Optical integrated circuit and optical integrated circuit module

Abstract

To provide an optical integrated circuit module which includes a heat generation structure and can maintain mechanical strength structurally, and furthermore enables improvement of efficiency of heat dissipation from the heat generation structure.SOLUTION: An optical integrated circuit according to the present invention comprises an optical waveguide which is provided on a substrate, a heat generating structure which is disposed facing the optical waveguide, wiring that is connected to the heat generating structure and feeds electricity, and an overclad layer which covers the optical waveguide, the heat generating structure and at least a connection portion in which wiring is connected to the heat generating structure, of the wiring. In the overclad layer, a substrate for coupling is disposed on the surface side on the side opposite to the optical waveguide, and the overclad layer is constituted in such a way that an under-fill material is filled in the overclad layer side reverse from the optical waveguide, and three heat dissipation structures are provided on the overclad layer between the under-fill material and the heat generating structure, and dissipate heat which is propagated when electricity is fed to the heat generating structure.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an optical integrated circuit, which is a waveguide-type optical circuit in which a heat generating structure provided in an optical waveguide formed on a Si substrate is heated and driven, and an optical integrated circuit module constructed by flip-chip mounting the same on a ceramic substrate or the like. [Background technology]

[0002] Conventionally, in a silicon photonics optical circuit, which is an example of an optical integrated circuit, a thin-film heater made of tungsten or the like is formed almost directly above a Si waveguide. As explained in Non-Patent Document 1, this thin-film heater is used to change the temperature of the Si waveguide, and the thermal-optic effect of the silicon waveguide can be used to adjust the phase of light passing through the Si waveguide.

[0003] FIG. 1 is a schematic diagram showing the basic configuration of an optical integrated circuit module 10A disclosed in Non-Patent Document 1. FIG. 1(a) is a plan view showing the optical integrated circuit module 10A from the top, with the ceramic substrate removed. FIG. 1(b) is a side cross-sectional view showing the optical integrated circuit module 10A, including the ceramic substrate 17, taken along line Ib-Ib in FIG. 1(a). FIG. 1(c) is a side cross-sectional view showing the optical integrated circuit module 10A, including the ceramic substrate 17, taken along line Ic-Ic in FIG. 1(a). In the following, a configuration in which an optical waveguide or the like is formed on a Si substrate will be considered an optical integrated circuit, and a configuration in which a ceramic substrate, an IC, or the like is mounted on an optical integrated circuit will be considered an optical integrated circuit module.

[0004] 1(a) to 1(c), in this optical integrated circuit module 10A, thin-film heaters 14a and 14b are disposed directly above a pair of optical waveguides 12a and 12b formed in a desired pattern by etching or the like on the main surface of a Si substrate 11. The thin-film heaters 14a and 14b can be considered heat-generating structures and are disposed on the main surface of the Si substrate 11 facing the optical waveguides 12a and 12b, respectively. Portions of wiring 15a and 15b are connected to both ends of the thin-film heaters 14a and 14b in the extension direction, respectively. The optical waveguides 12a and 12b, the thin-film heaters 14a and 14b, and the connection portions of the wiring 15a and 15b to the thin-film heaters 14a and 14b are covered with an overcladding layer 13 made of SiO2. It is assumed that an undercladding layer made of SiO2 is formed on the main surface of the Si substrate 11.

[0005] Bumps 18a, 18b made of Au or the like are provided on the other portions of the wirings 15a, 15b located on the surface opposite the optical waveguides 12a, 12b covered with the overcladding layer 13, providing thermally conductive connections. Furthermore, an underfill material 16 made of resin or the like is applied between the surface-side bumps 18a, 18b and wirings 15a, 15b and the main surface of the ceramic substrate 17, which is used for coupling to the silicon photonics circuit. The silicon photonics circuit includes the Si substrate 11, the optical waveguides 12a, 12b, the overcladding layer 13, the thin-film heaters 14a, 14b, and wirings 15a, 15b. The underfill material 16 is used for adhesion and fixation. This bonds the Si substrate 11 and the ceramic substrate 17. If necessary, a protective film made of SiN or the like may be provided on the surface-side portions not provided with the bumps 18a, 18b. Furthermore, the thickness of the Si substrate 11 and the ceramic substrate 17 is shown on a scale thinner than it actually is.

[0006] In this joined state, electrical continuity is possible from the conductor pattern of the ceramic substrate 17 through the bumps 18a and 18b and the wiring 15a and 15b to the thin film heaters 14a and 14b.

