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 this invention aims to solve is to provide a novel technique for removing strain layers introduced into a silicon carbide substrate by laser processing. This invention is a method for manufacturing a silicon carbide substrate, comprising: a processing step of performing laser processing to remove a portion of the silicon carbide substrate by irradiating it with a laser, and a strain layer removal step of removing the strain layer introduced into the silicon carbide substrate by heat treatment of the silicon carbide substrate. Furthermore, this invention is a method for removing strain layers introduced into a silicon carbide substrate by laser processing, which includes a strain layer removal step of heat treatment of 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 strain layer introduced into a silicon carbide substrate by laser processing. Background Technology

[0002] In the past, semiconductor substrates were manufactured by irradiating them with lasers.

[0003] Patent Document 1 discloses an invention in which a laser beam is irradiated onto a workpiece at a wavelength absorbable by the workpiece, and the laser beam is focused on the upper surface of the workpiece to perform ablation, thereby forming a groove on the upper surface of the workpiece. Furthermore, it can be understood that the invention described in Patent Document 1 is a method applicable to known semiconductor materials.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 10-305420 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] Furthermore, in the aforementioned method of irradiating the workpiece with a laser beam, strain is introduced into the semiconductor substrate that is the workpiece due to the irradiation.

[0009] For example, when dislocations are generated in a silicon carbide substrate, these dislocations may continue in a growth layer formed by epitaxial growth using the silicon carbide substrate as a base substrate. Therefore, it is desirable to remove the aforementioned strain in the silicon carbide substrate.

[0010] The problem to be solved by the present invention is to provide a novel technique for removing strain layers introduced into silicon carbide substrates by laser processing.

[0011] Problem-solving methods

[0012] The present invention, which solves the above-mentioned problems, is a method for manufacturing a silicon carbide substrate, comprising: 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 strain layer removal step of removing a strain layer introduced into the silicon carbide substrate by heat treatment of the silicon carbide substrate through the processing step. Thus, the present invention can remove the strain layer introduced into the silicon carbide substrate. That is, the present invention can remove the strain layer introduced into the silicon carbide substrate due to laser processing.

[0013] In a preferred embodiment of the invention, the processing step is the formation of through-holes on the silicon carbide substrate. Therefore, the present invention can create a lateral temperature gradient that serves as a driving force during crystal growth along the a-axis direction.

[0014] In a preferred embodiment of the present invention, the strain layer removal step is a step of etching the silicon carbide substrate within a quasi-enclosed space.

[0015] In a preferred embodiment of the invention, the strain layer removal step is a step of etching the silicon carbide substrate under a silicon atmosphere. Thus, the invention can planarize the upper portion and sidewalls of the silicon carbide substrate surface.

[0016] Furthermore, the present invention also relates to a method for removing a strain layer introduced into a silicon carbide substrate by laser processing, comprising a strain 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 strain layer introduced into a silicon carbide substrate by laser processing, comprising a strain layer removal step of heat-treating the silicon carbide substrate after laser processing.

[0017] In a preferred embodiment of the present invention, the strain layer removal step is a step of etching the silicon carbide substrate within a quasi-enclosed space.

[0018] In a preferred embodiment of the present invention, the strain layer removal step is a step of etching the silicon carbide substrate in a silicon atmosphere.

[0019] The effects of the invention

[0020] According to the disclosed technology, a novel technique can be provided to remove the strain layer introduced into a silicon carbide substrate by laser processing.

[0021] Other issues, features, and advantages will become apparent from reading the embodiments of the invention described below, in conjunction with the accompanying drawings and claims. Attached Figure Description

[0022] Figure 1 This is an explanatory diagram illustrating a method for manufacturing a silicon carbide substrate according to an embodiment.

[0023] Figure 2 This is an explanatory diagram illustrating the processing steps and strain layer removal steps according to the implementation method.

[0024] Figure 3 This is an explanatory diagram illustrating the crystal growth steps according to the embodiment.

[0025] Figure 4 This is an explanatory diagram illustrating the strain layer removal steps according to an embodiment.

[0026] Figure 5 This is an observation image of a silicon carbide substrate according to an embodiment.

[0027] Figure 6 This is an observation image of a silicon carbide substrate according to an embodiment.

