Composite substrate and manufacturing method therefor

Abstract

To provide a composite substrate 100 (100A) in which the variation in the number of carbon-containing layers formed on a SiC single crystal substrate 1 is reduced to one or fewer layers, and a manufacturing method for the composite substrate 100 (100A).SOLUTION: A composite substrate 100 (100A) includes: a SiC single crystal substrate 1 having an off-angle; and a carbon-containing layer including a laminate of a reconstructed surface layer 10a and a graphene layer 10, or a graphene layer 10 disposed in contact with a surface of the SiC single crystal substrate 1. When an outermost surface of the SiC single crystal substrate 1 is a Si-terminated surface 1si, the laminate is disposed above the SiC single crystal substrate 1, and the laminate includes one or two graphene layers. When the outermost surface of the SiC single crystal substrate 1 is a C-terminated surface 1c, one or two graphene layers 10 are arranged above the SiC single crystal substrate 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A known method for producing graphene involves removing an oxide film formed by natural oxidation that covers the surface of a silicon carbide (SiC) single crystal substrate, exposing the Si surface of the SiC single crystal substrate, and heating (pyrolyzing) the exposed SiC single crystal substrate in a vacuum or in an inert gas such as argon (Ar). By heating in a vacuum or in an inert gas such as argon (Ar), silicon (Si) sublimes and the remaining carbon (C) self-organizes, forming graphene layers on the SiC single crystal substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2010 / 023934 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a SiC single crystal substrate is thermally decomposed, carbon-containing layers such as graphene layers grow from the steps, but before the first layer completely covers the surface of the SiC single crystal, a second layer grows partially on the surface. In other words, thermal decomposition of the SiC single crystal substrate occurs locally, which may lead to large variations in the number of layers of the carbon-containing layer.

[0005] The present disclosure has been proposed in view of the above-mentioned circumstances, and has an object to provide a composite substrate in which the variation in the number of carbon-containing layers formed on a SiC single crystal substrate is reduced to 1 or less, and a method for manufacturing the composite substrate. [Means for solving the problem]

[0006] A composite substrate according to one embodiment of the present disclosure comprises a SiC single crystal substrate having an off-angle, and a carbon-containing layer including either a stack of a reconstructed surface layer and a graphene layer or a graphene layer, arranged in contact with the surface of the SiC single crystal substrate. When the outermost surface of the SiC single crystal substrate is a Si-terminated surface, a stack is arranged above the SiC single crystal substrate, and the stack has one or two graphene layers. When the outermost surface of the SiC single crystal substrate is a C-terminated surface, one or two graphene layers are arranged above the SiC single crystal substrate.

[0007] A method for producing a composite substrate according to one embodiment of the present disclosure includes the steps of depositing a carbon-containing thin film on a SiC single crystal substrate by using a deposition method controllable at the molecular layer level, and forming a carbon-containing layer on the SiC single crystal substrate using carbon supplied from the thin film by heat treatment, the carbon-containing layer including either a stack of a reconstructed surface layer and a graphene layer or a graphene layer, wherein the variation in the number of layers of the carbon-containing layer on the SiC single crystal substrate is 1 or less. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a composite substrate in which the variation in the number of carbon-containing layers formed on a SiC single crystal substrate is reduced to one layer or less, and a method for manufacturing the composite substrate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 shows a cross-sectional view of a composite substrate according to an embodiment. [Diagram 2] FIG. 2 shows a cross-sectional view of a composite substrate according to the first modification. [Diagram 3] FIG. 3 shows a cross-sectional view of a composite substrate according to the second modification. [Figure 4A] FIG. 4A is a cross-sectional view (part 1) showing one step in the manufacturing process of the composite substrate according to Modification 2. [Figure 4B] FIG. 4B is a cross-sectional view (part 2) showing one step in the manufacturing process of the composite substrate according to Modification 2. [Figure 4C]FIG. 4C is a cross-sectional view (part 3) showing a step in the manufacturing process of the composite substrate according to Modification 2. [Figure 4D] FIG. 4D is a cross-sectional view (part 4) showing a step in the manufacturing process of the composite substrate according to Modification 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Next, an embodiment will be described with reference to the drawings. In the description of the drawings described below, the same or similar parts are given the same or similar reference numerals. The drawings are schematic. Furthermore, the embodiment shown below is an example of an apparatus or method for embodying a technical idea, and does not specify the material, shape, structure, arrangement, etc. of parts. Various modifications can be made to the embodiment.

