Method for manufacturing SiC substrate

Abstract

The present invention addresses the problem of providing novel techniques for manufacturing a SiC substrate that enables reduced material loss when a strain layer is removed. The present invention is a method for manufacturing a SiC substrate 30 which includes a strain layer thinning step S1 for thinning a strain layer 12 of a SiC substrate body 10 by moving the strain layer 12 to a surface side. Including such a strain layer thinning step S1 in which the strain layer is moved to (concentrated toward) the surface side makes it possible to reduce material loss L when removing the strain layer 12.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a SiC substrate.

Background Art

[0002] An SiC (silicon carbide) substrate is formed by slicing an ingot of single crystal SiC. On the surface of the sliced SiC substrate, there exists a surface layer (hereinafter referred to as a processed altered layer) having crystal strain, scratches, etc. introduced during slicing. In order not to reduce the yield in the device manufacturing process, it is necessary to remove this processed altered layer.

[0003] Conventionally, in order to obtain an epi-ready SiC substrate capable of removing this processed altered layer and performing epitaxial growth for SiC device manufacturing, machining has been carried out. This machining generally goes through stages such as a rough grinding process using abrasive grains such as diamond, a finish grinding process using abrasive grains with a smaller particle size than those used in the rough grinding process, and a chemical mechanical polishing (CMP) process in which polishing is performed by combining the mechanical action of a polishing pad and the chemical action of a slurry (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, it is considered that the machined and modified layer has a crack layer having a large number of cracks (defects) and a strained layer in which strain has occurred in the crystal lattice. This strained layer is introduced at a deeper position in the SiC substrate than the crack layer. Therefore, in order to remove the strained layer, it was necessary to remove single-crystalline SiC of several tens of μm to several hundreds of μm. As a result, there was a problem that a large amount of material loss occurred.

[0006] In particular, when removing the strained layer by CMP, it is necessary to remove single-crystalline SiC of several μm to a dozen or so μm over several hours, and there are problems such as high cost for CMP and long processing time.

[0007] In view of the above-described problems, the problem to be solved by the present invention is to provide a novel technique for manufacturing a SiC substrate capable of reducing the amount of material loss when removing the strained layer.

Means for Solving the Problem

[0008] The present invention for solving the above-described problems is a method for manufacturing a SiC substrate, including a strained layer thinning step of thinning the strained layer by moving the strained layer of the SiC substrate body to the surface side. By including the step of moving (concentrating) the strained layer to the surface side in this way, it is possible to reduce the amount of material loss of the SiC substrate body in the strained layer removal step for removing the strained layer performed later. Furthermore, it is possible to reduce the processing cost and processing time in the strained layer removal step.

[0009] In a preferred embodiment of the present invention, it includes a strained layer removal step of removing the strained layer, The strained layer thinning step is a step of moving the strained layer after the strained layer thinning step to the surface side with respect to the reference depth, where the depth of the strained layer before the strained layer thinning step is used as the reference depth, The strained layer removal step is a step of removing at least a part on the surface side with respect to the reference depth. In this way, by moving the strained layer to the surface side and removing it with respect to the reference depth that has been conventionally removed, it is possible to reduce the amount of material loss of the SiC substrate body.

[0010] In a preferred embodiment of the present invention, the strained layer removal step is chemical mechanical polishing. In this way, by moving the strained layer of the SiC substrate body to the surface side to thin the strained layer and then performing chemical mechanical polishing, it is possible to form an epitaxial-like surface while reducing the amount of material loss and cost.

[0011] In a preferred embodiment of the present invention, the strained layer removal step is a thermal etching method. In this way, by adopting the thermal etching method in the strained layer removal step, it is possible to simultaneously perform the movement of the strained layer and the removal of the strained layer. That is, the strained layer thinning step and the strained layer removal step can be performed simultaneously.

[0012] In a preferred embodiment of the present invention, it further includes a slicing step of slicing an ingot to obtain a SiC substrate body, and the slicing step is a step of obtaining a SiC substrate body having a thickness obtained by adding a thickness of 100 μm or less to the thickness of the SiC substrate body after the strained layer removal step. Further, the slicing step is a step of obtaining a SiC substrate body having a thickness obtained by adding a thickness of 50 μm or less to the thickness of the SiC substrate body after the strained layer removal step. By slicing the SiC substrate body with such a thickness, the number of SiC substrate bodies obtained from one ingot can be increased, and the unit price per piece can be reduced.

[0013] In a preferred embodiment of the present invention, it further includes an etching step of etching the surface of the SiC substrate body, and the etching step is wet etching. In this way, by wet etching the SiC substrate body, it is possible to remove the impurities attached in the slicing step while flattening the surface.