[0028] Figure 7 This is a graph showing the strain distribution of a silicon carbide substrate according to an embodiment.

[0029] Figure 8 This is a graph showing the strain distribution of a silicon carbide substrate according to an embodiment. Detailed Implementation

[0030] The preferred embodiments of the method for manufacturing a silicon carbide substrate according to the present invention will be described in detail below with reference to the accompanying drawings.

[0031] The technical scope of this invention is not limited to the embodiments shown in the accompanying drawings, and can be appropriately modified within the scope of the claims.

[0032] The accompanying drawings in this specification are conceptual diagrams, and the relative dimensions of the components do not limit the invention.

[0033] In this specification, for the purpose of explaining the present invention, the terms "up" or "down" may be used based on the accompanying drawings, but are not limited to "up" or "down" in relation to the use of the silicon carbide substrate of the present invention.

[0034] Furthermore, in the following description and accompanying drawings of the embodiments, the same structures are referred to by the same reference numerals, and repeated descriptions are omitted.

[0035] Methods for manufacturing silicon carbide substrates

[0036] Figure 1 and Figure 2 The steps of a method for manufacturing a silicon carbide substrate (hereinafter referred to as "SiC substrate") according to an embodiment of the present invention are shown.

[0037] The method for manufacturing a SiC substrate according to the embodiment includes: a processing step S11 in which a portion of the SiC substrate is removed by laser processing to remove the SiC substrate by irradiating the silicon carbide substrate with laser L, and a strain layer removal step S12 in which the strain layer 12 introduced into the SiC substrate 10 by heat treatment is performed on the SiC substrate 10.

[0038] Furthermore, this embodiment can be understood as a method for removing the strain layer 12 introduced into the SiC substrate 10 by laser processing, including a strain layer removal step S12 of heat treatment of the SiC substrate 10 after laser processing.

[0039] The SiC substrate 10 (equivalent to a SiC wafer) can be a single-crystal SiC substrate, a polycrystalline SiC substrate, a wafer or substrate processed from bulk crystals, a wafer or substrate including an epitaxial growth layer, or a square wafer.

[0040] Furthermore, the SiC substrate 10 is not limited in terms of its crystal polymorphism, offset direction, offset angle, wafer size, substrate thickness, doping concentration, and the types of atoms of the added elements containing the doping elements.

[0041] The following is a detailed description of each step of the implementation method.

[0042] Processing step S11 is a step of performing laser processing to remove a portion of the SiC substrate 10 by irradiating the SiC substrate 10 with laser L.

[0043] In this specification, “laser processing” refers to a process in which a groove is formed on the upper surface of the SiC substrate 10 or a damaged area is formed inside the SiC substrate 10 by focusing a laser beam of a wavelength that is absorbent to the SiC substrate 10 on the upper surface or inside the SiC substrate 10 and irradiating the SiC substrate 10 with the laser beam.

[0044] In addition, laser processing refers to a method in which a portion of the object is selectively processed by irradiating and focusing a light wave with the same energy as the binding energy in the material constituting the object while controlling the laser irradiation part (equivalent to the focal point).

[0045] Furthermore, processing step S11 is preferably a step of irradiating the SiC substrate 10 with a laser L having a wavelength of 532 nm.

[0046] The wavelength of the laser L is preferably below 808nm, preferably below 650nm, more preferably below 635nm, more preferably below 589nm, more preferably below 532nm, more preferably below 473nm, more preferably below 460nm, more preferably below 445nm, and more preferably below 405nm.

[0047] Furthermore, the wavelength of the laser L is preferably 355nm or higher, more preferably 405nm or higher, more preferably 445nm or higher, more preferably 460nm or higher, more preferably 532nm or higher, more preferably 589nm or higher, more preferably 635nm or higher, and more preferably 650nm or higher.

[0048] The wavelength of laser L is, for example, a wavelength within the wavelength band classified as the visible light range.

[0049] Furthermore, the processing step S11 can be implemented based on a known or commonly used optical system.

[0050] Furthermore, processing step S11 may appropriately employ a known or commonly used light source, such as the wavelength of the laser L.

[0051] Furthermore, the active medium, oscillation mode, repetition frequency, pulse width, beam diameter, output power, and polarization characteristics of the laser L used in processing step S11 are not limited.

