Method for manufacturing silicon carbide substrate, silicon carbide substrate, and method for removing strain layer introduced into silicon carbide substrate by laser processing

Abstract

The problem addressed by the present invention is that of providing a novel technique that can remove a strain layer introduced into a silicon carbide substrate by laser processing. The present silicon carbide substrate manufacturing method involves a processing step for performing laser processing to remove part of a silicon carbide substrate by irradiating the silicon carbide substrate with a laser, and a strain layer removal step for removing a strain layer that was introduced in the silicon carbide substrate by the aforementioned processing step involving heat treatment of the silicon carbide substrate. In this way, the present invention, which is a method of removing a strain layer introduced into a silicon carbide substrate by laser processing, involves a strain layer removal step for heat treating the silicon carbide substrate.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a silicon carbide substrate, a silicon carbide substrate, and a method for removing a strained layer introduced into a silicon carbide substrate by laser processing. [Background technology]

[0002] 2. Description of the Related Art In the manufacture of semiconductor substrates, a method of processing a semiconductor substrate by irradiating the semiconductor substrate with a laser has been conventionally employed.

[0003] Patent Document 1 discloses an invention in which a focus point of a laser beam having a wavelength absorbed by the workpiece is positioned on the upper surface of the workpiece, the laser beam is irradiated onto the workpiece, and ablation processing is performed to form a groove on the upper surface of the workpiece. Note that the invention described in Patent Document 1 can be understood as a method that can be applied to known semiconductor materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-305420 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-described method of irradiating a workpiece with a laser beam, distortion may be introduced into the semiconductor substrate, which is the workpiece, due to the irradiation. Since the distortion can cause dislocations in the semiconductor substrate, it is desirable to remove the distortion.

[0006] For example, when dislocations occur in a silicon carbide substrate, there is a risk that the dislocations will be inherited by a growth layer formed by epitaxial growth using the silicon carbide substrate as a base substrate. Therefore, it is desirable to remove the strain in the silicon carbide substrate.

[0007] An object of the present invention is to provide a novel technique capable of removing a strained layer introduced into a silicon carbide substrate by laser processing. [Means for solving the problem]

[0008] The present invention, which solves the above-mentioned problems, provides a method for manufacturing a silicon carbide substrate, including a processing step of performing laser processing to remove a portion of the silicon carbide substrate by irradiating the silicon carbide substrate with a laser, and a strained layer removal step of removing the strained layer introduced into the silicon carbide substrate by the processing step by heat-treating the silicon carbide substrate. In this way, the present invention can remove the strained layer introduced into the silicon carbide substrate. In this way, the present invention can remove the strained layer introduced into the silicon carbide substrate by laser processing.

[0009] In a preferred embodiment of the present invention, the processing step is a step of forming through holes in the silicon carbide substrate. In this manner, the present invention can form a lateral temperature gradient that serves as a driving force for crystal growth along the a-axis direction.

[0010] In a preferred embodiment of the present invention, the strained layer removing step is a step of etching the silicon carbide substrate in a semi-closed space.

[0011] In a preferred embodiment of the present invention, the strained layer removing step is a step of etching the silicon carbide substrate in a silicon atmosphere. In this way, the present invention can flatten the top wall and side wall of the silicon carbide substrate surface.

[0012] The present invention also relates to a method for removing a strained layer introduced into a silicon carbide substrate by laser processing, which includes a strained layer removal step of heat-treating the silicon carbide substrate. That is, the present invention, which solves the above-mentioned problems, is a method for removing a strained layer introduced into a silicon carbide substrate by laser processing, which includes a strained layer removal step of heat-treating the silicon carbide substrate after laser processing of the silicon carbide substrate.

[0013] In a preferred embodiment of the present invention, the strained layer removing step is a step of etching the silicon carbide substrate in a semi-closed space.

[0014] In a preferred embodiment of the present invention, the strained layer removing step is a step of etching the silicon carbide substrate in a silicon atmosphere. [Effects of the Invention]

[0015] The disclosed technology can provide a novel technology that can remove a strained layer introduced into a silicon carbide substrate by laser processing.

