Sic composite substrate and manufacturing method therefor

Abstract

The present invention comprises: a SiC substrate having a C plane as a main surface; a carbon nanotube film formed on the main surface of the SiC substrate; and an epitaxial layer laminated on the carbon nanotube film, wherein the SiC substrate may contain polycrystalline SiC or single crystal SiC, and may include any one crystal polymorphism among cubic 3C and hexagonal 4H and 6H, and the epitaxial layer may contain a two-dimensional substance or a three-dimensional substance.

Description

SiC composite substrate and method of manufacturing same

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

[0002] For example, molybdenum disulfide (MoS ２ Layered materials such as niobium diselenide (NbSe) have a structure in which unit layers are stacked via van der Waals forces, and are easily cleaved along the unit layers, and the cleavage plane does not have active dangling bonds. ２ The van der Waals epitaxy method is known, in which a thin film of a two-dimensional material such as SiO 2 is heteroepitaxially grown under the influence of van der Waals forces (see Non-Patent Documents 1 and 2).

[0003] A. Koma et al., Microelectron. Eng. 2, 129 (1984) A. Koma, Applied Physics 62, 758 (1993)

[0004] [Summary] The van der Waals epitaxy method described above has the advantage that only weak van der Waals forces act in the out-of-plane direction of the thin film, but because it is not affected by the substrate, it has been difficult to control the nucleation and diffusion of the growing film. For example, there have been problems such as the inability to determine the nucleation point in the thin film and the inability to achieve uniform film growth within the plane.

[0005] The present disclosure has been proposed in view of the above-described circumstances, and aims to provide a SiC composite substrate in which an epitaxial layer is formed by stacking on a main surface of a SiC substrate under the influence of van der Waals forces, and in which nucleation and diffusion of the epitaxial layer can be controlled, and a method for manufacturing the same.

[0006] In order to solve the above-mentioned problems, one aspect of the SiC composite substrate of the present disclosure includes a SiC substrate having a C-plane as a main surface, a carbon nanotube film formed on the main surface of the SiC substrate, and an epitaxial layer stacked on the carbon nanotube film.

[0007] One aspect of the method for manufacturing a SiC composite substrate of the present disclosure includes the steps of providing a SiC substrate having a carbon nanotube film formed on a main surface thereof, and forming an epitaxial layer on the surface of the carbon nanotube film by van der Waals epitaxy.

[0008] Fig. 1 is a cross-sectional view of a SiC composite substrate of the present embodiment. Fig. 2 is an enlarged cross-sectional view of a main portion of the SiC composite substrate of Fig. 1. Fig. 3A is a process flow diagram of a method for manufacturing the SiC composite substrate of Fig. 1. Fig. 3B is a process flow diagram of a method for manufacturing the SiC composite substrate of Fig. 1. Fig. 3C is a process flow diagram of a method for manufacturing the SiC composite substrate of Fig. 1. Fig. 4 is a cross-sectional view of a SiC composite substrate of Example 1. Fig. 5 is a cross-sectional view of a SiC composite substrate of Example 2.

[0009] [Detailed Description] Hereinafter, embodiments of the SiC composite substrate and its manufacturing method according to the present disclosure will be described in detail with reference to the drawings. The embodiments are comprehensive or specific examples. The numerical values, shapes, materials, components, component installation positions, and connection forms shown in the embodiments are merely examples and are not intended to limit the scope of the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts will be described as optional components. Furthermore, the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions. Furthermore, the following embodiments and their variations may include similar components, and similar components will be assigned common reference numerals, and redundant explanations will be omitted.

[0010] (SiC Composite Substrate) FIG. 1 is a cross-sectional view showing a SiC composite substrate 1 according to the present embodiment. In the SiC composite substrate 1, a carbon nanotube film 12 is formed on the main surface of the C-plane of a SiC substrate 11, and an epitaxial layer 13 is laminated on the carbon nanotube film 12. The SiC substrate 11 has a polar C-plane as its main surface, and may be made of polycrystalline SiC or single-crystalline SiC. The SiC substrate 11 may also be made of a cubic crystal system such as 3C, or a hexagonal crystal system such as 4H or 6H. The SiC substrate 11 may have a diameter of 4 inches or more.