[0052] The optical system used in processing step S11 appropriately includes known or commonly used mirrors, a scanner equipped with an axis rotary motor for alignment, a condenser lens, and a grating.

[0053] The magnification and numerical aperture (NA) of the condenser lens of the optical system used in processing step S11 are not limited.

[0054] In addition, processing step S11 is the step of forming a through hole 11 on the SiC substrate 10.

[0055] Here, processing step S11 can be understood as an embrittlement process that reduces the strength of the SiC substrate 10 by forming through holes 11.

[0056] In addition, during the formation of the through hole 11, the processing step S11 scans the laser irradiation portion (equivalent to the focusing point) in the film thickness direction of the SiC substrate 10.

[0057] The through-hole 11 can be used as long as it is, for example, a shape (pattern) used to reduce the strength of the SiC substrate 10.

[0058] Furthermore, the through hole 11 can be used as long as it has a shape (pattern) that includes an inferior angle, for example.

[0059] Furthermore, it is desirable to set the desired shape (pattern) of the growth layer in epitaxial growth using SiC substrate 10 as the substrate.

[0060] At this point, in processing step S11, the interior of the surface of the SiC substrate 10 is scanned with laser L according to the shape (pattern).

[0061] Furthermore, it is desirable that the processing step S11 employs an optimal pattern based on the physical properties (crystal orientation, etc.) of the SiC substrate 10 or the semiconductor material of the growth layer, or the growth method. Additionally, the width and depth of this shape (pattern) are not limited.

[0062] In addition, processing step S11 is a step of processing the surface of SiC substrate 10 into a mesa shape.

[0063] In this specification, "table-shaped" is equivalent to a concave-convex shape, and the angle between the upper wall and the side wall in such a concave-convex shape is not limited.

[0064] Furthermore, the machining depth in machining step S11 is not limited.

[0065] In addition, when the processing step S11 is to process the surface of the SiC substrate 10 into a mesa shape, the processing step S11 forms a recess on the surface of the SiC substrate 10 instead of the through hole 11.

[0066] In addition, the processing step S11 forms a through hole 11 or a protrusion by scanning the focal point of the laser L from the surface (equivalent to the upper surface) of the SiC substrate 10 to the bottom surface (equivalent to the lower surface).

[0067] Furthermore, the processing step S11 may employ at least a portion of known technologies, such as those described in Japanese Patent Application Publication No. 10-305420, Japanese Patent Application Publication No. 2002-192370, and Japanese Patent Application Publication No. 2016-111147.

[0068] The strain layer removal step S12 is a step of removing the strain layer 12 introduced into the SiC substrate 10 through processing step S11 by heat treatment of the SiC substrate 10. Furthermore, the strain layer 12 can be understood as, for example, equivalent to a damage layer.

[0069] Furthermore, the strain layer removal step S12 can be performed by etching the SiC substrate 10 through heat treatment.

[0070] Furthermore, the strain layer removal step S12 can be performed using any means that can remove the strain layer 12.

[0071] Furthermore, the strain layer removal step S12 is a step of removing the strain layer 12 by thermal etching.

[0072] Furthermore, the strain layer removal step S12 is a step of etching the SiC substrate 10 within a quasi-enclosed space. Additionally, the term "quasi-enclosed space" in this specification refers to a space that, while allowing for evacuation within the container or sample chamber where the SiC substrate 10 is located, can also contain at least a portion of the vapor generated within the container or sample chamber.

[0073] Furthermore, the strain layer removal step S12 is a step of etching the SiC substrate 10 under a silicon atmosphere (Si silicon atmosphere). Additionally, "silicon atmosphere" in this specification refers to the vapor pressure of gaseous species containing Si.

[0074] In addition, the strain layer removal step S12 is, for example, a step of housing the SiC substrate 10 in a SiC container 50, housing the SiC container 50 in a high-melting-point container such as a TaC container 60, and heat-treating the high-melting-point container including the SiC substrate 10.

[0075] At this time, the high-melting-point container includes a Si vapor supply source 64 capable of supplying the vapor pressure of gaseous species containing Si to the outside of the SiC container 50.

[0076] In addition, the strain layer removal process S12 is, for example, a step of placing the SiC substrate 10 in the aforementioned high-melting-point container and performing heat treatment on the high-melting-point container including the SiC substrate 10.