[0016] Other objects, features and advantages will become apparent from a reading of the following detailed description when taken in conjunction with the drawings and claims. [Brief explanation of the drawings]

[0017] [Figure 1] 1A to 1C are explanatory diagrams illustrating a method for manufacturing a silicon carbide substrate according to an embodiment. [Figure 2] 10A to 10C are explanatory views illustrating a processing step and a strained layer removing step according to an embodiment. [Figure 3] FIG. 2 is an explanatory diagram illustrating a crystal growth process according to an embodiment. [Figure 4] 10A to 10C are explanatory views illustrating a strained layer removing step according to an embodiment of the present invention. [Figure 5] 1 is an observation image of a silicon carbide substrate according to an example. [Figure 6] 1 is an observation image of a silicon carbide substrate according to an example. [Figure 7] FIG. 10 is a diagram showing the strain distribution of a silicon carbide substrate according to an example. [Figure 8] FIG. 10 is a diagram showing the strain distribution of a silicon carbide substrate according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for manufacturing a silicon carbide substrate according to the present invention will be described in detail below with reference to the accompanying drawings.

[0019] The technical scope of the present invention is not limited to the embodiments shown in the accompanying drawings, and can be modified as appropriate within the scope of the claims.

[0020] The drawings attached to this specification are conceptual diagrams, and the relative dimensions of each component and the like do not limit the present invention.

[0021] For the purpose of explaining the invention, this specification may refer to the top or bottom based on the top and bottom of the drawings, but this does not limit the top or bottom in relation to the use mode of the silicon carbide substrate of the present invention, etc.

[0022] In the following description of the embodiments and the accompanying drawings, the same components are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0023] <Method for manufacturing silicon carbide substrate> 1 and 2 show steps in a method for manufacturing a silicon carbide substrate (hereinafter simply referred to as "SiC substrate") according to an embodiment of the present invention.

[0024] The manufacturing method of the SiC substrate according to the embodiment may include a processing step S11 in which laser processing is performed to remove a portion of the SiC substrate 10 by irradiating the SiC substrate 10 with a laser L, and a strained layer removal step S12 in which the strained layer 12 introduced into the SiC substrate 10 by the processing step S11 is removed by heat-treating the SiC substrate 10.

[0025] Furthermore, this embodiment can be understood as a method for removing strained layer 12 introduced into SiC substrate 10 by laser processing, which includes a strained layer removal step S12 in which SiC substrate 10 is heat-treated after laser processing of SiC substrate 10 is performed.

[0026] The SiC substrate 10 (corresponding to a SiC wafer) may be a single crystal SiC substrate, a polycrystalline SiC substrate, a wafer or substrate processed from a bulk crystal, a wafer or substrate including an epitaxially grown layer, or a square wafer.

[0027] Furthermore, the SiC substrate 10 is not limited in its crystal polytype, off-direction, off-angle, wafer size, substrate thickness, doping concentration, and atomic species of added elements including dopant elements.

[0028] Each step of the embodiment will be described in detail below.

[0029] The processing step S11 is a step of performing laser processing to remove a part of the SiC substrate 10 by irradiating the SiC substrate 10 with a laser L.

[0030] In the description in this specification, "laser processing" refers to processing in which a laser beam having a wavelength that is absorbed by the SiC substrate 10, which is the object to be processed, is focused on the upper surface or inside the SiC substrate 10, and the laser beam is irradiated onto the SiC substrate 10, thereby forming a groove on the upper surface of the SiC substrate 10 or forming a damaged area inside the SiC substrate 10.

[0031] Laser processing refers to a technique for selectively processing a portion of an object by controlling the laser irradiation area (corresponding to the focal point) and focusing the light waves, which have energy equivalent to the bond energy of the material that makes up the object.

[0032] Furthermore, the processing step S11 is preferably a step of irradiating the SiC substrate 10 with a laser L having a wavelength of 532 nm.

[0033] The wavelength of the laser L is preferably 808 nm or less, preferably 650 nm or less, preferably 635 nm or less, preferably 589 nm or less, preferably 532 nm or less, preferably 473 nm or less, preferably 460 nm or less, preferably 445 nm or less, and preferably 405 nm or less.

[0034] Furthermore, the wavelength of the laser L is preferably 355 nm or more, preferably 405 nm or more, preferably 445 nm or more, preferably 460 nm or more, preferably 532 nm or more, preferably 589 nm or more, preferably 635 nm or more, and preferably 650 nm or more.