[0007] With this configuration, the optical integrated circuit module 10A can utilize the thermo-optic effect by supplying power to the thin-film heaters 14a and 14b to heat them and change the temperature of the optical waveguides 12a and 12b, thereby enabling the optical integrated circuit module 10A to control the refractive index of light passing through the cores of the optical waveguides 12a and 12b in a temperature-dependent manner. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Comparison of heater architectures for thermal control of silicon photonic circuits Summary of the Invention [Problem to be solved by the invention]

[0009] The optical integrated circuit module utilizing the thermo-optic effect according to Non-Patent Document 1 described above has a problem in that, when used in a state utilizing the thermo-optic effect, the surface temperature of the overcladding layer directly above the thin-film heater, which is a heat-generating structure, becomes very high. This is undesirable in terms of performance, as it causes a rise in temperature near the ceramic substrate on which electronic devices are typically mounted. In other words, the optical integrated circuit according to Non-Patent Document 1 cannot efficiently remove heat from the heat-generating structure.

[0010] In recent years, flip-chip mounting has become more common than planar mounting in order to miniaturize and integrate optical integrated circuit modules. In flip-chip mounting, reliability is generally enhanced by filling the gap between the optical integrated circuit and its bonding substrate (ceramic substrate) with a resin underfill material. However, because thin-film heaters operate at temperatures above 100°C, if heat dissipation is not performed properly, the resin may be exposed to high temperatures and deform or deteriorate. This can lead to problems such as a deterioration in adhesive strength and a loss of structural reliability in terms of mechanical strength.

[0011] The present invention has been made to solve these problems, and its object is to provide an optical integrated circuit and an optical integrated circuit module that can improve the efficiency of heat removal from a heat-generating structure while maintaining structural mechanical strength. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, one aspect of the present invention is an optical integrated circuit having an optical waveguide provided on a main surface of a substrate, a heat-generating structure arranged opposite the optical waveguide, wiring connected to the heat-generating structure to supply power, and an overclad layer covering the optical waveguide, the heat-generating structure, and at least the connection points of the wiring to the heat-generating structure, wherein the overclad layer has a bonding substrate arranged on the surface side opposite the optical waveguide and is configured to be filled with an underfill material, and has three heat dissipation structures arranged on the overclad layer and between the underfill material and the heat-generating structure, extending along the extension direction of the heat-generating structure, and dissipating heat propagated when power is supplied to the heat-generating structure. [Effects of the Invention]

[0013] By employing the configuration of one aspect of the present invention, it becomes possible to improve the efficiency of heat dissipation from the heat-generating structure while maintaining the structural mechanical strength. [Brief explanation of the drawings]

[0014] [Figure 1] 1A is a schematic diagram showing the basic configuration of an optical integrated circuit module disclosed in Non-Patent Document 1. FIG. 1A is a plan view showing the optical integrated circuit module from the top with the ceramic substrate removed. FIG. 1B is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line Ib-Ib in FIG. 1A. FIG. 1C is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line Ic-Ic in FIG. 1A. [Figure 2]1 is a schematic diagram showing the basic configuration of an optical integrated circuit module according to a first embodiment of the present invention; (a) is a plan view showing the optical integrated circuit module from above with the ceramic substrate removed; (b) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IIb-IIb in (a); (c) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IIc-IIc in (a); and (d) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IId-IId in (a). [Figure 3] 1 is a schematic diagram showing the basic configuration of an optical integrated circuit module according to a second embodiment of the present invention. (a) is a plan view showing the optical integrated circuit module from above with the ceramic substrate removed. (b) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IIIb-IIIb in (a). (c) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IIIc-IIIc in (a). (d) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IIId-IIId in (a). [Figure 4] 1 is a schematic diagram showing the basic configuration of an optical integrated circuit module according to a third embodiment of the present invention. (a) is a plan view showing the optical integrated circuit module from above with the ceramic substrate removed. (b) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IVb-IVb in (a). (c) is a side cross-sectional view showing the optical integrated circuit module including the ceramic substrate, taken along line IVc-IVc in (a). [Figure 5]10A is a schematic diagram showing the basic configuration of an optical integrated circuit module according to a fifth embodiment of the present invention; (a) is a plan view showing the optical integrated circuit module from above with the ceramic substrate removed; (b) is a side cross-sectional view showing the optical integrated circuit module in the Vb-Vb line direction of (a) in a state where it is assembled upside down, including a substrate with electronic components mounted thereon and a ceramic substrate; (c) is a side cross-sectional view showing the optical integrated circuit module in the Vc-Vc line direction of (a) in a state where it is assembled upside down, including a substrate with electronic components mounted thereon and a ceramic substrate; DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, optical integrated circuits and optical integrated circuit modules according to embodiments of the present invention will be described in detail with reference to the drawings, taking several embodiments as examples.

[0016] (Embodiment 1) FIG. 2 is a schematic diagram showing the basic configuration of an optical integrated circuit module 20A according to the first embodiment of the present invention. FIG. 2(a) is a plan view showing the optical integrated circuit 20A from above with the ceramic substrate removed. FIG. 2(b) is a side cross-sectional view showing the optical integrated circuit module 20A including the ceramic substrate 27, taken along line IIb-IIb in FIG. 2(a). FIG. 2(c) is a side cross-sectional view showing the optical integrated circuit module 20A including the ceramic substrate 27, taken along line IIc-IIc in FIG. 2(a). FIG. 2(d) is a side cross-sectional view showing the optical integrated circuit module 20A including the ceramic substrate 27, taken along line IId-IId in FIG. 2(a).

