Composite substrate and manufacturing method therefor

Abstract

To provide a composite substrate 100 (100A) with reduced surface roughness (Ra) of a carbon-containing layer formed on a SiC single crystal substrate 1, and a manufacturing method for the composite substrate 100 (100A).SOLUTION: A composite substrate 100 (100A) includes: a SiC single crystal substrate 1; 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 observing with an atomic force microscope, surface roughness (Ra) of the carbon-containing layer in contact with the SiC single crystal substrate 1 is equal to or less than 1.0 nm per 2×2 μm2.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 heated at a temperature lower than the temperature at which graphene can be formed, step bunching occurs on the SiC single crystal substrate. When remote epitaxial growth is performed on graphene, the step bunching deteriorates the morphology of the epitaxial film, making it more likely to cause dielectric breakdown during device fabrication. In addition, the anchor effect may make it difficult to peel off the epitaxial film.

[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 surface roughness (Ra) of a carbon-containing layer formed on a SiC single crystal substrate is reduced, and a method for manufacturing the composite substrate is also provided. [Means for solving the problem]

[0006] The composite substrate according to one embodiment of the present disclosure includes a SiC single crystal substrate and 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 arranged in contact with a surface of the SiC single crystal substrate. The carbon-containing layer has a size of 2×2 μm when observed with an atomic force microscope. 2 The surface roughness (Ra) of the carbon-containing layer in contact with the SiC single crystal substrate is 1.0 nm or less around

[0007] A method for producing a composite substrate according to one embodiment of the present disclosure includes the steps of depositing a cap film on a SiC single crystal substrate to suppress thermal decomposition of the SiC single crystal substrate, removing the cap film by performing a heat treatment, and forming a carbon-containing layer on the SiC single crystal substrate by performing a 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 thickness of the cap film is configured to remain in at least a part of the temperature range from the temperature at which thermal decomposition of the SiC single crystal substrate begins to the temperature at which the graphene layer is formed. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a composite substrate in which the surface roughness (Ra) of a carbon-containing layer formed on a SiC single crystal substrate is reduced, 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. [Diagram 5] FIG. 5 is a cross-sectional view showing another step in the manufacturing process of the composite substrate according to the second modification. 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 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 is a graphene layer 10.

[0014] 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 can be obtained by sublimating raw material SiC powder in a graphite crucible filled with an inert gas such as nitrogen (N2) gas, and recrystallizing it into a SiC seed crystal controlled to a lower temperature than the raw material 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.

[0015] The SiC single crystal substrate 1 may have an off-angle. In this disclosure, the "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 (the direction perpendicular to the substrate plane, the film thickness direction) and cut. The off-angle is preferably 0.5° to 10°, and more preferably 4° to 8°.

[0016] The graphene layer 10 has a single-layer structure or a laminated structure formed of several or more layers. Here, several layers means two or more graphene layers 10. From the viewpoint of crystal growth of the epitaxial layer, the number of layers of the graphene layer 10 is preferably 1 to 5.

[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. By forming the graphene layer through low-temperature processing, it is possible to suppress the occurrence of step bunching in the SiC single crystal substrate, but in order to form a graphene layer with high crystallinity in which a large number of hexagons are formed, it is necessary to form the graphene layer through high-temperature processing.

[0018] In this embodiment, in order to suppress the occurrence of step bunching of the SiC single crystal substrate while forming a graphene layer with high crystallinity, a thin film containing carbon is deposited on the SiC single crystal substrate as a new carbon supply source in addition to the supply of carbon from the SiC single crystal substrate as described below. A cap film that suppresses thermal decomposition of the SiC single crystal substrate is deposited on the carbon-containing thin film, and then the thin film is carbonized by heat treatment to form a carbon-containing layer such as a graphene layer. This process can promote the growth of the carbon-containing layer before the occurrence of step bunching of the SiC single crystal substrate.

[0019] Since the SiC single crystal substrate in which step bunching is suppressed has a small surface roughness (Ra), the surface roughness (Ra) of the carbon-containing layer formed on the SiC single crystal substrate is also small, and the flatness of the surface on which the carbon-containing layer is formed is good. Therefore, a carbon-containing layer with high crystallinity can be formed. The surface roughness (Ra) can be determined, for example, in accordance with JIS B 0601:2013 or ISO 25178.