[0077] At this point, the high-melting-point container includes a Si vapor supply source 64 capable of supplying a vapor pressure of gaseous species containing Si.

[0078] The “Si vapor supply source 64” described in this specification is, for example, solid Si (Si particles such as Si sheets or Si powder) or Si compounds, and may be in the form of a thin film.

[0079] According to the present invention, the strain layer 12 introduced into the SiC substrate 10 by laser processing can be removed by including a strain layer removal step S12 that involves heat treatment of the SiC substrate 10.

[0080] The following description describes an embodiment in which a growth layer 20 is formed by epitaxial growth of a SiC substrate 10, on which the strain layer 12 has been removed by the strain layer removal step S12, as a substrate.

[0081] Furthermore, according to an embodiment of the present invention, the SiC substrate 10 with the strain layer 12 removed can be used as a substrate for epitaxial growth of materials such as SiC and AlN.

[0082] <Crystal growth step S20>

[0083] The crystal growth step S20 is the step of forming a growth layer 20 on the SiC substrate 10 after the strain layer removal step S12.

[0084] The material of the growth layer 20 can be the same as that of the SiC substrate 10 (equivalent to homoepitaxial growth) or a different material from that of the SiC substrate 10 (equivalent to heteroepitaxial growth).

[0085] The material of growth layer 20 can be any material commonly used for epitaxial growth.

[0086] Furthermore, the material of the growth layer 20 can be the material of the SiC substrate 10, a known material that can be used as the material of the SiC substrate 10, or a known material that can be epitaxially grown on the SiC substrate 10.

[0087] The material of the growth layer 20 according to the embodiment is, for example, AlN.

[0088] Furthermore, the crystal growth step S20 is preferably a step of forming the growth layer 20 using physical vapor transport (PVT).

[0089] As a growth method for the growth layer 20, the crystal growth step S20 can employ known vapor phase growth methods (equivalent to vapor phase epitaxy) such as PVT, sublimation recrystallization, modified Rayleigh method, and chemical vapor transport (CVT).

[0090] Alternatively, the crystal growth step S20 can be replaced by physical vapor deposition (PVD) instead of chemical vapor deposition (CVD).

[0091] In addition, as a growth method for the growth layer 20, the crystal growth step S20 can employ known liquid phase growth methods (equivalent to liquid phase epitaxy) such as the TSSG method (Top-Seeded Solution Growth) and the Metastable Solvent Epitaxy (MSE).

[0092] Furthermore, as a growth method for the growth layer 20, the crystal growth step S20 can employ the CZ method (Czochralski method, Czochralski method).

[0093] The crystal growth step S20 can be appropriately selected and the growth method can be adopted according to the materials of the SiC substrate 10 and the growth layer 20 respectively.

[0094] Figure 3 This is an explanatory diagram illustrating the crystal growth step S20 according to the embodiment.

[0095] According to the embodiment, the crystal growth step S20 is a step of placing the SiC substrate 10 and the semiconductor material 40, which becomes the raw material for the growth layer 20, opposite to each other in a crucible 30 having a quasi-enclosed space and heating them.

[0096] By heating the crucible 30 (SiC substrate 10 and semiconductor material 40), the raw material is transported from the semiconductor material 40 to the SiC substrate 10 through the raw material transport space 31.

[0097] Furthermore, a temperature gradient can be used in the crystal growth step S20 as a driving force for transporting raw materials between the SiC substrate 10 and the semiconductor material 40.

[0098] Here, in the crystal growth step S20, vapor composed of atomic species sublimated from semiconductor material 40 is transported by diffusion in raw material transport space 31 and reaches supersaturation and condenses on SiC substrate 10 where the temperature is set lower than that of semiconductor material 40.

[0099] Furthermore, as the driving force mentioned above, the crystal growth step S20 can utilize the chemical potential difference between the SiC substrate 10 and the semiconductor material 40.

[0100] Here, in the crystal growth step S20, vapor composed of atomic species sublimated from semiconductor material 40 is transported by diffusion in raw material transport space 31 and reaches supersaturation and condenses on SiC substrate 10 with a chemical potential lower than that of semiconductor material 40.

