Composite substrate

Abstract

To realize a composite substrate capable of efficiently releasing heat of a functional substrate to a support substrate side, and a manufacturing method of the same.SOLUTION: A composite substrate includes: a functional substrate including at least one of InP and a crystal of a material capable of being formed by an epitaxial growth on the crystal of the InP; 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 disposed closer to the support substrate than the first layer and formed of an amorphous body containing a rare gas element. The support substrate includes a first support layer, a second support layer disposed closer to the functional substrate than the first support layer and formed of the amorphous body of the semiconductor material containing a rare gas element, and a bonding layer in contact with the functional substrate and formed of the amorphous body of the semiconductor material.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, a composite substrate has been known which is formed by bonding a functional substrate made of InP (indium phosphide) and a support substrate made of a semiconductor material such as Si or SiC, and is used for applications such as photonic devices such as semiconductor lasers, photodiodes, and modulators, and high-frequency transistors such as HEMT (High Electron Mobility Transistor) and HBT (Heterojunction Bipolar Transistor). As a method for manufacturing such a composite substrate, there is known a method in which after performing an activation process by irradiating each bonding surface of the functional substrate and the support substrate with a fast atom beam (FAB: Fast Atom Beam), these bonding surfaces are directly bonded to each other. 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, there has been a problem that the In layer on the surface is easily peeled off from the InP substrate, and the bonding strength of the composite substrate is reduced (see Non-Patent Document 1).

[0003] Therefore, as a solution to the above problem, the technique of Patent Document 1 is known. Patent Document 1 discloses a direction in which a barrier layer of indium oxide is formed on an InP substrate, and this barrier layer and a silicon substrate are bonded via an amorphous layer. By this method, since the fast atom beam is prevented from directly irradiating the InP substrate by the barrier layer, formation of an In layer on the surface can be suppressed, and sufficient bonding strength without peeling can be obtained.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-500 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In recent years, photonic devices and high-frequency transistors composed of composite substrates using InP have been required to be miniaturized, highly integrated, and to have higher output power, which in turn has led to an increasing heat density per unit area. In these devices, if the InP temperature rises too high during operation, the desired performance cannot be achieved, and it can also lead to a decrease in reliability and lifespan. Therefore, it is necessary to have a structure that can efficiently dissipate the heat from the device. However, in the composite substrate structure of Patent Document 1, there is a barrier layer with low thermal conductivity at the bonding interface, making it difficult to efficiently dissipate the heat generated in the InP substrate to the support substrate.

[0007] In recent years, composite substrates have also been put into practical use, which consist of a substrate containing a semiconductor material formed by epitaxial growth on an InP crystal and a support substrate, on which devices such as photonic devices and high-frequency transistors are constructed. Similarly, in composite substrates with such structures, it is necessary to have a structure that efficiently dissipates the heat from the device to the support substrate.

[0008] The present invention has been made in view of the above, and its main objective is to realize a composite substrate and a method for manufacturing the same, in which a functional substrate containing crystals of a material that can be formed by epitaxial growth on InP or InP crystals is bonded to a support substrate via a bonding layer, and the functional substrate is capable of efficiently dissipating heat to the support substrate. [Means for solving the problem]

[0009] A composite substrate according to a first aspect of the present invention comprises a functional substrate comprising at least one of InP and a crystal of a material that can be formed by epitaxial growth on a crystal of InP, and a support substrate made of a semiconductor material, bonded to the functional substrate and supporting the functional substrate, wherein the functional substrate comprises a first layer and a second layer disposed closer to the support substrate than the first layer and made of an amorphous material containing a noble gas element, wherein the support substrate comprises a first support layer and a second support layer disposed closer to the functional substrate than the first support layer and made of an amorphous material of the semiconductor material containing the noble gas element, and a bonding layer in contact with the functional substrate and made of an amorphous material of the semiconductor material, wherein the content of the noble gas element has peaks in the second layer and the second support layer, respectively, 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. Furthermore, if the thickness of the bonding layer is t, then t is between 0.6 nm and 2.7 nm, and the distance is within the range of {2.2 + (t - 0.6)} nm and {4.0 + (t - 0.6)} nm. . A composite substrate according to a second aspect of the present invention comprises a functional substrate comprising at least one of InP and a crystal of a material that can be formed by epitaxial growth on a crystal of InP, and a support substrate made of a semiconductor material, bonded to the functional substrate and supporting the functional substrate, wherein the functional substrate comprises a first layer and a second layer disposed closer to the support substrate than the first layer and made of an amorphous material containing a noble gas element, wherein the support substrate comprises a first support layer and a second support layer disposed closer to the functional substrate than the first support layer and made of an amorphous material of the semiconductor material containing the noble gas element, and a bonding layer in contact with the functional substrate and made of an amorphous material of the semiconductor material, wherein the content of the noble gas element has peaks in the second layer and the second support layer, respectively, 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. Furthermore, if the thickness of the bonding layer is t, then t is between 0.3 nm and 3.0 nm, and the distance is within the range of {2.5 + (t - 0.3)} nm and {4.2 + (t - 0.3)} nm. . [Effects of the Invention]

[0010] According to the present invention, in a composite substrate in which a functional substrate containing crystals of a material that can be formed by epitaxial growth on InP or InP crystals is bonded to a support substrate via a bonding layer, it is possible to realize a composite substrate and a method for manufacturing the same that can efficiently dissipate heat from the functional substrate to the support substrate. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing the general configuration of a composite substrate according to the first embodiment of the present invention. [Figure 2] This figure shows an example of the manufacturing process for a composite substrate according to the first embodiment of the present invention. [Figure 3] This figure shows an example of the manufacturing process for a composite substrate according to the first embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view showing the general configuration of a composite substrate according to a second embodiment of the present invention. [Figure 5]It is a diagram showing an example of a manufacturing process of a composite substrate according to a second embodiment of the present invention. [Figure 6] It is a diagram showing an example of a manufacturing process of a composite substrate according to a second embodiment of the present invention. [Figure 7] It 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] It 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] It is a diagram showing observation photos of an example and a comparative example. [Figure 10] It is a table summarizing the FAB irradiation time, the presence or absence of peeling of the bonding interface during processing, the thickness of the oxide film, and the distance between Ar peaks in each of the example and the comparative example. [Figure 11] It is a graph showing the relationship between the FAB irradiation time to the functional substrate and the distance between Ar peaks when the support substrate is made of SiC. [Figure 12] It is a graph showing the relationship between the FAB irradiation time to the functional substrate and the distance between Ar peaks when the support substrate is made of Si.

