Composite substrate and manufacturing method for composite substrate

Abstract

A composite substrate according to the present invention comprises: a functional substrate that is configured to include at least one of InP and a crystal of a material which can be formed on an InP crystal by epitaxial growth; and a support substrate that comprises a semiconductor material and is bonded to the functional substrate to support the functional substrate. The functional substrate has: a first layer; and a second layer that is disposed on the side closer to the support substrate than the first layer and comprises an amorphous body containing a rare gas element. The support substrate has: a first support layer; a second support layer that is disposed on the side closer to the functional substrate than the first support layer and comprises an amorphous body of a semiconductor material containing a rare gas element; and a bonding layer that is in contact with the functional substrate and comprises an amorphous body of a semiconductor material.

Description

Composite substrate and method for manufacturing the composite substrate

[0001] The present invention relates to a composite substrate and a method for manufacturing the same.

[0002] Conventionally, composite substrates have been known that are formed by bonding a functional substrate made of indium phosphide (InP) to a support substrate made of a semiconductor material such as Si or SiC. These substrates are used in applications such as photonics devices, such as semiconductor lasers, photodiodes, and modulators, and high-frequency transistors, such as high electron mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs). One known method for fabricating such composite substrates involves irradiating the bonding surfaces of the functional substrate and the support substrate with a fast atom beam (FAB) to perform an activation process, followed by direct bonding of these bonding surfaces. However, this method results in selective sputtering of P on the InP substrate, forming an In layer on the surface. As a result, the In layer on the surface is prone to peeling off from the InP substrate, reducing the bonding strength of the composite substrate (see Non-Patent Document 1).

[0003] To solve the above problem, the technology disclosed in 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, thereby suppressing the formation of an In layer on the surface, thereby achieving sufficient bonding strength to prevent peeling.

[0004] 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

[0005] Japanese Patent Publication No. 2023-500

[0006] In recent years, photonics devices and high-frequency transistors constructed using InP composite substrates have been required to achieve miniaturization, high integration, and high output, which has resulted in an increasing heat density per unit area. In these devices, if the InP temperature rises too much during operation, the desired performance cannot be achieved and reliability and lifespan may be reduced. Therefore, a structure that can efficiently dissipate heat from the device is necessary. However, the composite substrate structure of Patent Document 1 has a barrier layer with low thermal conductivity at the bonding interface, making it difficult to efficiently dissipate heat generated in the InP substrate to the supporting substrate.

[0007] In recent years, composite substrates have been put to practical use, in which devices such as photonics devices and high-frequency transistors are constructed on a substrate that includes a semiconductor material formed by epitaxial growth on an InP crystal and a support substrate. Composite substrates with such structures 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 its main object 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 together via a bonding layer, and the composite substrate is capable of efficiently dissipating heat from the functional substrate to the support substrate, and a method for manufacturing the same.

[0009] The composite substrate according to the present invention comprises a functional substrate comprising at least one of InP and a crystalline material that can be formed by epitaxial growth on an InP crystalline material, and a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate, wherein the functional substrate comprises a first layer and a second layer that is arranged closer to the support substrate than the first layer and is made of an amorphous body containing a rare gas element, and the support substrate comprises a first support layer, a second support layer that is arranged 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. A method for manufacturing a composite substrate according to one aspect of the present invention is a method for manufacturing a composite substrate including a functional substrate made of InP and a support substrate made of a semiconductor material that supports the functional substrate, and includes an oxide film removal and activation step of irradiating a fast atomic beam onto an InP oxide film formed on the surface of the functional substrate and onto the surface of a semiconductor substrate made of the semiconductor material, respectively, to remove at least a portion of the oxide film and activate the surfaces of the functional substrate and the semiconductor substrate; a sputtering step that is carried out subsequent to the oxide film removal and activation step, in which, after stopping the irradiation of the fast atomic beam onto the surface of the functional substrate, the irradiation of the fast atomic beam onto the surface of the semiconductor substrate is continued to sputter the semiconductor material onto the surface of the functional substrate; and a bonding step of bonding the functional substrate with the semiconductor material sputtered by the sputtering step to the semiconductor substrate to obtain a bonded body.A method for manufacturing a composite substrate according to another aspect of the present invention is a method for manufacturing a composite substrate including a functional substrate having a material formed by epitaxial growth on an InP crystal, and a support substrate made of a semiconductor material and supporting the functional substrate, the method including: an oxide film removal and activation step of irradiating an oxide film of the material formed on the surface of the functional substrate and a surface of a semiconductor substrate made of the semiconductor material with a fast atomic beam, respectively, to remove at least a portion of the oxide film and activate the surfaces of the functional substrate and the semiconductor substrate; a sputtering step that is carried out subsequent to the oxide film removal and activation step, in which, after stopping the irradiation of the fast atomic beam on the surface of the functional substrate, the irradiation of the fast atomic beam on the surface of the semiconductor substrate is continued to sputter the semiconductor material onto the surface of the functional substrate; and a bonding step of bonding the functional substrate with the semiconductor material sputtered by the sputtering step to the semiconductor substrate to obtain a bonded body.