[0017] 2(a) to 2(d), in the optical integrated circuit 20A, thin-film heaters 24a and 24b are disposed directly above a pair of optical waveguides 22a and 22b formed in a required pattern by etching or the like on the principal surface of a Si substrate 21. The thin-film heaters 24a and 24b can be considered heat-generating structures and are disposed opposite the optical waveguides 22a and 22b, respectively, on the principal surface of the Si substrate 21. Portions of wiring 25a and 25b are connected to both ends of the thin-film heaters 24a and 24b in the extension direction, respectively. The optical waveguides 22a and 22b, the thin-film heaters 24a and 24b, and the connection portions of the wiring 25a and 25b to the thin-film heaters 24a and 24b are covered with an overcladding layer 23 made of SiO2. It is assumed that an undercladding layer made of SiO2 is formed on the principal surface of the Si substrate 21.

[0018] Furthermore, bumps 28a, 28b made of Au or the like, which serve as thermally conductive connection portions, are provided in other portions of the wirings 25a, 25b located on the surface opposite the optical waveguides 22a, 22b covered with the overcladding layer 23. A structural feature of this optical integrated circuit 20A is that a heat dissipation structure 29, which dissipates heat propagated when power is supplied to the thin-film heaters 24a, 24b, is provided on the surface opposite the optical waveguides 22a, 22b of the overcladding layer 23. The heat dissipation structure 29 is arranged around the thin-film heaters 24a, 24b in a non-contact manner.

[0019] The heat dissipation structure 29 is provided in the form of a single plate so as to cover most of the thin-film heaters 24a, 24b in the extension direction. Bumps 28c, which serve as connection points separate from the routing portions of the wiring 25a, 25b, are provided on the surface of the heat dissipation structure 29 opposite the optical waveguides 22a, 22b, along the extension direction of the thin-film heaters 24a, 24b. Specifically, a total of nine bumps 28c are provided, three at a time, at equal intervals along a center line, a left line, and a right line that are parallel to the extension direction of the thin-film heaters 24a, 24b.

[0020] The size of the heat dissipation structure 29 is much larger than the size of the bumps 28a, 28b, and 28c. The material of the heat dissipation structure 29 need only provide a heat dissipation effect, and can be the same material as the bumps 28a, 28b, and 28c and the wiring 25a and 25b, such as gold or aluminum. Similarly, the material of the bump 28c need only be thermally conductive, and can be the same material as the bumps 28a and 28b. The number of bumps 28c provided depends on the size of the heat dissipation structure 29, but can be any number as long as it is at least one.

[0021] Furthermore, an underfill material 26 such as a resin is applied between the surface-side portions of the bumps 28a, 28b, 28c and the wiring 25a, 25b and the main surface of the ceramic substrate 27 for coupling to the silicon photonics circuit. The silicon photonics circuit includes a Si substrate 21, optical waveguides 22a, 22b, an overclad layer 23, thin-film heaters 24a, 24b, and wiring 25a, 25b. The underfill material 26 is used for adhesion and fixation. This bonds the Si substrate 21 and the ceramic substrate 27.

[0022] The ceramic substrate 27 in the first embodiment is flip-chip mounted on the Si substrate 21, and an underfill material 26 is filled between the ceramic substrate 27 and the Si substrate 21 to bond them together. Note that a protective film made of SiN or the like may be provided as needed in areas where the bumps 28a, 28b, and 28c are not provided. The thicknesses of the Si substrate 21 and the ceramic substrate 27 are also shown on a scale thinner than they actually are.

[0023] In this bonded state, electrical continuity is established between the conductor pattern of ceramic substrate 27 and thin-film heaters 24a and 24b via wiring 25a and 25b via bumps 28a and 28b. Also, heat dissipation structure 29 is thermally connected via bump 28c, which is connected to the conductor pattern at the grounding portion of ceramic substrate 27.

[0024] With this configuration, the optical integrated circuit module 20A can utilize the thermo-optic effect by supplying power to the thin-film heaters 24a and 24b to heat them and change the temperature of the optical waveguides 22a and 22b, thereby enabling the optical integrated circuit module 20A to control the refractive index of light passing through the cores of the optical waveguides 22a and 22b in a temperature-dependent manner.

