provided on the upper surface of the substrate 121 at the location of the groove GR. This recess can be formed by etching, laser processing, a combination of laser and etching processing, cutting, etc. This recess may be provided with a size slightly larger than the depth D and width W of the groove GR, and the first cladding layer 122A may be interposed between the substrate 121 and the groove GR. In this case, the recessed portion provided on the upper surface of the substrate 121 can be protected by the first cladding layer 122A.

[0107] Next, an optical waveguide layer 122 is formed on the substrate 121. Specifically, a first cladding layer 122A, a core 122B, and a second cladding layer 122C are formed on the substrate 121 in this order.

[0108] The first cladding layer 122A can be obtained, for example, by coating an ionizing radiation-curable resin onto the substrate 121 and curing it by irradiating the entire surface of the coating with ionizing radiation, thereby obtaining a continuous film with substantially uniform thickness. Alternatively, the first cladding layer 122A can be obtained by coating a thermosetting resin onto the substrate 121 and curing it by heating the entire coating. The core 122B can be obtained, for example, by coating an ionizing radiation-curable resin onto the first cladding layer 122A, irradiating the portion of the coating where the core 122B is to be formed with ionizing radiation to cure these portions, and then subjecting the coating to a developing process. The second cladding layer 122C can be obtained, for example, by the same method as described above for the first cladding layer 122A.

[0109] Subsequently, the portion of the optical waveguide layer 122 obtained as described above that is located directly above the second portion P2 of the first cladding layer 122A is removed to obtain a composite substrate. For example, laser ablation, dry etching, or cutting can be used for this removal. This creates a first portion P1 with a greater thickness and a second portion P2 with a smaller thickness in the first cladding layer 122A, and exposes the end face EF1 of the core 122B at the boundary between the first portion P1 and the second portion P2.

[0110] Subsequently, grooves GR are formed in the second portion P2 of the first cladding layer 122A. The grooves GR can be formed by, for example, router processing, laser ablation, dry etching, or photolithography.

[0111] The first cladding layer 122A may be a multilayer structure including a continuous film and a patterned film provided thereon. In this case, if the core 122B and the second cladding layer 122C are formed only on the patterned film, the removal process described above is unnecessary.

[0112] Next, the assembled substrate is divided into multiple individual substrates with optical waveguides. Specifically, dicing is performed along the dicing lines. In this way, the substrate 12A with optical waveguides is obtained.

[0113] <1.4.3> Manufacturing method of composite substrates The composite substrate 10A is manufactured, for example, by the following method. Specifically, first, adhesive is applied to the second region R2 of the wiring board 11A. Next, the substrate 12A with optical waveguides is placed on the adhesive layer. Subsequently, the adhesive is cured. This results in a composite substrate 10A in which the substrate 12A with optical waveguides is fixed to the wiring board 11A via the adhesive layer 13.

[0114] <1.4.4> Method for manufacturing a photoelectric fusion device The photoelectric fusion device 1A is manufactured, for example, by the following method. Specifically, first, the first functional device 20 and the second functional device 30 are flip-chip mounted onto the composite substrate 10A. Next, preferably, their joints are sealed. For example, an underfill agent is injected between the composite substrate 10A and the first functional device 20, and between the composite substrate 10A and the second functional device 30, and cured to form an underfill layer. As the underfill agent, for example, a thermosetting epoxy resin is used. Note that the underfill agent is injected in a manner that prevents it from flowing between the end face EF1 of the core 122B and the first functional device 20. In this way, the photoelectric fusion apparatus 1A is obtained.

[0115] <1.5> Effect As described above, in the photoelectric fusion apparatus 1A, the surface of the optical waveguide substrate 12A on which the optical waveguide layer 122 is provided has a groove GR. In this case, compared to the case where the groove GR is not provided, when cleaning liquid is flowed from above the photoelectric fusion apparatus 1A into the narrow gap between the first functional device 20 and the optical waveguide substrate 12A, the cleaning liquid can flow more easily. This improves the cleanability of the end faces of the optical waveguide (i.e., the end face EF1 of the core 122B of the optical waveguide layer 122 of the optical waveguide substrate 12A and the end face EF2 of the core 21 of the optical waveguide of the first functional device 20), and reduces the loss of optical signals.

[0116] Furthermore, in the above-described photoelectric integration device 1A, a composite substrate 10A is formed by a wiring board 11A and a substrate with an optical waveguide 12A. Therefore, for example, by employing a low-cost manufacturing configuration for the wiring board 11A and using a substrate 121 with a smooth surface for the substrate with an optical waveguide 12A, an optical waveguide with excellent optical performance can be obtained.