[0011] The composite substrate according to this embodiment will be described with reference to the drawings.

[0012] FIG. 1 shows a cross-sectional view of a composite substrate 100 according to this embodiment.

[0013] The composite substrate 100 includes a SiC single crystal substrate 1 having an off-angle, and a carbon-containing layer disposed in contact with the surface of the SiC single crystal substrate 1. In this embodiment, the outermost surface of the SiC single crystal substrate 1 is a carbon (C)-terminated surface 1c, and the carbon-containing layer in contact with the C-terminated surface 1c has one or two graphene layers 10 disposed therein.

[0014] In this disclosure, "off-angle" refers to the rotation angle θ when the grown crystal is rotated at a certain angle along the in-plane from the C-axis direction (direction perpendicular to the substrate plane, film thickness direction) and cut. The off-angle of the SiC single crystal substrate 1 is preferably 0.5° to 10°, and more preferably 4° to 8°.

[0015] The SiC single crystal substrate 1 may have a crystal structure of either a hexagonal (4H,6H) crystal or a cubic (3C) crystal. For example, the SiC single crystal substrate 1 made of a hexagonal (4H) crystal is preferably made of nitrogen (N 2The SiC single crystal substrate 1 can be obtained by sublimating the raw SiC powder in a graphite crucible filled with an inert gas such as SiO2 gas, and recrystallizing it into SiC seed crystals controlled at a lower temperature than the raw powder (modified Lely process (seeded sublimation recrystallization method)). At this time, impurities that determine the conductivity type of the SiC single crystal substrate 1 may be added.

[0016] The graphene layer 10 has a single layer structure or a laminated structure formed of two layers. Since the number of layers of the graphene layer 10, which is a carbon-containing layer, is one or two, the variation in the number of layers of the carbon-containing layer is one layer or less. The number of layers of the carbon-containing layer can be observed, for example, by Raman spectroscopy, a TEM (Transmission Electron Microscope), or the like, and it is preferable to use Raman mapping when observing a wide range. From the viewpoint of the variation in the number of layers of the carbon-containing layer, it is preferable that the number of layers of the graphene layer 10 is one layer. When the variation in the number of layers of the carbon-containing layer is one layer or less, the crystal growth of an epitaxial layer that can be formed later is good.

[0017] Generally, when forming a carbon-containing layer such as a graphene layer on a SiC single crystal substrate, the SiC single crystal substrate is pyrolyzed, whereby the Si atoms of the SiC single crystal substrate sublimate and the remaining carbon (C) self-organizes to form a graphene layer on the SiC single crystal substrate.

[0018] In this embodiment, in order to reduce the variation in the number of layers of the carbon-containing layer, in addition to the supply of carbon from the SiC single crystal substrate 1 as described below, a thin film containing carbon is deposited on the SiC single crystal substrate 1 as a new carbon supply source using a deposition method that can be controlled at the molecular layer level. The thin film is then carbonized by heat treatment to form a carbon-containing layer such as a graphene layer 10. This process can promote the growth of the carbon-containing layer before step bunching occurs in the SiC single crystal substrate.

[0019] Here, when the carbon-containing layer is formed, if the carbon supply is solely from the SiC single crystal substrate, the in-plane variation of the carbon-containing layer increases due to differences in local pyrolysis speed. Therefore, as in the present embodiment, when the carbon-containing layer is formed, carbon is also supplied from the outside, so that even if the same single layer is obtained, the contribution of pyrolysis of the SiC single crystal substrate is relatively suppressed, improving the variation of the carbon-containing layer. In addition, since a carbon-containing layer with high crystallinity can be formed, the variation of epitaxial film growth in a semiconductor device can be reduced when a composite substrate including a carbon-containing layer is used as a material for the semiconductor device.

