Composite PCB

Abstract

The composite substrate includes a functional substrate including at least one of InP and a crystal of a material that can be formed by epitaxial growth on an InP crystal, and a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate. The functional substrate includes a first layer and a second layer made of an amorphous material containing a rare gas element and disposed closer to the support substrate than the first layer. The support substrate includes a first support layer, a second support layer made of an amorphous material of a semiconductor material containing a rare gas element and disposed closer to the functional substrate than the first support layer, and a bonding layer made of an amorphous material of a semiconductor material and in contact with the functional substrate.

Description

[Technical field]

[0001] The present invention relates to a composite group On the board Regarding. [Background technology]

[0002] Conventionally, composite substrates are known that are formed by bonding a functional substrate made of InP (indium phosphide) to a support substrate made of a semiconductor material such as Si or SiC, and are used for photonics devices such as semiconductor lasers, photodiodes, and modulators, and high-frequency transistors such as HEMTs (High Electron Mobility Transistors) and HBTs (Heterojunction Bipolar Transistors). As a method for producing such composite substrates, a method is known in which the bonding surfaces of the functional substrate and the support substrate are irradiated with a fast atom beam (FAB) to perform activation processing, and then these bonding surfaces are directly bonded together. However, in this method, P is selectively sputtered on the InP substrate side, and an In layer is formed on the surface. As a result, the In layer on the surface is easily peeled off from the InP substrate, which causes a problem of a decrease in the bonding strength of the composite substrate (see Non-Patent Document 1).

[0003] In order to solve the above problem, the technology of Patent Document 1 is known. Patent Document 1 discloses a method of forming an indium oxide barrier layer on an InP substrate and bonding this barrier layer to a silicon substrate via an amorphous layer. This method prevents the InP substrate from being directly irradiated with a fast atomic beam by the barrier layer, suppressing the formation of an In layer on the surface, thereby obtaining sufficient bonding strength that does not cause peeling. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] MMR Howlader, T. Watanabe, and T. Suga, "Characterization of the bonding strength and interface current of p-Si / n-InP wafers bonded by surface activated bonding method at room temperature", JOURNAL OF APPLIED PHYSICS, VOLUME 91, NUMBER 5, p. 3062-3066 [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-500 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, photonics devices and high-frequency transistors made of composite substrates using InP are required to be miniaturized, highly integrated, and have high output, and the heat density per unit area is increasing accordingly. In these devices, if the InP temperature rises too much during operation, the desired performance cannot be achieved, and reliability and lifespan are also reduced. Therefore, it is necessary to have a structure that can efficiently release the heat of the device. However, in the structure of the composite substrate of Patent Document 1, a barrier layer with low thermal conductivity exists at the bonding interface, making it difficult to efficiently release the heat generated in the InP substrate to the support substrate.

[0007] In recent years, photonic devices, high-frequency transistors, and other devices have been constructed on a composite substrate, which is made by bonding a substrate containing a semiconductor material formed by epitaxial growth on an InP crystal to a support substrate. Composite substrates with this type of structure also need to be designed to efficiently dissipate heat from the device to the support substrate.

[0008] The present invention has been made in view of the above, and a main object of the present invention is to provide a composite substrate in which a functional substrate including a crystal of InP or a material that can be formed by epitaxial growth on an InP crystal and a support substrate are bonded via a bonding layer, the composite substrate being capable of efficiently dissipating heat from the functional substrate to the support substrate, and a manufacturing method thereof. [Means for solving the problem]

[0009] The present invention First aspect of The composite substrate according to the present invention includes a functional substrate including at least one of InP and a crystal of a material that can be formed by epitaxial growth on an InP crystal, and a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate, the functional substrate includes a first layer and a second layer that is disposed closer to the support substrate than the first layer and is made of an amorphous body containing a rare gas element, the support substrate includes a first support layer, a second support layer that is disposed closer to the functional substrate than the first support layer and is made of an amorphous body of the semiconductor material containing the rare gas element, and a bonding layer that is in contact with the functional substrate and is made of an amorphous body of the semiconductor material. The functional substrate has a first functional layer made of an InP crystal and a second functional layer made of an InP amorphous body, the first layer is the first functional layer, the second layer is the second functional layer, and the functional substrate has an InP oxide film between the second layer and the support substrate. . A composite substrate according to a second aspect of the present invention includes a functional substrate including at least one of InP and a crystal of a material that can be formed on an InP crystal by epitaxial growth, and a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate, the functional substrate including a first layer and a second layer arranged closer to the support substrate than the first layer and made of an amorphous body containing a rare gas element, the support substrate including a first support layer and a second layer arranged closer to the functional substrate than the first support layer and made of an amorphous body containing the rare gas element. the functional substrate has a first functional layer made of an InP crystal, a second functional layer made of a crystal of the material formed by epitaxial growth on the first functional layer, and a third functional layer made of an amorphous body of the material, the first layer being the first functional layer and the second functional layer, the second layer being the third functional layer, and the functional substrate has an oxide film of the material between the second layer and the support substrate. A composite substrate according to a third aspect of the present invention includes a functional substrate including at least one of InP and a crystal of a material that can be formed by epitaxial growth on an InP crystal, and a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate, the functional substrate includes a first layer and a second layer arranged closer to the support substrate than the first layer and made of an amorphous body containing a rare gas element, the support substrate includes a first support layer and a second support layer arranged closer to the functional substrate than the first support layer and made of an amorphous body of the semiconductor material containing the rare gas element, and a bonding layer in contact with the functional substrate and made of an amorphous body of the semiconductor material, the functional substrate includes a second functional layer made of a crystal of the material and a third functional layer made of an amorphous body of the material, the first layer being the second functional layer, the second layer being the third functional layer, and the functional substrate includes an oxide film of the material between the second layer and the support substrate. Effect of the Invention

[0010] According to the present invention, in a composite substrate in which a functional substrate including a crystal of InP or a material that can be formed by epitaxial growth on an InP crystal and a support substrate are bonded via a bonding layer, it is possible to provide a composite substrate and a manufacturing method thereof that are capable of efficiently dissipating heat from the functional substrate to the support substrate side. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a first embodiment of the present invention. [Diagram 2] 2A to 2C are diagrams illustrating an example of a manufacturing process for the composite substrate according to the first embodiment of the present invention. [Diagram 3] 2A to 2C are diagrams illustrating an example of a manufacturing process for the composite substrate according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a second embodiment of the present invention. [Diagram 5] 6A to 6C are diagrams illustrating an example of a manufacturing process for a composite substrate according to a second embodiment of the present invention. [Figure 6] 6A to 6C are diagrams illustrating an example of a manufacturing process for a composite substrate according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a third embodiment of the present invention. [Figure 8] FIG. 11 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a fourth embodiment of the present invention. [Figure 9] FIG. 1 is a diagram showing observation photographs of an example and a comparative example. [Figure 10] 1 is a table summarizing the FAB irradiation time, the presence or absence of peeling at the bonding interface during processing, the thickness of the oxide film, and the distance between Ar peaks for each of the examples and comparative examples. [Figure 11] 13 is a graph showing the relationship between the FAB irradiation time and the distance between Ar peaks on a functional substrate when the support substrate is made of SiC. [Figure 12] 13 is a graph showing the relationship between the FAB irradiation time of a functional substrate and the distance between Ar peaks when the supporting substrate is made of Si. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, in order to clarify the description, the width, thickness, shape, etc. of each part may be shown more diagrammatically than in the embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0013] (First embodiment) 1 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a first embodiment of the present invention. The composite substrate 100 in this embodiment is used for various purposes, such as photonic devices such as semiconductor lasers, photodiodes, and modulators, and high-frequency transistors such as HEMTs and HBTs, and has a structure in which a functional substrate 1 having an InP layer 10 and an oxide film 20 is bonded to a support substrate 30.

[0014] For example, InP crystal is used as the material of the functional substrate 1. Part of the crystal structure in the InP layer 10 changes to an amorphous state during the manufacturing process of the composite substrate 100, and is contained in the amorphous state in the InP layer 10. This point will be described later.