[0117] This effect can be obtained even when the surface on which the optical waveguide substrate 12A is mounted on the wiring board 11A is substantially flat. However, in this case, in order to optically couple the first functional device 20 and the core 122B, the height of the bonding conductor 14 that connects the first functional device 20 and the wiring board 11A must be extremely large. It is difficult to form a bonding conductor 14 with such a large height with high dimensional accuracy. Furthermore, a photoelectric fusion device 1A in which the bonding conductor 14 has a large height has poor connection reliability between the first functional device 20 and the wiring board 11A.

[0118] In the composite substrate 10A, as described above, the height of the second region R2 is lower than the underside of the conductor pattern 113 located in the first region R1, i.e., the uppermost conductor pattern 113. When this configuration is adopted, the position of the core 122B can be lowered compared to the case where the surface on which the optical waveguide substrate 12A is mounted on the wiring substrate 11A is substantially flat. Therefore, the first functional device 20 and the core 122B can be optically coupled without increasing the height of the bonding conductor 14 that connects the first functional device 20 and the wiring substrate 11A to each other. In other words, by adopting the above configuration, optical coupling and electrical connection can be easily performed when mounting a functional device on a composite substrate including a conductor pattern and an optical waveguide.

[0119] Furthermore, by adopting the above-described configuration, the joining conductor 14 can be formed with high dimensional accuracy. In addition, the photoelectric integration device 1A employing the above-described configuration exhibits excellent connection reliability between the first functional device 20 and the wiring board 11A.

[0120] <1.6> Variant The above-described photoelectric fusion device 1A is capable of various modifications.

[0121] Figure 8 is a cross-sectional view showing a modified example of the substrate with an optical waveguide shown in Figures 3 and 4. The optical waveguide substrate 12B shown in Figure 8 may be used in place of the optical waveguide substrate 12A of the photoelectric fusion apparatus 1A described above. The optical waveguide substrate 12B shown in Figure 8 is the same as the optical waveguide substrate 12A shown in Figures 3 and 4, except for the following point. That is, in the optical waveguide substrate 12A, the bottom surface of the groove GR is covered by the first cladding layer 122A, whereas in the optical waveguide substrate 12B, the bottom surface of the groove GR is not covered by the first cladding layer 122A. In other words, in the optical waveguide substrate 12A, the bottom surface of the groove GR is part of the upper surface of the second portion P2 of the first cladding layer 122A, whereas in the optical waveguide substrate 12B, the bottom surface of the groove GR is part of the upper surface of the substrate 121.

[0122] Comparing the optical waveguide substrate 12A and the optical waveguide substrate 12B, in the optical waveguide substrate 12A, the bottom surface of the groove GR is covered by the first cladding layer 122A, so the substrate 121 can be protected by the first cladding layer 122A at the bottom surface of the groove GR. Also, in the optical waveguide substrate 12A, the entire top surface of the substrate 121 is covered by the first cladding layer 122A, so the surface of the flow path for the cleaning liquid can be made a surface with uniform affinity to the cleaning liquid, and the ease of flow of the cleaning liquid can be kept constant. On the other hand, in the optical waveguide substrate 12B, the bottom surface of the groove GR is not covered by the first cladding layer 122A, so a deeper groove GR can be formed.

[0123] Figure 9 is a cross-sectional view showing a modified example of the photoelectric fusion apparatus shown in Figures 5 and 6. The photoelectric fusion apparatus 1A2 shown in Figure 9 is the same as the photoelectric fusion apparatus 1A described above, except for the following: The photoelectric fusion apparatus 1A2 further includes a refractive index adjusting agent layer RIL. The refractive index adjusting agent layer RIL is provided between the end face EF1 of the core 122B of the optical waveguide layer 122 of the optical waveguide substrate 12A and the end face EF2 of the core 21 of the optical waveguide of the first functional device 20.

[0124] The refractive index adjusting agent layer RIL consists of a material having a refractive index approximately equal to that of the high refractive index material used in core 122B and core 21. For example, the refractive index adjusting agent layer RIL consists of a cured resin having a refractive index approximately equal to that of the high refractive index material used in core 122B and core 21. By providing the refractive index adjusting agent layer RIL, the loss of optical signals can be reduced.