[0010] According to the present invention, 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 together via a bonding layer can be realized, in which heat from the functional substrate can be efficiently released toward the support substrate, and a method for manufacturing the same can be realized.

[0011] FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to a first embodiment of the present invention. FIG. 2 is a view showing an example of a manufacturing process for a composite substrate according to the first embodiment of the present invention. FIG. 3 is a view showing an example of a manufacturing process for a composite substrate according to the first embodiment of the present invention. 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. FIG. 5 is a view showing an example of a manufacturing process for a composite substrate according to the second embodiment of the present invention. FIG. 6 is a view showing an example of a manufacturing process for a composite substrate according to the second embodiment of the present invention. 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. 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. FIG. 9 is a view showing observation photographs of examples and comparative examples. FIG. 10 is a table summarizing the FAB irradiation time, 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. FIG. 11 is a graph showing the relationship between the FAB irradiation time and the distance between Ar peaks for a functional substrate when the support substrate is made of SiC. FIG. 12 is a graph showing the relationship between the FAB irradiation time and the distance between Ar peaks for a functional substrate when the support substrate is made of Si.

[0012] Hereinafter, 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 drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the present invention.

[0013] 1 is a schematic cross-sectional view showing a general configuration of a composite substrate according to a first embodiment of the present invention. The composite substrate 100 according to 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 crystalline structure in the InP layer 10 is transformed into an amorphous body 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 part of the InP constituting the InP layer 10 in the 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 or a polycrystalline material. The oxide film 20 of the functional substrate 1 and the support substrate 30 are directly bonded to each other.

[0017] The support substrate 30 can be made of 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, the composite substrate 100 may further include any layer. The type, function, number, combination, arrangement, etc. of such layers may be appropriately set depending on the purpose.

[0019] The composite substrate 100 can be manufactured in any suitable shape. In one embodiment, the composite substrate 100 can be manufactured in the form of a so-called wafer. The size of the composite substrate 100 can be appropriately set depending on the purpose, for example, with a wafer (substrate) diameter of 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] 2A 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 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 by natural oxidation on the surface of the InP layer 10.

[0022] 2(b) shows the 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 the surfaces of the functional substrate 1 prepared in the preparation step of FIG. 2(a) and the semiconductor substrate 30A are irradiated with a fast atom beam (hereinafter referred to as FAB) using a rare gas such as Ar as the atomic species for a predetermined period of time. This removes and thins a portion of the oxide film 20 on the functional substrate 1, and activates the surfaces of the functional substrate 1 and the semiconductor substrate 30A. The FAB irradiation time at this time is preferably, for example, about 5 to 12 seconds.

[0023] 2(c) shows the sputtering step in the manufacturing process of the composite substrate 100. In this step, of the FAB irradiated to the functional substrate 1 and the semiconductor substrate 30A in the oxide film removal / activation step of FIG. 2(b), 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. 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] 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, thereby forming a support substrate 30 having a bonding interface 40 therein, and a bonded body as shown in Fig. 3(e) is obtained.

[0026] 3(e), a first functional layer 11 and a second functional layer 12 are formed on the InP layer 10 of the functional substrate 1, the first functional layer 11 being located closer to the support substrate 30 than the first functional layer 11. The first functional layer 11 is mainly composed of crystalline InP, and the second functional layer 12 is mainly composed of amorphous InP. 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 step of FIG.

[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 that 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 that contacts the bonding interface 40. The second support layer 32 is mainly composed 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 / activation step of FIG. 2(b) and the sputtering step of FIG. 2(c). The bonding layer 33 corresponds to the sputtered film 30B before bonding and is a layer that forms the 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] 3(f) shows a thinning step in the manufacturing process of the composite substrate 100. In this step, the InP layer 10 of the functional substrate 1 is polished to a predetermined thickness to thin the bonded body shown in FIG. 3(e). For example, the InP layer 10 can be polished to thin the bonded body by using grinding, CMP (Chemical Mechanical Polishing), surface planarization using a gas cluster ion beam, or the like.