[0020] The surface roughness (Ra) of the carbon-containing layer can be observed by an atomic force microscope. 2 The surface roughness (Ra) of the carbon-containing layer when observed is 1.0 nm or less. The surface roughness (Ra) of the carbon-containing layer is preferably 0.7 nm or less, and more preferably 0.5 nm or less.

[0021] According to this embodiment, a composite substrate can be obtained in which the surface roughness (Ra) of the carbon-containing layer formed on the SiC single crystal substrate is reduced.

[0022] 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.

[0023] <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.

[0024] 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.

[0025] 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.

[0026] In the first modification, as described above, step bunching of the SiC single crystal substrate is suppressed, so that the surface roughness (Ra) of the SiC single crystal substrate is reduced, and the surface roughness (Ra) of the carbon-containing layer formed on the SiC single crystal substrate is also reduced, resulting in good flatness of the surface on which the carbon-containing layer is formed. As a result, a carbon-containing layer with high crystallinity can be formed.

[0027] <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.

[0028] 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.

[0029] 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.

[0030] From the viewpoint of the crystal growth of the epitaxial layer 3, the number of layers of the graphene layer 10 is preferably 1 to 5. When the number of layers of the graphene layer 10 is 1 to 5, the graphene layer 10 itself can be prevented from becoming thick, and the crystal type of the SiC single crystal substrate 1 can be reflected in the crystal growth of the epitaxial layer 3.

[0031] As described above, in the second modification, step bunching of the SiC single crystal substrate is suppressed, so that the surface roughness (Ra) of the SiC single crystal substrate is reduced, and the surface roughness (Ra) of the carbon-containing layer formed on the SiC single crystal substrate is also reduced. Since the flatness of the formation surface of the carbon-containing layer is good, a carbon-containing layer with high crystallinity can be formed.

[0032] (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.

[0033] 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.

[0034] Next, as shown in Fig. 4B, a thin film 10A containing carbon is deposited on the SiC single crystal substrate 1 from which the native oxide film has been removed. The method for depositing the thin film 10A is not particularly limited, but for example, a physical vapor deposition method, a chemical vapor deposition method, a wet deposition method, or the like can be used. More specifically, a Langmuir-Blodgett method or a vapor deposition polymerization method can be used.

[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. 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 The heat treatment may be continued until the pressure reaches or below atmospheric pressure. After that, purging is performed using an inert gas such as argon gas, and after atmospheric pressure is reached, the SiC single crystal substrate 1 is heat-treated in an inert gas atmosphere to carbonize the monolayer and form the thin film 10A. The heat treatment temperature is, for example, 400°C.

[0036] The thin film 10A acts as a carbon supply source for forming a carbon-containing layer such as a graphene layer. The thickness of the thin film 10A may be such that the thin film 10A can act as a carbon supply source. The thickness of the thin film 10A 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.

[0037] Next, as shown in FIG. 4C, a cap film 20 for suppressing thermal decomposition of the SiC single crystal substrate 1 is deposited on the thin film 10A. The cap film 20 is configured to remain in at least a part of the temperature range from the temperature at which thermal decomposition of the SiC single crystal substrate 1 starts (e.g., 1200° C. to 1300° C.) to the temperature at which the graphene layer 10 contained in the carbon-containing layer is formed (e.g., 1600° C.) during heat treatment performed in a later step. The cap film 20 is finally removed by the heat treatment. A film containing silicon oxide or silicon nitride can be used as the cap film 20.

[0038] The method for depositing the cap film 20 is not particularly limited, and may be, for example, a physical vapor deposition method, a chemical vapor deposition method, a wet deposition method, etc. For example, a silicon oxide film of 10 nm can be formed by introducing silane as a precursor using an ECR (Electron Cyclotoron Resonance) plasma CVD (Chemical Vapor Deposition) device capable of forming a film at a low temperature.

[0039] The thickness of the cap film 20 may be configured so as to remain in at least a part of the temperature range from the temperature at which thermal decomposition of the SiC single crystal substrate 1 starts to the temperature at which the graphene layer 10 contained in the carbon-containing layer is formed during heat treatment performed in a later step. The thickness of the cap film 20 is, for example, 1 nm or more and 500 nm or less, or may be 10 nm or more and 450 nm or less, or may be 50 nm or more and 400 nm or less.