[0125] The refractive index adjusting agent layer (RIL) can be formed, for example, by the following procedure. The refractive index adjusting agent liquid is dropped from above the photoelectric fusion apparatus 1A2 into the narrow gap between the first functional device 20 and the substrate 12A with the optical waveguide, filling this gap with the refractive index adjusting agent liquid. This refractive index adjusting agent liquid is then cured, and any uncured portions are removed by washing. This allows the refractive index adjusting agent layer (RIL) to be formed as shown in Figure 9. Alternatively, the refractive index adjusting agent liquid may be injected into the groove GR from the side of the photoelectric fusion apparatus 1A2, and ejected from below to above the narrow gap between the first functional device 20 and the substrate 12A with the optical waveguide, filling this gap with the refractive index adjusting agent liquid.

[0126] In the photoelectric fusion apparatus 1A2, the surface of the optical waveguide substrate 12A on which the optical waveguide layer 122 is provided has grooves GR. Thanks to these grooves GR, whether the refractive index adjusting agent liquid is dropped into the narrow gap between the first functional device 20 and the optical waveguide substrate 12A from above the photoelectric fusion apparatus 1A2 and applied to this gap, or whether the refractive index adjusting agent liquid is applied to the narrow gap from the side of the photoelectric fusion apparatus 1A2 via grooves GR, the refractive index adjusting agent liquid flows easily and is easy to apply to the narrow gap.

[0127] Figure 10 is a top view of a photoelectric fusion apparatus with connectors, including the photoelectric fusion apparatus shown in Figures 5 and 6. The photoelectric fusion apparatus 1AC with connector shown in Figure 10 is the same as the photoelectric fusion apparatus 1A described above, except for the following: the photoelectric fusion apparatus 1AC with connector further includes a connector 15. The composite substrate 10A and the connector 15 constitute the composite substrate 10AC with connector. The connector 15 is configured to allow the optical wiring 40 to be detachably connected, facilitating optical coupling between the optical wiring 40 and the core 122B.

[0128] Figure 11 is a cross-sectional view showing a modified example of the photoelectric fusion device shown in Figures 5 and 6. The photoelectric fusion apparatus 1A3 shown in Figure 11 is the same as the photoelectric fusion apparatus 1A described above, except for the following point. That is, in the photoelectric fusion apparatus 1A3, the adhesive layer 13 of the composite substrate 10A is a stress relaxation layer.

[0129] In the photoelectric integration device 1A, the majority of the conductor pattern 113 is located in the portion of the wiring board 11A corresponding to the first region R1, and the first functional device 20 and the second functional device 30 are mounted in this portion. Furthermore, the portion of the wiring board 11A corresponding to the first region R1 is thicker than the portion corresponding to the second region R2. Therefore, for example, in a situation where the wiring board 11A warps due to the heat generated by the operation of the second functional device 30, the amount of deformation in the portion of the wiring board 11A corresponding to the second region R2 is greater than the amount of deformation in the portion of the wiring board 11A corresponding to the first region R1.

[0130] In the photoelectric integration device 1A, the first functional device 20 is fixed to the portion of the wiring board 11A corresponding to the first region R1 via a bonding conductor 14, and the electrical connection between the first functional device 20 and the wiring board 11A is not impaired by the aforementioned warping. However, if an adhesive layer 13 with a small stress relaxation effect is used, the aforementioned warping will also cause warping in the substrate 12A with the optical waveguide, and as a result, the optical axis between the first functional device 20 and the core 122B may be misaligned.

[0131] If the adhesive layer 13 is a stress relaxation layer, even if the wiring substrate 11A warps, the substrate 12A with the optical waveguide will not warp significantly as a result. Therefore, the photoelectric fusion device 1A3 is less likely to experience optical axis misalignment due to the warping of the wiring substrate 11A, and consequently, is less likely to experience increased optical coupling loss or loss of optical coupling due to this optical axis misalignment.

[0132] In this configuration, the stress relaxation layer is provided between the second region R2 and the end of the optical waveguide substrate 12A that is closer to the center of the wiring substrate 11A, but not between the second region R2 and the end of the optical waveguide substrate 12A that is further from the center of the wiring substrate 11A. This structure is advantageous in reducing the warping of the optical waveguide substrate 12A.

[0133] The stress relaxation layer may be provided over the entire area between the second region R2 and the optical waveguide substrate 12A. This structure is advantageous for securely fixing the optical waveguide substrate 12A to the wiring board 11A.