Mode for Carrying Out the Invention

[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. Further, for the purpose of making the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part as compared with the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0013] (First Embodiment) 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. The composite substrate 100 in the present embodiment is used for various applications 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, a crystalline form of InP is used as the material for the functional substrate 1. A portion of the crystalline structure in the InP layer 10 transforms into an amorphous state during the manufacturing process of the composite substrate 100, and is contained within the InP layer 10 in this amorphous state. This point will be discussed later.

[0015] The oxide film 20 is an oxide layer formed on the surface of the InP layer 10 by the spontaneous 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 placed 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, which includes the InP layer 10 and the oxide film 20. Any suitable substrate can be used as the support substrate 30. The support substrate 30 may be made 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 material used to construct the support substrate 30 can be a semiconductor material such as SiC or Si. Alternatively, the support substrate 30 may be constructed using AlN, diamond, or SOI (Silicon on Insulator). When SOI is used as the support substrate 30, this SOI substrate (support substrate 30) may include optical circuits, electrical circuits, etc., made of Si. The thickness of the support substrate 30 is, for example, 0.2 to 1 mm, but any other appropriate thickness can be adopted.

[0018] Although not shown in the figures, the composite substrate 100 may have additional layers of any choice. The type, function, number, combination, and arrangement of such layers can be appropriately determined according to 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 also be appropriately set according to the purpose, for example, with a wafer (substrate) diameter of 50 mm to 150 mm.

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

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

[0022] Figure 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 of a predetermined thickness is prepared, and the functional substrate 1 prepared in the preparation step of Figure 2(a) and the semiconductor substrate 30A are irradiated with a high-speed atomic beam (hereinafter referred to as FAB) using a noble gas such as Ar as the atomic species for a predetermined time. This removes a portion of the oxide film 20 on the functional substrate 1, making it thinner, and activates the surfaces of the functional substrate 1 and the semiconductor substrate 30A. The irradiation time of the FAB at this time is preferably about 5 to 12 seconds.

[0023] Figure 2(c) shows the sputtering process in the manufacturing process of the composite substrate 100. In this process, of the FABs that were irradiated onto the functional substrate 1 and the semiconductor substrate 30A respectively in the oxide film removal and activation process shown in Figure 2(b), the FAB irradiation on the functional substrate 1 is stopped, and the FAB irradiation on the semiconductor substrate 30A is continued for a predetermined time. The irradiation time of the FAB at this time is preferably, for example, about 30 seconds 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), forming a sputtered film 30B on the functional substrate 1 side made of the same semiconductor material as the semiconductor substrate 30A.

[0024] Figure 3(d) shows the bonding process in the manufacturing process of the composite substrate 100. In this process, the functional substrate 1, on which the sputtered film 30B has been formed in the sputtering process shown in Figure 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 a support substrate 30, and a bonded body of the functional substrate 1 and the support substrate 30 is obtained.

[0025] Figure 3(e) shows the bonded body obtained after the bonding process shown in Figure 3(d). Through the bonding process shown in Figure 3(d), the semiconductor substrate 30A and the sputtered film 30B are integrated as described above, forming a support substrate 30 having the bonding interface 40 inside, and thus a bonded body like that shown in Figure 3(e) is obtained.

[0026] In the bond shown in Figure 3(e), the InP layer 10 of the functional substrate 1 has a first functional layer 11 and a second functional layer 12 positioned 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 noble gas atoms such as Ar, which were irradiated as FAB in the oxide film removal and activation process shown in Figure 2(b).

[0027] Furthermore, in the bonded structure shown in Figure 3(e), the support substrate 30 has a first support layer 31 that does not contact the bonding interface 40, a second support layer 32 that is positioned 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 positioned 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 composed of amorphous semiconductor material and is a layer containing rare gas atoms such as Ar that were irradiated as FAB in the oxide film removal and activation process shown in Figure 2(b) and the sputtering process shown in Figure 2(c). The bonding layer 33 corresponds to the sputtered film 30B before bonding and is the layer that forms the bonding portion with the functional substrate 1.

[0028] Furthermore, 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 were mixed into these layers during the sputtering process shown in Figure 2(c), such as Fe atoms and Al atoms that constitute the jigs and base portions used to fix the semiconductor substrate 30A.

[0029] Figure 3(f) shows the 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 thin the bonded structure shown in Figure 3(e). For example, the InP layer 10 can be polished and thinned using grinding, CMP (Chemical Mechanical Polishing), or surface planarization using a gas cluster ion beam.

[0030] Through the above steps, a composite substrate 100 with the structure shown in Figure 1 is manufactured.

[0031] Furthermore, an annealing step may be performed between the bonding step shown in Figure 3(d) and the thin sheet processing step shown in Figure 3(f), in which the bonded body is heated to a predetermined temperature. The heating temperature at this time is preferably around 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) Figure 4 is a schematic cross-sectional view showing the general configuration of a composite substrate according to a second embodiment of the present invention. The composite substrate 110 in this embodiment has a structure in which the oxide film 20 is not disposed between the InP layer 10 and the support substrate 30, compared to the composite substrate 100 of Figure 1 described in the first embodiment. That is, the composite substrate 110 has a functional substrate 1a composed of an InP layer 10 and without an oxide film 20, instead of the functional substrate 1 in the composite substrate 100.

[0033] In this embodiment, as with the first embodiment described above, the composite substrate 110 may further have arbitrary layers. The type, function, number, combination, and arrangement of such layers can be appropriately set according to the purpose. Furthermore, the composite substrate 110 can be manufactured in any appropriate shape according to the purpose.