[0040] 4D, the SiC single crystal substrate 1 on which the thin film 10A and the cap film 20 are laminated is subjected to a heat treatment to remove the cap film 20, and then, using carbon supplied from the thin film 10A exposed by the removal of the cap film 20, a carbon-containing layer is formed in the region on the SiC single crystal substrate 1 from which the cap film 20 has been removed. The carbon-containing layer includes a laminate made of a reconstructed surface layer 10a in contact with the Si-terminated surface of the SiC single crystal substrate 1 and a graphene layer 10 in contact with the reconstructed surface layer 10a.

[0041] The heat treatment is performed at a temperature of, for example, 1200° C. to 2500° C. In addition, the heat treatment is performed at a temperature of, for example, 1×10 -4 N / m 2 Under vacuum or 1×10 4 N / m 2 More than 1×10 6 N / m 2 The heat treatment is carried out under an inert gas atmosphere. For example, argon gas is used as the inert gas. -4 N / m 2 The SiC single crystal substrate 1 on which the thin film 10A and the cap film 20 are 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 heating rate at this time is, for example, 400° C. / sec.

[0042] 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.

[0043] The source gas for forming the epitaxial layer 3 is not particularly limited, and for example, a mixture of propane (C3H8) and silane (SiH4) in a volume ratio of 1:3 can be used. Silane (SiH4) can be used as a precursor of Si, and propane (C3H8) can be used as a precursor of C. In addition, argon gas that suppresses etching of the graphene layer 10 can be used as a carrier gas for transporting the source gas.

[0044] The thickness of the epitaxial layer 3 is not particularly limited, but is, for example, 500 nm.

[0045] In the above-mentioned manufacturing method of the composite substrate, the thin film 10A acting as a carbon source for forming a carbon-containing layer such as a graphene layer is used, but the present invention is not limited thereto. For example, as shown in FIG. 5, the cap film 20 may be directly deposited on the SiC single crystal substrate 1 from which the natural oxide film has been removed. In this case, the thickness of the cap film 20 is adjusted to allow the cap film 20 to remain at a desired temperature, and the cap film 20 is removed by a subsequent process, and the carbon-containing layer is formed by carbon derived from the SiC single crystal substrate 1. In addition, in the manufacturing method in which the cap film 20 is directly deposited on the SiC single crystal substrate 1, the carbon source is only the SiC single crystal substrate 1, so the coating speed of the carbon-containing layer is slower than in the manufacturing method using the thin film 10A.

[0046] (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.

[0047] <Example of embodiment> Examples of this embodiment are given below: This embodiment is not limited to the following examples.

[0048] [Appendix 1] A step of depositing a cap film 20 on the SiC single crystal substrate 1 to suppress thermal decomposition of the SiC single crystal substrate 1; a step of removing the cap film 20 by performing a heat treatment; 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 performing a heat treatment; A method for manufacturing a composite substrate 100, 100A, or 100B, wherein the thickness of the cap film 20 is configured to remain in at least a portion of the temperature range from the temperature at which thermal decomposition of the SiC single crystal substrate 1 begins to the temperature at which the graphene layer 10 is formed.

[0049] [Appendix 2] The method further includes a step of depositing a thin film 10A containing carbon on the SiC single crystal substrate 1, The cap film 20 is deposited on the thin film 10A. A method for manufacturing the composite substrate 100, 100A, 100B described in [Appendix 1], comprising the steps of: performing a heat treatment to form a carbon-containing layer on the SiC single crystal substrate 1 using carbon supplied from the thin film 10A exposed by removing the cap film 20.

[0050] According to [Additional Note 1] or [Additional Note 2], the growth of the carbon-containing layer can be promoted before step bunching of the SiC single crystal substrate occurs, and a composite substrate can be obtained in which the surface roughness (Ra) of the carbon-containing layer including the highly crystalline graphene layer formed on the SiC single crystal substrate is reduced.