[0020] According to this embodiment, it is possible to obtain a composite substrate 100 in which the variation in the number of carbon-containing layers formed on the SiC single crystal substrate is reduced.

[0021] In the above-described composite substrate 100, the outermost surface of the SiC single crystal substrate 1 is the C-terminated surface 1c, but this is not limited thereto and various modifications such as those described below may be possible.

[0022] <Variation 1> A description will be given of the configuration of composite substrate 100A according to Modification 1. The above description will be used to refer to the points common to composite substrate 100 shown in Fig. 1 in Modification 1, and only the points of difference will be described below.

[0023] Fig. 2 is a cross-sectional view of a composite substrate 100A according to Modification 1. The composite substrate 100A according to Modification 1 differs from the composite substrate 100 shown in Fig. 1 above in that the outermost surface of the SiC single crystal substrate 1 is a silicon (Si)-terminated surface 1si, and the carbon-containing layer in contact with the Si-terminated surface 1si is a laminate in which a reconstructed surface layer 10a and a graphene layer 10 are laminated.

[0024] In the composite substrate 100A, since the outermost surface of the SiC single crystal substrate 1 is a Si-terminated surface 1si, when the graphene layer 10 is formed on the surface of the SiC single crystal substrate 1, a reconstructed surface layer 10a is formed on the surface of the SiC single crystal substrate 1, and the graphene layer 10 is formed on the reconstructed surface layer 10a. The reconstructed surface layer 10a plays a role in reducing lattice mismatch with the graphene layer 10, and is also referred to as a buffer layer or the 0th layer of the graphene layer.

[0025] In the first modified example as well, when forming the carbon-containing layer, carbon is supplied from the outside in addition to from the SiC single crystal substrate, and thus, even when the same single layer is obtained, the contribution of the thermal decomposition of the SiC single crystal substrate is relatively suppressed, thereby improving the variation of the carbon-containing layer.

[0026] <Variation 2> A description will be given of the configuration of composite substrate 100B according to Modification 2. The above description will be used to refer to the points common to composite substrate 100A shown in Fig. 2 in Modification 2, and only the points of difference will be described below.

[0027] Fig. 3 is a cross-sectional view of composite substrate 100B according to Modification 2. Composite substrate 100B according to Modification 2 differs from composite substrate 100A shown in Fig. 2 above in that it includes epitaxial layer 3 disposed on graphene layer 10.

[0028] In the composite substrate 100B, by using a SiC single crystal substrate 1 having an off-angle, the crystal type of the SiC single crystal substrate 1 is reflected in the crystal growth of the epitaxial layer 3 via the graphene layer 10. Therefore, it is possible to form an epitaxial layer 3 of SiC, which is a single crystal of the same crystal type as that of the SiC single crystal substrate 1. From the viewpoint of the crystal growth of the epitaxial layer 3, the off-angle is preferably 0.5° or more and 10° or less, and more preferably 4° or more and 8° or less.

[0029] In the second modification, when the carbon-containing layer is formed, carbon is supplied from the outside in addition to from the SiC single crystal substrate, so that the contribution of the thermal decomposition of the SiC single crystal substrate is relatively suppressed, and the variation of the carbon-containing layer is improved, even when the same single layer is obtained. Since the composite substrate 100B further has the reconstructed surface layer 10a compared to the above-mentioned composite substrate 100, it is easy to control the number of graphene layers, and the variation in the number of graphene layers is small, so that the crystallinity of the epitaxial layer 3 can be improved. That is, the same type of crystal as that of the SiC single crystal substrate can be grown on the graphene layer.

[0030] (Method of manufacturing composite substrate) Next, an example of a method for manufacturing a composite substrate will be described. Here, a method for manufacturing the above-mentioned composite substrate 100B will be described.

[0031] First, as shown in FIG. 4A, a native oxide film is removed from the Si-terminated surface 1si of the SiC single crystal substrate 1 using hydrofluoric acid. The SiC single crystal substrate 1 may be, for example, a 4H-SiC substrate having an off-angle of 4°. The size of the SiC single crystal substrate 1 is not particularly limited, but may be, for example, 10 mm. 2 The following can be used.