[0014] In a preferred embodiment of the present invention, the etching step includes one or more selected from the group consisting of a potassium hydroxide melt, a chemical solution containing hydrofluoric acid, a potassium permanganate-based chemical solution, and tetramethylammonium hydroxide as an etching solution.

[0015] In a preferred embodiment of the present invention, it includes a slicing step of slicing an ingot to obtain a SiC substrate body, and includes the slicing step, the etching step, and the strain layer thinning step in this order.

[0016] In a preferred embodiment of the present invention, the strain layer thinning step is a step of heating the SiC substrate body in an environment containing Si element.

[0017] In a preferred embodiment of the present invention, the strain layer thinning step is a step of heating the SiC substrate body in a semi-closed space containing a Si element supply source and a C element supply source.

[0018] In a preferred embodiment of the present invention, the strain layer thinning step is a step of heating the SiC substrate body in a main body container made of SiC material.

[0019] In a preferred embodiment of the present invention, the strain layer thinning step is a step of heating the SiC substrate body and the SiC material so that a temperature gradient is formed between the SiC substrate body and the SiC material.

[0020] In a preferred embodiment of the present invention, the strain layer thinning step is a step of heating the SiC substrate body in a Si vapor pressure environment.

[0021] In a preferred embodiment of the present invention, the strain layer thinning step is a metastable solvent epitaxy method.

[0022] In a preferred embodiment of the present invention, the heating temperature of the strain layer thinning step is 1400°C or higher and 1600°C or lower.

Effects of the Invention

[0023] According to the disclosed technology, it is possible to provide a novel technology for manufacturing an SiC substrate capable of reducing the amount of material loss when removing a strained layer.

[0024] Other problems, features, and advantages will become apparent by reading the following embodiments for carrying out the invention, when taken together with the drawings and the claims.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The technical scope of the present invention is not limited to the embodiments shown in the attached drawings, and can be appropriately changed within the scope described in the claims.

[0027] 《Method for Manufacturing SiC Substrate》 FIG. 1 and FIG. 2 are explanatory diagrams comparing the method for manufacturing an SiC substrate according to an embodiment of the present invention with the method for manufacturing an SiC substrate according to the conventional method. FIG. 1 shows an embodiment in which the strain layer 12 in the SiC substrate body 10 is thinned and removed. On the other hand, FIG. 2 shows an embodiment in which a SiC substrate 30 with a substrate thickness D is obtained from an ingot I with a thickness D0.

[0028] As shown in FIGS. 1(a) to 1(c) and FIG. 2(a), the manufacturing method of the SiC substrate 30 according to the present invention includes a strain layer thinning step S1 of thinning the strain layer 12 by moving (concentrating) the strain layer 12 of the SiC substrate body 10 to the surface side.

[0029] Specifically, in the strain layer thinning step S1, when the depth of the strain layer 12 before the strain layer thinning step is defined as the reference depth 20, the strain layer 12 after the strain layer thinning step is moved to the surface side with respect to the reference depth 20.

[0030] Further, the manufacturing method of the SiC substrate 30 according to the present invention includes a strain layer removing step S2 of removing the strain layer 12 moved by the strain layer thinning step S1. This strain layer removing step S2 is a step of removing at least a part on the surface side with respect to the reference depth 20.

[0031] FIG. 1(a) shows an embodiment in which the strain layer 12 is moved to the surface side while maintaining the substrate thickness of the SiC substrate body 10. FIG. 1(b) shows an embodiment in which the strain layer 12 is moved to the surface side while growing the SiC substrate body 10. FIG. 1(c) shows an embodiment in which the strain layer 12 is moved to the surface side while etching the SiC substrate body 10.

[0032] On the other hand, as shown in FIG. 1(d), the conventional method includes a strain layer removing step S2 of removing all of the strain layer 12. That is, in order to remove the strain layer 12, it is necessary to remove the SiC single crystal at least to the position reaching the reference depth 20. Thus, when all of the introduced strain layer 12 is removed, a large amount of material loss L will occur.

[0033] That is, according to the present invention, before removing the strain layer 12 (or while removing the strain layer 12), the strain layer thinning step S1 is included, in which the strain layer 12 of the SiC substrate body 10 is moved (concentrated) to the surface side to thin the strain layer 12. Thereby, the amount of material loss L of the SiC substrate body 10 can be reduced compared to the conventional method.