[0035] The wavelength of the laser L is, for example, a wavelength in a wavelength band classified as the visible light range.

[0036] Furthermore, the processing step S11 can be performed based on a known or conventional optical system.

[0037] In addition, in the processing step S11, a known or conventional light source can be used appropriately depending on the wavelength of the laser L and the like.

[0038] Furthermore, the laser L used in the processing step S11 is not limited in terms of its active medium, oscillation mode, repetition frequency, pulse width, beam spot diameter, output power, and polarization characteristics.

[0039] The optical system used in the processing step S11 suitably includes known or conventional mirrors, a scanner with a shaft rotation motor for alignment, a condenser lens, and a grating.

[0040] The condenser lens of the optical system used in the processing step S11 has no limitations on its magnification and numerical aperture (NA).

[0041] The processing step S11 is a step of forming through holes 11 in the SiC substrate 10.

[0042] Here, the processing step S11 can be understood as an embrittlement processing step in which the strength of the SiC substrate 10 is reduced by forming the through holes 11.

[0043] In the processing step S11, when forming the through-holes 11, the laser irradiation portion (corresponding to the focal point) is scanned in the film thickness direction of the SiC substrate 10.

[0044] For example, the through holes 11 can have any shape (pattern) that reduces the strength of the SiC substrate 10.

[0045] Furthermore, the through-holes 11 may have any shape (pattern) including a minor angle, for example.

[0046] Furthermore, in epitaxial growth using the SiC substrate 10 as a base substrate, it is desirable to set a shape (pattern) that will allow a desired growth layer to be obtained.

[0047] At this time, in the processing step S11, the laser L is scanned within the surface of the SiC substrate 10 in accordance with the shape (pattern).

[0048] In the processing step S11, it is desirable to adopt an optimum pattern depending on the physical properties (crystal orientation, etc.) of the SiC substrate 10 and the semiconductor material of the growth layer, and the growth method. There is no limitation on the width and depth of the shape (pattern).

[0049] The processing step S11 is a step of processing the surface of the SiC substrate 10 into a mesa shape.

[0050] The term "mesa shape" in the description of this specification corresponds to a concave-convex shape, and there is no limitation on the angle formed by the top wall and the side wall of the concave-convex shape.

[0051] Furthermore, there is no limit to the machining depth in the machining step S11.

[0052] When the processing step S11 is a step of processing the surface of the SiC substrate 10 into a mesa shape, recesses are formed in the surface of the SiC substrate 10 instead of the through holes 11 described above in the processing step S11.

[0053] In the processing step S11, the focus of the laser L is scanned from the surface (corresponding to the upper surface) of the SiC substrate 10 to the bottom surface (corresponding to the lower surface) to form the through-holes 11 or the protrusions.

[0054] Furthermore, in the processing step S11, at least a part of known techniques such as the methods described in, for example, Japanese Patent Application Laid-Open Nos. 10-305420, 2002-192370, and 2016-111147 can be appropriately adopted.

[0055] The strained layer removal step S12 is a step of removing the strained layer 12 introduced into the SiC substrate 10 in the processing step S11 by heat treating the SiC substrate 10. The strained layer 12 can be understood to correspond to a damaged layer, for example.

[0056] In addition, the strained layer removing step S12 can employ a method of etching the SiC substrate 10 by subjecting the SiC substrate 10 to a heat treatment.

[0057] Furthermore, in the strained layer removing step S12, any means capable of removing the strained layer 12 can naturally be employed.

[0058] The strained layer removal step S12 is a step of removing the strained layer 12 by thermal etching.

[0059] The strained layer removal step S12 is a step of etching the SiC substrate 10 in a semi-closed space. Note that the "semi-closed space" in the description of this specification refers to a space in which it is possible to evacuate the inside of a container or a sample chamber in which the SiC substrate 10 is placed, but which is also possible to confine at least a portion of the vapor generated in the container or the sample chamber.

[0060] The strained layer removal step S12 is a step of etching the SiC substrate 10 in a silicon atmosphere (Si atmosphere). Note that the "silicon atmosphere" in the description herein corresponds to the vapor pressure of a gas phase species containing Si elements.

[0061] The strained layer removal process S12 is, for example, a process of placing the SiC substrate 10 in a SiC container 50, placing the SiC container 50 in a high-melting-point container such as a TaC container 60, and heat-treating the high-melting-point container containing the SiC substrate 10.