[0011] Carbon nanotube film 12 is formed by growing carbon nanotubes by pyrolysis on the C-plane, which is the main surface of SiC substrate 11. Carbon nanotube film 12 is configured such that carbon nanotubes grow from the C-plane, which is the main surface of SiC substrate 11, extend in the vertical direction, and are spread all over the main surface in the direction of its extension.

[0012] The epitaxial layer 13 is formed on the surface of the carbon nanotube film 12 under the influence of van der Waals forces from the carbon nanotubes, and is also called a van der Waals epitaxial layer. The epitaxial layer 13 may be made of a two-dimensional material containing at least one of a transition metal dichalcogenide and boron nitride (BN). Here, the transition metal dichalcogenide is represented by MX, where M is a transition metal and X is a chalcogen (a group 16 element). ２ It is a layered material represented by MoS ２ , NbSe ２ The epitaxial layer 13 may be made of gallium nitride (GaN), silicon carbide (SiC), gallium arsenide (GaAs), aluminum nitride (AlN), diamond, gallium oxide (Ga ２ O ３ The GaN layer may be made of a three-dimensional material containing at least one wide bandgap semiconductor such as AlN.

[0013] 2 is an enlarged cross-sectional view of a key portion of the SiC composite substrate 1 shown in FIG. 1 , showing the vicinity of the interface between the carbon nanotube film 12 and the epitaxial layer 13. On the surface of the carbon nanotube film 12, the tips of rounded carbon nanotubes are lined up to form a two-dimensional plane, and physical depressions, indicated by arrows, exist at the boundaries between adjacent carbon nanotubes. These depressions act as physical diffusion barriers (height differences) for adatoms as the epitaxial layer 13 grows, serving as nucleation points, enabling control of the nucleation and diffusion of the growing epitaxial layer 13.

[0014] Furthermore, because the carbon nanotube film 12 has no bonds in the out-of-plane direction, the epitaxial layer 13 grown on the surface of the carbon nanotube film 12 can maintain its own crystal structure while growing. Therefore, it is also possible to use the epitaxial layer 13 as a template to further grow another epitaxial layer made of a material different from that of the epitaxial layer 13 on the surface of the epitaxial layer 13.

[0015] (Manufacturing Method) FIGS. 3A to 3C are process flow diagrams for the SiC composite substrate 1 shown in FIG. 1. First, a SiC substrate 11 is provided as shown in FIG. 3A. The SiC substrate 11 has a C-plane as its main surface. In the SiC substrate 11, the back surface opposite the C-plane of the main surface is the Si-plane. The SiC substrate 11 may be made of polycrystalline SiC or single-crystalline SiC. Furthermore, the SiC substrate 11 may be made of a cubic crystal system such as 3C, or a hexagonal crystal system such as 4H and 6H. The SiC substrate 11 may have a diameter of 4 inches or more.

[0016] As shown in FIG. 3B, carbon nanotubes are grown by thermal decomposition on the C-plane, the main surface of the SiC substrate 11, to form a carbon nanotube film 12. For example, 1×10 －２ By heating the SiC substrate 11 in a vacuum of about Pa, carbon nanotubes can be grown from the C-plane, which is the main surface of the SiC substrate 11, to form the carbon nanotube film 12.

[0017] 3C , epitaxial layer 13 is hetero-grown on the surface of carbon nanotube film 12 formed on the main surface of SiC substrate 11 under the influence of van der Waals forces from carbon nanotube film 12. This method of manufacturing epitaxial layer 13 is also called van der Waals epitaxy, and epitaxial layer 13 is also called van der Waals epitaxial layer.