[0034] Also, the embodiment of the present invention shown in Fig. 2(a) includes a slicing step S3 of slicing the ingot I to obtain the SiC substrate body 10, an etching step S4 of etching the surface of the SiC substrate body 10, a strain layer thinning step S1 of thinning the strain layer 12 by moving (concentrating) the strain layer 12 of the SiC substrate body 10 to the surface side, and a strain layer removing step S2 of removing the moved strain layer 12, which is a method for manufacturing the SiC substrate 30.

[0035] According to the present invention, the amount of material loss L can be reduced by the strain layer thinning step S1. Therefore, the SiC substrate body 10 can be sliced at a substrate thickness D1 thinner than the conventional method. In Fig. 2(a), a state of obtaining four SiC substrates 30 with a substrate thickness D from the ingot I with a thickness D0 is shown.

[0036] On the other hand, as shown in Fig. 2(b), the conventional method includes a strain layer removing step S2 of removing all of the strain layer 12 introduced into the SiC substrate body 10. Therefore, in order to manufacture the SiC substrate 30 with a substrate thickness D manufactured by the present invention, it is necessary to slice at a substrate thickness D2 thicker than the substrate thickness D1. In Fig. 2(b), a state of obtaining three SiC substrates 30 with a substrate thickness D from the ingot I with a thickness D0 is shown.

[0037] Thus, when obtaining the SiC substrate 30 with the same substrate thickness D starting from the ingot I with a thickness D0, the number of SiC substrates 30 obtained is different between the present invention including the strain layer thinning step S1 and the conventional method not including the strain layer thinning step S1.

[0038] That is, according to the present embodiment, by moving (concentrating) the strained layer 12 of the SiC substrate body 10 to the surface side, the strained layer thinning step S1 for thinning the strained layer 12 is included, so that the number of SiC substrates 30 taken from one ingot can be increased, and the unit price per sheet can be reduced.

[0039] Hereinafter, in the order of the slicing step S3, the etching step S4, the strained layer thinning step S1, and the strained layer removing step S2, detailed description will be given along the embodiment shown in FIG. 2.

[0040] 〈Slicing Step〉 The slicing step S3 is a step of slicing the SiC substrate body 10 from the ingot I. As the slicing method in the slicing step S3, multi-wire saw cutting in which a plurality of wires are reciprocated to cut the ingot I at a predetermined interval, an electrical discharge machining method in which plasma discharge is intermittently generated for cutting, cutting using a laser that irradiates and condenses the laser in the ingot I to form a layer serving as a cutting base point, etc. can be exemplified.

[0041] The substrate thickness of the SiC substrate body 10 is determined by the interval at which cutting is performed in this slicing step S3. This substrate thickness is set to a thickness considering the single-crystalline SiC (material loss L) to be removed in subsequent processes. Thus, since the slicing thickness from the ingot I is set in consideration of the amount of material loss L after all processing steps, the specific numerical value thereof will be described after explaining all the steps.

[0042] 〈Etching Step〉 The etching step S4 is a step of etching the surface of the SiC substrate body 10 after the slicing step S3. As the etching method in the etching step S4, thermal etching methods such as the SiVE method and the hydrogen etching method, wet etching methods using a potassium hydroxide melt, a chemical solution containing hydrofluoric acid, a chemical solution based on potassium permanganate, a chemical solution containing tetramethylammonium hydroxide, etc. can be exemplified. Note that usually, any chemical solution used in wet etching can be adopted.

[0043] Among these, in the etching step S4, it is preferable to etch the surface of the SiC substrate body 10 using a potassium hydroxide melt. By etching the surface of the SiC substrate body 10 by so-called KOH etching, it is possible to flatten the surface while removing impurities adhering in the slicing step S3.

[0044] Specifically, an etching step S4 using a potassium hydroxide melt may be performed on the SiC substrate body 10 after the slicing step S3, and then the strain layer thinning step S1 and the strain layer removing step S2 may be performed.

[0045] 〈Strain layer thinning step〉 The strain layer thinning step S1 is a step of heating the SiC substrate body 10 to at least 1400° C. or higher in an environment containing Si element. By heating the SiC substrate body 10 in such an environment, the strain layer 12 can be moved and concentrated on the surface side of the SiC substrate body 10 without carbonizing the surface of the SiC substrate body 10.

[0046] As a method applicable to the strain layer thinning step S1, a metastable solvent epitaxy (MSE) method of growing single crystal SiC by heating a sandwich structure in which polycrystalline SiC and single crystal SiC are arranged via single crystal Si, or a Si vapor etching (SiVE) method of etching single crystal SiC by heating under Si vapor pressure can be exemplified.

[0047] That is, the heat treatment environment of the SiC substrate body 10 in the strain layer thinning step S1 is desirably a gas phase environment containing Si element or a liquid phase environment containing Si element. In addition to the above-described SiVE method and MSE method, the following methods can be exemplified.