[0134] The elastic modulus of the stress relaxation layer is preferably in the range of 0.1 MPa to 3 GPa, and more preferably in the range of 0.3 MPa to 1 GPa. Here, "elastic modulus" is the dynamic storage modulus at 25°C. Materials with a low elastic modulus often have a significantly different coefficient of thermal expansion from the wiring board 11A, etc., and therefore, if such materials are used for the stress relaxation layer, the warping of the optical waveguide substrate 12A may not be sufficiently suppressed. If materials with a high elastic modulus are used for the stress relaxation layer, the deformation of the stress relaxation layer in response to stress will be insufficient, and therefore, the warping of the optical waveguide substrate 12A may not be sufficiently suppressed.

[0135] The thickness of the stress relaxation layer is preferably in the range of 5 μm to 50 μm, and more preferably in the range of 10 μm to 40 μm. If the stress relaxation layer is made thinner, it may become difficult to securely fix the substrate 12A with the optical waveguide to the wiring substrate 11A. If the stress relaxation layer is made thicker, the thickness of the composite substrate 10A increases.

[0136] <2> Second Embodiment Figure 12 is a top view of a composite substrate according to a second embodiment of the present invention.

[0137] The composite substrate 10C shown in Figure 12 is the same as the composite substrate 10A described above, except for the following: The composite substrate 10C includes a wiring board 11B instead of a wiring board 11A. The wiring board 11B is the same as the wiring board 11A described above, except for the following: The first surface S1 has four second regions R2. These second regions R2 are arranged so as to be adjacent to each of the four edges of the first surface S1. And, four optical waveguide substrates 12A are arranged in each of these four second regions R2.

[0138] Figure 13 is a top view of the photoelectric fusion apparatus with connectors, including the composite substrate shown in Figure 12. The photoelectric fusion apparatus with connectors 1CC shown in Figure 13 is the same as the photoelectric fusion apparatus with connectors 1AC, except for the following: The photoelectric fusion apparatus with connectors 1CC includes a composite substrate 10C instead of a composite substrate 10A. Four first functional devices 20 are mounted on the composite substrate 10C. Each of these first functional devices 20 is electrically connected to a second functional device 30 via a wiring board 11B. Four connectors 15 are also attached to the composite substrate 10C. The composite substrate 10C and the connectors 15 constitute the composite substrate with connectors 10CC.

[0139] In the second embodiment, the same effects as in the first embodiment can be obtained. Furthermore, as shown in the second embodiment, the number of first functional devices included in the photoelectric fusion device may be two or more.

[0140] <3> Third Embodiment Figure 14 is a top view of a composite substrate according to a third embodiment of the present invention. Figure 15 is a cross-sectional view of the composite substrate shown in Figure 14 along the line XV-XV.

[0141] The composite substrate 10D shown in Figures 14 and 15 is the same as the composite substrate 10A, except for the following: the composite substrate 10D includes a wiring substrate 11C and an optical waveguide substrate 12C instead of the wiring substrate 11A and the optical waveguide substrate 12A.

[0142] The wiring board 11C is the same as the wiring board 11A, except for the following: the wiring board 11C is configured to mount two first functional devices 20 and two second functional devices 30. The second region R2 is provided between the region on which one second functional device 30 is to be mounted and the region on which the other second functional device 30 is to be mounted.

[0143] The optical waveguide substrate 12C is the same as the optical waveguide substrate 12A, except as follows: In the optical waveguide substrate 12C, the first cladding layer 122A has two smaller second portions P2. The thicker first portion P1 of the first cladding layer 122A is interposed between the two second portions P2. The second cladding layer 122C covers the first portion P1 of the first cladding layer 122A without covering the second portions P2 of the first cladding layer 122A. Each of the cores 122B is interposed between the first portion P1 of the first cladding layer 122A and the second cladding layer 122C and extends in the direction of the arrangement of the second portions P2. The optical waveguide substrate 12C is placed in the second region R2 such that the length direction of the cores 122B coincides with the direction of the arrangement of the area on which the two second functional devices 30 are to be mounted.

[0144] Figure 16 is a top view of the photoelectric fusion apparatus including the composite substrate shown in Figures 14 and 15. Figure 17 is a cross-sectional view of the photoelectric fusion apparatus shown in Figure 16 along the line XVII-XVII.

[0145] The photoelectric fusion apparatus 1D shown in Figures 16 and 17 is the same as the photoelectric fusion apparatus 1A, except for the following: the photoelectric fusion apparatus 1D includes a composite substrate 10D instead of composite substrate 10A. Also, in the photoelectric fusion apparatus 1D, the number of first functional devices 20 is 2, and the number of second functional devices 30 is also 2.