[0032] Next, as shown in FIG. 4B, a thin film 30 containing carbon is deposited on the SiC single crystal substrate 1 from which the native oxide film has been removed. The thin film 30 is deposited using a deposition method that can be controlled at the molecular layer level. For example, physical vapor deposition, chemical vapor deposition, and wet deposition methods can be used for the thin film 30. More specifically, the Langmuir-Blodgett method or the vapor deposition polymerization method can be used.

[0033] The thin film 30 may be a Langmuir-Blodgett film using the Langmuir-Blodgett method or a self-assembled monolayer. The thin film 30 may also include a molecular film having a weight-average molecular weight of 100 to 1000. An example of a molecular film having a weight-average molecular weight of 100 to 1000 is a saturated fatty acid such as stearic acid (C 17 H35 COOH), palmitic acid (C 15 H 31 COOH) etc.

[0034] The thin film 30 acts as a carbon supply source for forming a carbon-containing layer such as a graphene layer. The thin film 30 may have any thickness as long as it can act as a carbon supply source. The thickness of the thin film 30 is, for example, 0.3 nm or more and 100 nm or less, or may be 1 nm or more and 90 nm or less, or may be 10 nm or more and 80 nm or less.

[0035] Here, stearic acid (C 17 H 35 COOH) is dissolved in hexane at a concentration of 1 mM, and the solution is dropped into pure water to form a solution, in which the SiC single crystal substrate 1 from which the native oxide film has been removed is immersed, pulled up vertically, and dried, thereby coating the SiC single crystal substrate 1 with a monomolecular film, which is a thin film 30. The drying time is, for example, 60 minutes. The SiC single crystal substrate 1 coated with the monomolecular film is then placed in a high-frequency induction heating furnace, and a vacuum is drawn. The vacuum is drawn at a pressure of, for example, 1×10 -3 N / m 2 You can continue until the following occurs:

[0036] Next, as shown in Fig. 4C, the SiC single crystal substrate 1 is subjected to a first heat treatment to carbonize the thin film 30 to form the thin film 30A. The first heat treatment is performed at a temperature of 300°C or higher and 1000°C or lower, for example, at a temperature of 1 x 10 -4 N / m 2 Under vacuum or 1×10 4 N / m 2 More than 1×10 6 N / m 2 The treatment is carried out under an inert gas atmosphere, such as argon gas.

[0037] Here, after the monomolecular film, which is the thin film 30, is coated on the SiC single crystal substrate 1, an inert gas such as argon gas is used for purging, and after atmospheric pressure is reached, the SiC single crystal substrate 1 is heat-treated in the inert gas atmosphere to carbonize the monomolecular film and form the thin film 30A. The heat treatment temperature is, for example, 400°C.

[0038] Furthermore, the thin film 30 may be further subjected to a heat treatment before the first heat treatment. The heat treatment may be performed at a temperature rise rate of, for example, 100° C. / min to 18,000° C. / min, and may be resistance heating, lamp annealing, or high-frequency induction heating. By performing the heat treatment on the thin film 30, the thin film 30 can be efficiently carbonized in the first heat treatment.

[0039] 4D, a second heat treatment is performed on the SiC single crystal substrate 1 on which the thin film 30A is laminated, and carbon supplied from the thin film 30A is used to form a carbon-containing layer on the SiC single crystal substrate 1. The carbon-containing layer includes a laminate made of a reconstructed surface layer 10a in contact with the Si-terminated surface 1Si of the SiC single crystal substrate 1 and a graphene layer 10 in contact with the reconstructed surface layer 10a.

[0040] The second heat treatment is performed at a temperature of, for example, 1000° C. or more and 2000° C. or less. -4 N / m 2 The SiC single crystal substrate 1 on which the thin film 30A is laminated is heated at 1600° C. for 5 minutes in a vacuum atmosphere to form a carbon-containing layer on the surface of the SiC single crystal substrate 1. The temperature rise rate at this time is, for example, 400° C. / sec. The formed carbon-containing layer has an area ratio of only the reconstructed surface layer 10a to a laminate consisting of the reconstructed surface layer 10a and the graphene layer 10 of, for example, 80:20.