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

[0031] 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 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 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. Composite substrate 110 according to 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 of Fig. 1 described in the first embodiment. That is, composite substrate 110 has functional substrate 1a that 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, the composite substrate 110 may further include any layer. The type, function, number, combination, arrangement, etc. of such layers may be appropriately set depending on the purpose. Furthermore, the 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] 5A shows a preparation step in the manufacturing process of the composite substrate 110. In this step, similar to the step shown in FIG. 2A 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 by natural oxidation on the surface of the InP layer 10.

[0036] FIG. 5B shows the oxide film removal and activation step in the manufacturing process of the composite substrate 110. In this step, similar to the step shown in FIG. 2B described in the first embodiment, a semiconductor substrate 30A made of a semiconductor material with a predetermined thickness is prepared, and the surfaces of the functional substrate 1 prepared in the preparation step shown in FIG. 5A and the semiconductor substrate 30A are irradiated with FAB using a rare gas such as Ar as the atomic species for a predetermined period of time. In this embodiment, the FAB irradiation of the oxide film 20 is continued until the oxide film 20 is completely removed from the functional substrate 1, exposing the InP layer 10 on the surface. The FAB irradiation time at this time is preferably, for example, about 13 to 24 seconds. As a result, a functional substrate 1a having only the InP layer 10 but 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, similar to the step shown in FIG. 2(c) described in the first embodiment, the FAB irradiation on the functional substrate 1 side, which is irradiated to the functional substrate 1 and the semiconductor substrate 30A in the oxide film removal / activation step shown in FIG. 5(b), is stopped, and the FAB irradiation on the semiconductor substrate 30A side is continued for a predetermined time. As a result, the semiconductor material constituting the semiconductor substrate 30A is sputtered and deposited on the surface of the functional substrate 1a from which the oxide film 20 has been completely removed, i.e., on 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] 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, thereby 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). Further, a first support layer 31 that does not contact the bonding interface 40, a second support layer 32 that is 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 that is 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 thinning process in the manufacturing process of the composite substrate 110. In this process, similar to the process 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 thin the functional substrate 1a.

[0042] Through the above steps, the 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] 7A and 7B are schematic cross-sectional views showing the general 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. 7A includes 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. 7B is formed by removing the InP layer 10 from the composite substrate 120 shown in Fig. 7A.

[0045] The epitaxial layer 50 is a layer made of a crystal of any 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 a crystal of any 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 of part of the epitaxial material constituting the epitaxial layer 50 in the air 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 through the same processes as those described in the first embodiment and illustrated in FIGS. 2A to 3F. Specifically, 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. The oxide film removal and activation process illustrated in FIG. 2B is then performed on this functional substrate 1b to thin it by removing a portion of the oxide film 60 and activate the surfaces of the functional substrate 1b and the semiconductor substrate 30A. The sputtering process illustrated in FIG. 2C and the bonding process illustrated in FIG. 3D are then performed to form a bonded body of the functional substrate 1b and the support substrate 30. The thinning process illustrated in FIG. 3F is then performed on this bonded body to produce the composite substrate 120 having the structure illustrated in FIG. 7A.

[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 within the epitaxial layer 50. The second functional layer 52 is mainly composed of a crystal of the epitaxial material, and the third functional layer 53 is mainly composed of an amorphous 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 located closer to the support substrate 30 than the second functional layer 52.

[0049] In the composite substrate 120, similar to the composite substrates 100 and 110 described in the first and second embodiments, a bonding interface 40, a first support layer 31, a second support layer 32, and a bonding layer 33 are formed in the support 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. 7B 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 epitaxial material, and the third functional layer 53 is mainly composed of an amorphous epitaxial material. The structure of the support substrate 30 is similar to that of the composite substrate 120.

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

[0052] The composite substrate 130 of this embodiment is manufactured through the same processes as those described in the second embodiment and shown in FIGS. 5A to 6F. Specifically, 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. The oxide film removal and activation process shown in FIG. 5B is then performed on this functional substrate 1b to completely remove the oxide film 60, forming a functional substrate 1c, and activating the surfaces of the functional substrate 1c and the semiconductor substrate 30A. The sputtering process shown in FIG. 5C and the bonding process shown in FIG. 6D are then performed to form a bonded assembly of the functional substrate 1c and the support substrate 30. The thin-plate processing process shown in FIG. 6F is then performed on this bonded assembly to produce the composite substrate 130 having the structure shown in FIG. 8A.