[0146] In the third embodiment, the same effects as in the first embodiment can be obtained. Furthermore, as shown in the third embodiment, the number of first functional devices included in the photoelectric fusion device may be two or more, and the number of second functional devices included in the photoelectric fusion device may also be two or more. Also, as shown in the third embodiment, instead of optically coupling the optical waveguide layer 122 to the first functional device and the optical wiring, it may optically couple to a plurality of first functional devices.

[0147] <4> Fourth Embodiment <4.1> Composite substrate Figure 18 is a top view of a composite substrate according to a fourth embodiment of the present invention. Figure 19 is a cross-sectional view of the composite substrate shown in Figure 18 along the line XIX-XIX. Figure 20 is a top view of a substrate with an optical waveguide included in the composite substrates shown in Figures 18 and 19. Figure 21 is a cross-sectional view of the substrate with an optical waveguide shown in Figure 20.

[0148] The composite substrate 10E shown in Figures 18 and 19 is the same as the composite substrate 10A described above, except that it includes a wiring board 11E instead of a wiring board 11A, and includes a substrate with an optical waveguide 12E instead of a substrate with an optical waveguide 12A.

[0149] Specifically, the wiring board 11E is the same as the wiring board 11A, except for the following: The wiring board 11E omits the conductor pattern 113 for electrical connection with the first functional device 20, and the through-holes provided in the insulating layer 114 to expose it.

[0150] Furthermore, the optical waveguide substrate 12E is the same as the optical waveguide substrate 12A, except for the following: The optical waveguide substrate 12E further includes a second conductor pattern 123 interposed between the substrate 121 and the optical waveguide layer 122. Hereinafter, the second conductor pattern 123 will be referred to as "conductor pattern 123". The conductor pattern 123 mediates the electrical connection between the first functional device 20 and the second functional device 30. The conductor pattern 123 is covered by a first cladding layer 122A. The first cladding layer 122A has a plurality of through holes at the location of the second portion P2, each extending to the conductor pattern 123.

[0151] The conductor pattern 123 is a wiring layer that includes a lead layer. The conductor pattern 123 may have a single-layer structure or a multi-layer structure. The lead layer is made of a metallic material such as copper. Each of the conductor patterns 123 may further include one or more other layers, such as an adhesion layer and a seed layer. Here, the number of conductor patterns 123 is 2, but it may be 1 or 3 or more.

[0152] Each of the conductor patterns 123 has a rectangular shape extending in the longitudinal direction of the substrate 121. These conductor patterns 123 are arranged in the width direction of the substrate 121. The shape and arrangement of the conductor patterns 123 can be arbitrarily set.

[0153] Here, each of the conductor patterns 123 consists of a wiring that includes two pad sections and one wiring section. Each wiring section has one end connected to one of the pad sections and the other end connected to the other pad section. In each of the conductor patterns 123, the two pad sections are arranged in the longitudinal direction of the substrate 121.

[0154] The through-holes in the first cladding layer 122A are provided at the locations of the pad portions included in the conductor pattern 123. Specifically, two of the four through-holes in the first cladding layer 122A are located above the two pad portions included in one of the two conductor patterns 123, and these two through-holes are aligned in the longitudinal direction of the substrate 121. The remaining two of the four through-holes in the first cladding layer 122A are located above the two pad portions included in the other conductor pattern 123. These two through-holes are aligned in the longitudinal direction of the substrate 121. A portion of the upper surface of the conductor pattern 123 is exposed at the locations of the through-holes.

[0155] <4.2> Photoelectric fusion device Figure 22 is a top view of the photoelectric fusion apparatus including the composite substrate shown in Figures 18 and 19. Figure 23 is a cross-sectional view of the photoelectric fusion apparatus shown in Figure 22 along the line XXIII-XXIII.

[0156] The photoelectric fusion apparatus 1E shown in Figures 22 and 23 is the same as the photoelectric fusion apparatus 1A described above, except that it includes a composite substrate 10E instead of composite substrate 10A, and the electrical connection between the first functional device 20 and the second functional device 30 is made via a conductor pattern (second conductor pattern) 123 instead of via a conductor pattern (first conductor pattern) 113.

[0157] <4.3> Effects In the fourth embodiment, the same effects as in the first embodiment can be obtained. Furthermore, in the composite substrate 10E, as described above, the first functional device 20 is mounted on the substrate 12E with an optical waveguide. This structure is advantageous in that it makes it difficult for optical axis misalignment to occur between the first functional device 20 and the core 122B, for example, when the wiring substrate 11E warps. .