[0062] In this case, the high-melting-point container includes a Si vapor supply source 64 capable of supplying the vapor pressure of a gaseous species containing Si element to the outside of the SiC container 50.

[0063] The strained layer removing step S12 is, for example, a step of placing the SiC substrate 10 in the high-melting-point container and heat-treating the high-melting-point container containing the SiC substrate 10.

[0064] In this case, the high-melting-point vessel is provided with a Si vapor supply source 64 capable of supplying the vapor pressure of a gaseous species containing Si element.

[0065] The "Si vapor supply source 64" in the description herein is, for example, solid Si (Si pellets such as Si pieces or Si powder) or a Si compound, and may be in the form of a thin film.

[0066] According to the present invention, by including the strained layer removing step S12 of heat-treating the SiC substrate 10, the strained layer 12 introduced into the SiC substrate 10 by laser processing can be removed.

[0067] In the following, the present specification will describe an embodiment in which the growth layer 20 is formed by epitaxial growth using the SiC substrate 10 from which the strained layer 12 has been removed in the strained layer removal step S12 as a base substrate.

[0068] According to the embodiment of the present invention, the SiC substrate 10 from which the strained layer 12 has been removed can be used as a base substrate for epitaxial growth of materials such as SiC and AlN.

[0069] <Crystal growth process S20> The crystal growth step S20 is a step of forming a growth layer 20 on the SiC substrate 10 after the strained layer removal step S12.

[0070] The material of the growth layer 20 may be the same as that of the SiC substrate 10 (corresponding to homoepitaxial growth), or may be a different material from that of the SiC substrate 10 (corresponding to heteroepitaxial growth).

[0071] The material of the growth layer 20 may be any material that is typically grown epitaxially.

[0072] Furthermore, the material of the growth layer 20 may be the material of the SiC substrate 10, or may be a known material that can be adopted as the material of the SiC substrate 10, or may be a known material that can be epitaxially grown on the SiC substrate 10.

[0073] The material of the growth layer 20 according to the embodiment is, for example, AlN.

[0074] The crystal growth step S20 is preferably a step of forming the growth layer 20 by physical vapor transport (PVT).

[0075] In the crystal growth step S20, a known vapor phase growth method (corresponding to a vapor phase epitaxial method) such as PVT, sublimation recrystallization, modified Rayleigh method, or chemical vapor transport (CVT) can be used as a growth method for the growth layer 20.

[0076] In addition, the crystal growth step S20 can employ physical vapor deposition (PVD) instead of PVT, and in addition, the crystal growth step S20 can employ chemical vapor deposition (CVD) instead of CVT.

[0077] In addition, the crystal growth process S20 can employ known liquid phase growth methods (equivalent to liquid phase epitaxial methods) such as the TSSG method (Top-Seeded Solution Growth method) and the Metastable Solvent Epitaxy (MSE) method as the growth method for the growth layer 20.

[0078] Furthermore, in the crystal growth step S20, the CZ method (Czochralski method) can be adopted as the growth method for the growth layer 20.

[0079] In the crystal growth step S20, a growth method can be selected and adopted as appropriate depending on the materials of the SiC substrate 10 and the growth layer 20, respectively.

[0080] FIG. 3 is an explanatory diagram illustrating the crystal growth step S20 according to the embodiment.

[0081] The crystal growth step S20 according to the embodiment is a step of arranging the SiC substrate 10 and the semiconductor material 40 serving as the raw material for the growth layer 20 so as to face each other in a crucible 30 having a semi-closed space, and heating them.

[0082] By heating the crucible 30 (SiC substrate 10 and semiconductor material 40), the raw material is transported from the semiconductor material 40 onto the SiC substrate 10 via the raw material transport space 31.

[0083] Furthermore, in the crystal growth step S20, a temperature gradient can be used as a driving force for transporting the raw material between the SiC substrate 10 and the semiconductor material 40.

[0084] Here, in the crystal growth process S20, vapor consisting of atomic species sublimated from the semiconductor material 40 is transported by diffusion in the raw material transport space 31, and condenses in a supersaturated state on the SiC substrate 10, which is set at a temperature lower than that of the semiconductor material 40.