[0048] The strain layer thinning step S1 according to the embodiment of the present invention is a step of heating the SiC substrate body 10 in a semi-closed space containing a Si element supply source and a C element supply source. Specifically, as shown in FIG. 3, a SiC substrate body 10 is disposed in a main body container 50 in which a SiC material 40 (Si element supply source and C element supply source) is exposed. By heating this main body container 50, a vapor phase environment containing Si element can be formed in the container.

[0049] Note that the "quasi-closed space" in this specification refers to a space in which evacuation of the container is possible, but at least a part of the vapor generated in the container can be confined. This quasi-closed space can be formed in the main body container 50 or the high melting point container 70 described later.

[0050] The SiC substrate body 10 can be exemplified by a single crystal SiC processed into a plate shape. Specifically, a SiC wafer sliced into a disk shape from a SiC ingot produced by the sublimation method or the like can be exemplified. Note that any polytype of the crystal polytype of single crystal SiC can be adopted.

[0051] Normally, the SiC substrate body 10 that has undergone mechanical processing (for example, slicing, grinding, and polishing) or laser processing has a strained layer 12 in which the crystal lattice is distorted due to processing damage, and a bulk layer 11 into which such processing damage has not been introduced (see FIG. 1). In order to manufacture a high-quality SiC substrate 30, it is preferable to remove the strained layer 12 and expose the bulk layer 11 into which no processing damage has been introduced.

[0052] Note that usually, due to processing damage, in addition to the strained layer 12, a crack layer having a large number of cracks (defects) is introduced, but since it is introduced at a position shallower than the strained layer 12, it is omitted. The crack layer and the strained layer 12 together are called a processed modified layer.

[0053] The presence or absence and depth of this strained layer 12 can be confirmed by the SEM-EBSD method, TEM, μXRD, Raman spectroscopy, or the like.

[0054] The SiC material 40 includes a SiC substrate and a SiC container (the main body container 50 itself). That is, a form in which a SiC substrate serving as the SiC material 40 is disposed in a container separately from the SiC substrate body 10 can be exemplified (see FIGS. 4 and 5). Also, a form in which at least a part of the container that houses the SiC substrate body 10 is formed of the SiC material 40 can be exemplified (see FIG. 7). In this case, the entire container may be formed of the SiC material 40, or a portion facing the SiC substrate body 10 may be formed of the SiC material 40. When single-crystalline SiC is employed for the SiC material 40, any polytype can be adopted.

[0055] It is desirable that the inside of the heated quasi-closed space be a vapor pressure environment of a mixed system of gas-phase species containing Si element and gas-phase species containing C element. Examples of the gas-phase species containing Si element include Si, Si2, Si3, Si2C, SiC2, and SiC. Examples of the gas-phase species containing C element include Si2C, SiC2, SiC, and C. That is, it is preferable that a SiC-based gas exists in the quasi-closed space.

[0056] The heating temperature in the strain layer thinning step S1 is preferably set in the range of 1400 to 2300 °C. More preferably, it is set in the range of 1400 to 1600 °C. The heating time in the strain layer thinning step S1 can be set to an arbitrary time so as to obtain a desired depth of the strain layer 12.

[0057] By heating the SiC substrate body 10 in such an environment, the strain layer 12 can be moved (concentrated) to the surface side, and the strain layer 12 can be thinned (see FIG. 3).

[0058] Also, in the strain layer thinning step S1 according to the present embodiment, the SiC substrate body 10 and the SiC material 40 are disposed opposite to each other, and the SiC substrate body 10 is heated so that a temperature gradient is formed between the SiC substrate body 10 and the SiC material 40, whereby the strain layer 12 can be thinned while the SiC substrate body 10 is crystal-grown or etched. Hereinafter, a detailed description will be given separately for the case involving etching and the case involving crystal growth.

[0059] [Strain layer thinning process S1 involving crystal growth] FIG. 1(b) and FIG. 4 are explanatory diagrams showing the outline of the strain layer thinning process S1 involving crystal growth. As shown in FIG. 4, the SiC substrate body 10 and the SiC material 40 are arranged opposite to each other, and by providing a temperature gradient between them and heating, raw materials (Si element and C element) can be transported from the SiC material 40 to the SiC substrate body 10, and single crystal SiC can be grown.

[0060] In this strain layer thinning process S1, the SiC substrate body 10 is placed in a quasi-closed space where the SiC material 40 is exposed, and by heating in the temperature range of 1400 °C or higher and 2300 °C or lower, the following reactions 1) to 5) are continuously carried out, and as a result, crystal growth is considered to progress (see FIG. 4(b)).