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

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

[0036] Figure 5(b) shows the oxide film removal and activation step in the manufacturing process of the composite substrate 110. In this step, similar to the step in Figure 2(b) described in the first embodiment, a semiconductor substrate 30A made of a semiconductor material of a predetermined thickness is prepared, and the functional substrate 1 prepared in the preparation step in Figure 5(a) and the semiconductor substrate 30A are irradiated with a FAB using a rare gas such as Ar as an atomic species for a predetermined 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 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. 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] Figure 5(c) shows the sputtering process in the manufacturing process of the composite substrate 110. In this process, similar to the process in Figure 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 predetermined time, compared to the FAB irradiation on the functional substrate 1 and the semiconductor substrate 30A side in the oxide film removal and activation process in Figure 5(b). As a result, the semiconductor material constituting the semiconductor substrate 30A is sputtered and deposited on the surface of the functional substrate 1a, i.e., the surface of the InP layer 10, from which the oxide film 20 has been completely removed, forming a sputtered film 30B on the functional substrate 1a side made of the same semiconductor material as the semiconductor substrate 30A.

[0038] Figure 6(d) shows the bonding process in the manufacturing process of the composite substrate 110. In this process, similar to the process shown in Figure 3(d) described in the first embodiment, the functional substrate 1a, on which the sputtered film 30B has been formed in the sputtering process shown in Figure 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 a support substrate 30, and a bonded body of the functional substrate 1a and the support substrate 30 is obtained.

[0039] Figure 6(e) shows the bonded body obtained after the bonding process shown in Figure 6(d). Through the bonding process shown in Figure 6(d), the semiconductor substrate 30A and the sputtered film 30B are integrated as described above, forming a support substrate 30 having the bonding interface 40 inside, and a bonded body like that shown in Figure 6(e) is obtained.

[0040] In the bonded structure shown in Figure 6(e), similar to the bonded structure shown in Figure 3(e) described in the first embodiment, the functional substrate 1a (InP layer 10) has a first functional layer 11 and a second functional layer 12 positioned closer to the support substrate 30 than the first functional layer 11. The support substrate 30 has a first support layer 31 that does not contact the bonding interface 40, a second support layer 32 positioned closer to the functional substrate 1a than the first support layer 31 and in contact with the bonding interface 40, and a bonding layer 33 positioned closer to the functional substrate 1a than the second support layer 32 and in contact with the bonding interface 40.

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

[0042] Through the above steps, a composite substrate 110 with the structure shown in Figure 4 is manufactured.

[0043] In this embodiment, as in the first embodiment, an annealing step may be performed between the joining step in Figure 6(d) and the thin sheet processing step in Figure 6(f) to heat the joined body to a predetermined temperature.

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

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

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

[0047] The composite substrate 120 of this embodiment is manufactured by the same process as the processes shown in Figures 2(a) to 3(f) described in the first embodiment. Specifically, a functional substrate 1b of a predetermined thickness having an InP layer 10, an epitaxial layer 50, and an oxide film 60 is prepared, and the oxide film removal and activation process shown in Figure 2(b) is performed on this functional substrate 1b to remove a portion of the oxide film 60 and make it thinner, and to activate the surfaces of the functional substrate 1b and the semiconductor substrate 30A. Subsequently, the sputtering process shown in Figure 2(c) and the bonding process shown in Figure 3(d) are performed to form a bond between the functional substrate 1b and the support substrate 30, and the thinning process shown in Figure 3(f) is performed on this bond to manufacture the composite substrate 120 having the structure shown in Figure 7(a).

[0048] In the composite substrate 120, the functional substrate 1b includes 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 crystalline epitaxial material, and the third functional layer 53 is mainly composed of amorphous epitaxial material. The third functional layer 53 is a layer containing rare gas atoms such as Ar, which were 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] Furthermore, in the composite substrate 120, a bonding interface 40, a first support layer 31, a second support layer 32, and a bonding layer 33 are formed within the support substrate 30, similar to the composite substrates 100 and 110 described in the first and second embodiments, respectively. These are formed in the bonded body obtained by the bonding process described above.

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

[0051] (Fourth embodiment) Figure 8 is a schematic cross-sectional view showing the general configuration of a composite substrate according to the fourth embodiment of the present invention. In this embodiment, the composite substrate 130 shown in Figure 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 shown in Figure 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 does not contain an oxide film 60, instead of the functional substrate 1b in the composite substrate 120. Furthermore, the composite substrate 131 shown in Figure 8(b) is formed by removing the InP layer 10 from the composite substrate 130 of Figure 8(a).

[0052] The composite substrate 130 of this embodiment is manufactured by the same process as the processes shown in Figures 5(a) to 6(f) described in the second embodiment. Specifically, a functional substrate 1b of a predetermined thickness having an InP layer 10, an epitaxial layer 50, and an oxide film 60 is prepared, and the oxide film removal and activation process shown in Figure 5(b) is performed on this functional substrate 1b to remove all of the oxide film 60 and form a functional substrate 1c, and at the same time activate the surfaces of the functional substrate 1c and the semiconductor substrate 30A. Subsequently, the sputtering process shown in Figure 5(c) and the bonding process shown in Figure 6(d) are performed to form a bond between the functional substrate 1c and the support substrate 30, and the thin sheet processing process shown in Figure 6(f) is performed on this bond to manufacture the composite substrate 130 having the structure shown in Figure 8(a).

[0053] In this embodiment, the composite substrate 130, like the composite substrate 120 described in the third embodiment, 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. Furthermore, the support substrate 30 has a bonding interface 40, a first support layer 31, a second support layer 32, and a bonding layer 33 formed within it.

[0054] Furthermore, by removing the InP layer 10 from the composite substrate 130, a composite substrate 131 with the structure shown in Figure 8(b) is manufactured. Similar to the third embodiment, the removal of the InP layer 10 can be performed, for example, by wet etching. In this composite substrate 131, the functional substrate 1c has 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 crystalline epitaxial material, and the third functional layer 53 is mainly composed of amorphous epitaxial material. The structure of the support substrate 30 is the same as that of the composite substrate 130. [Examples]

[0055] The following describes specific examples for verifying the structure of the composite substrate according to the present invention. Unless otherwise specified, the following procedures were performed at room temperature.