[0158] In other words, for example, in a situation where the wiring board 11E warps due to heat generated by the operation of the second functional device 30, the optical waveguide substrate 12E experiences less deformation due to warping compared to the wiring board 11E. Therefore, by adopting the above structure, it is possible to reduce the likelihood of optical axis misalignment due to warping of the wiring board 11A compared to the case where the first functional device 20 is mounted on the portion of the wiring board 11E corresponding to the first region R1. Thus, in the composite substrate 10E, it is less likely to increase optical coupling loss or lose optical coupling due to optical axis misalignment.

[0159] Thus, the photoelectric integration device 1E employing the above-described configuration exhibits excellent connection reliability between the first functional device 20 and the wiring board 11E.

[0160] <4.4> Variant The above-described photoelectric fusion device 1E is capable of various modifications.

[0161] For example, in the photoelectric fusion apparatus 1E, the bottom surface of the groove GR provided on the optical waveguide substrate 12E is covered with the first cladding layer 122A. However, as shown in Figure 8, the bottom surface of the groove GR does not necessarily have to be covered with the first cladding layer 122A.

[0162] Furthermore, in the photoelectric fusion apparatus 1E, a refractive index adjusting agent layer RIL may be provided between the end face EF1 of the core 122B of the optical waveguide layer 122 of the optical waveguide substrate 12E and the end face EF2 of the core 21 of the optical waveguide of the first functional device 20, as shown in Figure 9.

[0163] Alternatively, a photoelectric fusion device with a connector may be obtained by providing the photoelectric fusion device 1E with a connector similar to the connector 15 described above for the photoelectric fusion device 1AC.

[0164] Furthermore, the photoelectric fusion apparatus 1E may be provided with the stress relaxation layer described above between the wiring board 11E and the optical waveguide substrate 12E. In the photoelectric fusion apparatus 1E, as described above, even if the wiring board 11E warps, it is less likely that an optical axis misalignment will occur between the first functional device 20 and the core 122B. If a stress relaxation layer is provided in the photoelectric fusion apparatus 1E, even if the wiring board 11E warps, it becomes possible to more effectively suppress the large warping of the optical waveguide substrate 12E that occurs as a result. Therefore, the photoelectric fusion apparatus 1E can more effectively suppress the optical axis misalignment caused by the warping of the wiring board 11E, and consequently, it is less likely that an increase in optical coupling loss or loss of optical coupling will occur due to this optical axis misalignment.

[0165] Furthermore, the optical waveguide substrate 12E1 shown in Figure 24 may be used in place of the optical waveguide substrate 12E of the photoelectric integration device 1E. Figure 24 is a top view showing a modified example of the optical waveguide substrate shown in Figures 20 and 21. The optical waveguide substrate 12E1 shown in Figure 24 is the same as the optical waveguide substrate 12E except for the following: In the optical waveguide substrate 12E1, the conductor pattern 123 includes alignment marks 124 in addition to rectangular wiring on which a portion of the top surface is exposed at the location of the through-hole.

[0166] The alignment marks 124 are provided on the substrate 121 and covered by the first cladding layer 122A. The alignment marks 124 can be formed in the same manner as the method for forming the conductor pattern 123, for example, in the same process as the process for forming the rectangular wiring described above. In this case, the alignment marks 124 can be formed without adding any new steps.

[0167] By forming alignment marks 124 on the substrate 121, it becomes easier to achieve high positional accuracy in the manufacturing of the optical waveguide substrate 12E or the photoelectric integration device 1E. Specifically, by using the alignment marks 124 for alignment, it becomes easier to form the core 122B with high positional accuracy and to form through holes with high positional accuracy. Furthermore, by using the alignment marks 124 for alignment, it becomes easier to mount the first functional device 20 onto the optical waveguide substrate 12E with high positional accuracy.

[0168] The shape, number, and arrangement of the alignment marks 124 can be set arbitrarily. Here, the alignment marks 124 consist of a total of three marks: two marks arranged in the longitudinal direction of the substrate 121, and two marks arranged in the width direction of the substrate 121, including one of the two marks mentioned above. These alignment marks 124 have a cross shape.

[0169] The alignment marks 124 can be any geometric shape, including the cross shape shown in Figure 24, as well as squares, triangles, dots, star shapes, and more. Furthermore, the number of alignment marks 124 is not limited to the three shown in Figure 24; there may be four or more.

[0170] <5> Variation Various modifications are possible to the composite substrate and photoelectric integration device described above. For example, the configurations adopted in the embodiments and modifications described above may be combined as appropriate.