[0015] The oxide film 20 is an oxide layer formed on the surface of the InP layer 10 by natural oxidation of a portion of the InP constituting the InP layer 10 in air before the functional substrate 1 is bonded to the support substrate 30, and is disposed between the InP layer 10 and the support substrate 30 in the composite substrate 100.

[0016] The support substrate 30 supports the functional substrate 1 including the InP layer 10 and the oxide film 20. Any appropriate substrate can be used as the support substrate 30. The support substrate 30 may be composed of a single crystal body or a polycrystalline body. The oxide film 20 of the functional substrate 1 and the support substrate 30 are directly bonded to each other.

[0017] The material constituting the support substrate 30 may be a semiconductor material such as SiC or Si. Alternatively, the support substrate 30 may be made of AlN, diamond, SOI (Silicon on Insulator), or the like. When SOI is used as the support substrate 30, the SOI substrate (support substrate 30) may include an optical circuit, an electric circuit, or the like made of Si. The thickness of the support substrate 30 is, for example, 0.2 to 1 mm, but any other appropriate thickness may be adopted.

[0018] Although not shown, composite substrate 100 may further include any layer. The types, functions, number, combination, arrangement, etc. of such layers may be appropriately set depending on the purpose.

[0019] The composite substrate 100 may be manufactured in any appropriate shape. In one embodiment, the composite substrate 100 may be manufactured in the form of a so-called wafer. The size of the composite substrate 100 may be appropriately set depending on the purpose, for example, the diameter of the wafer (substrate) may be 50 mm to 150 mm.

[0020] 2 and 3 are diagrams showing an example of a manufacturing process for the composite substrate according to the first embodiment of the present invention.

[0021] 2(a) shows a preparation step in the manufacturing process of the composite substrate 100. In this step, a functional substrate 1 made of an InP crystal having a predetermined thickness is prepared. This functional substrate 1 has an InP layer 10 made of an InP crystal, and an InP oxide film 20 formed on the surface of the InP layer 10 by natural oxidation.

[0022] FIG. 2(b) shows an oxide film removal and activation step in the manufacturing process of the composite substrate 100. In this step, for example, a semiconductor substrate 30A made of a semiconductor material with a predetermined thickness is prepared, and a fast atomic beam (hereinafter referred to as FAB) using a rare gas such as Ar as an atomic species is irradiated onto the surfaces of the functional substrate 1 prepared in the preparation step of FIG. 2(a) and the semiconductor substrate 30A for a predetermined time. As a result, a part of the oxide film 20 on the functional substrate 1 is removed to make it thinner, and the surfaces of the functional substrate 1 and the semiconductor substrate 30A are activated. The irradiation time of the FAB at this time is preferably about 5 to 12 seconds, for example.

[0023] FIG. 2(c) shows a sputtering step in the manufacturing process of the composite substrate 100. In this step, the FAB irradiation on the functional substrate 1 side, which is irradiated with FAB on the functional substrate 1 and the semiconductor substrate 30A in the oxide film removal and activation step in FIG. 2(b), is stopped, and the FAB irradiation on the semiconductor substrate 30A side is continued for a further predetermined time. The FAB irradiation time at this time is preferably, for example, about 30 to 600 seconds. As a result, the semiconductor material constituting the semiconductor substrate 30A is sputtered and attached to the surface of the functional substrate 1 (oxide film 20), and a sputtered film 30B made of the same semiconductor material as the semiconductor substrate 30A is formed on the functional substrate 1 side.

[0024] Fig. 3(d) shows a bonding step in the manufacturing process of the composite substrate 100. In this step, the functional substrate 1 on which the sputtered film 30B has been formed in the sputtering step of Fig. 2(c) is bonded to the semiconductor substrate 30A. As a result, the semiconductor substrate 30A and the sputtered film 30B are integrated to form the support substrate 30, and a bonded body of the functional substrate 1 and the support substrate 30 is obtained.

[0025] Fig. 3(e) shows a bonded body obtained after the bonding step of Fig. 3(d). By the bonding step of Fig. 3(d), the semiconductor substrate 30A and the sputtered film 30B are integrated as described above, forming a support substrate 30 having a bonding interface 40 therein, and a bonded body as shown in Fig. 3(e) is obtained.

[0026] In the bonded body of Fig. 3(e), a first functional layer 11 and a second functional layer 12 arranged on the support substrate 30 side of the first functional layer 11 are formed on the InP layer 10 of the functional substrate 1. The first functional layer 11 is mainly composed of InP crystals, and the second functional layer 12 is mainly composed of InP amorphous body. The second functional layer 12 is a layer containing rare gas atoms such as Ar irradiated as FAB in the oxide film removal and activation process of Fig. 2(b).

[0027] 3(e), the support substrate 30 is provided with a first support layer 31 that does not contact the bonding interface 40, a second support layer 32 that is disposed closer to the functional substrate 1 than the first support layer 31 and contacts the bonding interface 40, and a bonding layer 33 that is disposed closer to the functional substrate 1 than the second support layer 32 and contacts the bonding interface 40. The second support layer 32 is mainly made of an amorphous semiconductor material, and is a layer that contains rare gas atoms such as Ar irradiated as FAB in the oxide film removal and activation process of FIG. 2(b) and the sputtering process of FIG. 2(c). The bonding layer 33 corresponds to the sputtered film 30B before bonding, and is a layer that forms a bonding portion with the functional substrate 1.

[0028] In addition, the second functional layer 12 in the functional substrate 1, and the second support layer 32 and bonding layer 33 in the support substrate 30 may contain other atomic species that are mixed into these layers during the sputtering process of Figure 2(c), such as Fe atoms and Al atoms that constitute the jig or base portion used to fix the semiconductor substrate 30A.

[0029] Fig. 3(f) shows a thinning process in the manufacturing process of the composite substrate 100. In this process, the InP layer 10 of the functional substrate 1 is polished to a predetermined thickness to be thinned with respect to the bonded body shown in Fig. 3(e). For example, the InP layer 10 can be polished to be thinned using grinding, CMP (Chemical Mechanical Polish) processing, surface planarization processing using a gas cluster ion beam, or the like.

[0030] Through the above steps, composite substrate 100 having the structure shown in FIG. 1 is manufactured.

[0031] In addition, an annealing step of heating the bonded body to a predetermined temperature may be performed between the bonding step of Fig. 3(d) and the thin plate processing step of Fig. 3(f). The heating temperature at this time is preferably, for example, about 75 to 250°C, and more preferably 100 to 250°C. This can improve the bonding strength of the composite substrate 100.

[0032] Second embodiment 4 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a second embodiment of the present invention. Composite substrate 110 in this embodiment has a structure in which oxide film 20 is not disposed between InP layer 10 and support substrate 30, as compared with composite substrate 100 in FIG. 1 described in the first embodiment. That is, composite substrate 110 has functional substrate 1a which is composed of InP layer 10 and does not include oxide film 20, instead of functional substrate 1 in composite substrate 100.

[0033] In this embodiment, as in the first embodiment, composite substrate 110 may further include any layer. The types, functions, numbers, combinations, arrangements, etc. of such layers may be appropriately set depending on the purpose. Furthermore, composite substrate 110 may be manufactured in any appropriate shape depending on the purpose.

[0034] 5 and 6 are diagrams showing an example of a manufacturing process for a composite substrate according to the second embodiment of the present invention.

[0035] Fig. 5(a) shows a preparation step in the manufacturing process of the composite substrate 110. In this step, similar to the step of Fig. 2(a) described in the first embodiment, a functional substrate 1 made of an InP crystal with a predetermined thickness is prepared. This functional substrate 1 has an InP layer 10 made of an InP crystal, and an InP oxide film 20 formed on the surface of the InP layer 10 by natural oxidation.