[0018] The epitaxial layer 13 may be composed of a two-dimensional material containing at least one of a transition metal dichalcogenide and boron nitride (BN). Here, the transition metal dichalcogenide is represented by MX, where M is a transition metal and X is a chalcogen (a group 16 element). ２It is a layered material represented by MoS ２ , NbSe ２ The epitaxial layer 13 may be made of gallium nitride (GaN), silicon carbide (SiC), gallium arsenide (GaAs), aluminum nitride (AlN), diamond, gallium oxide (Ga ２ O ３ However, GaN can be formed on an AlN substrate.

[0019] As shown in FIG. 3C , the epitaxial layer 13 stacked on the carbon nanotube film 12 can be peeled off from the carbon nanotube film 12 to form a thin film. Because weak van der Waals forces act on the epitaxial layer 13 from the surface of the carbon nanotube film 12, the epitaxial layer 13 can be easily peeled off from the carbon nanotube film 12. The carbon nanotubes forming the carbon nanotube film 12 are firmly bonded to the C-plane, the main surface of the SiC substrate formed by pyrolysis. Therefore, the carbon nanotube film 12 can withstand peeling of the epitaxial layer 13 formed on its surface. For example, the formation and peeling of the epitaxial layer 13 can be repeated 200 times or more.

[0020] The van der Waals epitaxy method of this embodiment grows an epitaxial layer 13 on the surface of a carbon nanotube film 12. The surface of the carbon nanotube film 12 is formed by rounded tips of carbon nanotubes, which are one-dimensional substances extending in the normal direction to the main surface of a SiC substrate 11 and are two-dimensionally arranged. The epitaxial layer 13 formed on the surface of the carbon nanotube film 12 is free from the stress of the SiC substrate 11. Furthermore, as shown in FIG. 2 , physical depressions exist between adjacent carbon nanotubes on the surface of the carbon nanotube film 12. These depressions act as physical diffusion barriers (height differences) for adatoms during the growth of the epitaxial layer 13, serving as nucleation points, enabling control of the nucleation and diffusion of the growing epitaxial layer 13.

[0021] Since the carbon nanotube film 12 has no bonds in the out-of-plane direction, the epitaxial layer 13 grown on the carbon nanotube film 12 can maintain its own crystal structure while growing. Therefore, the epitaxial layer 13 can be used as a template to further grow another epitaxial layer made of a material different from that of the epitaxial layer 13 on the surface of the epitaxial layer 13.

[0022] Fig. 4 is a cross-sectional view of a SiC composite substrate 2 of Example 1. The SiC composite substrate 2 of Example 1 differs from the SiC composite substrate 1 of Fig. 1 in which the material of the epitaxial layer 13 is not specified, in that the epitaxial layer 21 is composed of a two-dimensional material, boron nitride (BN). Since the other configurations of the SiC composite substrate 2 are similar to those of the SiC composite substrate 1 of Fig. 1, corresponding components are assigned common reference numerals to clarify the correspondence.

[0023] The SiC composite substrate 2 of Example 1 was fabricated by the following process. First, a single-crystal SiC substrate 11 was provided, with its main surface being a (000-1) C-plane. This SiC substrate 11 was placed in a high-frequency induction heating furnace and heated at 1500°C for 5 hours, growing carbon nanotubes with a height of 200 nm on the main surface to form a carbon nanotube film 12. The average diameter of the carbon nanotubes was 5 nm.

[0024] Next, diborane (4) (B ２ H ４ ) and nitrogen gas (N ２ ) as a source gas, metal organic chemical vapor deposition (MOCVD) growth was performed to grow a 5-nm-thick epitaxial layer 21 of a two-dimensional hexagonal BN (h-BN) material. The h-BN epitaxial layer 21 was formed on the surface of the carbon nanotube film 12 by van der Waals epitaxy, which allows for control of the nucleation and diffusion of the growing epitaxial layer 13. Furthermore, the epitaxial layer 21 can grow while maintaining its own crystal structure.