[0025] Additionally, in the case of the optical integrated circuit module 20A, the heat dissipation structure 29 provided on the surface of the overcladding layer 23, whose surface temperature increases during normal use, is connected via bumps 28c to the conductor pattern at the grounding location of the ceramic substrate 27. This promotes heat dissipation from the surface of the heat dissipation structure 29 when the temperature of the overcladding layer 23 rises due to heat generated by the thin-film heaters 24a and 24b, and the heat is further propagated to the ceramic substrate 27 via the bumps 28c. As a result, the heat dissipation properties of the surface of the overcladding layer 23 are improved, and the heat applied to the underfill material 26 is reduced. Note that, as will be the case hereinafter, heat propagation here may also be considered as heat transfer.

[0026] The optical integrated circuit module 20A according to the first embodiment can improve the efficiency of heat dissipation due to heat generated by the thin-film heaters 24a and 24b, and prevent deterioration of the adhesive strength of the underfill material 26. Furthermore, the optical integrated circuit module 20A as an interferometer can reduce thermal interference with other optical waveguides. Furthermore, when the optical integrated circuit module 20A is viewed as a multilayer optical waveguide structure, heat transfer between layers can be reduced, and the impact of heat generation on other layers can be reduced. As a result, the optical integrated circuit module 20A can improve the efficiency of heat dissipation from the heat dissipation structure while structurally maintaining mechanical strength.

[0027] (Embodiment 2) FIG. 3 is a schematic diagram showing the basic configuration of an optical integrated circuit module 30A according to a second embodiment of the present invention. FIG. 3(a) is a plan view showing the optical integrated circuit module 30A from above with the ceramic substrate removed. FIG. 3(b) is a side cross-sectional view of the optical integrated circuit module 30A, taken along line IIIb-IIIb in FIG. 3(a), including the ceramic substrate 37. FIG. 3(c) is a side cross-sectional view of the optical integrated circuit module 30A, taken along line IIIc-IIIc in FIG. 3(a), including the ceramic substrate 37. FIG. 3(d) is a side cross-sectional view of the optical integrated circuit module 30A, taken along line IIId-IIId in FIG. 3(a), including the ceramic substrate 37.

[0028] 3(a) to 3(d), this optical integrated circuit 30A differs from the optical integrated circuit 20A of the first embodiment in that it has three divided heat dissipation structures 39a, 39b, and 39c. These heat dissipation structures 39a, 39b, and 39c are arranged around the thin-film heaters 34a and 34b without contacting them. Specifically, the heat dissipation structures 39a, 39b, and 39c are provided on the surface of the overcladding layer 33 opposite the optical waveguides 32a and 32b. The rest of the structure is the same as in the optical integrated circuit 20A. It is assumed that an undercladding layer made of SiO2 is formed on the main surface of the Si substrate 31.

[0029] That is, in the optical integrated circuit 30A, thin-film heaters 34a and 34b are also disposed directly above a pair of optical waveguides 32a and 32b formed in a required pattern by etching or the like on the main surface of the Si substrate 31. The thin-film heaters 34a and 34b can be considered heat-generating structures and are disposed opposite the optical waveguides 32a and 32b, respectively, on the main surface of the Si substrate 31. Portions of wiring 35a and 35b are connected to both ends of the thin-film heaters 34a and 34b in their extension direction. The optical waveguides 32a and 32b, the thin-film heaters 34a and 34b, and the connection portions of the wiring 35a and 35b to the thin-film heaters 34a and 34b are covered with an overclad layer 33 made of SiO2. Bumps 38a, 38b made of Au or the like are provided at other portions of the wiring 35a, 35b located on the surface opposite to the optical waveguides 32a, 32b covered with the overclad layer 33, respectively, to serve as thermally conductive connection points.

[0030] The heat dissipation structures 39a, 39b, and 39c are divided into three sections and arranged to surround the thin-film heaters 34a and 34b in the extension direction. Bumps 38c made of Au or the like are arranged on the surfaces of the heat dissipation structures 39a, 39b, and 39c opposite the optical waveguides 32a and 32b along the extension direction of the thin-film heaters 34a and 34b. These bumps 38c serve as thermally conductive connection points separate from the wiring 35a and 35b. Specifically, the heat dissipation structures 39a, 39b, and 39c are arranged with three bumps 38c each at equal intervals along a middle center line, a left center line, and a right center line, each of which is parallel to the extension direction of the thin-film heaters 34a and 34b, for a total of nine bumps 38c.

[0031] Here again, the size of the heat dissipation structures 39a, 39b, and 39c is much larger than the size of the bumps 38a, 38b, and 38c. The material of the heat dissipation structures 39a, 39b, and 39c and the number of the bumps 38a, 38b, and 38c may be changed as desired.

[0032] Furthermore, an underfill material 36 such as a resin is applied between the surface-side portions of the bumps 38a, 38b, 38c and the wiring 35a, 35b and the main surface of a ceramic substrate 37 for coupling to the silicon photonics circuit. The silicon photonics circuit includes a Si substrate 31, optical waveguides 32a, 32b, an overclad layer 33, thin-film heaters 34a, 34b, and wiring 35a, 35b. The underfill material 36 is used for adhesion and fixation. This bonds the Si substrate 31 and the ceramic substrate 37.