[0036] FIG. 5(b) shows an oxide film removal and activation step in the manufacturing process of the composite substrate 110. In this step, similar to the step of FIG. 2(b) described in the first embodiment, a semiconductor substrate 30A made of a semiconductor material with a predetermined thickness is prepared, and the functional substrate 1 prepared in the preparation step of FIG. 5(a) and the semiconductor substrate 30A are irradiated with FAB using a rare gas such as Ar as an atomic species for a predetermined time on their respective surfaces. In this embodiment, the FAB irradiation to the oxide film 20 is continued until the oxide film 20 is completely removed from the functional substrate 1 and the InP layer 10 is exposed on the surface. The irradiation time of the FAB at this time is preferably about 13 to 24 seconds, for example. As a result, a functional substrate 1a having only the InP layer 10 and not the oxide film 20 is formed from the functional substrate 1 having the InP layer 10 and the oxide film 20.

[0037] 5(c) shows a sputtering step in the manufacturing process of the composite substrate 110. In this step, as in the step of FIG. 2(c) described in the first embodiment, the FAB irradiation on the functional substrate 1 side is stopped and the FAB irradiation on the semiconductor substrate 30A side is continued for a further predetermined time among the FAB irradiated on the functional substrate 1 and the semiconductor substrate 30A in the oxide film removal and activation step of FIG. 5(b). As a result, the semiconductor material constituting the semiconductor substrate 30A is sputtered and attached to the surface of the functional substrate 1a from which the oxide film 20 has been completely removed, i.e., the surface of the InP layer 10, and a sputtered film 30B made of the same semiconductor material as the semiconductor substrate 30A is formed on the functional substrate 1a side.

[0038] Fig. 6(d) shows a bonding step in the manufacturing process of the composite substrate 110. In this step, similar to the step of Fig. 3(d) described in the first embodiment, the functional substrate 1a on which the sputtered film 30B has been formed in the sputtering step of Fig. 5(c) is bonded to the semiconductor substrate 30A. As a result, the semiconductor substrate 30A and the sputtered film 30B are bonded and integrated to form the support substrate 30, and a bonded body of the functional substrate 1a and the support substrate 30 is obtained.

[0039] Fig. 6(e) shows a bonded body obtained after the bonding step of Fig. 6(d). By the bonding step of Fig. 6(d), the semiconductor substrate 30A and the sputtered film 30B are integrated as described above, forming a support substrate 30 having a bonding interface 40 therein, and a bonded body as shown in Fig. 6(e) is obtained.

[0040] 6(e), similarly to the bonded body of FIG. 3(e) described in the first embodiment, a first functional layer 11 and a second functional layer 12 arranged on the support substrate 30 side of the first functional layer 11 are formed on the functional substrate 1a (InP layer 10). In addition, a first support layer 31 not in contact with the bonding interface 40, a second support layer 32 arranged on the functional substrate 1a side of the first support layer 31 and in contact with the bonding interface 40, and a bonding layer 33 arranged on the functional substrate 1a side of the second support layer 32 and in contact with the bonding interface 40 are formed on the support substrate 30.

[0041] Fig. 6(f) shows a thin plate processing step in the manufacturing process of the composite substrate 110. In this step, similar to the step of Fig. 3(f) described in the first embodiment, the functional substrate 1a (InP layer 10) of the bonded body shown in Fig. 6(e) is polished to a predetermined thickness to be thinned.

[0042] Through the above steps, composite substrate 110 having the structure shown in FIG. 4 is manufactured.

[0043] In this embodiment, similarly to the first embodiment, an annealing step of heating the bonded body to a predetermined temperature may be performed between the bonding step of FIG. 6(d) and the thin plate processing step of FIG. 6(f).

[0044] (Third embodiment) Fig. 7 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a third embodiment of the present invention. In this embodiment, a functional substrate 1b of a composite substrate 120 shown in Fig. 7(a) has an InP layer 10 made of an InP crystal, an epitaxial layer 50, and an oxide film 60. A composite substrate 121 shown in Fig. 7(b) is formed by removing the InP layer 10 from the composite substrate 120 of Fig. 7(a).

[0045] The epitaxial layer 50 is a layer made of crystals of various materials (e.g., InP, BeZnSeTe, BeZnCdSe, MgZnCdSe, InGaAsP, InGaAlAs, InGaAs, InAs, AlAsSb, InAlAs, etc., hereinafter referred to as "epitaxial materials") that can be formed by epitaxial growth on the InP layer 10. The epitaxial layer 50 is formed by forming a layer made of crystals of these materials on the InP layer 10 by epitaxial growth. Note that the epitaxial layer 50 may contain a mixture of multiple types of epitaxial materials.

[0046] The oxide film 60 is an oxide layer formed on the surface of the epitaxial layer 50 by natural oxidation in air of a portion of the epitaxial material constituting the epitaxial layer 50 before the functional substrate 1b is bonded to the support substrate 30, and is disposed between the epitaxial layer 50 and the support substrate 30.

[0047] The composite substrate 120 of this embodiment is manufactured by the same steps as those of Fig. 2(a) to Fig. 3(f) described in the first embodiment. That is, a functional substrate 1b having a predetermined thickness and including an InP layer 10, an epitaxial layer 50, and an oxide film 60 is prepared, and the oxide film removal and activation step of Fig. 2(b) is performed on this functional substrate 1b to remove a part of the oxide film 60 to make it thinner, and to activate the surfaces of the functional substrate 1b and the semiconductor substrate 30A. Then, a sputtering step of Fig. 2(c) and a bonding step of Fig. 3(d) are performed to form a bonded body of the functional substrate 1b and the support substrate 30, and the thin plate processing step of Fig. 3(f) is performed on this bonded body to manufacture the composite substrate 120 having the structure shown in Fig. 7(a).

[0048] In the composite substrate 120, the functional substrate 1b has a first functional layer 51 composed of an InP layer 10 made of InP crystals, and a second functional layer 52 and a third functional layer 53 formed in an epitaxial layer 50. The second functional layer 52 is mainly composed of a crystal of an epitaxial material, and the third functional layer 53 is mainly composed of an amorphous body of an epitaxial material. The third functional layer 53 is a layer containing rare gas atoms such as Ar irradiated as FAB in the oxide film removal and activation process, and is disposed closer to the support substrate 30 than the second functional layer 52.

[0049] In the composite substrate 120, similarly to the composite substrates 100 and 110 described in the first and second embodiments, a bonding interface 40, a first supporting layer 31, a second supporting layer 32, and a bonding layer 33 are formed in the supporting substrate 30. These are formed in the bonded body obtained in the bonding step described above.

[0050] Furthermore, by removing the InP layer 10 from the composite substrate 120, a composite substrate 121 having the structure shown in FIG. 7(b) is manufactured. The InP layer 10 can be removed by, for example, wet etching. In this composite substrate 121, the functional substrate 1b has a second functional layer 52 and a third functional layer 53 formed in the epitaxial layer 50. The second functional layer 52 is mainly composed of a crystalline body of the epitaxial material, and the third functional layer 53 is mainly composed of an amorphous body of the epitaxial material. The structure of the support substrate 30 is the same as that of the composite substrate 120.

[0051] (Fourth embodiment) FIG. 8 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a fourth embodiment of the present invention. In this embodiment, the composite substrate 130 shown in FIG. 8(a) has a structure in which the oxide film 60 is not disposed between the epitaxial layer 50 and the support substrate 30, compared to the composite substrate 120 of FIG. 7(a) described in the third embodiment. That is, the composite substrate 130 has a functional substrate 1c composed of an InP layer 10 and an epitaxial layer 50 and not including an oxide film 60, instead of the functional substrate 1b in the composite substrate 120. Also, the composite substrate 131 shown in FIG. 8(b) is formed by removing the InP layer 10 from the composite substrate 130 of FIG. 8(a).

[0052] The composite substrate 130 of this embodiment is manufactured by the same steps as those of FIG. 5(a) to FIG. 6(f) described in the second embodiment. That is, a functional substrate 1b having a predetermined thickness and including an InP layer 10, an epitaxial layer 50, and an oxide film 60 is prepared, and the oxide film 60 is entirely removed by performing the oxide film removal and activation step of FIG. 5(b) on this functional substrate 1b to form a functional substrate 1c, and the surfaces of the functional substrate 1c and the semiconductor substrate 30A are activated. Thereafter, a sputtering step of FIG. 5(c) and a bonding step of FIG. 6(d) are performed to form a bonded body of the functional substrate 1c and the support substrate 30, and the thin plate processing step of FIG. 6(f) is performed on this bonded body to manufacture the composite substrate 130 having the structure shown in FIG. 8(a).