[0025] 5 is a cross-sectional view of a SiC composite substrate 3 of Example 2. The SiC composite substrate 3 of Example 2 differs from the SiC composite substrate 1 of FIG. 1 in that the material of the epitaxial layer 13 is not specified and no other epitaxial layer 23 is included, in that the epitaxial layer 22 is composed of aluminum nitride (AlN), a three-dimensional material, and another epitaxial layer 23 similarly composed of gallium nitride (GaN), a three-dimensional material, is stacked on the epitaxial layer 22. Since the other configuration of the SiC composite substrate 3 is the same as that of the SiC composite substrate 1 of FIG. 1, corresponding components are assigned common reference numerals to clarify the correspondence.

[0026] The SiC composite substrate 3 of Example 2 was fabricated by the following process. As in Example 1, carbon nanotubes having a height of 200 nm were grown on the main surface of a single-crystal SiC substrate 11, the main surface of which was a (000-1) C-plane, to form a carbon nanotube film 12. The average diameter of the carbon nanotubes was 5 nm.

[0027] Next, trimethylaluminum (Al(CH ３ ) ３ ) and ammonium (NH ４ ＋ ) was used as a material gas to perform MOCVD growth, and an epitaxial layer 22 of AlN, a three-dimensional material, was grown to a height of 0.5 μm in an atmosphere of 1000° C. Furthermore, trimethylgallium (Ga(CH ３ ) ３ ) and ammonium (NH ４ ＋ ) was used as a material gas for MOCVD growth, and GaN, which is a three-dimensional material, was grown to a height of 3 μm in an atmosphere of 1100° C. using the AlN epitaxial layer 22 as a base template to form another epitaxial layer 23.

[0028] The AlN epitaxial layer 22 is formed on the surface of the carbon nanotube film 12 by van der Waals epitaxy, which allows for control of the nucleation and diffusion of the growing epitaxial layer 22. Furthermore, the epitaxial layer 22 can grow while maintaining its own crystal structure. This allows the epitaxial layer 22 to serve as an appropriate base or template for another GaN epitaxial layer 23 to be layered on the epitaxial layer 22.

[0029] Although the present disclosure has been described in detail above, it will be apparent to those skilled in the art that the present disclosure is not limited to the embodiments described herein. One or more elements of one embodiment can be combined with one or more elements of another embodiment. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure, as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and explanatory, and is not intended to be limiting of the present disclosure.

[0030] (Supplementary Notes) The technical ideas that can be understood from the present disclosure are described below. Note that, for the purpose of aiding understanding and not intending to be limiting, the components described in the Supplementary Notes are given the reference symbols of the corresponding components in the embodiments. The reference symbols are shown as examples to aid understanding, and the components described in each Supplementary Note should not be limited to the components indicated by the reference symbols.

[0031] (Supplementary Note 1) SiC composite substrate 1 includes SiC substrate 11 having a C-plane as its main surface, carbon nanotube film 12 formed on the main surface of SiC substrate 11, and epitaxial layer 13 stacked on carbon nanotube film 12. Recesses present at the boundaries between adjacent carbon nanotubes on the surface of carbon nanotube film 12 act as physical diffusion barriers (height differences) for adatoms when epitaxial layer 13 grows, and serve as nucleation points, making it possible to control the nucleation and diffusion of the growing epitaxial layer 13.

[0032] (Supplementary Note 2) The SiC composite substrate 1 described in Supplementary Note 1 may contain polycrystalline SiC or single-crystal SiC. The SiC constituting the SiC substrate 11 may be either polycrystalline or single-crystal.

[0033] (Supplementary Note 3) The SiC substrate 11 described in Supplementary Note 1 or 2 may include any one of the crystalline polytypes of cubic 3C and hexagonal 4H and 6H. The SiC constituting the SiC substrate 11 may be of any of the crystalline polytypes of cubic 3C and hexagonal 4H and 6H.

[0034] (Supplementary Note 4) In the SiC composite substrate 1 according to any one of Supplementary Notes 1 to 3, the epitaxial layer 13 may include a two-dimensional material. The epitaxial layer 13 may be a two-dimensional material that extends along the surface of the carbon nanotube film 12.

