Optical waveguide device and optical waveguide-mounted substrate

Abstract

To provide an optical waveguide device that can be easily mounted on an interconnect substrate.SOLUTION: An optical waveguide device comprises a silicon photonic chip in which a silicon waveguide and an electrode are provided on a side of a main surface, and an optical waveguide laminated on the main surface of the silicon photonic chip. The optical waveguide includes: a core layer optically coupled to the silicon waveguide; a cladding layer having a first surface and a second surface opposite the first surface, the first surface being in contact with the main surface, the cladding layer covering at least part of the core layer; and a through interconnect penetrating the cladding layer and having one end surface connected to the electrode and another end surface exposed at the second surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical waveguide device and an optical waveguide mounted substrate. [Background technology]

[0002] In data centers and other locations where various computers and devices for data communication are installed, optical signals are transmitted and received using optical waveguide devices having silicon photonics chips and optical waveguides. In such optical waveguide devices, a core layer of the optical waveguide is optically coupled to the silicon waveguide of the silicon photonics chip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 014720 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned optical waveguide device, the core layer of the optical waveguide needs to be covered with a cladding layer, while the electrodes of the silicon photonics chip need to be exposed, so no layer is provided to cover the electrodes. In other words, there is a step between the bottom surface of the optical waveguide and the electrode formation surface of the silicon photonics chip. Therefore, it cannot be easily mounted on a wiring board.

[0005] The present invention has been made in view of the above-mentioned points, and has an object to provide an optical waveguide device that can be easily mounted on a wiring board. [Means for solving the problem]

[0006] This optical waveguide device has a silicon photonics chip having a silicon waveguide and an electrode on a main surface side, and an optical waveguide stacked on the main surface of the silicon photonics chip, wherein the optical waveguide has a core layer optically coupled to the silicon waveguide, a clad layer having a first surface and a second surface opposite to the first surface, the first surface being in contact with the main surface and covering at least a portion of the core layer, and a through wiring that penetrates the clad layer and has one end surface connected to the electrode and the other end surface exposed from the second surface. Effect of the Invention

[0007] According to the disclosed technique, it is possible to provide an optical waveguide device that can be easily mounted on a wiring board. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view illustrating an optical waveguide device according to a first embodiment. [Diagram 2] 4 is a cross-sectional view illustrating an optical waveguide device according to a modified example of the first embodiment. FIG. [Diagram 3] 11 is a cross-sectional view illustrating an optical waveguide mounted substrate according to a second embodiment. FIG. [Figure 4] 13 is a cross-sectional view illustrating an optical waveguide mounted substrate according to a modified example of the second embodiment. FIG. [Diagram 5] 11 is a cross-sectional view illustrating an optical waveguide mounted substrate according to a third embodiment. FIG. [Figure 6] 13 is a cross-sectional view illustrating an optical waveguide mounted substrate according to a modified example of the third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated explanations may be omitted.

[0010] First embodiment Fig. 1 is a cross-sectional view illustrating an optical waveguide device according to a first embodiment. Referring to Fig. 1, the optical waveguide device 1 has a silicon photonics chip 10 and an optical waveguide 20 laminated on a main surface 10a of the silicon photonics chip 10.

[0011] The silicon photonics chip 10 has a silicon substrate 11, an insulating layer 12, a silicon waveguide 13, and an electrode 14. One surface of the silicon substrate 11 is covered with the insulating layer 12. The silicon waveguide 13 and the electrode 14 are provided on the main surface 10a side of the silicon photonics chip 10.

[0012] The silicon substrate 11 has a thickness of, for example, about 100 μm to 800 μm. The silicon waveguide 13 is a fine optical waveguide, and in the example of Fig. 1, is provided on an insulating layer 12. The insulating layer 12 is, for example, SiO2 or SiO X The insulating layer 12 may have a thickness of, for example, about 2 μm to 6 μm.

[0013] 1, the silicon waveguide 13 may be embedded in the silicon substrate 11. In that case, the surface of the silicon waveguide 13 on the core layer 21 side may or may not be exposed from the silicon substrate 11.

[0014] The electrode 14 is electrically connected to an integrated circuit provided on the silicon photonics chip 10. The electrode 14 can be made of a metal such as copper or aluminum. In the example of FIG. 1, the electrode 14 is provided on the insulating layer 12, but may be embedded in the silicon substrate 11. In that case, a part of the electrode 14 is exposed from the silicon substrate 11.