[0053] In the composite substrate 130 of this embodiment, similarly to the composite substrate 120 described in the third embodiment, the functional substrate 1c has a first functional layer 51 constituted by an InP layer 10 made of an InP crystal, and a second functional layer 52 and a third functional layer 53 formed in an epitaxial layer 50. In addition, in the support substrate 30, a bonding interface 40, a first support layer 31, a second support layer 32, and a bonding layer 33 are formed.

[0054] Furthermore, by removing the InP layer 10 from the composite substrate 130, a composite substrate 131 having the structure shown in FIG. 8(b) is manufactured. As in the third embodiment, the InP layer 10 can be removed by, for example, wet etching. In this composite substrate 131, the functional substrate 1c has a second functional layer 52 and a third functional layer 53 formed in the epitaxial layer 50. The second functional layer 52 is mainly composed of a crystalline body of the epitaxial material, and the third functional layer 53 is mainly composed of an amorphous body of the epitaxial material. The structure of the support substrate 30 is similar to that of the composite substrate 130. EXAMPLES

[0055] Examples for verifying the structure of the composite substrate according to the present invention will be specifically described below. Note that, unless otherwise specified, the following procedures were carried out at room temperature.

[0056] Example 1 A bonded body was produced according to the manufacturing process described with reference to Figures 2 and 3. Specifically, an InP wafer and a SiC wafer of a predetermined size were prepared, and the InP wafer was used as the functional substrate 1, and the SiC wafer was used as the semiconductor substrate 30A.

[0057] Then, after cleaning the surfaces of the functional substrate 1 and the semiconductor substrate 30A, the functional substrate 1 and the semiconductor substrate 30A were placed in a vacuum chamber in which the fabrication guns were installed facing upward and downward, so that the substrates were located within the irradiation ranges of the fabrication guns and the surfaces of the two substrates faced each other. In this state, the inside of the vacuum chamber was left for 10 -6 The vacuum was drawn to the Pa range, and FAB (acceleration voltage 0.9 kV, current 100 mA) using Ar gas was irradiated from each FAB gun to the surfaces of the functional substrate 1 and the semiconductor substrate 30A simultaneously for 1.5 seconds. As a result, a part of the oxide film 20 formed on the surface of the functional substrate 1 was removed, making it thinner than its original thickness.

[0058] Thereafter, the FAB irradiation on the functional substrate 1 side was stopped, while the FAB irradiation on the semiconductor substrate 30A side was continued for another 180 seconds (a total of 181.5 seconds). In order to prevent the internal pressure of the vacuum chamber from changing before and after the FAB irradiation on the functional substrate 1 side was stopped, the FAB irradiation from the FAB gun on the functional substrate 1 side to the surface of the functional substrate 1 was stopped while the supply of Ar gas to the FAB gun on the functional substrate 1 side was continued. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1 (oxide film 20).

[0059] Next, the functional substrate 1 on which the sputtered film 30B was formed was directly bonded to the semiconductor substrate 30A. Specifically, the beam-irradiated surfaces of both substrates were overlapped, and the two substrates were bonded together by applying a pressure of 10,000 N at room temperature for 2 minutes to obtain a bonded body. As a result, a composite substrate 100 having the structure shown in FIG. 1 was obtained.

[0060] Example 2 2 and 3, a bonded body was produced by prolonging the FAB irradiation time of the functional substrate 1 compared to that of Example 1. Specifically, the functional substrate 1 and the semiconductor substrate 30A similar to those of Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated for 10 -6 In a state where the vacuum was drawn to the Pa range, the surfaces of the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with FAB using Ar gas for 6.5 seconds from each FAB gun under the same conditions as in Example 1. As a result, a part of the oxide film 20 formed on the surface of the functional substrate 1 was removed, and the thickness became thinner than the original thickness and even thinner than in Example 1.

[0061] Thereafter, the FAB irradiation on the functional substrate 1 side was stopped, while the FAB irradiation on the semiconductor substrate 30A side was continued for another 180 seconds (a total of 186.5 seconds). At this time, as in Example 1, in order to prevent the internal pressure of the vacuum chamber from changing before and after the FAB irradiation on the functional substrate 1 side was stopped, while the supply of Ar gas to the FAB gun on the functional substrate 1 side was continued. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1 (oxide film 20).

[0062] Next, similarly to Example 1, the functional substrate 1 on which the sputtered film 30B was formed and the semiconductor substrate 30A were directly bonded to obtain the composite substrate 100 having the structure shown in FIG.

[0063] Example 3 2 and 3, a bonded body was produced by prolonging the FAB irradiation time of the functional substrate 1 compared to Examples 1 and 2. Specifically, the functional substrate 1 and the semiconductor substrate 30A similar to those in Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated for 10 -6 In a state where the vacuum was drawn to the Pa range, the surfaces of the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with FAB using Ar gas for 10.5 seconds from each FAB gun under the same conditions as in Example 1. As a result, a part of the oxide film 20 formed on the surface of the functional substrate 1 was removed, and the thickness became thinner than the original thickness and even thinner than in Example 2.

[0064] Thereafter, the FAB irradiation on the functional substrate 1 side was stopped, while the FAB irradiation on the semiconductor substrate 30A side was continued for another 180 seconds (total of 190.5 seconds). At this time, as in Examples 1 and 2, in order to prevent the internal pressure of the vacuum chamber from changing before and after the FAB irradiation on the functional substrate 1 side was stopped, while the supply of Ar gas to the FAB gun on the functional substrate 1 side was continued. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1 (oxide film 20).

[0065] Next, similarly to Examples 1 and 2, the functional substrate 1 on which the sputtered film 30B was formed and the semiconductor substrate 30A were directly bonded to obtain the composite substrate 100 having the structure shown in FIG.

[0066] Example 4 A bonded body was produced according to the manufacturing process described with reference to Fig. 5 and Fig. 6. Specifically, the functional substrate 1 and the semiconductor substrate 30A similar to those in Example 1 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated for 10-6 In a state where the vacuum was drawn to the Pa range, the surfaces of the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with FAB using Ar gas for 14.5 seconds from each FAB gun under the same conditions as in Example 1. As a result, the oxide film 20 formed on the surface of the functional substrate 1 was entirely removed, and a functional substrate 1a having only the InP layer 10 and not including the oxide film 20 was formed.

[0067] Thereafter, the FAB irradiation on the functional substrate 1a side was stopped, while the FAB irradiation on the semiconductor substrate 30A side was continued for another 180 seconds (total of 194.5 seconds). At this time, as in Examples 1 to 3, in order to prevent the internal pressure of the vacuum chamber from changing before and after the FAB irradiation on the functional substrate 1a side was stopped from the FAB gun on the functional substrate 1a side while continuing to supply Ar gas to the FAB gun on the functional substrate 1a side. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1a.

[0068] Next, similarly to Examples 1 to 3, the functional substrate 1a on which the sputtered film 30B was formed and the semiconductor substrate 30A were directly bonded to obtain a composite substrate 110 having the structure shown in FIG.

[0069] Example 5 5 and 6, a bonded body was produced by prolonging the FAB irradiation time of the functional substrate 1 compared to Example 4. Specifically, the functional substrate 1 and the semiconductor substrate 30A similar to those of Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated for 10 -6 In a state where the vacuum was drawn to the Pa range, the surfaces of the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with FAB using Ar gas for 18.5 seconds from each FAB gun under the same conditions as in Example 1. As a result, the oxide film 20 formed on the surface of the functional substrate 1 was entirely removed, and a functional substrate 1a having only the InP layer 10 and not including the oxide film 20 was formed.

[0070] Thereafter, the FAB irradiation on the functional substrate 1a side was stopped, while the FAB irradiation on the semiconductor substrate 30A side was continued for another 180 seconds (total of 198.5 seconds). At this time, as in Examples 1 to 4, in order to prevent the internal pressure of the vacuum chamber from changing before and after the FAB irradiation on the functional substrate 1a side was stopped from the FAB gun on the functional substrate 1a side while continuing to supply Ar gas to the FAB gun on the functional substrate 1a side. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1a.