[0033] The ceramic substrate 37 in the second embodiment is also flip-chip mounted to the Si substrate 31, and an underfill material 36 is filled between the ceramic substrate 37 and the Si substrate 31 for bonding. Note that a protective film made of SiN or the like may be provided as needed in areas where bumps 38a, 38b, and 38c are not provided. The thicknesses of the Si substrate 31 and the ceramic substrate 37 are also shown on a scale thinner than they actually are.

[0034] In this bonded state, electrical continuity is established between the conductive pattern of ceramic substrate 37 and thin-film heaters 34a and 34b via wiring 35a and 35b via bumps 38a and 38b. Also, heat dissipation structures 39a, 39b, and 39c are thermally connected to each other via bump 38c, which is connected to the conductive pattern at the grounding portion of ceramic substrate 37.

[0035] With this configuration, the optical integrated circuit module 30A can utilize the thermo-optic effect by supplying power to the thin-film heaters 34a and 34b to heat them and change the temperature of the optical waveguides 32a and 32b, thereby enabling the optical integrated circuit module 30A to control the refractive index of light passing through the cores of the optical waveguides 32a and 32b in a temperature-dependent manner.

[0036] Additionally, in the case of this optical integrated circuit module 30A, heat dissipation structures 39a, 39b, and 39c provided separately on the surface of the overcladding layer 33, whose surface temperature increases during normal use, are connected via bumps 38c to the conductor pattern at the grounding location of the ceramic substrate 37. As a result, when the temperature of the overcladding layer 33 increases due to heat generated by the thin-film heaters 34a and 34b, heat dissipation from the surfaces of the heat dissipation structures 39a, 39b, and 39c is promoted, and the heat is further propagated to the ceramic substrate 37 via the bumps 38c. As a result, the heat dissipation properties of the surface of the overcladding layer 33 are improved, and the heat applied to the underfill material 36 is reduced.

[0037] The optical integrated circuit module 30A according to the second embodiment not only achieves the same effects as the previous optical integrated circuit module 20A, but also has three divided heat dissipation structures 39a, 39b, and 39c that prevent voids from forming when the underfill material 36 is bonded. That is, the underfill material 36 flows easily in the longitudinal direction of the optical waveguides 32a and 32b when the underfill material 36 is applied, making it less likely that voids will form in the underfill material 36. If voids do not form when the underfill material 36 is bonded, the adhesion of the optical integrated circuit module 30A is improved, further improving the reliability of the mechanical strength of the bonded state and enabling improved heat dissipation.

[0038] (Embodiment 3) Fig. 4 is a schematic diagram showing the basic configuration of an optical integrated circuit module 40A according to a third embodiment of the present invention. Fig. 4(a) is a plan view showing the optical integrated circuit module 40A from above with the ceramic substrate removed. Fig. 4(b) is a side cross-sectional view showing the optical integrated circuit module 40A, including the ceramic substrate 47, taken along line IVb-IVb in Fig. 4(a). Fig. 4(c) is a side cross-sectional view showing the optical integrated circuit module 40A, including the ceramic substrate 47, taken along line IVc-IVc in Fig. 4(a).

[0039] 4(a) to 4(c), the optical integrated circuit 40A differs from the optical integrated circuit 30A of the second embodiment in the shape of the three divided heat dissipation structures 49a, 49b, and 49c and the arrangement of the bumps 48c, as described below. The heat dissipation structures 49a, 49b, and 49c are also arranged around the thin-film heaters 44a and 44b without contacting them. Specifically, the heat dissipation structures 49a, 49b, and 49c extend from the surface of the overcladding layer 43 opposite the optical waveguides 42a and 42b in the stacking direction of the overcladding layer 43, with their ends close to the Si substrate 41. The rest of the structure is substantially the same as that of the optical integrated circuit 30A. It is assumed that an undercladding layer made of SiO2 is formed on the main surface of the Si substrate 41. It is also possible to configure the heat dissipation structures 49a, 49b, and 49c so that their ends are in contact with the Si substrate 41 or are embedded therein.

[0040] That is, in the optical integrated circuit 40A, thin-film heaters 44a and 44b are also disposed directly above a pair of optical waveguides 42a and 42b formed in a required pattern by etching or the like on the main surface of a Si substrate 41. The thin-film heaters 44a and 44b can also be considered heat-generating structures, and are disposed opposite the optical waveguides 42a and 42b, respectively, on the main surface of the Si substrate 41. Portions of wiring 45a and 45b are connected to both ends of the thin-film heaters 44a and 44b in their extension direction, respectively. The optical waveguides 42a and 42b, the thin-film heaters 44a and 44b, and the connection portions of the wiring 45a and 45b to the thin-film heaters 44a and 44b are covered with an overclad layer 43 made of SiO2. Bumps 48a, 48b made of Au or the like are provided at other portions of the wiring 45a, 45b located on the surface opposite to the optical waveguides 42a, 42b covered with the overclad layer 43, respectively, to serve as thermally conductive connection points.