[0015] The optical waveguide 20 is laminated on the main surface 10a of the silicon photonics chip 10. The optical waveguide 20 has a core layer 21, a cladding layer 22, and a through-wire .

[0016] The core layer 21 is in contact with the main surface 10a of the silicon photonics chip 10, and is optically coupled to the silicon waveguide 13. The form of optical coupling between the core layer 21 and the silicon waveguide 13 is not important. For example, the core layer 21 may be adiabatic coupled to the silicon waveguide 13, or may be directly coupled.

[0017] The width of the core layer 21 may be, for example, about 6 μm to 10 μm. The thickness of the core layer 21 may be, for example, about 6 μm to 10 μm. The refractive index of the core layer 21 is higher than the refractive index of the cladding layer 22, and may be, for example, about 1.6. The core layer 21 may be made of a photosensitive resin such as a polyimide resin, an acrylic resin, an epoxy resin, a polyolefin resin, or a polynorbornene resin. A plurality of core layers 21 may be arranged side by side on the main surface 10a of the silicon photonics chip 10.

[0018] The cladding layer 22 has a first surface 22a and a second surface 22b opposite to the first surface 22a. The first surface 22a of the cladding layer 22 is in contact with the main surface 10a of the silicon photonics chip 10. The cladding layer 22 covers at least a part of the core layer 21. In the example of FIG. 1, the cladding layer 22 covers the entire surface of the core layer 21 opposite to the main surface 10a and one end of the core layer 21 in the longitudinal direction, and the other end of the core layer 21 in the longitudinal direction is exposed from the cladding layer 22.

[0019] It is preferable that the first surface 22a of the cladding layer 22 contacts the entire main surface 10a of the silicon photonics chip 10, except for the portion covering the core layer 21. This makes it difficult for thermal stress to occur in the cladding layer 22, thereby reducing the risk of cracks occurring in the cladding layer 22 and peeling between the cladding layer 22 and the silicon photonics chip 10.

[0020] The thickness of the cladding layer 22 may be, for example, about 10 μm to 30 μm. The refractive index of the cladding layer 22 may be, for example, about 1.5. The cladding layer 22 may be formed of, for example, a material appropriately selected from the materials exemplified for the core layer 21.

[0021] The through wiring 23 penetrates the cladding layer 22, and one end surface 23a is connected to the electrode 14 of the silicon photonics chip 10, and the other end surface 23b is exposed from the second surface 22b of the cladding layer 22. For example, the area of ​​the one end surface 23a of the through wiring 23 is smaller than the area of ​​the other end surface 23b. For example, the through wiring 23 may be in the shape of a truncated cone whose diameter gradually decreases from the other end surface 23b side toward the one end surface 23a side. For example, the other end surface 23b of the through wiring 23 may be flush with the second surface 22b.

[0022] To form the through wiring 23, for example, a laser beam is irradiated from the second surface 22b side of the cladding layer 22 to form a through hole penetrating the cladding layer 22. The through hole is then filled with copper or the like to form the through wiring 23. To fill the through hole with copper or the like, for example, a semi-additive method can be used. If necessary, the second surface 22b and the other end surface 23b may be polished and flattened.

[0023] In the optical waveguide device 1, the second surface 22b of the cladding layer 22 is the mounting surface to the wiring board, but the second surface 22b does not have a step that occurs between the lower surface of the optical waveguide and the electrode formation surface of the silicon photonics chip in Patent Document 1. Therefore, it can be handled in the same way as when a normal semiconductor chip is mounted on a wiring board, and mounting on the wiring board is easy.

[0024] In addition, in Patent Document 1, the connection to the wiring board is made by soldering, so solder with a height equivalent to the step is required. Naturally, the width of the solder is also wide, so it is difficult to narrow the pitch of the electrodes of the silicon photonics chip. In contrast, the optical waveguide device 1 does not have a structure that has a step on the second surface 22b side of the cladding layer 22, which is the mounting surface. Therefore, there is no need to use high-tall and wide solder for connection to the wiring board, and the electrodes 14 can be narrowed in pitch.

[0025] Modification of the First Embodiment In the first modification of the first embodiment, an example of an optical waveguide device having an optical waveguide structure different from that of the first embodiment is shown. In the first modification of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0026] 2 is a cross-sectional view illustrating an optical waveguide device according to a modified example of the first embodiment. Referring to FIG. 2, the optical waveguide device 1A is different from the optical waveguide device 1 in that a part of the lower surface 21b of the core layer 21 opposite to the main surface 10a of the silicon photonics chip 10 is exposed from the cladding layer 22.