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

[0054] Furthermore, by removing the InP layer 10 from the composite substrate 130, a composite substrate 131 having the structure shown in FIG. 8B 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 epitaxial material, and the third functional layer 53 is mainly composed of an amorphous epitaxial material. The structure of the support substrate 30 is similar to that of the composite substrate 130.

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

[0056] Example 1 A bonded body was fabricated 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 FAB guns were installed facing up and down, so that the substrates were positioned within the irradiation ranges of the FAB guns and the surfaces of the two substrates faced each other. In this state, the vacuum chamber was heated for 10 －６ The chamber was evacuated to a pressure in the Pa range, and the surfaces of the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with Ar gas FAB (acceleration voltage 0.9 kV, current 100 mA) from each FAB gun for 1.5 seconds. As a result, 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). At this time, 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. This resulted in the composite substrate 100 having the structure shown in FIG. 1.

[0060] 2 and 3, a bonded body was produced by prolonging the FAB irradiation time of the functional substrate 1 compared to Example 1. Specifically, the same functional substrate 1 and semiconductor substrate 30A as those in Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated to 1000 K. －６ With the vacuum pumped to the Pa range, FAB using Ar gas was simultaneously irradiated from each FAB gun onto the surfaces of the functional substrate 1 and the semiconductor substrate 30A for 6.5 seconds under the same conditions as in Example 1. As a result, part of the oxide film 20 formed on the surface of the functional substrate 1 was removed, making it thinner than its 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, 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).

[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] 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 same functional substrate 1 and semiconductor substrate 30A as those in Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated to 1000 K. －６ With the vacuum pumped to the Pa range, FAB using Ar gas was irradiated simultaneously from each FAB gun toward the surfaces of the functional substrate 1 and the semiconductor substrate 30A for 10.5 seconds under the same conditions as in Example 1. As a result, part of the oxide film 20 formed on the surface of the functional substrate 1 was removed, making it thinner than its 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 (a total of 190.5 seconds). At this time, as in Examples 1 and 2, in order to prevent a change in the internal pressure of the vacuum chamber 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).

[0065] Next, similarly to Examples 1 and 2, the functional substrate 1 on which the sputtered film 30B was formed was directly bonded to the semiconductor substrate 30A, thereby obtaining 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 Figures 5 and 6. Specifically, the same functional substrate 1 and semiconductor substrate 30A as those in Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated to 100°C. －６ In a state where the vacuum was drawn to the Pa range, FAB using Ar gas was simultaneously irradiated from each FAB gun toward the surfaces of the functional substrate 1 and the semiconductor substrate 30A for 14.5 seconds 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 completely 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 (a 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, while the supply of Ar gas to the FAB gun on the functional substrate 1a side was continued. 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 was directly bonded to the semiconductor substrate 30A, thereby obtaining a composite substrate 110 having the structure shown in FIG.

[0069] 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 same functional substrate 1 and semiconductor substrate 30A as those in Example 1 were placed in a vacuum chamber, and the vacuum chamber was heated to 1000 K. －６ In a state where the vacuum was drawn to the Pa range, FAB using Ar gas was simultaneously irradiated from each FAB gun toward the surfaces of the functional substrate 1 and the semiconductor substrate 30A for 18.5 seconds 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 completely 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 (a 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, while the supply of Ar gas to the FAB gun on the functional substrate 1a side was continued. 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 was directly bonded to the semiconductor substrate 30A, thereby obtaining a composite substrate 110 having the structure shown in FIG.

[0072] In Examples 1 to 5, the FAB irradiation from the FAB gun to the functional substrate 1, 1a and the semiconductor substrate 30A was performed for a predetermined time, and then the FAB irradiation on the functional substrate 1, 1a side was stopped first. This allows the time required to form the sputtered film 30B to be used for cooling the functional substrate 1, 1a, thereby reducing the impact of warpage on the bonded composite substrate 100, 110. 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 be more effective in reducing warpage 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 minutes. －６ With the chamber evacuated to a pressure in the Pa range, FAB irradiation was performed only on the semiconductor substrate 30A side for 180 seconds, without 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 was directly bonded to the semiconductor substrate 30A, thereby obtaining the composite substrate 100 having the structure shown in FIG.