[0071] Next, similarly to Examples 1 to 4, the functional substrate 1a on which the sputtered film 30B was formed and the semiconductor substrate 30A were directly bonded to obtain a composite substrate 110 having the structure shown in FIG.

[0072] In the above-mentioned Examples 1 to 5, the FAB irradiation from the FAB gun to the functional substrate 1, 1a and the semiconductor substrate 30A is performed for a predetermined time, and then the FAB irradiation on the functional substrate 1, 1a side is stopped first. This allows the time required for forming the sputtered film 30B to be used for cooling the functional substrate 1, 1a, so that the effect of warping on the composite substrate 100, 110 after bonding can be reduced. In particular, when the functional substrate 1, 1a has a larger thermal expansion coefficient than the semiconductor substrate 30A, stopping the FAB irradiation on the functional substrate 1, 1a side first can provide a higher effect in reducing warping after bonding.

[0073] Comparative Example 1 In order to confirm the effect of the present invention, as Comparative Example 1, the functional substrate 1 and the semiconductor substrate 30A similar to those in Examples 1 to 5 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated for 10 -6 In a state where the vacuum was drawn down to the Pa range, FAB irradiation was performed only on the semiconductor substrate 30A side for 180 seconds without performing FAB irradiation on the functional substrate 1 side. The FAB irradiation conditions on the semiconductor substrate 30A side at this time were the same as those in Examples 1 to 5. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1.

[0074] Next, similarly to Examples 1 to 5, the functional substrate 1 on which the sputtered film 30B was formed and the semiconductor substrate 30A were directly bonded to obtain the composite substrate 100 having the structure shown in FIG.

[0075] Comparative Example 2 Furthermore, as a comparative example 2, the functional substrate 1 and the semiconductor substrate 30A similar to those in the examples 1 to 5 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated for 10 -6 In a state where the vacuum was drawn to the Pa range, FAB irradiation was performed for both the functional substrate 1 and the semiconductor substrate 30A for 24.5 seconds, and then the FAB irradiation on the functional substrate 1 side was stopped, while the FAB irradiation on the semiconductor substrate 30A side was continued for another 180 seconds (total of 204.5 seconds). The FAB irradiation conditions on the semiconductor substrate 30A side at this time were the same as those in Examples 1 to 5. As a result, the oxide film 20 formed on the surface of the functional substrate 1 was completely removed, and a functional substrate 1a having only the InP layer 10 and not including the oxide film 20 was formed, and a sputtered film 30B was formed on the surface of the functional substrate 1a.

[0076] Next, similarly to Examples 1 to 5, the functional substrate 1a on which the sputtered film 30B was formed and the semiconductor substrate 30A were directly bonded to obtain a composite substrate 110 having the structure shown in Fig. 4. In the composite substrate 110 of Comparative Example 2, peeling occurred at the bonding interface 40 during the thin plate processing step. This is believed to be because the FAB irradiation time on the semiconductor substrate 30A side was too long, which increased the surface roughness of the bonding interface 40 and reduced the bonding strength.

[0077] (Checking the laminated structure) The cross sections including the bonding interface 40 of the composite substrates 100, 110 produced in Examples 1 to 5 and Comparative Example 1 were observed with a transmission electron microscope (TEM) to confirm the laminated structures of the composite substrates 100, 110. Fig. 9(a) shows Comparative Example 1, Fig. 9(b) shows Example 1, Fig. 9(c) shows Example 2, Fig. 9(d) shows Example 3, Fig. 9(e) shows Example 4, and Fig. 9(f) shows Example 5. Note that Comparative Example 1 and Examples 1 to 3 shown in Figs. 9(a) to 9(d) correspond to the composite substrate 100 in which the functional substrate 1 after bonding has the oxide film 20, and Examples 4 and 5 shown in Figs. 9(e) and 9(f) correspond to the composite substrate 110 in which the functional substrate 1a after bonding does not have the oxide film 20.

[0078] From the observation photographs of Examples 1 to 3 shown in Figs. 9(b), 9(c), and 9(d), it can be seen that two layers are formed inside the InP layer 10 in the functional substrate 1. These layers are referred to as a first functional layer 11 and a second functional layer 12, in order from the side farthest from the support substrate 30. It can also be seen that three layers are formed inside the support substrate 30. These layers are referred to as a first support layer 31, a second support layer 32, and a bonding layer 33, in order from the side farthest from the functional substrate 1. The bonding layer 33 is in contact with the oxide film 20 of the functional substrate 1, and a bonding interface 40 formed in the above-mentioned bonding process exists between the second support layer 32 and the bonding layer 33. That is, in the bonding process, the surface of the second support layer 32 in the semiconductor substrate 30A before bonding and the surface of the sputtered film 30B formed on the oxide film 20 in the functional substrate 1 before bonding are bonded to each other, so that the sputtered film 30B becomes the bonding layer 33, and a bonded body of the functional substrate 1 and the support substrate 30 having a bonding interface 40 inside the support substrate 30 is formed.

[0079] Similarly, the observation photographs of Examples 4 and 5 shown in Figures 9(e) and 9(f) show that a first functional layer 11 and a second functional layer 12 are formed inside the functional substrate 1a (InP layer 10), that a first support layer 31, a second support layer 32 and a bonding layer 33 are formed inside the support substrate 30, and that a bonding interface 40 exists between the second support layer 32 and the bonding layer 33.

[0080] 9(b) to 9(f), it can be seen that the second functional layer 12 does not have a crystalline structure and is composed of amorphous InP, whereas the first functional layer 11 is composed of InP crystals. That is, in Examples 1 to 5, the second functional layer 12, which corresponds to a portion of the functional substrate 1, 1a before bonding from the surface irradiated with FAB in the oxide film removal and activation process to a predetermined depth, is formed as a layer of amorphous InP, which is the material of the functional substrate 1, 1a.

[0081] 9(b) to 9(f), it can be seen that the second support layer 32 and the bonding layer 33 do not have a crystalline structure and are composed of amorphous SiC, whereas the first support layer 31 is composed of crystalline SiC. That is, in Examples 1 to 5, the second support layer 32, which corresponds to a portion of the semiconductor substrate 30A before bonding from the surface irradiated with FAB in the oxide film removal / activation step and the sputtering step to a predetermined depth, and the bonding layer 33, which corresponds to the sputtered film 30B formed on the surface of the functional substrate 1, 1a in the sputtering step, are each formed as a layer in which the SiC, which is the material of the support substrate 30, has been made amorphous.

[0082] On the other hand, in the observation photograph of Comparative Example 1 shown in Figure 9(a), the InP layer 10 in the functional substrate 1 is composed only of a first functional layer 11 having a crystalline structure, and the second functional layer 12 as in Examples 1 to 5 is not formed on the InP layer 10. That is, in Comparative Example 1, the oxide film removal and activation process is not performed on the functional substrate 1 before bonding, and therefore it can be seen that the second functional layer 12 made of an amorphous InP film is not formed.

[0083] (Oxide film thickness) For the composite substrates 100 produced in Examples 1 to 3, the thickness of the oxide film 20 was measured from the observation photographs of Figs. 9(b), 9(c), and 9(d), and was 0.9 nm in Example 1 and 0.6 nm in Examples 2 and 3. On the other hand, in Comparative Example 1, the thickness of the oxide film 20 was measured from the observation photograph of Fig. 9(a), and was 1 nm. That is, in Examples 1 to 3, it can be seen that a part of the oxide film 20 is removed by FAB irradiation in the oxide film removal and activation process, and thus the thickness is smaller than that of the original oxide film 20. Note that in Examples 4 and 5, the oxide film 20 is entirely removed in the oxide film removal and activation process, and therefore the thickness of the oxide film 20 is 0.

[0084] (Thickness of bonding layer) For the composite substrates 100, 110 produced in Comparative Example 1 and Examples 1 to 5, the thickness of the bonding layer 33 was measured from the observation photographs of Figures 9(a) to 9(d), and the results were 0.4 nm in Comparative Example 1, 0.8 nm in Example 1, 0.6 nm in Examples 2 to 4, and 0.7 nm in Example 5.