[0027] In this manner, a part of the lower surface 21b of the core layer 21 may be exposed from the cladding layer 22. This makes it possible to use a part of the lower surface 21b of the core layer 21 for optical coupling with another waveguide or the like.

[0028] In the optical waveguide device 1A, a step exists at the boundary between the second surface 22b of the cladding layer 22 and the lower surface 21b of the core layer 21. However, unlike Patent Document 1, the step does not exist in the direction in which the electrodes are recessed, and the other end surface 23b of the through wiring 23 is located below the lower surface 21b, so that there is little adverse effect when the device is mounted on a wiring board.

[0029] Second Embodiment In the second embodiment, an example of an optical waveguide mounted substrate on which the optical waveguide device according to the first embodiment is mounted will be described. In the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0030] Fig. 3 is a cross-sectional view illustrating an optical waveguide mounted substrate according to the second embodiment. Referring to Fig. 3, the optical waveguide mounted substrate 2 has an optical waveguide device 1 and a wiring substrate 30 having a connection terminal 32 on one side.

[0031] The wiring board 30 has an insulating layer 31, and the connection terminals 32 are disposed on the insulating layer 31. The wiring board 30 may be a rigid board having high rigidity, or a flexible board having low rigidity. The wiring board 30 is, for example, a build-up board. The wiring board 30 may be a silicon board or a ceramic board.

[0032] The optical waveguide device 1 is mounted on one side of the wiring board 30 with the optical waveguide 20 facing the connection terminal 32. The through wiring 23 of the optical waveguide device 1 is joined to the connection terminal 32 of the wiring board 30 via a joining member 40. The joining member 40 is, for example, solder.

[0033] In addition, it is preferable in terms of reliability to place an underfill resin 50 covering the bonding member 40 between the opposing surfaces of the wiring board 30 and the optical waveguide 20 .

[0034] In the optical waveguide device 1, the second surface 22b of the cladding layer 22, which is the mounting surface to the wiring board 30, is stepless, so that the optical waveguide mounting substrate 2 can be easily mounted on one side of the wiring board 30.

[0035] <Modification of the second embodiment> In the modified example of the second embodiment, an example of an optical waveguide mounted substrate on which an optical waveguide device according to the modified example of the first embodiment is mounted is shown. In the modified example of the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0036] Fig. 4 is a cross-sectional view illustrating an optical waveguide mounted substrate according to a modified example of the second embodiment. Referring to Fig. 4, an optical waveguide mounted substrate 2A has an optical waveguide device 1A and a wiring substrate 30 having a connection terminal 32 on one side. That is, it is the same as the optical waveguide mounted substrate 2, except that the optical waveguide device 1 is replaced with the optical waveguide device 1A.

[0037] In the optical waveguide device 1A, a step exists at the boundary between the second surface 22b of the cladding layer 22, which is the mounting surface to the wiring board 30, and the lower surface 21b of the core layer 21, but as described above, this has little adverse effect when mounting the optical waveguide device 1A on the wiring board 30. Therefore, the optical waveguide device 1A can be easily mounted on one side of the wiring board 30 to realize the optical waveguide mounted substrate 2A.

[0038] Third embodiment In the third embodiment, an example is shown in which a second optical waveguide device is further mounted on the optical waveguide mounting substrate according to the second embodiment. In the third embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0039] 5 is a cross-sectional view illustrating an optical waveguide mounted substrate according to the third embodiment. Referring to Fig. 5, the optical waveguide mounted substrate 2B differs from the optical waveguide mounted substrate 2 in that the optical waveguide mounted substrate 2B has a second optical waveguide device 60 mounted adjacent to the optical waveguide device 1 on one side of the wiring substrate 30.

[0040] The second optical waveguide device 60 includes a support portion 61 and an optical fiber 62 provided on the support portion 61. The support portion 61 can be made of, for example, resin. An end portion of the optical fiber 62 faces an end portion in the longitudinal direction of the core layer 21 of the optical waveguide device 1. The core layer 21 of the optical waveguide device 1 is optically coupled to the optical fiber 62.

[0041] In addition, since there is a gap of about several tens of μm between the longitudinal end of the core layer 21 and the end of the optical fiber 62, it is preferable in terms of reliability to place an optical adhesive 70 in the gap.