[0075] Comparative Example 2 Furthermore, as Comparative Example 2, 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 With the vacuum pumped to the Pa range, FAB irradiation was performed on both the functional substrate 1 and the semiconductor substrate 30A for 24.5 seconds, after which 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 204.5 seconds). The FAB irradiation conditions on the semiconductor substrate 30A side at this time were the same as 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 containing 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 the 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 thinning process. This is thought 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] (Confirmation of laminate structure) The laminate structure of the composite substrates 100, 110 was confirmed by performing transmission electron microscope (TEM) observation on the cross section including the bonding interface 40 of the composite substrates 100, 110 produced in Examples 1 to 5 and Comparative Example 1. 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 observation photographs of 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] 9(b), 9(c), and 9(d) show that two layers are formed inside the InP layer 10 in the functional substrate 1. These layers are designated, in order from the side furthest from the support substrate 30, as a first functional layer 11 and a second functional layer 12. It can also be seen that three layers are formed inside the support substrate 30. These layers are designated, in order from the side furthest from the functional substrate 1, as a first support layer 31, a second support layer 32, and a bonding layer 33. 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-described 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 a 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), and 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) show 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 crystalline InP. That is, in Examples 1 to 5, the second functional layer 12, which corresponds to the portion of the functional substrates 1 and 1a before bonding from the surface irradiated with FAB in the oxide film removal and activation step to a predetermined depth, is formed as a layer of amorphous InP, which is the material of the functional substrates 1 and 1a.

[0081] 9(b) to 9(f) show that, in contrast to the first support layer 31 made of crystalline SiC, the second support layer 32 and the bonding layer 33 do not have a crystalline structure and are made of amorphous SiC. That is, in Examples 1 to 5, the second support layer 32, which corresponds to the 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 an amorphized layer of SiC, the material of the support substrate 30.

[0082] 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] (Thickness of oxide film) 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). The thickness 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). That is, in Examples 1 to 3, a portion of the oxide film 20 was removed by FAB irradiation in the oxide film removal and activation process, resulting in a thickness that was smaller than the original oxide film 20. In Examples 4 and 5, the oxide film 20 was completely removed in the oxide film removal and activation process, and therefore the thickness of the oxide film 20 was 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 FIGS. 9( a) to 9(d). The thickness was 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 on the semiconductor substrate 30A side during the sputtering process after the FAB irradiation on the functional substrate 1, 1a side was stopped was 180 seconds in all cases. As described above, the bonding layer 33 corresponds to the pre-bonded sputtered film 30B formed on the functional substrate 1, 1a side during the sputtering process, and therefore the thickness of the bonding layer 33 is considered to be determined by the FAB irradiation time on the semiconductor substrate 30A side. Therefore, taking into account measurement errors and the like, 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] (Distance between Ar peaks) A structural analysis of the composite substrates 100, 110 was performed 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, an element of the rare gas used in the FAB irradiation, had 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 exists on the functional substrate 1 side.

[0088] 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 for 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 of the functional substrates 1 and 1a, the greater the distance between Ar peaks.

[0089] (Relationship between FAB irradiation time and Ar peak-to-peak distance) FIG. 11 is a graph showing the relationship between the FAB irradiation time and the Ar peak-to-peak distance for functional substrates 1 and 1a when the support substrate 30 is made of SiC. In FIG. 11, the horizontal axis represents the FAB irradiation time for functional substrates 1 and 1a, and the vertical axis represents the Ar peak-to-peak distance. Furthermore, each of plot points 71a to 71f, indicated by a black circle, represents a combination of the FAB irradiation time and the Ar peak-to-peak distance obtained for each example and each comparative example. Specifically, plot point 71a represents the combination of the FAB irradiation time and the Ar peak-to-peak distance for Example 1, plot point 71b represents the combination of the FAB irradiation time and the Ar peak-to-peak distance for Example 2, plot point 71c represents the combination of the FAB irradiation time and the Ar peak-to-peak distance for Example 3, plot point 71d represents the combination of the FAB irradiation time and the Ar peak-to-peak distance for Example 4, plot point 71e represents the combination of the FAB irradiation time and the Ar peak-to-peak distance for Example 5, and plot point 71f represents the combination of the FAB irradiation time and the Ar peak-to-peak distance for Comparative Example 2. However, as mentioned above, Comparative Example 1 does not have a peak on the functional substrate 1 side, and therefore Comparative Example 1 is excluded from the plotting targets in FIG. 11, and there is no plot point corresponding to it.