[0051] [Appendix 3] A method for producing the composite substrate 100, 100A, 100B described in [Appendix 2], in which the deposition of the thin film 10A is carried out by any method selected from the group consisting of physical vapor deposition, chemical vapor deposition, and wet deposition.

[0052] [Appendix 4] A method for producing the composite substrate 100, 100A, 100B according to [Appendix 2] or [Appendix 3], wherein the thickness of the thin film 10A is 0.3 nm or more and 100 nm or less.

[0053] According to [Additional Note 3] or [Additional Note 4], the thin film 10A can be used as a carbon source for forming a carbon-containing layer such as a graphene layer, the coating speed of the carbon-containing layer can be increased, and the carbon-containing layer can be quickly formed before step bunching of the SiC single crystal substrate occurs.

[0054] [Appendix 5] A method for producing the composite substrate 100, 100A, 100B according to any one of [Appendix 1] to [Appendix 4], wherein, in a heat treatment, following a step of removing the cap film 20, a carbon-containing layer is formed in a region on the SiC single crystal substrate 1 from which the cap film 20 has been removed.

[0055] [Appendix 6] A method for producing a composite substrate (100, 100A, 100B) according to any one of [Appendix 1] to [Appendix 5], wherein the cap film (20) is a film containing silicon oxide or silicon nitride.

[0056] [Appendix 7] A method for manufacturing the composite substrate 100, 100A, 100B described in any one of [Appendix 1] to [Appendix 6], in which the deposition of the cap film 20 is performed by any method selected from the group consisting of physical vapor deposition, chemical vapor deposition, and wet deposition.

[0057] [Appendix 8] A method for producing the composite substrate 100, 100A, 100B according to any one of [Appendix 1] to [Appendix 7], wherein the thickness of the cap film 20 is 1 nm or more and 500 nm or less.

[0058] [Appendix 9] A method for producing composite substrate 100, 100A, 100B according to any one of [Appendix 1] to [Appendix 8], wherein the heat treatment is carried out at a temperature of 1200° C. or higher and 2500° C. or lower.

[0059] [Appendix 10] 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, 100B according to any one of [Appendix 1] to [Appendix 9], which is carried out under an inert gas atmosphere as described below.

[0060] According to [Addendum 5] to [Addendum 10], by controlling the configuration of the cap film 20 and the heat treatment conditions, the cap film 20 is configured to remain in at least a part of the temperature range from the temperature at which thermal decomposition of the SiC single crystal substrate 1 begins to the temperature at which the graphene layer 10 contained in the carbon-containing layer is formed, and further, the cap film 20 is continuously removed, and carbon supplied from the exposed thin film 10A is used to form a carbon-containing layer on the SiC single crystal substrate 1.

[0061] [Appendix 11] A method for producing a composite substrate 100B according to any one of [Appendix 1] to [Appendix 10], further comprising a step of forming an epitaxial layer 3 on a graphene layer 10 included in the carbon-containing layer.

[0062] [Appendix 12] A method for producing a composite substrate 100B according to [Appendix 11], in which epitaxial layer 3 is deposited by any method selected from the group consisting of physical vapor deposition and chemical vapor deposition.

[0063] [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.

[0064] According to [Additional Notes 11] to [Additional Notes 13], epitaxial layer 3 having a small surface roughness (Ra) can be formed, and epitaxial layer 3 can be easily peeled off from composite substrate 100B.

[0065] [Appendix 14] A SiC single crystal substrate 1; 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; Observation by atomic force microscope shows 2×2μm 2 The surface roughness (Ra) of the carbon-containing layer in contact with the SiC single crystal substrate around the substrate is 1.0 nm or less.

[0066] [Appendix 15] the carbon-containing layer comprises a laminate; The composite substrates 100A and 100B according to [Appendix 14], wherein the reconstructed surface layer 10a of the laminate is in contact with the Si-terminated surface 1si of the SiC single crystal substrate 1.

[0067] [Appendix 16] The composite substrate 100, 100A, or 100B described in [Appendix 14], wherein the graphene layer 10 included in the carbon-containing layer is in contact with the C-terminated surface 1c or the reconstructed surface layer 10a of the SiC single crystal substrate 1.