[0041] Next, as shown in FIG. 3, an epitaxial layer 3 is formed on the graphene layer 10 included in the carbon-containing layer. In this manner, a composite substrate 100B is completed. The method for forming (depositing) the epitaxial layer 3 is not particularly limited, and for example, physical vapor deposition and chemical vapor deposition can be used. The epitaxial layer 3 can be formed at a substrate temperature of 1000° C. or higher and 2000° C. or lower.

[0042] The source gas for forming the epitaxial layer 3 is not particularly limited, but for example, propane (C 3 H 8 ) and silane (SiH 4 ) can be used in a volume ratio of 1:3. 4 ) is the precursor of Si, and propane (C 3 H 8 ) can each be used as a precursor of C. In addition, argon gas that suppresses etching of the graphene layer 10 may be used as a carrier gas for transporting the raw material gas.

[0043] The thickness of the epitaxial layer 3 is not particularly limited, but is, for example, 500 nm.

[0044] (Other embodiments) As described above, several embodiments have been described, but the descriptions and drawings forming part of the disclosure are illustrative and should not be understood as limiting. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art. Thus, the embodiments include various embodiments not described herein.

[0045] <Example of embodiment> Examples of this embodiment are given below: This embodiment is not limited to the following examples.

[0046] [Appendix 1] A step of depositing a carbon-containing thin film 30 on a SiC single crystal substrate 1 using a deposition method that can be controlled at the molecular layer level; and forming a carbon-containing layer including either a stack of the reconstructed surface layer 10a and the graphene layer 10 or the graphene layer 10 on the SiC single crystal substrate 1 by using carbon supplied from the thin film 30 through a heat treatment; A method for producing composite substrates 100, 100A, 100B in which the variation in the number of carbon-containing layers on a SiC single crystal substrate 1 is one layer or less.

[0047] [Appendix 2] A method for producing the composite substrate 100, 100A, 100B described in [Appendix 1], wherein the thin film 30 includes a molecular film having a weight average molecular weight of 100 or more and 1000 or less.

[0048] [Appendix 3] A method for producing the composite substrate 100, 100A, 100B according to [Appendix 1] or [Appendix 2], wherein the thin film 30 is a Langmuir-Blodgett film or a self-assembled monolayer.

[0049] [Appendix 4] A method for producing the composite substrate 100, 100A, 100B described in any one of [Appendix 1] to [Appendix 3], in which the deposition of the thin film 30 is carried out by any method selected from the group consisting of physical vapor deposition, chemical vapor deposition, and wet deposition.

[0050] [Appendix 5] The deposition of the thin film 30 is performed by the Langmuir-Blodgett method or the vapor deposition polymerization method. [Appendix 4] A method for producing the composite substrates 100, 100A, and 100B.

[0051] [Appendix 6] A method for producing the composite substrate 100, 100A, 100B according to any one of [Appendix 1] to [Appendix 5], wherein the thin film 30 has a thickness of 0.3 nm or more and 100 nm or less.

[0052] According to [Supplementary Note 1] to [Supplementary Note 6], when the carbon-containing layer is formed, the variation of the carbon-containing layer is improved by supplying carbon from the outside in addition to from the SiC single crystal substrate. Also, when the composite substrate 100, 100A, or 100B including the carbon-containing layer is used as a material for a semiconductor device or the like, the variation of the epitaxial film growth in the semiconductor device can be reduced.

[0053] [Appendix 7] The heat treatment includes a first heat treatment performed at 300° C. or more and 1000° C. or less in a vacuum atmosphere or an inert gas atmosphere; A method for producing composite substrate 100, 100A, 100B according to any one of [Appendix 1] to [Appendix 6], wherein thin film 30 is carbonized in the first heat treatment.

[0054] [Appendix 8] A method for producing the composite substrate 100, 100A, or 100B described in [Appendix 7], wherein, prior to the first heat treatment, the thin film is subjected to a heat treatment at a temperature increase rate of 100°C / min or more and 18,000°C / min or less, and by any method selected from the group consisting of resistance heating, lamp annealing, and high-frequency induction heating.