[0090] Linear interpolation of the plotted points 71a to 71f yields a straight line 71. This straight line 71 represents the relationship between the FAB irradiation time of the functional substrates 1 and 1a and the distance between 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 during the sputtering process, and the Ar peak-to-peak distance also changes depending on the thickness of the bonding layer 33. In other words, it is believed that as the thickness of the bonding layer 33 increases or decreases, the Ar peak-to-peak distance also increases or decreases accordingly. Furthermore, 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, considering factors such as thermal conductivity and optical propagation, it is preferable that the thickness of the bonding layer 33 be as small as possible. Based on these conditions, when the support substrate 30 is made of SiC, the thickness of the bonding layer 33 in the composite substrates 100 and 110 is preferably within the range of approximately 0.6 nm to 2.7 nm.

[0092] 11, plot points 72a to 72f, indicated by white circles, represent combinations 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 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 of the functional substrates 1 and 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] 11, the range 73 surrounded by plot points 71a, 71b, 71c, 72a, 72b, and 72c indicates the range of possible combinations of FAB irradiation time and Ar peak-to-peak distance for a composite substrate 100 in which the oxide film 20 has been processed to a thickness thinner than the original thickness by FAB irradiation in the oxide film removal and activation process, as in Examples 1 to 3. Furthermore, the range 74 surrounded by plot points 71d, 71e, 72d, and 72e indicates the range of possible combinations of FAB irradiation time and Ar peak-to-peak distance for a composite substrate 110 in which the oxide film 20 has been completely removed by FAB irradiation in the oxide film removal and activation process, as in Examples 4 and 5. The range between range 73 and 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, represented by Examples 1 to 5, the combination of the FAB irradiation time and the Ar peak-to-peak distance falls within 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 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 falls within the range from plot point 71a to 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, the Ar peak-to-peak distance is preferably 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 Ar peak-to-peak distance 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 Ar peak-to-peak distance 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-to-peak distance for the functional substrate 1, 1a when the support substrate 30 is made of Si. As with FIG. 11 , in FIG. 12 , the horizontal axis represents the FAB irradiation time for the functional substrate 1, 1a, and the vertical axis represents the Ar peak-to-peak distance. Furthermore, each of the plot points 81a-81f indicated by a black circle represents a combination of the FAB irradiation time and the Ar peak-to-peak distance when the support substrate 30 is made of Si, calculated from the combinations of the FAB irradiation time and the Ar peak-to-peak distance obtained in the aforementioned examples and comparative examples. These plot points 81a-81f correspond to the plot points 71a-71f in FIG. 11 , respectively. Similarly, each of the plot points 82a-82f indicated by a white circle represents a combination of the FAB irradiation time and the Ar peak-to-peak distance when the support substrate 30 is made of Si. These plot points 82a-82f correspond to the plot points 72a-72f in FIG. 11 , respectively.

[0097] When the support substrate 30 is made of Si, based on the above-mentioned conditions, it is desirable that the thickness of the bonding layer 33 in the composite substrates 100, 110 be within a range of approximately 0.3 nm to 3 nm. In FIG. 12 , linear interpolation of plot points 81a to 81f results in a straight line 81. 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, linear interpolation of plot points 82a to 82f results in a straight line 82. 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 Figure 12, the range 83 surrounded by plot points 81a, 81b, 81c, 82a, 82b, and 82c, similar to the range 73 in Figure 11, indicates the range of possible combinations of FAB irradiation time and Ar peak-to-peak distance for a composite substrate 100 in which the oxide film 20 has been processed to be thinner than its original thickness by FAB irradiation in the oxide film removal / activation process. Also, the range 84 surrounded by plot points 81d, 81e, 82d, and 82e, similar to the range 83 in Figure 11, indicates the range of possible combinations of FAB irradiation time and Ar peak-to-peak distance for a composite substrate 110 in which the oxide film 20 has been completely removed by FAB irradiation in the oxide film removal / activation process while maintaining bonding strength. The range between ranges 83 and 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 Ar peak-to-peak distance falls within the ranges 83 and 84 and any of the ranges therebetween. That is, in the composite substrates 100 and 110 according to the first and second embodiments, the Ar peak-to-peak distance in the second functional layer 12 on the functional substrate 1 or 1a side and the second support layer 32 on the support substrate 30 side falls within the range from plot point 81b to 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, the Ar peak-to-peak distance is preferably 2.5 nm or more and 6.9 nm or less.