[0085] In Comparative Example 1 and Examples 1 to 5, the FAB irradiation time to the semiconductor substrate 30A side in the sputtering process after the FAB irradiation to the functional substrate 1, 1a side is stopped is 180 seconds in all cases. As described above, the bonding layer 33 is a portion corresponding to the sputtered film 30B before bonding formed on the functional substrate 1, 1a side in the sputtering process, so the thickness of the bonding layer 33 is considered to be determined by the FAB irradiation time to the semiconductor substrate 30A side. Therefore, taking into account measurement errors, etc., the actual thicknesses of the bonding layer 33 in Comparative Examples 1 and 2 and Examples 1 to 5 are considered to be approximately the same, about 0.6 nm.

[0086] (Ar peak distance) A structural analysis of the composite substrates 100, 110 was carried out by performing EDX analysis on a cross section including the bonding interface 40 of the composite substrates 100, 110 produced in Examples 1 to 5 and Comparative Example 2. As a result, it was found that the content of Ar, which is an element of the rare gas used in the FAB irradiation, has a peak in the second functional layer 12 on the functional substrate 1, 1a side and in the second support layer 32 on the support substrate 30 side. The distance between these peaks was 2.2 nm in Example 1, 2.8 nm in Example 2, 3.2 nm in Example 3, 3.5 nm in Example 4, 4.0 nm in Example 5, and 4.6 nm in Comparative Example 2.

[0087] In addition, in the composite substrate 100 produced in Comparative Example 1, FAB irradiation was not performed on the functional substrate 1 side, so the content of Ar, which is an element of the rare gas used for FAB irradiation, has a peak only in the second support layer 32 on the support substrate 30 side, and no peak is present on the functional substrate 1 side.

[0088] Fig. 10 is a table summarizing the FAB irradiation time, the presence or absence of peeling at the bonding interface 40 during processing, the thickness of the oxide film 20, and the distance between Ar peaks in each of Examples 1 to 5 and Comparative Examples 1 and 2. It can be seen from the table in Fig. 10 that the longer the FAB irradiation time for the functional substrates 1 and 1a, the greater the distance between Ar peaks.

[0089] (Relationship between FAB irradiation time and distance between Ar peaks) FIG. 11 is a graph showing the relationship between the FAB irradiation time and the Ar peak distance on the functional substrates 1, 1a when the support substrate 30 is made of SiC. In FIG. 11, the horizontal axis represents the FAB irradiation time on the functional substrates 1, 1a, and the vertical axis represents the Ar peak distance. Also, each of the plot points 71a to 71f shown by black circles indicates a combination of the FAB irradiation time and the Ar peak distance obtained in each example and each comparative example. Specifically, the plot point 71a indicates the combination of the FAB irradiation time and the Ar peak distance in Example 1, the plot point 71b indicates the combination of the FAB irradiation time and the Ar peak distance in Example 2, the plot point 71c indicates the combination of the FAB irradiation time and the Ar peak distance in Example 3, the plot point 71d indicates the combination of the FAB irradiation time and the Ar peak distance in Example 4, the plot point 71e indicates the combination of the comparative example 2, and the plot point 71f indicates the combination of the FAB irradiation time and the Ar peak distance in Example 1, Example 2, the plot point 71c indicates the combination of the FAB irradiation time and the Ar peak distance in Example 3, the plot point 71d indicates the combination of the FAB irradiation time and the Ar peak distance in Example 4, the plot point 71e indicates the combination of the comparative example 2, and the plot point 71f indicates the combination of the comparative example 2, respectively. However, since there is no peak on the functional substrate 1 side in Comparative Example 1 as described above, Comparative Example 1 is excluded from the plotting target in FIG. 11, and there is no plot point corresponding to it.

[0090] Linear interpolation of the plot points 71a to 71f results in a straight line 71. This straight line 71 represents the relationship between the FAB irradiation time on the functional substrates 1, 1a and the distance between the Ar peaks when the thickness of the bonding layer 33 is 0.6 nm.

[0091] As described above, the thickness of the bonding layer 33 is determined by the FAB irradiation time on the semiconductor substrate 30A side in the sputtering process, and the Ar peak distance also changes depending on the thickness of the bonding layer 33. In other words, it is considered that when the thickness of the bonding layer 33 increases or decreases, the Ar peak distance also increases or decreases accordingly. In addition, in the composite substrates 100 and 110, the greater the thickness of the bonding layer 33, the higher the bonding strength between the functional substrate 1, 1a and the support substrate 30. On the other hand, in consideration of thermal conductivity, light propagation, and the like, it is preferable that the thickness of the bonding layer 33 is as small as possible. From these conditions, when the support substrate 30 is made of SiC, it is preferable that the thickness of the bonding layer 33 in the composite substrates 100 and 110 is within the range of about 0.6 nm to 2.7 nm.

[0092] In Fig. 11, each of plot points 72a to 72f indicated by a white circle indicates a combination of the FAB irradiation time and the Ar peak-to-peak distance when plot points 71a to 71f are slid along the vertical axis of the graph so that the value of the Ar peak-to-peak distance increases by 2.1 nm. Linear interpolation of these plot points 72a to 72f results in a straight line 72. This straight line 72 represents the relationship between the FAB irradiation time to the functional substrates 1, 1a and the Ar peak-to-peak distance when the thickness of the bonding layer 33 is 0.6 + 2.1 = 2.7 nm.

[0093] In the graph shown in FIG. 11, the range 73 surrounded by the plot points 71a, 71b, 71c, 72a, 72b, and 72c indicates the range of possible combinations of the FAB irradiation time and the Ar peak distance for the composite substrate 100 in which the oxide film 20 is processed to be thinner than the original thickness by FAB irradiation in the oxide film removal and activation process, for example, as in Examples 1 to 3. Also, the range 74 surrounded by the plot points 71d, 71e, 72d, and 72e indicates the range of possible combinations of the FAB irradiation time and the Ar peak distance while maintaining the bonding strength for the composite substrate 110 in which the oxide film 20 is completely removed by FAB irradiation in the oxide film removal and activation process, for example, as in Examples 4 and 5. The range between the range 73 and the range 74 corresponds to either the composite substrate 100 or the composite substrate 110.

[0094] As described above, when the support substrate 30 is made of SiC, in the composite substrates 100 and 110 according to the first and second embodiments of the present invention, which are represented by Examples 1 to 5, the combination of the FAB irradiation time and the value of the Ar peak-to-peak distance is included in the ranges 73 and 74 and any of the ranges therebetween. That is, in the composite substrates 100 and 110 according to the first and second embodiments, the value of the Ar peak-to-peak distance in the second functional layer 12 on the functional substrate 1, 1a side and the second support layer 32 on the support substrate 30 side is in the range from the plot point 71a to the plot point 72e, specifically, 2.2 nm or more and 6.1 nm or less. Therefore, when the semiconductor material used in the support substrate 30 is SiC, it is preferable that the Ar peak-to-peak distance is 2.2 nm or more and 6.1 nm or less.

[0095] 11 shows the combination of the FAB irradiation time and the value of the distance between Ar peaks when the support substrate 30 is made of SiC, but the same relationship holds when the support substrate 30 is made of another semiconductor material, for example, Si. However, since the depth to which Ar penetrates into the support substrate 30 during FAB irradiation differs between SiC and Si, the value of the distance between Ar peaks for each FAB irradiation time must be corrected taking into account this difference in depth.

[0096] FIG. 12 is a graph showing the relationship between the FAB irradiation time and the Ar peak distance on the functional substrate 1, 1a when the support substrate 30 is made of Si. In FIG. 12, as in FIG. 11, the horizontal axis represents the FAB irradiation time on the functional substrate 1, 1a, and the vertical axis represents the Ar peak distance. Also, each of the plot points 81a to 81f shown by black circles indicates a combination of the FAB irradiation time and the Ar peak distance when the support substrate 30 is Si, calculated from the combination of the FAB irradiation time and the Ar peak distance obtained in each of the above-mentioned examples and comparative examples. These plot points 81a to 81f correspond to the plot points 71a to 71f in FIG. 11, respectively. Similarly, each of the plot points 82a to 82f shown by white circles indicates a combination of the FAB irradiation time and the Ar peak distance when the support substrate 30 is Si. These plot points 82a to 82f correspond to the plot points 72a to 72f in FIG. 11, respectively.