[0056] (Example 1) A bonded structure was fabricated according to the manufacturing process described with reference to Figures 2 and 3. Specifically, an InP wafer and a SiC wafer of predetermined sizes were prepared, and the InP wafer was used as functional substrate 1, and the SiC wafer as 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 positioned in a vacuum chamber, with FAB guns installed facing upwards and downwards, such that the substrates were within the irradiation range of each FAB gun and their surfaces faced each other. In this state, the inside of the vacuum chamber was 10 -6The surfaces were vacuumed to a Pa level, and Ar gas-assisted FAB (acceleration voltage 0.9kV, current 100mA) was simultaneously irradiated from each FAB gun onto the surfaces of the functional substrate 1 and the semiconductor substrate 30A for 1.5 seconds. As a result, a portion of the oxide film 20 formed on the surface of the functional substrate 1 was removed, making it thinner than its original thickness.

[0058] Subsequently, the FAB irradiation on the functional substrate 1 was stopped, while the FAB irradiation on the semiconductor substrate 30A was continued for another 180 seconds (a total of 181.5 seconds). To prevent a change in the internal pressure of the vacuum chamber before and after the FAB irradiation on the functional substrate 1 was stopped, the supply of Ar gas to the FAB gun on the functional substrate 1 was continued while the FAB irradiation from the FAB gun to the surface of the functional substrate 1 was stopped. 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 and the semiconductor substrate 30A were directly bonded together. Specifically, the beam-irradiated surfaces of both substrates were overlapped, and the two substrates were bonded together by applying pressure of 10,000 N for 2 minutes at room temperature to obtain a bonded body. This resulted in a composite substrate 100 with the structure shown in Figure 1.

[0060] (Example 2) Following the manufacturing process described with reference to Figures 2 and 3, a bonded body was fabricated by extending the FAB irradiation time of the functional substrate 1 compared to Example 1. Specifically, the same functional substrate 1 and semiconductor substrate 30A as in Example 1 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated for 10 minutes. -6 With the system evacuated to a Pa level, the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with Ar gas FAB for 6.5 seconds from each FAB gun under the same conditions as in Example 1. As a result, a portion 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] Subsequently, while stopping the FAB irradiation on the functional substrate 1 side, 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 a change in the internal pressure of the vacuum chamber before and after stopping the FAB irradiation on the functional substrate 1 side, the supply of Ar gas to the FAB gun on the functional substrate 1 side was continued, and the FAB irradiation from the FAB gun to the surface of the functional substrate 1 was stopped. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1 (oxide film 20).

[0062] Next, similar to Example 1, a composite substrate 100 with the structure shown in Figure 1 was obtained by directly bonding the functional substrate 1 on which the sputtered film 30B was formed with the semiconductor substrate 30A.

[0063] (Example 3) Following the manufacturing process described with reference to Figures 2 and 3, a bonded body was fabricated by extending 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 in Example 1 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated for 10 minutes. -6 With the system evacuated to a Pa level, the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with Ar gas FAB from each FAB gun for 10.5 seconds under the same conditions as in Example 1. As a result, a portion 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] Subsequently, while stopping the FAB irradiation on the functional substrate 1 side, 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 stopping the FAB irradiation on the functional substrate 1 side, the supply of Ar gas to the FAB gun on the functional substrate 1 side was continued, and the FAB irradiation from the FAB gun to the surface of the functional substrate 1 was stopped. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1 (oxide film 20).

[0065] Next, similar to Examples 1 and 2, a composite substrate 100 with the structure shown in Figure 1 was obtained by directly bonding the functional substrate 1 on which the sputtered film 30B was formed with the semiconductor substrate 30A.

[0066] (Example 4) A bonded body was fabricated according to the manufacturing process described with reference to Figures 5 and 6. Specifically, a functional substrate 1 and a semiconductor substrate 30A, similar to those in Example 1, were placed in a vacuum chamber, and the inside of the vacuum chamber was heated to 10°C. -6 With the system evacuated to a Pa level, the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with Ar gas FAB from each FAB gun 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 was formed that had only the InP layer 10 and did not contain the oxide film 20.

[0067] Subsequently, while stopping the FAB irradiation on the functional substrate 1a side, 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 a change in the internal pressure of the vacuum chamber before and after stopping the FAB irradiation on the functional substrate 1a side, the supply of Ar gas to the FAB gun on the functional substrate 1a side was continued, and the FAB irradiation from the FAB gun to the surface of the functional substrate 1a was stopped. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1a.

[0068] Next, similar to Examples 1 to 3, a composite substrate 110 with the structure shown in Figure 4 was obtained by directly bonding the functional substrate 1a on which the sputtered film 30B was formed with the semiconductor substrate 30A.

[0069] (Example 5) Following the manufacturing process described with reference to Figures 5 and 6, a bonded body was fabricated by extending the FAB irradiation time of the functional substrate 1 compared to Example 4. Specifically, the same functional substrate 1 and semiconductor substrate 30A as in Example 1 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated for 10 minutes. -6With the system evacuated to a Pa level, the functional substrate 1 and the semiconductor substrate 30A were simultaneously irradiated with Ar gas FAB from each FAB gun 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 was formed that had only the InP layer 10 and did not contain the oxide film 20.

[0070] Subsequently, while stopping the FAB irradiation on the functional substrate 1a side, 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 a change in the internal pressure of the vacuum chamber before and after stopping the FAB irradiation on the functional substrate 1a side, the supply of Ar gas to the FAB gun on the functional substrate 1a side was continued, and the FAB irradiation from the FAB gun to the surface of the functional substrate 1a was stopped. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1a.

[0071] Next, similar to Examples 1 to 4, a composite substrate 110 with the structure shown in Figure 4 was obtained by directly bonding the functional substrate 1a on which the sputtered film 30B was formed with the semiconductor substrate 30A.