[0100] Although the relationship between the FAB exposure time and the distance between Ar peaks has been described above for the composite substrates 100 and 110 having the functional substrates 1 and 1a formed using InP crystals as their material, as described in the third and fourth embodiments, a similar relationship between the FAB exposure time and the distance between Ar peaks also holds for the composite substrates 120, 121, 130, and 131 having the functional substrates 1b and 1c in which the epitaxial layer 50 made of an epitaxial material is formed on the InP layer 10. That is, the relationships between the FAB exposure time and the distance between Ar peaks shown in the graphs of Figures 11 and 12, respectively, can also be applied to the composite substrates 120, 121, 130, and 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) The composite substrates 100 to 131 each include a functional substrate 1, 1a, 1b, or 1c 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 30 made of a semiconductor material and bonded to the functional substrate 1, 1a, 1b, or 1c to support the functional substrate 1, 1a, 1b, or 1c. The functional substrate 1, 1a, 1b, or 1c includes a first layer (a first functional layer 11, or a first functional layer 51 and a second functional layer 52) and a second layer (a second functional layer 12 or a third functional layer 53) that is arranged closer to the support substrate 30 than the first layer and is made of an amorphous material containing a rare gas element. The support substrate 30 has a first support layer 31, a second support layer 32 that is arranged closer to the functional substrates 1, 1a, 1b, and 1c than the first support layer 31 and is made of an amorphous semiconductor material containing a rare gas element, and a bonding layer 33 that is in contact with the functional substrates 1, 1a, 1b, and 1c and is made of an amorphous semiconductor material. As a result, in composite substrates 100 to 131 in which the functional substrates 1, 1a, 1b, and 1c that include a crystalline 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, it is possible to realize composite substrates 100 to 131 that can efficiently release heat from the functional substrates 1, 1a, 1b, and 1c toward the support substrate 30.

[0103] Additionally, in the photonics field, a technology has been developed to miniaturize devices by directly bonding an SOI substrate containing an optical circuit made of Si to an InP substrate and then fabricating a device such as an InP-based semiconductor laser on this optical circuit to form an optical transceiver. In photonics devices with this structure, light propagates across the bonded interface between the SOI substrate and the InP substrate. Therefore, the interface must be free of any other material, or, if any material is present, the material must have low energy loss in the wavelength band being used. Therefore, it is undesirable to have a barrier layer such as indium oxide at the bonded interface, as in the composite substrate described in the aforementioned Patent Document 1. In this regard, the oxide film 20 in the composite substrates 100-131 has been removed or thinned, making it easy to achieve the above requirements.

[0104] (2) In the composite substrates 100 and 110, the functional substrates 1 and 1a have 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, the composite substrates 100 and 110 can be realized that can obtain sufficient bonding strength even when the functional substrates 1 and 1a made of InP crystals are 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 toward the support substrate 30 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 can be realized, which are capable of obtaining sufficient bonding strength.

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

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

[0111] (9) In the composite substrates 100 to 131, the content of the rare gas element Ar has peaks 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. Furthermore, 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, composite substrates 100 to 131 can be realized that can efficiently dissipate heat from the functional substrates 1, 1a, 1b, and 1c toward the support substrate 30 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 step (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 method includes a sputtering step (FIGS. 2(c) and 5(c)), which is carried out following the oxide film removal and activation step, 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 step (FIGS. 3(d) and 6(d)), in which the functional substrate 1, 1a onto which the semiconductor material has been sputtered in the sputtering step is bonded 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 functional substrates 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 substrates 1b, 1c, includes: an oxide film removal / activation step in which 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 are irradiated with FAB, respectively, to remove at least a portion 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 subsequent to 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 the semiconductor material onto the surfaces of the functional substrates 1b, 1c; and a bonding step in which the functional substrates 1b, 1c onto which the semiconductor material has been sputtered in the sputtering step are bonded to the semiconductor substrate 30A to obtain a bonded body. In this way, semiconductor substrate 30A and sputtered film 30B are integrated to form support substrate 30, and composite substrates 120 and 130 can be fabricated.

[0114] In the above-described embodiments of the present invention, the oxide film removal and activation process involves simultaneously irradiating the surfaces of the functional substrates 1 and 1b with FAB from the first FAB gun and irradiating the surfaces of the semiconductor substrate 30A with FAB from the second FAB gun. This prevents impurities, such as oxide films, formed on the surfaces of the semiconductor substrate 30A from adhering to the surfaces of the functional substrates 1, 1a, 1b, and 1c. However, the present invention is not limited to this. For example, a method may be employed in which the first FAB gun first starts irradiating the functional substrates 1 and 1b, and then a predetermined time later, the second FAB gun starts irradiating the semiconductor substrate 30A with FAB, and then the FAB irradiation on the functional substrates 1, 1a, 1b, and 1c is stopped first. This method also achieves the same effects as described above.