[0035] (Supplementary Note 5) In the SiC composite substrate 1 described in Supplementary Note 4, the two-dimensional material may include at least one of a transition metal dichalcogenide and boron nitride.

[0036] (Supplementary Note 6) In the SiC composite substrate 1 according to any one of Supplementary Notes 1 to 3, the epitaxial layer 13 may include a three-dimensional material. The epitaxial layer 13 may be a three-dimensional material that spreads along the surface of the carbon nanotube film 12 and extends in the normal direction to the surface.

[0037] (Supplementary Note 7) In the SiC composite substrate 1 described in Supplementary Note 6, the three-dimensional material may include a wide-gap semiconductor.

[0038] (Supplementary Note 8) The SiC composite substrate 1 according to any one of Supplementary Notes 1 to 7 may further include another epitaxial layer 23 containing a material different from the epitaxial layer stacked on the epitaxial layer 22. The other epitaxial layer 23 can be formed using the epitaxial layer 22 as a template.

[0039] (Supplementary Note 9) The method for manufacturing SiC composite substrate 1 includes the steps of providing SiC substrate 11 having carbon nanotube film 12 formed on a main surface thereof, and forming epitaxial layer 13 by van der Waals epitaxy on the surface of carbon nanotube film 12. Recesses present at the boundaries between adjacent carbon nanotubes on the surface of carbon nanotube film 12 act as physical diffusion barriers (height differences) for adatoms when epitaxial layer 13 grows, and serve as nucleation points, making it possible to control the nucleation and diffusion of the growing epitaxial layer 13.

[0040] (Supplementary Note 10) In the method for manufacturing the SiC composite substrate 1 described in Supplementary Note 9, the SiC substrate 11 may contain polycrystalline SiC or single-crystal SiC. The SiC constituting the SiC substrate 11 may be either polycrystalline or single-crystal.

[0041] (Supplementary Note 11) In the method for manufacturing the SiC composite substrate 1 described in Supplementary Note 9 or 10, the SiC substrate 11 may contain any one of the cubic 3C and hexagonal 4H and 6H crystal polytypes. The SiC constituting the SiC substrate 11 may be any of the cubic 3C and hexagonal 4H and 6H crystal polytypes.

[0042] (Supplementary Note 12) In the method for manufacturing SiC composite substrate 1 according to any one of Supplementary Notes 9 to 11, the step of providing SiC substrate 11 having carbon nanotube film 12 formed on a main surface thereof may include the steps of providing SiC substrate 11 having a C-plane as the main surface, and growing carbon nanotubes on the main surface of SiC substrate 11 to form carbon nanotube film 12. Carbon nanotube film 12 can be formed by growing carbon nanotubes on the main surface of SiC substrate 11.

[0043] (Supplementary Note 13) In the method for manufacturing SiC composite substrate 1 described in Supplementary Note 12, the step of forming carbon nanotube film 12 may include growing carbon nanotubes by a thermal decomposition method. Carbon nanotubes can be grown on the C-plane, which is the main surface of SiC substrate 11, by a thermal decomposition method.

[0044] (Supplementary Note 14) In the method for manufacturing the SiC composite substrate 1 according to any one of Supplementary Notes 9 to 13, the step of forming the epitaxial layer 13 may include forming the epitaxial layer 13 using a two-dimensional material. The epitaxial layer 13 may be a two-dimensional material that spreads along the surface of the carbon nanotube film 12.

[0045] (Supplementary Note 15) In the method for manufacturing SiC composite substrate 1 described in Supplementary Note 14, the two-dimensional material may contain at least one of transition metal dichalcogenide and boron nitride.

[0046] (Supplementary Note 16) In the method for manufacturing SiC composite substrate 1 according to any one of Supplementary Notes 9 to 13, the step of forming epitaxial layer 13 may include forming epitaxial layer 13 using a three-dimensional material. Epitaxial layer 13 may be a three-dimensional material that spreads along the surface of carbon nanotube film 12 and extends in the normal direction to the surface.