[0072] In the above embodiments 1 to 5, after performing FAB irradiation from the FAB gun to the functional substrates 1, 1a and the semiconductor substrate 30A for a predetermined time, the FAB irradiation on the functional substrates 1, 1a was stopped first. This allows the time required for the formation of the sputtered film 30B to be used for cooling the functional substrates 1, 1a, thereby reducing the effect of warping in the composite substrates 100, 110 after bonding. In particular, when the functional substrate 1, 1a has a larger coefficient of thermal expansion than the semiconductor substrate 30A, stopping the FAB irradiation on the functional substrate 1, 1a first can be more effective in reducing warping after bonding.

[0073] (Comparative Example 1) To confirm the effects of the present invention, as Comparative Example 1, a functional substrate 1 and a 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 to 10°C.-6 With the system evacuated to the Pa level, FAB irradiation was performed on the semiconductor substrate 30A only for 180 seconds, without FAB irradiation on the functional substrate 1. The FAB irradiation conditions for the semiconductor substrate 30A at this time were the same as in Examples 1 to 5. As a result, a sputtered film 30B was formed on the surface of the functional substrate 1.

[0074] Next, similar to Examples 1 to 5, a composite substrate 100 with the structure shown in Figure 1 was obtained by directly bonding the functional substrate 1 on which the sputtered film 30B was formed with the semiconductor substrate 30A.

[0075] (Comparative Example 2) Furthermore, as Comparative Example 2, the same functional substrate 1 and semiconductor substrate 30A as in Examples 1 to 5 were placed in a vacuum chamber, and the inside of the vacuum chamber was heated to 10 -6 With the system evacuated to a Pa level, both the functional substrate 1 and the semiconductor substrate 30A were subjected to FAB irradiation for 24.5 seconds. After that, the FAB irradiation on the functional substrate 1 was stopped, while the FAB irradiation on the semiconductor substrate 30A was continued for another 180 seconds (a total of 204.5 seconds). The FAB irradiation conditions for the semiconductor substrate 30A at this time were the same as those in Examples 1 to 5. As a result, all of the oxide film 20 formed on the surface of the functional substrate 1 was removed, and a functional substrate 1a was formed that had only the InP layer 10 and did not contain the oxide film 20, and a sputtered film 30B was formed on the surface of the functional substrate 1a.

[0076] Next, similar to Examples 1 to 5, a composite substrate 110 with the structure shown in Figure 4 was obtained by directly bonding the functional substrate 1a on which the sputtered film 30B was formed to the semiconductor substrate 30A. In this comparative example 2 composite substrate 110, delamination occurred at the bonding interface 40 during the thin sheet processing step. This is thought to be because the FAB irradiation time on the semiconductor substrate 30A side was too long, increasing the surface roughness of the bonding interface 40 and reducing the bonding strength.

[0077] (Confirmation of layered structure) The layered structure of the composite substrates 100 and 110 was confirmed by performing transmission electron microscopy (TEM) observation of the cross-sections including the bonding interface 40 of the composite substrates 100 and 110 prepared in Examples 1 to 5 and Comparative Example 1, respectively. Figure 9(a) shows the observation photograph of Comparative Example 1, Figure 9(b) shows the observation photograph of Example 1, Figure 9(c) shows the observation photograph of Example 2, Figure 9(d) shows the observation photograph of Example 3, Figure 9(e) shows the observation photograph of Example 4, and Figure 9(f) shows the observation photograph of Example 5. In Comparative Example 1 and Examples 1 to 3 shown in Figures 9(a) to 9(d), the functional substrate 1 after bonding corresponds to a composite substrate 100 having an oxide film 20, while in Examples 4 and 5 shown in Figures 9(e) and 9(f), the functional substrate 1a after bonding corresponds to a composite substrate 110 that does not have an oxide film 20.

[0078] From the observation photographs of Examples 1 to 3 shown in Figures 9(b), 9(c), and 9(d), it can be seen that two layers are formed inside the InP layer 10 of the functional substrate 1. These layers are designated as the first functional layer 11 and the second functional layer 12, starting from the side furthest from the support substrate 30. It can also be seen that three layers are formed inside the support substrate 30. These layers are designated as the first support layer 31, the second support layer 32, and the bonding layer 33, starting from the side furthest 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 aforementioned bonding process exists between the second support layer 32 and the bonding layer 33. In other words, during the bonding process, the surface of the second support layer 32 on the semiconductor substrate 30A before bonding and the surface of the sputtered film 30B formed on the oxide film 20 on 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 is formed, having a bonding interface 40 inside the support substrate 30.

[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), a first support layer 31, a second support layer 32, and a bonding layer 33 are formed inside the support substrate 30, and a bonding interface 40 exists between the second support layer 32 and the bonding layer 33.

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

[0081] Similarly, the observation photographs in Figures 9(b) to 9(f) show that, unlike the first support layer 31 which is made of crystalline SiC, the second support layer 32 and the bonding layer 33 do not have a crystalline structure and are composed of amorphous SiC. In other words, in Examples 1 to 5, the second support layer 32, which corresponds to the portion from the surface to a predetermined depth after the FAB was irradiated in the oxide film removal / activation process and the sputtering process on the semiconductor substrate 30A before bonding, and the bonding layer 33, which corresponds to the sputtered film 30B formed on the surface of the functional substrates 1,1a in the sputtering process, are formed as amorphous layers of SiC, which is the material of the support substrate 30.

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

[0083] (Thickness of the oxide film) For the composite substrates 100 fabricated in Examples 1 to 3, the thickness of the oxide film 20 was measured from the observation photographs in Figures 9(b), 9(c), and 9(d). In Example 1, the thickness was 0.9 nm, and in Examples 2 and 3, it was 0.6 nm. On the other hand, in Comparative Example 1, the thickness of the oxide film 20 was measured from the observation photograph in Figure 9(a) and it was 1 nm. In other words, in Examples 1 to 3, a portion of the oxide film 20 is removed by FAB irradiation during the oxide film removal and activation process, resulting in a thickness less than the original oxide film 20. In Examples 4 and 5, the oxide film 20 is completely removed during the oxide film removal and activation process, so the thickness of the oxide film 20 is 0.