[0042] In the optical waveguide mounting substrate 2B, the optical waveguide device 1 and the second optical waveguide device 60 are mounted adjacent to each other on the same side of the wiring board 30, so that the optical waveguide device 1 and the second optical waveguide device 60 can be easily optically coupled.

[0043] <Modification of the third embodiment> In the third embodiment, an example is shown in which a second optical waveguide device is further mounted on the optical waveguide mounting substrate according to the modified example of the second embodiment. In the modified example of the third embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0044] Fig. 6 is a cross-sectional view illustrating an optical waveguide mounted substrate according to a modified example of the third embodiment. Referring to Fig. 6, the optical waveguide mounted substrate 2C differs from the optical waveguide mounted substrate 2A in that the optical waveguide mounted substrate 2C has a second optical waveguide device 60A mounted adjacent to the optical waveguide device 1A on one side of the wiring substrate 30.

[0045] The second optical waveguide device 60A includes a support 61, an optical fiber 62 provided on the support 61, and a second core layer 63 provided on the support 61. The second core layer 63 can be formed, for example, from the same material as the core layer 21. The support 61 can be formed, for example, from the same material as the cladding layer 22.

[0046] The second core layer 63 has a region that overlaps in a plan view with the surface of the core layer 21 exposed from the cladding layer 22. The core layer 21 is adiabatically bonded to the second core layer 63, and the second core layer 63 is directly bonded to an optical fiber.

[0047] In the optical waveguide mounting substrate 2C, the optical waveguide device 1A and the second optical waveguide device 60A are mounted adjacent to each other on the same side of the wiring board 30, so that the optical waveguide device 1A and the second optical waveguide device 60A can be easily optically coupled.

[0048] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0049] 1,1A optical waveguide device 2,2A,2B,2C Optical waveguide mounting board 10 Silicon photonics chip 10a Main surface 11 Silicon substrate 12 Insulating layer 13 Silicon Waveguide 14 electrodes 20 Optical waveguide 21 Core layer 21b Bottom side 22 Cladding layer 22a 1st page 22b 2nd side 23 Through Wiring 23a One end face 23b Other end surface 30 Wiring board 31 Insulating layer 32 Connection terminal 40 Joint materials 50 Underfill resin 60,60A 2nd optical waveguide device 61 Support part 62 Optical Fiber 63 Second Core Layer 70 Optical Adhesives

Claims

1. a silicon photonics chip having a silicon waveguide and electrodes provided on a main surface side; an optical waveguide laminated on the main surface of the silicon photonics chip; The optical waveguide is a core layer optically coupled to the silicon waveguide; a clad layer including a first surface and a second surface opposite to the first surface, the first surface being in contact with the main surface and covering at least a portion of the core layer; a through-wire that penetrates the cladding layer, has one end surface connected to the electrode, and has the other end surface exposed from the second surface.

2. The optical waveguide device according to claim 1 , wherein the first surface is in contact with the entire main surface except for a portion covering the core layer.

3. The optical waveguide device according to claim 1 , wherein the other end face is flush with the second face.

4. 3. The optical waveguide device according to claim 1, wherein one end in the longitudinal direction of the core layer is covered by the cladding layer, and the other end in the longitudinal direction of the core layer is exposed from the cladding layer.

5. The optical waveguide device according to claim 4 , wherein a portion of the surface of the core layer opposite to the main surface is exposed from the cladding layer.

6. The optical waveguide device according to claim 4 ; A wiring board having a connection terminal on one side thereof, the optical waveguide device is mounted on one side of the wiring board with the optical waveguide facing the connection terminal; The through-hole wiring is joined to the connection terminal via a joining member.

7. a second optical waveguide device mounted adjacent to the optical waveguide device on one side of the wiring board; the second optical waveguide device comprises a support portion and an optical fiber provided on the support portion; The optical waveguide mounted substrate according to claim 6 , wherein the core layer is optically coupled to the optical fiber.

8. The optical waveguide device according to claim 5 ; A wiring board having a connection terminal on one side thereof, the optical waveguide device is mounted on one side of the wiring board with the optical waveguide facing the connection terminal; The through-hole wiring is joined to the connection terminal via a joining member.

9. a second optical waveguide device mounted adjacent to the optical waveguide device on one side of the wiring board; the second optical waveguide device comprises a support portion, an optical fiber provided on the support portion, and a second core layer provided on the support portion; The optical waveguide mounted substrate according to claim 8 , wherein the core layer is adiabatically bonded to the second core layer, and the second core layer is directly bonded to the optical fiber.

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