[0047] (Supplementary Note 17) In the method for manufacturing SiC composite substrate 1 according to Supplementary Note 16, the three-dimensional material may include a wide-gap semiconductor.

[0048] (Appendix 18) The method for manufacturing the SiC composite substrate 1 according to any one of Appendices 9 to 17 may further include a step of stacking, on the epitaxial layer 22, another epitaxial layer 23 containing a material different from that of the epitaxial layer 22. The other epitaxial layer 23 can be formed using the epitaxial layer 22 as a template.

[0049] (Supplementary Note 19) In the SiC composite substrate 1 produced by the method for producing a SiC composite substrate 1 according to any one of claims 9 to 17, a thin film may be produced by peeling off the epitaxial layer 13 from the carbon nanotube film 12. Because the carbon nanotubes constituting the carbon nanotube film 12 are firmly bonded to the C-plane, which is the main surface of the SiC substrate 11, the epitaxial layer 13 can be grown and peeled off from the carbon nanotube film 12 to produce a thin film repeatedly.

[0050] REFERENCE SIGNS LIST 1 SiC composite substrate 11 SiC substrate 12 Carbon nanotube film 13 Epitaxial layer

Claims

1. A SiC composite substrate comprising: a SiC substrate having a C-plane as a main surface; a carbon nanotube film formed on the main surface of the SiC substrate; and an epitaxial layer stacked on the carbon nanotube film.

2. The SiC composite substrate according to claim 1, wherein the SiC substrate comprises polycrystalline SiC or single crystal SiC.

3. The SiC composite substrate according to claim 1 or 2, wherein the SiC substrate contains one of the crystalline polytypes of cubic 3C and hexagonal 4H and 6H.

4. The SiC composite substrate according to any one of claims 1 to 3, wherein the epitaxial layer comprises a two-dimensional material.

5. The SiC composite substrate according to claim 4, wherein the two-dimensional material includes at least one of a transition metal dichalcogenide and boron nitride.

6. The SiC composite substrate according to any one of claims 1 to 3, wherein the epitaxial layer comprises a three-dimensional material.

7. The SiC composite substrate according to claim 6, wherein the three-dimensional material includes a wide-gap semiconductor.

8. A SiC composite substrate according to any one of claims 1 to 7, further comprising another epitaxial layer stacked on the epitaxial layer and containing a material different from that of the epitaxial layer.

9. A method for manufacturing a SiC composite substrate, comprising: providing a SiC substrate having a carbon nanotube film formed on a main surface thereof; and forming an epitaxial layer on the surface of the carbon nanotube film under the influence of van der Waals forces from the carbon nanotube film.

10. The method for producing a SiC composite substrate according to claim 9, wherein the SiC substrate comprises polycrystalline SiC or single crystal SiC.

11. The method for producing a SiC composite substrate according to claim 9 or 10, wherein the SiC substrate contains one of the crystalline polytypes of cubic 3C and hexagonal 4H and 6H.

12. A method for manufacturing a SiC composite substrate according to any one of claims 9 to 11, wherein the step of providing a SiC substrate having the carbon nanotube film formed on the main surface comprises the steps of: providing a SiC substrate whose main surface is a C-plane; and growing carbon nanotubes on the main surface of the SiC substrate to form the carbon nanotube film.

13. The method for producing a SiC composite substrate according to claim 12, wherein the step of forming the carbon nanotube film comprises growing the carbon nanotubes by a thermal decomposition method.

14. A method for producing a SiC composite substrate according to any one of claims 9 to 13, wherein the step of forming the epitaxial layer forms the epitaxial layer using a two-dimensional material or a three-dimensional material.

15. A method for producing a SiC composite substrate according to any one of claims 9 to 14, further comprising the step of stacking, on the epitaxial layer, another epitaxial layer containing a material different from that of the epitaxial layer.

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