[0041] The heat dissipation structures 49a, 49b, and 49c are divided into three sections and arranged to surround the thin-film heaters 44a and 44b in the extension direction. Bumps 48c made of Au or the like are arranged on the surfaces of the heat dissipation structures 49a, 49b, and 49c opposite the optical waveguides 42a and 42b along the extension direction of the thin-film heaters 44a and 44b. These bumps 48c serve as thermally conductive connection points separate from the routing portions of the wiring 45a and 45b. Specifically, two bumps 48c are arranged at equal intervals on the heat dissipation structures 49a, 49b, and 49c along a middle center line, a left center line, and a right center line, each of which is parallel to the extension direction of the thin-film heaters 44a and 44b, for a total of six bumps 48c.

[0042] Here again, the size of the heat dissipation structures 49a, 49b, and 49c is much larger than the size of the bumps 48a, 48b, and 48c. The material of the heat dissipation structures 49a, 49b, and 49c and the number of the bumps 48a, 48b, and 48c may be changed arbitrarily.

[0043] Furthermore, an underfill material 46 such as a resin is applied between the front surface of the bumps 48a, 48b, 48c and the wiring 45a, 45b and the main surface of the ceramic substrate 47 for bonding to the silicon photonics circuit. The silicon photonics circuit includes a Si substrate 41, optical waveguides 42a, 42b, an overclad layer 43, thin-film heaters 44a, 44b, and wiring 45a, 45b. This bonds the Si substrate 41 and the ceramic substrate 47.

[0044] The ceramic substrate 47 in the third embodiment is also flip-chip mounted to the Si substrate 41, and the ceramic substrate 47 and the Si substrate 41 are joined together by filling an underfill material 46 between them. Note that a protective film made of SiN or the like may be provided as needed in areas where bumps 48a, 48b, and 48c are not provided. The thicknesses of the Si substrate 41 and the ceramic substrate 47 are also shown on a scale thinner than they actually are.

[0045] In this bonded state, electrical continuity is established between the conductive pattern of the ceramic substrate 47 and the thin-film heaters 44a and 44b via the wirings 45a and 45b via the bumps 48a and 48b. Also, the heat dissipation structures 49a, 49b, and 49c are thermally connected to each other via the bump 48c connected to the conductive pattern at the grounding portion of the ceramic substrate 47.

[0046] With this configuration, the optical integrated circuit module 40A can utilize the thermo-optic effect by supplying power to the thin-film heaters 44a and 44b to heat them and change the temperature of the optical waveguides 42a and 42b, thereby enabling the optical integrated circuit module 40A to control the refractive index of light passing through the cores of the optical waveguides 42a and 42b in a temperature-dependent manner.

[0047] Additionally, in the optical integrated circuit module 40A, not only is the surface of the overcladding layer 43, whose surface temperature becomes high during normal use, but divided heat dissipation structures 49a, 49b, and 49c are provided so that their ends are close to the Si substrate 41 through the interior. These heat dissipation structures 49a, 49b, and 49c are connected to the conductor pattern at the grounding portion of the ceramic substrate 47 via bumps 48c. As a result, when the temperature of the overcladding layer 43 rises due to heat generated by the thin-film heaters 44a and 44b, heat dissipation from the surfaces of the heat dissipation structures 49a, 49b, and 49c is promoted, and the heat is further propagated to the ceramic substrate 47 via the bumps 48c. As a result, the heat dissipation property of the surface of the overcladding layer 43 is better than in the optical integrated circuit module 30A, and the heat applied to the underfill material 46 is reduced.

[0048] The optical integrated circuit module 40A according to the third embodiment not only achieves the same effects as the previous optical integrated circuit module 30A, but also has three divided heat dissipation structures 39a, 39b, and 39c that are divided into three so as to extend into the overcladding layer 43 and into the Si substrate 41. This improves the heat dissipation performance of the surface of the overcladding layer 43 compared to the previous optical integrated circuit module 30A. If the ends of the heat dissipation structures 49a, 49b, and 49c are configured to contact or be embedded in the Si substrate 41, heat is dissipated toward the Si substrate 41, thereby improving the heat dissipation performance.

[0049] (Embodiment 4) Fig. 5 is a schematic diagram showing the basic configuration of an optical integrated circuit module 50A according to a fourth embodiment of the present invention. Fig. 5(a) is a plan view showing the optical integrated circuit module 50A from above with the ceramic substrate removed. Fig. 5(b) is a side cross-sectional view showing a state in which an electronic component-mounted substrate and a ceramic substrate 57 are assembled in a direction in which the optical integrated circuit module 50A is turned upside down in the Vb-Vb line direction in Fig. 5(a). Fig. 5(c) is a side cross-sectional view showing a state in which an electronic component-mounted substrate and a ceramic substrate 57 are assembled in a direction in which the optical integrated circuit module 50A is turned upside down in the Vc-Vc line direction in Fig. 5(a).