[0055] [Appendix 9] The first heat treatment is 1×10 -4 N / m 2 Under vacuum or 1×10 4 N / m 2 More than 1×10 6 N / m 2 A method for producing the composite substrate 100, 100A, or 100B described in [Appendix 7] or [Appendix 8], which is carried out under an inert gas atmosphere as follows.

[0056] [Appendix 10] The heat treatment includes a second heat treatment performed at a temperature of 1000° C. or more and 2000° C. or less after the first heat treatment; A method for producing composite substrate 100, 100A, 100B according to any one of [Appendix 7] to [Appendix 9], wherein thin film 30A is formed on the carbon-containing layer in the second heat treatment.

[0057] According to [Additional Notes 7] to [Additional Notes 10], by controlling the heat treatment conditions, the thin film 30 can be efficiently carbonized, and a carbon-containing layer can be formed on the SiC single crystal substrate 1 using carbon supplied from the thin film 30.

[0058] [Appendix 11] The method for producing the composite substrate 100B according to any one of [Appendix 1] to [Appendix 10] further comprises a step of forming an epitaxial layer 3 growing on the carbon-containing layer on the SiC single crystal substrate 1 after forming the thin film 30 on the carbon-containing layer.

[0059] [Appendix 12] A method for producing a composite substrate 100B according to [Appendix 11], in which deposition of the epitaxial layer 3 is carried out by any method selected from the group consisting of physical vapor deposition and chemical vapor deposition.

[0060] [Appendix 13] A method for producing composite substrate 100B according to [Appendix 11] or [Appendix 12], in which epitaxial layer 3 is formed at a substrate temperature of 1000°C or higher and 2000°C or lower.

[0061] According to [Additional Note 11] to [Additional Note 13], the number of graphene layers varies little, and the crystallinity of the epitaxial layer 3 can be improved.

[0062] [Appendix 14] A SiC single crystal substrate 1 having an off-angle; A carbon-containing layer including either a stack of a reconstructed surface layer 10a and a graphene layer 10 or a graphene layer 10, the stack being disposed in contact with the surface of a SiC single crystal substrate 1; When the outermost surface of the SiC single crystal substrate 1 is a Si-terminated surface 1si, a laminate is disposed above the SiC single crystal substrate 1, and the laminate has one or two graphene layers 10; When the outermost surface of the SiC single crystal substrate 1 is a C-terminated surface 1c, one or two graphene layers 10 are disposed above the SiC single crystal substrate 1 in the composite substrates 100, 100A, and 100B.

[0063] [Appendix 15] The composite substrate 100, 100A, or 100B according to [Appendix 14], wherein the off angle is 0.5° or more and 10° or less.

[0064] [Appendix 16] The composite substrate 100, 100A, 100B, in which the SiC single crystal substrate 1 has a crystal structure of either a hexagonal crystal or a cubic crystal, is described in [Appendix 14] or [Appendix 15].

[0065] [Appendix 17] The composite substrate 100, 100A, or 100B according to any one of [Appendix 14] to [Appendix 16], wherein the number of graphene layers 10 included in the carbon-containing layer is one.

[0066] According to [Appendix 14] to [Appendix 17], when the carbon-containing layer is formed, the variation of the carbon-containing layer is improved by supplying carbon from the outside in addition to from the SiC single crystal substrate. Also, when the composite substrate 100, 100A, 100B including the carbon-containing layer is used as a material for a semiconductor device or the like, the variation of the epitaxial film growth in the semiconductor device can be reduced.

[0067] [Appendix 18] The carbon-containing layer further includes an epitaxial layer 3 disposed above the graphene layer 10, Composite substrate 100B according to any one of [Appendix 14] to [Appendix 17], wherein epitaxial layer 3 has the same crystal system as that of SiC single crystal substrate 1.