[0085] Furthermore, the crystal growth step S20 can employ the chemical potential difference between the SiC substrate 10 and the semiconductor material 40 as the driving force.

[0086] Here, in the crystal growth process S20, vapor consisting of atomic species sublimated from the semiconductor material 40 is transported by diffusion in the raw material transport space 31, and condenses in a supersaturated state on the SiC substrate 10, which has a lower chemical potential than the semiconductor material 40.

[0087] Furthermore, the crystal growth step S20 is a step of forming land portions 21 by performing crystal growth (corresponding to c-axis dominant growth) from SiC substrate 10 along the c-axis direction, and then forming wing portions 22 by performing crystal growth (corresponding to a-axis dominant growth) from land portions 21 along the a-axis direction, thereby forming growth layer 20. Note that a-axis dominant growth may include crystal growth along the a-axis direction from the side surface of through hole 11 or the side surface of the recess.

[0088] The growth layer 20 includes a land portion 21 and a wing portion 22. The through-hole 11 or the recess according to the embodiment is located directly below the wing portion 22.

[0089] The "c-axis dominant growth" and "a-axis dominant growth" described in this specification can be appropriately controlled based on the heating conditions in the crystal growth step S20.

[0090] The heating conditions may be, for example, temperature gradients in the c-axis and a-axis directions, and may include their history, which corresponds to the transition or change of the temperature gradient during heating.

[0091] The heating conditions may include, for example, the back pressure and partial pressure of the inert gas containing nitrogen gas, and may also include the history thereof. The history corresponds to the transition or change of the back pressure during heating.

[0092] The heating conditions may be, for example, the heating temperature, and may include its history, which corresponds to the transition or change of the heating temperature during heating.

[0093] In addition, the crystal growth step S20 may control / switch between c-axis dominant growth and a-axis dominant growth based on the conditions and techniques described in, for example, D. Dojima, et al., Journal of Crystal Growth, 483, 206 (2018).

[0094] In the crystal growth step S20, a doping gas may be used to adjust the doping concentration of the growth layer 20. In the crystal growth step S20, the doping concentration of the growth layer 20 may be adjusted by employing a semiconductor material 40 having a doping concentration different from that of the SiC substrate 10.

[0095] Example The present invention will be explained more specifically with reference to examples.

[0096] (SiC substrate 10) Semiconductor material: 4H-SiC Board size: 10mm wide x 10mm long x 524μm thick

[0097] (Processing process S11) The processing step S11 according to the embodiment is a step of irradiating a laser onto the SiC substrate 10 to form the through-holes 11.

[0098] (Laser processing conditions) Wavelength: 532nm Output power: 3W / cm 2 Spot diameter: 40 μm

[0099] (Strained layer removal process S12) FIG. 4 is an explanatory diagram illustrating the strained layer removing step S12 according to the embodiment.

[0100] In the strained layer removing step S12 according to the embodiment, the SiC substrate 10 is housed in a SiC container 50, and the SiC container 50 is housed in a TaC container 60 and heated.

[0101] (SiC container 50) Material: Polycrystalline SiC Container size: diameter 60mm x height 4mm Distance between the SiC substrate 10 and the bottom surface of the SiC container 50: 2 mm

[0102] (Details of the SiC container 50) As shown in FIG. 6, the SiC container 50 is a fitting container that includes an upper container 51 and a lower container 52 that can fit together.

[0103] A minute gap 53 is formed at the mating portion between the upper container 51 and the lower container 52, and the SiC container 50 is configured so that the inside of the SiC container 50 can be evacuated (vacuumed) through this gap 53.

[0104] The SiC container 50 has an etching space 54 formed by opposing a part of the SiC container 50, which is located on the low temperature side of the temperature gradient, to the SiC substrate 10, with the SiC substrate 10 being located on the high temperature side of the temperature gradient.

[0105] The etching space 54 is a space where Si atoms and C atoms are transported from the SiC substrate 10 to the SiC container 50 using the temperature difference between the SiC substrate 10 and the bottom surface of the SiC container 50 as a driving force for etching.

[0106] The SiC container 50 also has a substrate holder 55 that holds the SiC substrate 10 in a hollow space to form an etching space 54 .

[0107] The SiC container 50 may not need to be provided with the substrate holder 55 depending on the direction of the temperature gradient of the heating furnace.