[0101] Furthermore, the crystal growth step S20 involves forming the pad portion 21 by performing crystal growth from the SiC substrate 10 along the c-axis direction (equivalent to c-axis dominant growth), forming the wing portion 22 by performing crystal growth from the pad portion 21 along the a-axis direction (equivalent to a-axis dominant growth), and forming the growth layer 20. Additionally, a-axis dominant growth may include crystal growth along the a-axis direction from the side surface of the through-hole 11 or the side surface of the recess.

[0102] Additionally, the growth layer 20 includes a pad portion 21 and a wing portion 22. According to the embodiment, the through-hole 11 or recess is located directly below the wing portion 22.

[0103] The “c-axis dominant growth” and “a-axis dominant growth” described in this specification can be appropriately controlled based on the heating conditions in crystal growth step S20.

[0104] The heating conditions described above are, for example, temperature gradients along the c-axis and a-axis, and may include their history. This history corresponds to the shift or change of the temperature gradient during heating.

[0105] Furthermore, the aforementioned heating conditions are, for example, the back pressure or partial pressure of an inert gas containing nitrogen, and may include its history. This history corresponds to the shift or change in back pressure, etc., during heating.

[0106] Furthermore, the aforementioned heating conditions are, for example, heating temperatures, and may include their history. This history corresponds to the shift or change in heating temperatures, etc., during the heating process.

[0107] Alternatively, the crystal growth step S20 can also be controlled / switched between c-axis dominant growth and a-axis dominant growth, for example, based on the conditions or methods described by D. Dojima et al. in Journal of Crystal Growth, 483, 206 (2018).

[0108] Alternatively, the doping concentration of the growth layer 20 can be adjusted in the crystal growth step S20 by using a doping gas. Alternatively, the doping concentration of the growth layer 20 can be adjusted in the crystal growth step S20 by using a semiconductor material 40 with a different doping concentration than the SiC substrate 10.

[0109] Example 1

[0110] The present invention will be described in more detail by way of examples.

[0111] (SiC substrate 10)

[0112] Semiconductor material: 4H-SiC

[0113] Substrate dimensions: 10mm wide × 10mm long × 524μm thick

[0114] (Processing step S11)

[0115] According to the embodiment, processing step S11 is the step of irradiating the SiC substrate 10 with a laser to form a through hole 11.

[0116] (Laser processing conditions)

[0117] Wavelength: 532nm

[0118] Output power: 3W / cm 2

[0119] Spot diameter: 40μm

[0120] (Strain layer removal step S12)

[0121] Figure 4 This is an explanatory diagram illustrating the strain layer removal step S12 according to an embodiment.

[0122] According to the embodiment, in the strain layer removal step S12, the SiC substrate 10 is housed in the SiC container 50, and the SiC container 50 is further housed in the TaC container 60 and heated.

[0123] (SiC container 50)

[0124] Material: Polycrystalline SiC

[0125] Container dimensions: 60mm in diameter × 4mm in height

[0126] Distance between the bottom surfaces of SiC substrate 10 and SiC container 50: 2mm

[0127] (Details of SiC container 50)

[0128] like Figure 6 As shown, the SiC container 50 is a fitted container that includes an upper container 51 and a lower container 52 that can fit together.

[0129] A tiny gap 53 is formed at the fitting part of the upper container 51 and the lower container 52, which enables the venting (vacuuming) of the SiC container 50 through the gap 53.

[0130] The SiC container 50 has an etched space 54, which is formed by placing a portion of the SiC container 50 disposed on the low-temperature side of the temperature gradient opposite to the SiC substrate 10 while the SiC substrate 10 is disposed on the high-temperature side of the temperature gradient.

[0131] The etching space 54 is a space used to transport Si atoms and C atoms from the SiC substrate 10 to the SiC container 50 and etch them using the temperature difference between the bottom surfaces of the SiC substrate 10 and the SiC container 50 as the driving force.

[0132] In addition, the SiC container 50 has a substrate holder 55 for holding the SiC substrate 10 in mid-air and forming an etch space 54.

[0133] Alternatively, the SiC container 50 may not have a substrate holder 55 depending on the direction of the temperature gradient of the heating furnace.

[0134] For example, in the case where a temperature gradient is formed in the heating furnace so that the temperature drops from the lower container 52 to the upper container 51, the SiC container 50 may also have the SiC substrate 10 disposed on the bottom surface of the lower container 52 without the substrate holder 55.