[0068] According to [Additional Note 18], the graphene layer 10 can improve the crystallinity of the epitaxial layer 3. [Explanation of symbols]

[0069] 1. SiC single crystal substrate 1c C end face 1si Si termination surface 3 Epitaxial layer 10 graphene layers 10a Reconstructed surface layer 30, 30A thin film 100, 100A, 100B composite board

Claims

1. Depositing a carbon-containing thin film on a SiC single crystal substrate using a deposition method that can be controlled at the molecular layer level; and forming a carbon-containing layer including either a stack of a reconstructed surface layer and a graphene layer or a graphene layer on the SiC single crystal substrate by using carbon supplied from the thin film by performing a heat treatment, a variation in the number of the carbon-containing layers on the SiC single crystal substrate is one layer or less.

2. The method for producing a composite substrate according to claim 1 , wherein the thin film comprises a molecular film having a weight average molecular weight of 100 or more and 1,000 or less.

3. The method for producing a composite substrate according to claim 1 , wherein the thin film is a Langmuir-Blodgett film or a self-assembled monolayer.

4. The method for producing a composite substrate according to claim 1 , wherein the deposition of the thin film is carried out by any method selected from the group consisting of physical vapor deposition, chemical vapor deposition, and wet deposition.

5. The method for producing a composite substrate according to claim 4 , wherein the thin film is deposited by a Langmuir-Blodgett method or a vapor deposition polymerization method.

6. The method for producing a composite substrate according to claim 1 , wherein the thin film has a thickness of 0.3 nm or more and 100 nm or less.

7. The heat treatment includes a first heat treatment performed at 300° C. or more and 1000° C. or less in a vacuum atmosphere or an inert gas atmosphere, The method for producing a composite substrate according to claim 1 , wherein the thin film is carbonized in the first heat treatment.

8. 8. The method for producing a composite substrate according to claim 7, wherein, before the first heat treatment, a heat treatment is performed on the thin film at a temperature increase rate of 100° C. / min to 18000° C. / min and by any one selected from the group consisting of resistance heating, lamp annealing, and high-frequency induction heating.

9. The first heat treatment is performed at a temperature of 1×10 －４ N / m ２ Under vacuum or 1×10 ４ N / m ２ Above 1 x 10 ６ N / m ２ The method for producing a composite substrate according to claim 7, which is carried out under an inert gas atmosphere as follows:

10. The heat treatment includes a second heat treatment performed at a temperature of 1000° C. or more and 2000° C. or less after the first heat treatment, The method for producing a composite substrate according to claim 7 , wherein the thin film is formed on a carbon-containing layer in the second heat treatment.

11. The method for producing a composite substrate according to claim 1 , further comprising the step of forming an epitaxial layer that grows through the carbon-containing layer on the SiC single crystal substrate after forming the thin film on the carbon-containing layer.

12. The method for producing a composite substrate according to claim 11 , wherein the deposition of the epitaxial layer is carried out by any method selected from the group consisting of physical vapor deposition and chemical vapor deposition.

13. The method for producing a composite substrate according to claim 11 , wherein the epitaxial layer is formed at a substrate temperature of 1000° C. or more and 2000° C. or less.

14. A SiC single crystal substrate having an off-angle; A carbon-containing layer including either a stack of a reconstructed surface layer and a graphene layer or a graphene layer, the carbon-containing layer being disposed in contact with a surface of the SiC single crystal substrate; When the outermost surface of the SiC single crystal substrate is a Si-terminated surface, the laminate is disposed above the SiC single crystal substrate, and the graphene layer of the laminate is one layer or two layers; A composite substrate, wherein when the outermost surface of the SiC single crystal substrate is a C-terminated surface, one or two graphene layers are arranged above the SiC single crystal substrate.

15. The composite substrate according to claim 14 , wherein the off angle is 0.5° or more and 10° or less.

16. The composite substrate of claim 14 , wherein the SiC single crystal substrate has a crystal structure that is either a hexagonal crystal or a cubic crystal.

17. The composite substrate according to claim 14 , wherein the number of graphene layers included in the carbon-containing layer is one.

18. The carbon-containing layer further includes an epitaxial layer disposed above the graphene layer, The composite substrate of claim 14 , wherein the epitaxial layer has the same crystal system as the SiC single crystal substrate.

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