[0097] When the support substrate 30 is made of Si, it is desirable that the thickness of the bonding layer 33 in the composite substrates 100, 110 be within a range of about 0.3 nm to 3 nm, based on the above conditions. In FIG. 12, a straight line 81 is obtained by linearly interpolating plot points 81a to 81f. This straight line 81 represents the relationship between the FAB irradiation time of the functional substrates 1, 1a and the distance between Ar peaks when the bonding layer 33 has a thickness of 0.3 nm. Similarly, a straight line 82 is obtained by linearly interpolating plot points 82a to 82f. This straight line 82 represents the relationship between the FAB irradiation time of the functional substrates 1, 1a and the distance between Ar peaks when the bonding layer 33 has a thickness of 3 nm.

[0098] In the graph shown in FIG. 12, the range 83 surrounded by the plot points 81a, 81b, 81c, 82a, 82b, and 82c indicates the range of possible combinations of the FAB irradiation time and the Ar peak distance for the composite substrate 100 in which the oxide film 20 has been processed to be thinner than the original thickness by the FAB irradiation in the oxide film removal and activation process, similar to the range 73 in FIG. 11. Also, the range 84 surrounded by the plot points 81d, 81e, 82d, and 82e indicates the range of possible combinations of the FAB irradiation time and the Ar peak distance while maintaining the bonding strength for the composite substrate 110 in which the oxide film 20 has been completely removed by the FAB irradiation in the oxide film removal and activation process, similar to the range 83 in FIG. 11. Note that the range between the range 83 and the range 84 corresponds to either the composite substrate 100 or the composite substrate 110.

[0099] As described above, when the support substrate 30 is made of Si, in the composite substrates 100 and 110 according to the first and second embodiments of the present invention, the combination of the FAB irradiation time and the value of the Ar peak-to-peak distance is included in the ranges 83 and 84 and the ranges therebetween. That is, in the composite substrates 100 and 110 according to the first and second embodiments, the value of the Ar peak-to-peak distance in the second functional layer 12 on the functional substrate 1, 1a side and the second support layer 32 on the support substrate 30 side is in the range from the plot point 81b to the plot point 82e, specifically, 2.5 nm or more and 6.9 nm or less. Therefore, when the semiconductor material used in the support substrate 30 is Si, it is preferable that the Ar peak-to-peak distance is 2.5 nm or more and 6.9 nm or less.

[0100] In the above, the relationship between the FAB irradiation time and the distance between Ar peaks has been described for the composite substrates 100, 110 having the functional substrates 1, 1a made of InP crystals, but as described in the third and fourth embodiments, the same relationship between the FAB irradiation time and the distance between Ar peaks also holds for the composite substrates 120, 121, 130, 131 having the functional substrates 1b, 1c in which the epitaxial layer 50 made of an epitaxial material is formed on the InP layer 10. That is, the relationship between the FAB irradiation time and the distance between Ar peaks shown in the graphs of Figs. 11 and 12 can also be applied to the composite substrates 120, 121, 130, 131 in which the support substrate 30 is made of SiC or Si.

[0101] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0102] (1) Composite substrates 100-131 each include functional substrates 1, 1a, 1b, 1c each including at least one of InP and a crystal of a material that can be formed on an InP crystal by epitaxial growth, and a support substrate 30 made of a semiconductor material and bonded to the functional substrates 1, 1a, 1b, 1c to support the functional substrates 1, 1a, 1b, 1c. The functional substrates 1, 1a, 1b, 1c each include a first layer (first functional layer 11, or first functional layer 51 and second functional layer 52) and a second layer (second functional layer 12 or third functional layer 53) made of an amorphous material containing a rare gas element and disposed closer to the support substrate 30 than the first layer. The support substrate 30 has a first support layer 31, a second support layer 32 arranged closer to the functional substrates 1, 1a, 1b, 1c than the first support layer 31 and made of an amorphous semiconductor material containing a rare gas element, and a bonding layer 33 made of an amorphous semiconductor material in contact with the functional substrates 1, 1a, 1b, 1c. As a result, in the composite substrates 100-131 in which the functional substrates 1, 1a, 1b, 1c containing a crystal of a material that can be formed by epitaxial growth on InP or an InP crystal are bonded to the support substrate 30 via the bonding layer 33, the composite substrates 100-131 capable of efficiently dissipating heat from the functional substrates 1, 1a, 1b, 1c to the support substrate 30 can be realized.

[0103] In the photonics field, a technology has also been developed to miniaturize devices by directly bonding an SOI substrate including an optical circuit made of Si to an InP substrate, and creating a device such as a semiconductor laser using InP on this optical circuit to form an optical transceiver. In a photonics device having such a structure, since light propagates through the bonding interface between the SOI substrate and the InP substrate, it is required that no other material is sandwiched at this interface, or even if some material is sandwiched, the material has a small energy loss in the wavelength band to be used. Therefore, it is not desirable for a barrier layer such as indium oxide to exist at the bonding interface, as in the composite substrate described in the above-mentioned Patent Document 1. In this regard, the oxide film 20 is removed or has a thin thickness in the composite substrates 100 to 131, so that the above requirement can be easily achieved.

[0104] (2) In the composite substrate 100, 110, the functional substrate 1, 1a has a first functional layer 11 made of InP crystals and a second functional layer 12 made of InP amorphous material. In this configuration, the first layer is the first functional layer 11, and the second layer is the second functional layer 12. As a result, it is possible to realize the composite substrate 100, 110 that can obtain sufficient bonding strength even when the functional substrate 1, 1a made of InP crystals is directly bonded to the support substrate 30.

[0105] (3) In the composite substrate 100, the functional substrate 1 has an InP oxide film 20 between the second layer (second functional layer 12) and the support substrate 30. This makes it possible to realize a composite substrate 100 that can efficiently release heat from the functional substrate 1 to the support substrate 30 side while leaving the oxide film 20 formed by natural oxidation of InP.

[0106] (4) In the composite substrates 120 and 130, the functional substrates 1b and 1c have a first functional layer 51 made of an InP crystal, a second functional layer 52 made of a crystal of a material formed by epitaxial growth on the first functional layer 51, and a third functional layer 53 made of an amorphous body of this material. In this configuration, the first layer is the first functional layer 51 and the second functional layer 52, and the second layer is the third functional layer 53. As a result, even when the functional substrates 1b and 1c having the epitaxial layer 50 made of various epitaxial materials formed by epitaxial growth on the InP layer 10 made of an InP crystal are directly bonded to the support substrate 30, the composite substrates 120 and 130 capable of obtaining sufficient bonding strength can be realized.

[0107] (5) In the composite substrate 120, the functional substrate 1b has an oxide film 60 of an epitaxial material between the second layer (third functional layer 53) and the support substrate 30. This makes it possible to realize a composite substrate 120 that can efficiently release heat from the functional substrate 1b to the support substrate 30 side while leaving the oxide film 60 formed by natural oxidation of the epitaxial material.

[0108] (6) In the composite substrates 121 and 131, the functional substrates 1b and 1c have a second functional layer 52 made of a crystal of a material that can be formed by epitaxial growth on an InP crystal, and a third functional layer 53 made of an amorphous body of this material. In this configuration, the first layer is the second functional layer 52, and the second layer is the third functional layer 53. As a result, sufficient bonding strength can be obtained between the functional substrates 1b and 1c and the support substrate 30 in the composite substrates 121 and 131 formed by removing the InP layer 10 from the composite substrates 120 and 130, respectively.

[0109] (7) In the composite substrate 121, the functional substrate 1b has an oxide film 60 of an epitaxial material between the second layer (third functional layer 53) and the supporting substrate 30. As a result, similar to the composite substrate 120, the oxide film 60 formed by natural oxidation of the epitaxial material remains, and heat from the functional substrate 1b can be efficiently released to the supporting substrate 30 side.