[0171] For example, in the photoelectric fusion apparatus 1A2 (Figure 9), the photoelectric fusion apparatus 1AC with connector (Figure 10), the photoelectric fusion apparatus 1A3 (Figure 11), the composite substrate 10C (Figure 12), the photoelectric fusion apparatus 1CC with connector (Figure 13), the composite substrate 10D (Figures 14 and 15), and the photoelectric fusion apparatus 1D (Figures 16 and 17), the groove GR configuration shown in Figure 8, that is, the groove GR configuration in which the bottom surface is not covered by the first cladding layer 122A, may be adopted.

[0172] In another example, a refractive index adjusting layer RIL may be provided in the photoelectric fusion apparatus 1AC with connector (Figure 10), photoelectric fusion apparatus 1A3 (Figure 11), composite substrate 10C (Figure 12), photoelectric fusion apparatus 1CC with connector (Figure 13), composite substrate 10D (Figures 14 and 15), and photoelectric fusion apparatus 1D (Figures 16 and 17).

[0173] In yet another example, in the photoelectric fusion apparatus with connector 1AC (Figure 10), composite substrate 10C (Figure 12), photoelectric fusion apparatus with connector 1CC (Figure 13), composite substrate 10D (Figures 14 and 15), and photoelectric fusion apparatus 1D (Figures 16 and 17), the adhesive layer 13 may be used as a stress relaxation layer. [Explanation of symbols]

[0174] 1A...Photoelectric fusion device, 1A2...Photoelectric fusion device, 1A3...Photoelectric fusion device, 1AC...Photoelectric fusion device with connector, 1CC...Photoelectric fusion device with connector, 1D...Photoelectric fusion device, 1E...Photoelectric fusion device, 10A...Composite substrate, 10AC...Composite substrate with connector, 10C...Composite substrate, 10CC...Composite substrate with connector, 10D...Composite substrate, 10E...Composite substrate, 11A...Wiring board, 11B...Wiring board, 11C...Wiring board, 11E...Wiring board, 12A...Substrate with optical waveguide, 12B...Substrate with optical waveguide, 12C...Substrate with optical waveguide, 12E...Substrate with optical waveguide, 12E1...Substrate with optical waveguide, 13...Adhesive layer, 1 4...Joining conductor, 15...Connector, 20...First functional device, 21...Core, 30...Second functional device, 40...Optical wiring, 111...Core insulating layer, 112...Insulating layer, 113...Conductor pattern (first conductor pattern), 114...Insulating layer, 121...Substrate, 122...Optical waveguide layer, 122A...First cladding layer, 122B...Core, 122C...Second cladding layer, 123...Conductor pattern (second conductor pattern), EF1...End face, EF2...End face, GR...Groove, P1...First part, P2...Second part, R1...First region, R2...Second region, R3...Third region, R4...Fourth region, RIL...Refractive index adjusting layer, S1...First surface, S2...Second surface.

Claims

1. A wiring board comprising one or more insulating layers and one or more first conductor patterns, having a first surface and a second surface which is its back surface, wherein the first surface comprises one or more first regions and one or more second regions which are recessed from the one or more first regions, one of the one or more first conductor patterns is located in the one or more first regions, and the height of the one or more second regions is lower than the lower surface of the first conductor pattern located in the one or more first regions, A substrate comprising a substrate and an optical waveguide layer provided thereon, wherein each optical waveguide layer comprises a first cladding layer provided on the substrate, a second cladding layer provided on the first cladding layer, and one or more cores provided between the first cladding layer and the second cladding layer, wherein the optical waveguide layers are each placed on the one or more second regions such that they are located above the substrate, and the height of the lower surface of the one or more cores is higher than that of the one or more first regions, and Equipped with, At least one of the one or more optical waveguide substrates is a composite substrate on which the surface on which the optical waveguide layer is provided includes a third region on which the second cladding layer is provided and a fourth region on which the second cladding layer is not provided, the fourth region has a groove extending along the boundary between the third region and the fourth region, and the one or more cores have end faces adjacent to the space above the groove, and a first functional device that is optically coupled to at least one of the one or more optical waveguide substrates by butt coupling and a second functional device that is electrically connected to the first functional device are mounted.

2. The composite substrate according to claim 1, wherein the depth of the groove is in the range of 20 μm or more and 50 μm or less.

3. The composite substrate according to claim 1, wherein the width of the groove is within the range of 20 μm or more and 200 μm or less.