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

[0085] In Comparative Example 1 and Examples 1-5, the FAB irradiation time to the semiconductor substrate 30A during the sputtering process after stopping the FAB irradiation on the functional substrate 1,1a side was 180 seconds in all cases. As mentioned above, the bonding layer 33 corresponds to the sputtered film 30B formed on the functional substrate 1,1a side before bonding during 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, considering measurement errors, etc., the actual thickness of the bonding layer 33 in Comparative Examples 1, 2 and Examples 1-5 is considered to be approximately the same, around 0.6 nm.

[0086] (Ar peak distance) Structural analysis of the composite substrates 100 and 110 was performed by EDX analysis on cross-sections including the bonding interface 40 of the composite substrates 100 and 110 prepared in Examples 1 to 5 and Comparative Example 2. As a result, it was found that the content of Ar, a noble gas element used in FAB irradiation, had peaks in the second functional layer 12 on the functional substrate 1 and 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 prepared in Comparative Example 1, since FAB irradiation was not performed on the functional substrate 1 side, the content of Ar, a noble gas element used in FAB irradiation, shows a peak only in the second support layer 32 on the support substrate 30 side, and there is no peak on the functional substrate 1 side.

[0088] Figure 10 is a table summarizing the FAB irradiation time, presence or absence of delamination of the bonding interface 40 during processing, thickness of the oxide film 20, and distance between Ar peaks for each of Examples 1-5 and Comparative Examples 1 and 2. From the table in Figure 10, it can be seen that the distance between Ar peaks increases as the FAB irradiation time on the functional substrates 1 and 1a increases.

[0089] (Relationship between FAB irradiation time and Ar peak distance) Figure 11 is a graph showing the relationship between FAB irradiation time and Ar peak distance to functional substrates 1 and 1a when the support substrate 30 is made of SiC. In Figure 11, the horizontal axis represents the FAB irradiation time to functional substrates 1 and 1a, and the vertical axis represents the Ar peak distance. The plot points 71a to 71f, indicated by black circles, represent the combinations of FAB irradiation time and Ar peak distance values ​​obtained in each example and comparative example. Specifically, plot point 71a represents Example 1, plot point 71b represents Example 2, plot point 71c represents Example 3, plot point 71d represents Example 4, plot point 71e represents Example 5, and plot point 71f represents Comparative Example 2. However, as mentioned above, since there is no peak on the functional substrate 1 side in Comparative Example 1, Comparative Example 1 is excluded from the plotting in Figure 11, and there is no corresponding plot point.

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

[0091] As mentioned 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 distance between Ar peaks also changes according to the thickness of this bonding layer 33. In other words, it is thought that if the thickness of the bonding layer 33 increases or decreases, the distance between Ar peaks will also increase or decrease by the same amount. 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 substrates 1 and 1a and the support substrate 30. On the other hand, considering thermal conductivity and light 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, it is desirable that the thickness of the bonding layer 33 in the composite substrates 100 and 110 be in the range of approximately 0.6 nm to 2.7 nm.

[0092] In Figure 11, the plot points 72a to 72f, indicated by white circles, represent combinations of FAB irradiation time and Ar peak distance when plot points 71a to 71f are slid along the vertical axis of the graph, respectively, so that the value of the Ar peak distance increases by 2.1 nm. Linear interpolation of these plot points 72a to 72f yields a straight line 72. This straight line 72 represents the relationship between FAB irradiation time and Ar peak distance on functional substrates 1,1a when the thickness of the junction layer 33 is 0.6 + 2.1 = 2.7 nm.

[0093] In the graph shown in Figure 11, the range 73 enclosed by plotted points 71a, 71b, 71c, 72a, 72b, and 72c represents the range of possible combinations of FAB irradiation time and Ar peak distance values ​​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 and activation process, as in Examples 1 to 3. The range 74 enclosed by plotted points 71d, 71e, 72d, and 72e represents the range of possible combinations of FAB irradiation time and Ar peak distance values ​​while maintaining bonding strength 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 composite substrate 100 or composite substrate 110.

[0094] As explained above, when the support substrate 30 is composed 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 FAB irradiation time and the value of the Ar peak distance falls within one of the ranges 73, 74, or the range in between. That is, in the composite substrates 100 and 110 according to the first and second embodiments, the value of the Ar peak distance between the second functional layer 12 on the functional substrate 1 and 1a side and the second support layer 32 on the support substrate 30 side is in the range from plot point 71a to plot point 72e, specifically between 2.2 nm and 6.1 nm. Therefore, when the semiconductor material used in the support substrate 30 is SiC, it is preferable that the Ar peak distance is between 2.2 nm and 6.1 nm.

[0095] Figure 11 shows the combination of FAB irradiation time and Ar peak distance values ​​when the support substrate 30 is made of SiC, but similar relationships hold even when the support substrate 30 is made of other semiconductor materials, such as Si. However, since the depth to which Ar penetrates the support substrate 30 during FAB irradiation differs between SiC and Si, it is necessary to correct the Ar peak distance values ​​for each FAB irradiation time to account for this difference in depth.

[0096] Figure 12 is a graph showing the relationship between FAB irradiation time and Ar peak distance for functional substrates 1 and 1a when the support substrate 30 is composed of Si. Similar to Figure 11, the horizontal axis in Figure 12 represents the FAB irradiation time for functional substrates 1 and 1a, and the vertical axis represents the Ar peak distance. The black circles at plot points 81a to 81f indicate combinations of FAB irradiation time and Ar peak distance values ​​for the case where the support substrate 30 is Si, calculated from the combinations of FAB irradiation time and Ar peak distance values ​​obtained in the aforementioned examples and comparative examples. These plot points 81a to 81f correspond to plot points 71a to 71f in Figure 11. Similarly, the white circles at plot points 82a to 82f also indicate combinations of FAB irradiation time and Ar peak distance values ​​for the case where the support substrate 30 is Si. These plot points 82a to 82f correspond to plot points 72a to 72f in Figure 11.