[0050] 5(a) to 5(c), this optical integrated circuit 50A has electronic devices 60, such as a driver IC and a TIA (transimpedance amplifier), mounted on a Si substrate 51. Therefore, the arrangement pattern of the optical waveguides 52a, 52b and the thin-film heaters 54a, 54b embedded in the overcladding layer 53 has been devised, and the shape and structure of the heat dissipation structure 59 have been modified to improve heat dissipation. However, as with the above-described embodiments, the heat dissipation structure 59 is also disposed around the thin-film heaters 54a, 54b without contacting them. It is assumed that an undercladding layer made of SiO2 is formed on the main surface of the Si substrate 51.

[0051] In this optical integrated circuit 50A, a base for an overcladding layer 53 is formed before waveguides 52a and 52b are formed on the main surface of a Si substrate 51, and then a heat dissipation structure bottom 59c, which becomes part of a heat dissipation structure 59, is formed on the base. Furthermore, optical waveguides 52a and 52b are formed to extend parallel to each other at selected, spaced locations on heat dissipation structure bottom 59c. Furthermore, thin-film heaters 54a and 54b are disposed directly above the optical waveguides 52a and 52b, and wiring 55a and 55b are provided to connect to the thin-film heaters 54a and 54b.

[0052] In addition, heat dissipation structure sidewalls 59a and 59b, which form the other part of the heat dissipation structure 59, are provided around the optical waveguides 52a and 52b, the thin-film heaters 54a and 54b, and the wirings 55a and 55b so as to connect to the heat dissipation structure bottom 59c. Here, the optical waveguides 52a and 52b, the thin-film heaters 54a and 54b, and the connection parts of the wirings 55a and 55b to the thin-film heaters 54a and 54b are covered with the overclad layer 53. That is, the entire heat dissipation structure bottom 59c of the heat dissipation structure 59 and most of the heat dissipation structure sidewalls 59a and 59b are covered with the overclad layer 53. The other structures are almost the same as those of the optical integrated circuit 40A.

[0053] That is, bumps 58a, 58b made of Au or the like, which serve as thermally conductive connection points, are provided on the surfaces of the wirings 55a, 55b opposite the optical waveguides 52a, 52b covered with the overcladding layer 53. Bumps 58c made of Au or the like, which serve as thermally conductive connection points separate from the wirings 55a, 55b, are provided on the surfaces of the heat dissipation structure sidewalls 59a, 59b of the heat dissipation structure 59 opposite the optical waveguides 52a, 52b, along the extension direction of the thin-film heaters 54a, 54b. Specifically, a total of six bumps 58c are provided on the heat dissipation structure sidewalls 59a, 59b of the heat dissipation structure 59, three bumps each, at equal intervals along a left-side center line and a right-side center line parallel to the extension direction of the thin-film heaters 54a, 54b.

[0054] Again, the size of each part of the heat dissipation structure 59 is much larger than the size of the bumps 58a, 58b, and 58c. The material of the heat dissipation structure 59 and the number of the bumps 58a, 58b, and 58c may be changed as desired.

[0055] Furthermore, an underfill material 56 such as a resin is applied between the surface-side portions of the bumps 58a, 58b, and 58c and the wiring 55a and 55b and the main surface of the ceramic substrate 57 for coupling to the silicon photonics circuit. The silicon photonics circuit includes a Si substrate 51, optical waveguides 52a and 52b, an overclad layer 53, thin-film heaters 54a and 54b, and wiring 55a and 55b. The underfill material 56 is used for attachment and fixation. However, as described above, the optical integrated circuit 50A is assembled upside down at this time. This bonds the Si substrate 51 and the ceramic substrate 57.

[0056] The ceramic substrate 57 in the fourth embodiment is also flip-chip mounted to the Si substrate 51, and an underfill material 56 is filled between the ceramic substrate 57 and the Si substrate 51 for bonding. A protective film made of SiN or the like may be provided as needed in areas where bumps 58a, 58b, and 58c are not provided. The thicknesses of the Si substrate 51 and the ceramic substrate 57 are also shown thinner than they actually are on the scale.

[0057] In this bonded state, multiple electronic devices 60 are mounted on the Si substrate 51, and electrical continuity is possible from the conductor pattern of the ceramic substrate 57 to the thin-film heaters 54a, 54b via the wiring 55a, 55b via the bumps 58a, 58b. Also, the heat dissipation structure sidewall portions 59a, 59b (with flattened tips) of the heat dissipation structure 59 are thermally connected via the bump 58c connected to the conductor pattern at the grounding portion of the ceramic substrate 57.