[0110] (8) In the composite substrates 100, 120, 121, the thickness of the oxide films 20, 60 is preferably less than 1 nm. In this way, a part of the oxide films 20, 60 formed by natural oxidation on the functional substrates 1, 1b before bonding is removed to make them thinner, thereby improving the thermal conductivity from the functional substrates 1, 1b to the support substrate 30.

[0111] (9) In the composite substrates 100-131, the content of Ar, which is a rare gas element, has a peak in the second layer (the second functional layer 12 or the third functional layer 53) and the second support layer 32. When the semiconductor material used in the support substrate 30 is SiC, the distance between these peaks is preferably 2.2 nm or more and 6.1 nm or less. When the semiconductor material used in the support substrate 30 is Si, the distance between these peaks is preferably 2.5 nm or more and 6.9 nm or less. In this way, the composite substrates 100-131 can be realized that can efficiently release heat from the functional substrates 1, 1a, 1b, and 1c to the support substrate 30 side while maintaining sufficient bonding strength.

[0112] (10) A method for manufacturing a composite substrate 100, 110 including a functional substrate 1, 1a made of InP and a support substrate 30 made of a semiconductor material and supporting the functional substrate 1, 1a, includes an oxide film removal and activation process (FIG. 2(b)) in which an oxide film 20 of InP formed on the surface of the functional substrate 1 and a surface of a semiconductor substrate 30A made of a semiconductor material are irradiated with FAB, respectively, to remove at least a part of the oxide film 20 and activate the surfaces of the functional substrate 1, 1a and the semiconductor substrate 30A. The process includes a sputtering process (FIGS. 2(c), 5(c)) which is carried out following the oxide film removal and activation process, in which after stopping the irradiation of the FAB on the surface of the functional substrate 1, 1a, the irradiation of the FAB on the surface of the semiconductor substrate 30A is continued to sputter a semiconductor material onto the surface of the functional substrate 1, 1a, and a bonding process (FIGS. 3(d), 6(d)) which bonds the functional substrate 1, 1a on which the semiconductor material has been sputtered by the sputtering process to the semiconductor substrate 30A to obtain a bonded body. In this way, the semiconductor substrate 30A and the sputtered film 30B are integrated to form the support substrate 30, and the composite substrates 100, 110 can be produced.

[0113] (11) A method for manufacturing a composite substrate 120, 130 including a functional substrate 1b, 1c having a material formed by epitaxial growth on an InP crystal, and a support substrate 30 made of a semiconductor material and supporting the functional substrate 1b, 1c, includes an oxide film removal / activation step of irradiating an oxide film 60 of the epitaxial material formed on the surface of the functional substrate 1b and a surface of a semiconductor substrate 30A made of a semiconductor material with FAB, respectively, to remove at least a part of the oxide film 60 and activate the surfaces of the functional substrates 1b, 1c and the semiconductor substrate 30A, a sputtering step that is performed following the oxide film removal / activation step, in which after stopping the irradiation of the FAB on the surfaces of the functional substrates 1b, 1c, the irradiation of the FAB on the surface of the semiconductor substrate 30A is continued to sputter a semiconductor material onto the surfaces of the functional substrates 1b, 1c, and a bonding step of bonding the functional substrates 1b, 1c on which the semiconductor material has been sputtered by the sputtering step to the semiconductor substrate 30A to obtain a bonded body. In this manner, supporting substrate 30 is formed by integrating semiconductor substrate 30A and sputtered film 30B, and composite substrates 120, 130 can be fabricated.

[0114] In each embodiment of the present invention described above, in the oxide film removal and activation process, the first FA gun irradiates the surface of the functional substrate 1, 1b with FA and the second FA gun irradiates the surface of the semiconductor substrate 30A with FA. This makes it possible to prevent impurities such as oxide films formed on the surface of the semiconductor substrate 30A from adhering to the surfaces of the functional substrates 1, 1a, 1b, 1c. However, the present invention is not limited to this. For example, a method may be adopted in which the FA irradiation from the first FA gun to the functional substrate 1, 1b side is started first, the FA irradiation from the second FA gun to the semiconductor substrate 30A side is started a predetermined time later, and then the FA irradiation on the functional substrates 1, 1a, 1b, 1c side is stopped first. In this way, the same effect as described above can be obtained.

[0115] The present invention is not limited to the above-described embodiment, and can be implemented using any components without departing from the spirit of the present invention.

[0116] The above-mentioned embodiments and modifications are merely examples, and the present invention is not limited to these contents as long as the characteristics of the invention are not impaired. In addition, although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects that are conceivable within the scope of the technical idea of ​​the present invention are also included in the scope of the present invention. [Explanation of symbols]

[0117] 1, 1a, 1b, 1c: Functional substrate 10:InP layer 11: 1st functional layer 12:Second functional layer 20: Oxide film 30: Support substrate 30A: Semiconductor substrate 30B: Sputtered film 31: 1st support layer 32:Second support layer 33: Bonding layer 40: Bonding interface 50: Epitaxial layer 51: 1st functional layer 52:Second functional layer 53: 3rd functional layer 60:Oxide film 100, 110, 120, 121, 130, 131: Composite board

Claims

1. a functional substrate including at least one of InP and a crystal of a material that can be formed on an InP crystal by epitaxial growth; a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate; the functional substrate has a first layer and a second layer that is disposed closer to the support substrate than the first layer and is made of an amorphous material containing a rare gas element; the support substrate includes a first support layer, a second support layer that is disposed closer to the functional substrate than the first support layer and is made of an amorphous body of the semiconductor material containing the rare gas element, and a bonding layer that is in contact with the functional substrate and is made of an amorphous body of the semiconductor material, the functional substrate has a first functional layer made of InP crystalline material and a second functional layer made of InP amorphous material, the first layer is the first functional layer, the second layer is the second functional layer, The functional substrate is a composite substrate having an InP oxide film between the second layer and the support substrate.

2. a functional substrate including at least one of InP and a crystal of a material that can be formed on an InP crystal by epitaxial growth; a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate; the functional substrate has a first layer and a second layer that is disposed closer to the support substrate than the first layer and is made of an amorphous material containing a rare gas element; the support substrate includes a first support layer, a second support layer that is disposed closer to the functional substrate than the first support layer and is made of an amorphous body of the semiconductor material containing the rare gas element, and a bonding layer that is in contact with the functional substrate and is made of an amorphous body of the semiconductor material, the functional substrate has a first functional layer made of a crystal of InP, a second functional layer made of a crystal of the material formed by epitaxial growth on the first functional layer, and a third functional layer made of an amorphous body of the material, the first layer is the first functional layer and the second functional layer; the second layer is the third functional layer, The functional substrate is a composite substrate having an oxide film of the material between the second layer and the support substrate.

3. a functional substrate including at least one of InP and a crystal of a material that can be formed on an InP crystal by epitaxial growth; a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate; the functional substrate has a first layer and a second layer that is disposed closer to the support substrate than the first layer and is made of an amorphous material containing a rare gas element; the support substrate includes a first support layer, a second support layer that is disposed closer to the functional substrate than the first support layer and is made of an amorphous body of the semiconductor material containing the rare gas element, and a bonding layer that is in contact with the functional substrate and is made of an amorphous body of the semiconductor material, the functional substrate has a second functional layer made of a crystalline body of the material and a third functional layer made of an amorphous body of the material, the first layer is the second functional layer, the second layer is the third functional layer, The functional substrate is a composite substrate having an oxide film of the material between the second layer and the support substrate.

4. The composite substrate according to any one of claims 1 to 3, The oxide film has a thickness of less than 1 nm.

5. The composite substrate according to any one of claims 1 to 3, A composite substrate, wherein the content of the rare gas element has a peak in each of the second layer and the second support layer.

6. The composite substrate according to claim 5, the semiconductor material is SiC; A composite substrate, wherein the distance between the peak in the second layer and the peak in the second support layer is 2.2 nm or more and 6.1 nm or less.

7. The composite substrate according to claim 5, the semiconductor material is Si; A composite substrate, wherein the distance between the peak in the second layer and the peak in the second support layer is 2.5 nm or more and 6.9 nm or less.

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