[0135] (Details of TaC container 60)

[0136] Similar to the SiC container 50, the TaC container 60 is a fitted container including an upper container 61 and a lower container 62 that can fit together, and is configured to accommodate the SiC container 50.

[0137] A tiny gap 63 is formed at the fitting part of the upper container 61 and the lower container 62, which enables the TaC container 60 to be vented (vacuumed) through the gap 63.

[0138] The TaC container 60 has a Si vapor supply source 64 capable of supplying a vapor pressure of gaseous species containing Si within the TaC container 60.

[0139] The Si vapor supply source 64 can be any structure that generates a vapor pressure of gaseous species containing Si elements within the TaC container 60 during heat treatment.

[0140] (Heating conditions)

[0141] The SiC substrate 10 configured under the above conditions will be subjected to heat treatment under the following conditions.

[0142] Heating temperature: 1800℃

[0143] Etching depth: 8μm

[0144] In addition, the heating time and temperature gradient are appropriately set in the strain layer removal step S12 to achieve the following etching amount.

[0145] Figure 5 Cross-sectional SEM images and top-view SEM images of the SiC substrate 10 after processing step S11 are shown.

[0146] Figure 6 Cross-sectional SEM images and top-view SEM images of the SiC substrate 10 after processing step S11 and strain layer removal step S12 are shown.

[0147] according to Figure 5 and Figure 6 It is understandable that the surface of the SiC substrate 10 is planarized through the strain layer removal step S12.

[0148] Figure 7 An EBSD mapping image of the SiC substrate 10 after processing step S11 is shown.

[0149] Figure 8 An EBSD mapping image of the SiC substrate 10 after processing step S11 and strain layer removal step S12 is shown.

[0150] Figure 7 and Figure 8 The shear strain component E is shown. 12 The mapped image.

[0151] according to Figure 7 and Figure 8 This can be understood as the strain on the SiC substrate 10 being removed through the strain layer removal step S12.

[0152] According to the present invention, the strain layer 12 introduced into the SiC substrate 10 during the patterning process by laser processing can be removed.

[0153] This reduces the density of defects such as dislocations near the top and sidewalls of the pattern and suppresses the continuation of defects such as dislocations during crystal growth (equivalent to epitaxial growth) from the top and / or sidewalls of the growth surface.

[0154] Explanation of reference numerals in the attached figures

[0155] 10 SiC substrate

[0156] 11 Through Holes

[0157] 12 Strain Layer

[0158] 30 crucibles

[0159] 31 Raw material conveying space

[0160] 40 Semiconductor Materials

[0161] 50 SiC container

[0162] 60 TaC container

[0163] S11 Processing Steps

[0164] S12 Strain Layer Removal Steps

Claims

1. A method of manufacturing a silicon carbide substrate, comprising: The process includes a laser processing step to remove a portion of a silicon carbide substrate by irradiating it with a laser, and a strain layer removal step to remove the strain layer introduced into the silicon carbide substrate by heat treatment of the substrate, wherein... The strain layer removal step is a process of thermally etching the silicon carbide substrate by placing the silicon carbide substrate in a SiC container, placing the SiC container in a TaC container, and heat-treating the TaC container.

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

3. The method for manufacturing a silicon carbide substrate according to claim 1 or 2, wherein, The strain layer removal step is a step of etching the silicon carbide substrate within a quasi-enclosed space.

4. The method for manufacturing a silicon carbide substrate according to claim 1 or 2, wherein, The strain layer removal step is a step of etching the silicon carbide substrate in a silicon atmosphere.

5. A method for removing a strain layer introduced into a silicon carbide substrate by laser processing, comprising a strain layer removal step of heat-treating the silicon carbide substrate, wherein, The strain layer removal step is a process of thermally etching the silicon carbide substrate by placing the silicon carbide substrate in a SiC container, placing the SiC container in a TaC container, and heat-treating the TaC container.

6. The method of claim 5, wherein, The strain layer removal step is a step of etching the silicon carbide substrate within a quasi-enclosed space.

7. The method of claim 5 or 6, wherein, The strain layer removal step is a step of etching the silicon carbide substrate in a silicon atmosphere.

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