[0058] With this configuration, the optical integrated circuit module 50A can utilize the thermo-optic effect by supplying power to the thin-film heaters 54a and 54b to heat them and change the temperature of the optical waveguides 52a and 52b, thereby enabling the optical integrated circuit module 50A to control the refractive index of light passing through the cores of the optical waveguides 52a and 52b in a temperature-dependent manner.

[0059] Additionally, in the optical integrated circuit module 50A, a box-shaped heat dissipation structure 59 is provided so that most of it is embedded inside the overcladding layer 53, whose surface temperature becomes high during normal use. The heat dissipation structure sidewalls 59a and 59b of the heat dissipation structure 59 are connected to the conductor pattern at the grounding portion of the ceramic substrate 57 via the bumps 58c. This promotes heat dissipation from the surface of the heat dissipation structure sidewalls 59a and 59b of the heat dissipation structure 59 when the temperature of the overcladding layer 53 increases due to heat generated by the thin-film heaters 54a and 54b. The heat is then further transferred to the ceramic substrate 57 via the bumps 58c. As a result, the heat dissipation performance of the surface of the overcladding layer 53 is improved, and the heat applied to the underfill material 56 is reduced. Furthermore, heat generated by the electronic device 60 provided on the Si substrate 51 is also efficiently dissipated from the surface of the heat dissipation structure sidewalls 59a and 59b of the heat dissipation structure 59.

[0060] According to the optical integrated circuit module 50A of the fourth embodiment, the heat dissipation structure 59 embedded inside the overcladding layer 53 has sufficient heat generation performance, and can reduce the effect of heat on the optical integrated circuit module 50A. That is, when the overcladding layer 53 generates heat by supplying power to the thin-film heaters 54a and 54b, and when the electronic device 60 provided on the Si substrate 51 generates heat, heat is efficiently dissipated, reducing the power consumption of the phase shifter and improving the response speed. [Explanation of symbols]

[0061] 10A, 20A, 30A, 40A, 50A Optical Integrated Circuit Module 11, 21, 31, 41, 51 Si substrate 12a, 12b, 22a, 22b, 32a, 32b, 42a, 42b, 52a, 52b optical waveguide 13, 23, 33, 43, 53 Overcladding layer 14a, 14b, 24a, 24b, 34a, 34b, 44a, 44b, 54a, 54b Thin film heaters 15a, 15b, 25a, 25b, 35a, 35b, 45a, 45b, 55a, 55b wiring 16, 26, 36, 46, 56 Underfill material 17, 27, 37, 47, 57 Ceramic substrate 18a, 18b, 28a, 28b, 28c, 38a, 38b, 38c, 48a, 48b, 48c, 58a, 58b, 58c Bump 29, 39a, 39b, 39c, 49a, 49b, 49c, 59 Heat dissipation structure 59a, 59b Side wall for heat dissipation structure 59c Bottom part for heat dissipation structure 60 Electronic Devices

Claims

1. An optical integrated circuit comprising: an optical waveguide provided on a main surface of a substrate; a heat-generating structure disposed opposite the optical waveguide; wiring connected to the heat-generating structure for power supply; and an overcladding layer covering the optical waveguide, the heat-generating structure, and at least a connection portion of the wiring to the heat-generating structure, The overclad layer further includes an underfill material filled between the overclad layer and a bonding substrate disposed on a surface side opposite to the optical waveguide; The heat dissipation structure includes three heat dissipation structures that are provided on the overcladding layer and between the underfill material and the heat dissipation structure, extending along the extending direction of the heat dissipation structure and dissipating heat propagated when power is supplied to the heat dissipation structure.

1. An optical integrated circuit comprising:

2. The optical integrated circuit according to claim 1, characterized in that the three heat dissipation structures extend in the stacking direction of the overclad layer from the surface side of the overclad layer opposite the optical waveguide, and each of the ends is close to or in contact with the substrate.

3. The heat dissipation structure is disposed around the heat generation structure without contacting the heat generation structure.

3. An optical integrated circuit according to claim 1 or 2.

4. The heat dissipation structure is thermally connected to the outside using a connection point different from the wiring routed portion.

4. An optical integrated circuit according to claim 1, wherein the first and second electrodes are arranged parallel to each other.

5. The size of the heat dissipation structure is larger than the connection point of the wiring portion and the other connection point.

5. An optical integrated circuit according to claim 4.

6. The separate connection points on the heat dissipation structure are at least one or more thermally conductive bumps, and the bumps are arranged at equal intervals along a center line, a left line, and a right line that are parallel to an extension direction of the heat dissipation structure.

6. An optical integrated circuit according to claim 4 or 5.

7. The bumps of the other connection points of the heat dissipation structure are connected to ground points of the substrate for coupling to the substrate.

7. An optical integrated circuit according to claim 6.

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