[0097] When the support substrate 30 is Si, based on the above conditions, it is desirable that the thickness of the bonding layer 33 in the composite substrates 100 and 110 be in the range of approximately 0.3 nm to 3 nm. In Figure 12, linear interpolation of plotted points 81a to 81f yields a straight line 81. This straight line 81 represents the relationship between the FAB irradiation time to the functional substrates 1 and 1a and the distance between Ar peaks when the thickness of the bonding layer 33 is 0.3 nm. Similarly, linear interpolation of plotted points 82a to 82f yields a straight line 82. This straight line 82 represents the relationship between the FAB irradiation time to the functional substrates 1 and 1a and the distance between Ar peaks when the thickness of the bonding layer 33 is 3 nm.

[0098] In the graph shown in Figure 12, the range 83 enclosed by plotted points 81a, 81b, 81c, 82a, 82b, and 82c represents the range of possible combinations of FAB irradiation time and Ar peak distance values ​​for 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 and activation process, similar to the range 73 in Figure 11. Similarly, the range 84 enclosed by plotted points 81d, 81e, 82d, and 82e represents the range of possible combinations of FAB irradiation time and Ar peak distance values ​​while maintaining bonding strength for composite substrate 110, in which the oxide film 20 has been completely removed by FAB irradiation in the oxide film removal and activation process, similar to the range 83 in Figure 11. The range between range 83 and range 84 corresponds to either composite substrate 100 or composite substrate 110.

[0099] As described above, when the support substrate 30 is composed of Si, in the composite substrates 100 and 110 according to the first and second embodiments of the present invention, the combination of FAB irradiation time and the value of the Ar peak distance falls within the range 83, 84, or the range in between. That is, in the composite substrates 100 and 110 according to the first and second embodiments, the value of the Ar peak distance between the second functional layer 12 on the functional substrate 1 and 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 between 2.5 nm and 6.9 nm. Therefore, when the semiconductor material used in the support substrate 30 is Si, it is preferable that the Ar peak distance is between 2.5 nm and 6.9 nm.

[0100] In the above, the relationship between FAB irradiation time and Ar peak distance was explained for composite substrates 100 and 110 having functional substrates 1 and 1a made of InP crystal material. However, as explained in the third and fourth embodiments, a similar relationship between FAB irradiation time and Ar peak distance also holds for composite substrates 120, 121, 130, and 131 having functional substrates 1b and 1c on which an epitaxial layer 50 made of an epitaxial material is formed on the InP layer 10. That is, the relationship between FAB irradiation time and Ar peak distance shown in the graphs of Figures 11 and 12 is also applicable to composite substrates 120, 121, 130, and 131 in which the support substrate 30 is made of SiC or Si.

[0101] According to the embodiments of the present invention described above, the following effects and advantages are achieved.

[0102] (1) The composite substrates 100 to 131 include functional substrates 1, 1a, 1b, and 1c, each comprising at least one of InP and a crystal of a material that can be formed by epitaxial growth on a crystal of InP, and a support substrate 30 made of a semiconductor material, which is bonded to the functional substrates 1, 1a, 1b, and 1c and supports the functional substrates 1, 1a, 1b, and 1c. The functional substrates 1, 1a, 1b, and 1c each have 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 noble gas element, which is located closer to the support substrate 30 than the first layer. The support substrate 30 includes a first support layer 31, a second support layer 32 located closer to the functional substrates 1,1a,1b,1c than the first support layer 31 and made of an amorphous semiconductor material containing a noble gas element, and a bonding layer 33 in contact with the functional substrates 1,1a,1b,1c and made of an amorphous semiconductor material. In this manner, in composite substrates 100 to 131 in which functional substrates 1,1a,1b,1c containing crystals of a material that can be formed by epitaxial growth on InP crystals and the support substrate 30 are bonded via the bonding layer 33, it is possible to realize composite substrates 100 to 131 that can efficiently dissipate heat from the functional substrates 1,1a,1b,1c to the support substrate 30.

[0103] Furthermore, in the field of photonics, 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 creating a semiconductor laser or other device using InP on this optical circuit to form an optical transceiver. In photonic devices with 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 if some material is sandwiched, that material must have low energy loss in the wavelength band used. For this reason, it is undesirable for a barrier layer such as indium oxide to be present at the bonding interface, as in the composite substrate described in Patent Document 1 mentioned above. In this regard, the oxide film 20 is removed or reduced in thickness in the composite substrates 100 to 131, so the above requirement can be easily met.

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

[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. In this way, a composite substrate 100 can be realized that efficiently dissipates heat from the functional substrate 1 to the support substrate 30 side while leaving the oxide film 20 formed by the 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 InP crystals, a second functional layer 52 made of crystals of a material formed on the first functional layer 51 by epitaxial growth, and a third functional layer 53 made of an amorphous form of the same 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. In this way, even when functional substrates 1b and 1c having epitaxial layers 50 made of various epitaxial materials formed on an InP layer 10 made of InP crystals are directly bonded to a support substrate 30, composite substrates 120 and 130 can be realized that can obtain 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. In this way, a composite substrate 120 can be realized that efficiently dissipates the heat of the functional substrate 1b to the support substrate 30 side while leaving the oxide film 60 formed by the 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 a crystalline InP, and a third functional layer 53 made of an amorphous form 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. In this way, even in the composite substrates 121 and 131 formed by removing the InP layer 10 from the composite substrates 120 and 130 respectively, sufficient bonding strength can be obtained between the functional substrates 1b and 1c and the support substrate 30.

[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. In this way, similar to the composite substrate 120, the heat of the functional substrate 1b can be efficiently dissipated to the support substrate 30 side while leaving the oxide film 60 formed by the natural oxidation of the epitaxial material.