4. The composite substrate according to claim 1, wherein the upper surface of the substrate is recessed at the position of the groove, corresponding to the groove.

5. A wiring board comprising one or more insulating layers and one or more first conductor patterns, having a first surface and a second surface which is the back surface thereof, wherein the first surface comprises one or more first regions and one or more second regions which are recessed from the one or more first regions, one of the one or more first conductor patterns is located in the one or more first regions, and the height of the one or more second regions is lower than the lower surface of the first conductor pattern located in the one or more first regions, A substrate comprising a substrate and an optical waveguide layer provided thereon, wherein each optical waveguide layer comprises a first cladding layer provided on the substrate, a second cladding layer provided on the first cladding layer, and one or more cores provided between the first cladding layer and the second cladding layer, wherein the optical waveguide layers are each placed on the one or more second regions such that they are located above the substrate, and the height of the lower surface of the one or more cores is higher than that of the one or more first regions, and Equipped with, At least one of the one or more optical waveguide substrates has a surface on which the optical waveguide layer is provided that includes a third region on which the second cladding layer is provided and a fourth region on which the second cladding layer is not provided, the fourth region having a groove extending along the boundary between the third region and the fourth region, and the one or more cores having an end face adjacent to the upper space of the groove. In at least one of the one or more optical waveguide substrates, the first cladding layer is a composite substrate comprising a first portion provided in the third region and a second portion provided in the fourth region.

6. The composite substrate according to claim 5, wherein the bottom surface of the groove is part of the upper surface of the second portion.

7. The composite substrate according to claim 5, wherein the bottom surface of the groove is part of the upper surface of the substrate.

8. The composite substrate according to claim 1, wherein the height of the upper surface of the substrate is lower than the height of the one or more first regions.

9. The composite substrate according to claim 1, wherein the lower surface of the one or more cores has a height of 100 μm or less with respect to the one or more first regions.

10. The composite substrate according to claim 1, further comprising one or more stress relaxation layers interposed between the one or more optical waveguide substrates and the one or more second regions.

11. The composite substrate according to claim 10, wherein each of the one or more stress relaxation layers has an elastic modulus in the range of 0.1 MPa to 3 GPa.

12. The composite substrate according to claim 10, wherein each of the one or more stress relaxation layers has a thickness within the range of 5 μm to 50 μm.

13. A wiring board comprising one or more insulating layers and one or more first conductor patterns, having a first surface and a second surface which is the back surface thereof, wherein the first surface comprises one or more first regions and one or more second regions which are recessed from the one or more first regions, one of the one or more first conductor patterns is located in the one or more first regions, and the height of the one or more second regions is lower than the lower surface of the first conductor pattern located in the one or more first regions, A substrate comprising a substrate and an optical waveguide layer provided thereon, wherein each optical waveguide layer comprises a first cladding layer provided on the substrate, a second cladding layer provided on the first cladding layer, and one or more cores provided between the first cladding layer and the second cladding layer, wherein the optical waveguide layers are each placed on the one or more second regions such that they are located above the substrate, and the height of the lower surface of the one or more cores is higher than that of the one or more first regions, and Equipped with, At least one of the one or more optical waveguide substrates has a surface on which the optical waveguide layer is provided that includes a third region on which the second cladding layer is provided and a fourth region on which the second cladding layer is not provided, the fourth region having a groove extending along the boundary between the third region and the fourth region, and the one or more cores having an end face adjacent to the upper space of the groove. At least one of the one or more optical waveguide substrates further includes a second conductor pattern provided between the substrate and the optical waveguide layer, A composite substrate comprising each of the at least one optical waveguide substrates further including the second conductor pattern, wherein the second cladding layer is provided such that a portion of the upper surface of the first cladding layer is exposed, and the exposed portion is provided with a plurality of through holes, each extending to the second conductor pattern.

14. The composite substrate according to claim 1, wherein the one or more insulating layers include an insulating resin layer, and the substrate includes a glass substrate.

15. The composite substrate according to claim 1, which is an interposer.

16. A composite substrate according to any one of claims 5 to 7 and 13, A first functional device mounted on the composite substrate and optically coupled to at least one of the one or more optical waveguide substrates by butt coupling, A second functional device mounted on the composite substrate and electrically connected to the first functional device, A photoelectric fusion device equipped with [a specific feature].

17. The photoelectric fusion apparatus according to claim 16, further comprising a refractive index adjusting agent layer having a portion interposed between the first functional device and at least one of the one or more optical waveguide substrates.

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