[0108] For example, when the heating furnace forms a temperature gradient such that the temperature decreases from the lower container 52 to the upper container 51, the SiC container 50 may not be provided with the substrate holder 55, and the SiC substrate 10 may be placed on the bottom surface of the lower container 52.

[0109] (Details of TaC container 60) Similar to the SiC container 50, the TaC container 60 is a fitting container including an upper container 61 and a lower container 62 that can fit together, and is configured to be able to house the SiC container 50 therein.

[0110] A minute gap 63 is formed at the mating portion between the upper container 61 and the lower container 62, and the TaC container 60 is configured so that the inside of the TaC container 60 can be evacuated (evacuated) through this gap 63.

[0111] The TaC container 60 has a Si vapor supply source 64 capable of supplying the vapor pressure of a gaseous species containing Si element into the TaC container 60 .

[0112] The Si vapor supply source 64 may be configured to generate vapor pressure of a gaseous species containing Si element within the TaC container 60 during heat treatment.

[0113] (Heating conditions) The SiC substrate 10 arranged under the above conditions was subjected to a heat treatment under the following conditions. Heating temperature: 1800℃ Etching amount: 8 μm In the strained layer removing step S12, the heating time and temperature gradient are appropriately set to achieve the following etching amount.

[0114] FIG. 5 shows a cross-sectional SEM image and a bird's-eye SEM image of SiC substrate 10 after processing step S11.

[0115] FIG. 6 shows a cross-sectional SEM image and a bird's-eye SEM image of the SiC substrate 10 after the processing step S11 and the strained layer removing step S12.

[0116] 5 and 6, it can be seen that the surface of the SiC substrate 10 is planarized by the strained layer removing step S12.

[0117] FIG. 7 shows an EBSD mapping image of the SiC substrate 10 after the processing step S11.

[0118] FIG. 8 shows an EBSD mapping image of the SiC substrate 10 that has undergone the processing step S11 and the strained layer removing step S12.

[0119] 7 and 8 show the shear strain component E 12 The mapping image is shown.

[0120] 7 and 8, it can be seen that the strain in the SiC substrate 10 is removed by the strained layer removing step S12.

[0121] According to the present invention, the strained layer 12 introduced into the SiC substrate 10 during the pattern formation process by laser processing can be removed.

[0122] This reduces the density of defects such as dislocations near the top wall and side wall of the pattern, and suppresses the inheritance of defects such as dislocations during crystal growth (equivalent to epitaxial growth) in which the growth surface progresses from the top wall and / or side wall.

[0123] 10 SiC substrate 11 Through hole 12 Strain layer 30 Crucible 31 Raw material transportation space 40 Semiconductor Materials 50 SiC container 60 TaC container S11 Processing process S12 Strained layer removal process

Claims

1. The method includes a laser processing step of irradiating a silicon carbide substrate with a laser to remove a portion of the silicon carbide substrate, and a strained layer removal step of heat-treating the silicon carbide substrate to remove the strained layer introduced into the silicon carbide substrate by the processing step, The method for manufacturing a silicon carbide substrate, wherein the strained layer removing step is a step of thermally etching the SiC substrate by housing the silicon carbide substrate in a SiC container made of SiC and performing a heat treatment thereon.

2. The method for manufacturing a silicon carbide substrate according to claim 1 , wherein the processing step is a step of forming a through hole in the silicon carbide substrate.

3. 3. The method for manufacturing a silicon carbide substrate according to claim 1, wherein the strained layer removing step is a step of etching the silicon carbide substrate in a semi-closed space.

4. 4. The method for manufacturing a silicon carbide substrate according to claim 1, wherein the strained layer removing step is a step of etching the silicon carbide substrate in a silicon atmosphere.

5. A method for removing a strained layer introduced into a silicon carbide substrate by laser processing, the method including a strained layer removal step of heat-treating the silicon carbide substrate, The method, wherein the strained layer removing step is a step of thermally etching the silicon carbide substrate by housing the silicon carbide substrate in a SiC container made of SiC and performing a heat treatment thereon.

6. The method of claim 5 , wherein the strained layer removal step is a step of etching the silicon carbide substrate in a semi-closed space.

7. 7. The method according to claim 5, wherein the strained layer removing step is a step of etching the silicon carbide substrate in a silicon atmosphere.

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