[0110] (8) In the composite substrates 100, 120, and 121, it is preferable that the thickness of the oxide films 20 and 60 is less than 1 nm. In this way, a portion of the oxide films 20 and 60 formed by spontaneous oxidation on the functional substrates 1 and 1b before bonding can be removed and thinned, 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 noble gas element Ar has peaks in the second layer (second functional layer 12 or third functional layer 53) and the second support layer 32, respectively. 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, composite substrates 100 to 131 can be realized that efficiently dissipate the 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 composite substrates 100, 110 comprising functional substrates 1, 1a made of InP and a support substrate 30 made of a semiconductor material that supports the functional substrates 1, 1a is performed by irradiating the surface of the functional substrate 1 with FAB and the surface of the semiconductor substrate 30A made of a semiconductor material with FAB to remove at least a portion of the oxide film 20 and to activate the surfaces of the functional substrate 1, 1a and the semiconductor substrate 30A (Figure 2(b)). Figure 5(b)) shows the following steps: a sputtering step (Figures 2(c), 5(c)) performed after the oxide film removal and activation step, in which the irradiation of the FAB on the surface of the functional substrates 1, 1a is stopped, and the irradiation of the FAB on the surface of the semiconductor substrate 30A is continued to sputter the semiconductor material onto the surface of the functional substrates 1, 1a; and a bonding step (Figures 3(d), 6(d)) in which the functional substrates 1, 1a, which have been sputtered with semiconductor material by the sputtering step, and the semiconductor substrate 30A are joined together to obtain a bonded body. In this way, a support substrate 30 can be formed by integrating the semiconductor substrate 30A and the sputtered film 30B, and composite substrates 100, 110 can be manufactured.

[0113] (11) A method for manufacturing composite substrates 120, 130 comprising functional substrates 1b, 1c having a material formed by epitaxial growth on a crystal of InP, and a support substrate 30 made of a semiconductor material that supports the functional substrates 1b, 1c, includes an oxide film removal and activation step in which an oxide film 60 of the epitaxial material formed on the surface of the functional substrate 1b and the surface of the semiconductor substrate 30A made of a semiconductor material are irradiated with FAB to remove at least a portion of the oxide film 60 and to activate the surfaces of the functional substrates 1b, 1c and the semiconductor substrate 30A; a sputtering step performed following the oxide film removal and activation step, in which the irradiation of the surface of the functional substrates 1b, 1c with FAB is stopped, and the irradiation of the surface of the semiconductor substrate 30A with FAB 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 to which the semiconductor material has been sputtered by the sputtering step and the semiconductor substrate 30A are bonded together to obtain a bonded body. In this way, the semiconductor substrate 30A and the sputtered film 30B are integrated to form a support substrate 30, and composite substrates 120 and 130 can be manufactured.

[0114] In each embodiment of the present invention described above, the oxide film removal and activation process involves simultaneously irradiating the surface of the functional substrates 1 and 1b with FAB from the first FAB gun and irradiating the surface of the semiconductor substrate 30A with FAB from the second FAB gun. This prevents 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, and 1c. However, the present invention is not limited to this. For example, the FAB irradiation from the first FAB gun to the functional substrates 1 and 1b may be started first, followed by a predetermined delay before starting the FAB irradiation from the second FAB gun to the semiconductor substrate 30A, and then stopping the FAB irradiation on the functional substrates 1, 1a, 1b, and 1c. The same effects as described above can be obtained by doing so.

[0115] It should be noted that the present invention is not limited to the embodiments described above, and can be implemented using any components without departing from the spirit of the invention.

[0116] The embodiments and modifications described above are merely examples, and the present invention is not limited to these, 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. Other embodiments conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0117] 1,1a,1b,1c: Functional substrates 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 substrate

Claims

1. A functional substrate comprising at least one of InP and a crystal of a material that can be formed by epitaxial growth on a crystal of InP, It comprises a support substrate made of a semiconductor material, which is bonded to the functional substrate and supports the functional substrate, The functional substrate comprises a first layer and a second layer, which is disposed closer to the support substrate than the first layer and is made of an amorphous material containing a noble gas element. The support substrate comprises a first support layer, a second support layer positioned closer to the functional substrate than the first support layer and made of an amorphous form of the semiconductor material containing the noble gas element, and a bonding layer in contact with the functional substrate and made of an amorphous form of the semiconductor material. The content of the aforementioned noble gas elements has peaks in the second layer and the second support layer, respectively. The semiconductor material is SiC, 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. A composite substrate in which the thickness of the bonding layer is t, t is between 0.6 nm and 2.7 nm, and the distance is within the range of {2.2 + (t - 0.6)} nm and {4.0 + (t - 0.6)} nm.

2. A functional substrate comprising at least one of InP and a crystal of a material that can be formed by epitaxial growth on a crystal of InP, It comprises a support substrate made of a semiconductor material, which is bonded to the functional substrate and supports the functional substrate, The functional substrate comprises a first layer and a second layer, which is disposed closer to the support substrate than the first layer and is made of an amorphous material containing a noble gas element. The support substrate comprises a first support layer, a second support layer positioned closer to the functional substrate than the first support layer and made of an amorphous form of the semiconductor material containing the noble gas element, and a bonding layer in contact with the functional substrate and made of an amorphous form of the semiconductor material. The content of the aforementioned noble gas elements has peaks in the second layer and the second support layer, respectively. The semiconductor material is Si, 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. A composite substrate in which the thickness of the bonding layer is t, where t is 0.3 nm or more and 3.0 nm or less, and the distance is within the range of {2.5 + (t - 0.3)} nm or more and {4.2 + (t - 0.3)} nm or less.

3. In the composite substrate according to claim 1 or 2, The functional substrate comprises a first functional layer made of crystalline InP and a second functional layer made of amorphous InP. The first layer is the first functional layer, A composite substrate in which the second layer is the second functional layer.

4. In the composite substrate according to claim 3, The functional substrate is a composite substrate having an InP oxide film between the second layer and the support substrate.

5. In the composite substrate according to claim 1 or 2, The functional substrate comprises a first functional layer made of InP crystals, a second functional layer made of the material crystals formed on the first functional layer by epitaxial growth, and a third functional layer made of the material amorphous. The first layer is the first functional layer and the second functional layer, A composite substrate in which the second layer is the third functional layer.

6. In the composite substrate according to claim 5, The functional substrate is a composite substrate having an oxide film of the material between the second layer and the support substrate.

7. In the composite substrate according to claim 1 or 2, The functional substrate comprises a second functional layer made of the crystalline material and a third functional layer made of the amorphous material. The first layer is the second functional layer, A composite substrate in which the second layer is the third functional layer.

8. In the composite substrate according to claim 7, The functional substrate is a composite substrate having an oxide film of the material between the second layer and the support substrate.

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