[0068] According to [Additional Note 14] to [Additional Note 16], a composite substrate can be obtained in which the surface roughness (Ra) of the carbon-containing layer, which is formed on the SiC single crystal substrate and includes a highly crystalline graphene layer, is reduced.

[0069] [Appendix 17] Composite substrate 100, 100A, 100B according to any one of [Appendix 14] to [Appendix 16], wherein SiC single crystal substrate 1 has an off angle of 0.5° or more and 10° or less.

[0070] [Appendix 18] Composite substrate 100, 100A, 100B according to any one of [Appendix 14] to [Appendix 17], wherein SiC single crystal substrate 1 has a crystal structure of either a hexagonal crystal or a cubic crystal.

[0071] [Appendix 19] The composite substrate 100, 100A, or 100B according to any one of [Appendix 14] to [Appendix 18], wherein the number of graphene layers 10 included in the carbon-containing layer is 1 to 5.

[0072] [Appendix 20] The composite substrate 100B according to any one of [Additional Note 14] to [Additional Note 19], further comprising an epitaxial layer 3 disposed on the graphene layer 10 included in the carbon-containing layer.

[0073] According to [Additional Note 17] to [Additional Note 20], epitaxial layer 3 having a small surface roughness (Ra) can be formed, and epitaxial layer 3 can be easily peeled off from composite substrate 100B. [Explanation of symbols]

[0074] 1. SiC single crystal substrate 1c C end face 1si Si termination surface 3 Epitaxial layer 10 graphene layers 10a Reconstructed surface layer 10A thin film 100, 100A, 100B composite board

Claims

1. depositing a cap film on a SiC single crystal substrate to suppress thermal decomposition of the SiC single crystal substrate; removing the cap film by performing a heat treatment; 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 performing the heat treatment, a thickness of the cap film is configured to remain in at least a part of a temperature range from a temperature at which thermal decomposition of the SiC single crystal substrate starts to a temperature at which the graphene layer is formed.

2. The method further comprises depositing a thin film containing carbon on the SiC single crystal substrate; the cap film is deposited on the thin film; The method for producing a composite substrate according to claim 1 , wherein the carbon-containing layer is formed on the SiC single crystal substrate by using carbon supplied from the thin film exposed by removing the cap film during the heat treatment.

3. The method for producing a composite substrate according to claim 2 , 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.

4. The method for producing a composite substrate according to claim 2 , wherein the thin film has a thickness of 0.3 nm or more and 100 nm or less.

5. The method for producing a composite substrate according to claim 1 , wherein, in the heat treatment, the carbon-containing layer is formed in a region on the SiC single crystal substrate from which the cap film has been removed, immediately following the step of removing the cap film.

6. The method for manufacturing a composite substrate according to claim 1 , wherein the cap film is a film containing silicon oxide or silicon nitride.

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

8. The method for manufacturing a composite substrate according to claim 1 , wherein the cap film has a thickness of 1 nm or more and 500 nm or less.

9. The method for producing a composite substrate according to claim 1 , wherein the heat treatment is performed at a temperature of 1200° C. or more and 2500° C. or less.

10. The heat treatment is performed at 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 1 , which is carried out under an inert gas atmosphere as follows:

11. The method for producing a composite substrate according to claim 1 , further comprising the step of forming an epitaxial layer on the graphene layer included in 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; 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; A composite substrate, wherein the surface roughness (Ra) of the carbon-containing layer in contact with the SiC single crystal substrate is 1.0 nm or less per 2 μm×2 μm square when observed with an atomic force microscope.

15. the carbon-containing layer includes the laminate, The composite substrate according to claim 14 , wherein the reconstructed surface layer of the laminate is in contact with a Si-terminated surface of the SiC single crystal substrate.

16. The composite substrate according to claim 14 , wherein the graphene layer included in the carbon-containing layer is in contact with a C-terminated surface or the reconstructed surface layer of the SiC single crystal substrate.

17. The composite substrate according to claim 14 , wherein the SiC single crystal substrate has an off angle of 0.5° or more and 10° or less.

18. 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.

19. The composite substrate according to claim 14 , wherein the number of graphene layers included in the carbon-containing layer is 1 to 5.

20. The composite substrate of claim 14 , further comprising an epitaxial layer disposed on a graphene layer included in the carbon-containing layer.

Images