[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-described embodiments and modifications are merely examples, and the present invention is not limited to these details as long as the features of the invention are not impaired. Furthermore, although various embodiments and modifications have been described above, the present invention is not limited to these details. Other aspects that can be considered within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0117] 1, 1a, 1b, 1c: functional substrate 10: InP layer 11: first functional layer 12: second functional layer 20: oxide film 30: support substrate 30A: semiconductor substrate 30B: sputtered film 31: first support layer 32: second support layer 33: bonding layer 40: bonding interface 50: epitaxial layer 51: first functional layer 52: second functional layer 53: third functional layer 60: oxide film 100, 110, 120, 121, 130, 131: composite substrate

Claims

1. A composite substrate comprising: a functional substrate comprising at least one of InP and a crystalline material that can be formed by epitaxial growth on an InP crystalline material; and a support substrate made of a semiconductor material and bonded to the functional substrate to support the functional substrate, wherein the functional substrate comprises a first layer and a second layer made of an amorphous material containing a rare gas element, which is located closer to the support substrate than the first layer; and the support substrate comprises a first support layer, a second support layer made of an amorphous material of the semiconductor material containing the rare gas element, which is located closer to the functional substrate than the first support layer, and a bonding layer made of an amorphous material of the semiconductor material, which is in contact with the functional substrate.

2. A composite substrate according to claim 1, wherein 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 being the first functional layer, and the second layer being the second functional layer.

3. A composite substrate according to claim 2, wherein the functional substrate has an InP oxide film between the second layer and the support substrate.

4. A composite substrate according to claim 1, wherein the functional substrate has a first functional layer made of InP crystals, 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, wherein the first layer is the first functional layer and the second functional layer, and the second layer is the third functional layer.

5. A composite substrate according to claim 4, wherein the functional substrate has an oxide film of the material between the second layer and the support substrate.

6. A composite substrate according to claim 1, wherein 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 being the second functional layer, and the second layer being the third functional layer.

7. A composite substrate according to claim 6, wherein the functional substrate has an oxide film of the material between the second layer and the support substrate.

8. A composite substrate according to claim 3, 5 or 7, wherein the oxide film has a thickness of less than 1 nm.

9. A composite substrate according to any one of claims 1 to 7, wherein the content of the rare gas element has a peak in each of the second layer and the second support layer.

10. A composite substrate according to claim 9, wherein the semiconductor material is SiC, and 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.

11. A composite substrate according to claim 9, wherein the semiconductor material is Si, and 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.

12. A method for manufacturing a composite substrate comprising a functional substrate made of InP and a support substrate made of a semiconductor material that supports the functional substrate, the method comprising: an oxide film removal and activation process in which a fast atomic beam is irradiated onto an InP oxide film formed on the surface of the functional substrate and onto the surface of a semiconductor substrate made of the semiconductor material, respectively, to remove at least a portion of the oxide film and activate the surfaces of the functional substrate and the semiconductor substrate; a sputtering process that is carried out subsequent to the oxide film removal and activation process, in which, after terminating the irradiation of the fast atomic beam onto the surface of the functional substrate, the irradiation of the fast atomic beam onto the surface of the semiconductor substrate is continued to sputter the semiconductor material onto the surface of the functional substrate; and a bonding process in which the functional substrate onto which the semiconductor material has been sputtered in the sputtering process is bonded to the semiconductor substrate to obtain a bonded body.

13. A method for manufacturing a composite substrate comprising a functional substrate having a material formed by epitaxial growth on an InP crystal, and a support substrate made of a semiconductor material and supporting the functional substrate, the method comprising: an oxide film removal and activation process in which an oxide film of the material formed on the surface of the functional substrate and a surface of a semiconductor substrate made of the semiconductor material are irradiated with a fast atomic beam, respectively, to remove at least a portion of the oxide film and activate the surfaces of the functional substrate and the semiconductor substrate; a sputtering process that is carried out subsequent to the oxide film removal and activation process, in which, after stopping the irradiation of the fast atomic beam onto the surface of the functional substrate, the irradiation of the fast atomic beam onto the surface of the semiconductor substrate is continued to sputter the semiconductor material onto the surface of the functional substrate; and a bonding process in which the functional substrate with the semiconductor material sputtered thereon is bonded to the semiconductor substrate to obtain a bonded body.

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