[0061] 1) Poly-SiC(s) → Si(v) + C(s) 2) 2C(s) + Si(v) → SiC2(v) 3) C(s) + 2Si(v) → Si2C(v) 4) Si(v) + SiC2(v) → 2SiC(s) 5) Si2C(v) → Si(v) + SiC(s)

[0062] Explanation of 1): When the SiC material (Poly-SiC(s)) is heated, Si atoms (Si(v)) are desorbed from SiC by thermal decomposition. Explanation of 2) and 3): The remaining C atoms (C(s)) after the desorption of Si atoms (Si(v)) react with the Si vapor (Si(v)) in the quasi-closed space. As a result, the C atoms (C(s)) sublimate into the quasi-closed space as Si2C or SiC2, etc. Explanation of 4) and 5): The sublimated Si2C or SiC2, etc. reach and diffuse to the terraces of the SiC substrate body 10 due to the temperature gradient (or chemical potential difference) and reach the steps, and then grow while inheriting the polytype of the underlying SiC substrate body 10 (step flow growth).

[0063] Thus, the strain layer thinning process S1 involving crystal growth includes an Si atom sublimation process of thermally sublimating Si atoms from the surface of the SiC material 40, a C atom sublimation process of sublimating the C atoms remaining on the surface of the SiC material 40 by reacting with Si vapor in a quasi-closed space, a raw material transport process of transporting the raw material to the surface of the SiC substrate body 10 using a temperature gradient and a chemical potential difference as driving forces, and a step flow growth process of growing when the raw material reaches the steps of the SiC substrate body 10.

[0064] That is, the strain layer thinning process S1 involving crystal growth is a process of disposing the SiC substrate body 10 and the SiC material 40 opposite to each other and heating them such that the SiC substrate body 10 is on the low-temperature side and the SiC material 40 is on the high-temperature side. Thereby, a crystal growth space X is formed between the SiC substrate body 10 and the SiC material 40, and the SiC substrate body 10 can be grown crystallographically using the temperature gradient as a driving force, and the strain layer 12 can be moved to the surface side of the SiC substrate body 10.

[0065] [Strain layer thinning process S1 involving etching] FIG. 1(c) and FIG. 5 are explanatory diagrams showing an overview of the strain layer thinning process S1 involving etching. As shown in FIG. 5, by disposing the SiC substrate body 10 and the SiC material 40 opposite to each other and providing a temperature gradient therebetween for heating, it is possible to transport the raw materials (Si element and C element) from the SiC substrate body 10 to the SiC material 40 and etch the SiC substrate body 10.

[0066] In this strain layer thinning process S1, by disposing the SiC substrate body 10 in a quasi-closed space where the SiC material 40 is exposed and heating it in a temperature range of 1400°C or higher and 2300°C or lower, the following reactions 1) to 5) are continuously carried out, and as a result, etching is considered to progress (see FIG. 5(b)).

[0067] 1) SiC(s) → Si(v) + C(s) 2) 2C(s) + Si(v) → SiC2(v) 3) C(s) + 2Si(v) → Si2C(v) 4) Si(v)+SiC2(v)→2SiC(s) 5) Si2C(v)→Si(v)+SiC(s)

[0068] Explanation of 1): When the SiC substrate body 10 (SiC(s)) is heated, Si atoms (Si(v)) are desorbed from the surface of the SiC substrate body 10 by thermal decomposition (Si atom sublimation process). Explanation of 2) and 3): When Si atoms (Si(v)) are desorbed, C (C(s)) remaining on the surface of the SiC substrate body 10 reacts with Si vapor (Si(v)) in the quasi-closed space. As a result, C (C(s)) sublimates from the surface of the SiC substrate body 10 as Si2C or SiC2, etc. (C atom sublimation process). Explanation of 4) and 5): The sublimated Si2C or SiC2, etc. reaches the SiC material 40 in the quasi-closed space due to the temperature gradient and crystal growth occurs.

[0069] Thus, the strain layer thinning process S1 involving etching includes a Si atom sublimation process of thermally sublimating Si atoms from the surface of the SiC substrate body 10 and a C atom sublimation process of sublimating from the surface of the SiC substrate body 10 by reacting C atoms remaining on the surface of the SiC substrate body 10 with Si vapor in the quasi-closed space.

[0070] That is, the strain layer thinning process S1 involving etching is a process of arranging the SiC substrate body 10 and the SiC material 40 relative to each other and heating them so that the SiC substrate body 10 is on the high-temperature side and the SiC material 40 is on the low-temperature side. Thereby, an etching space Y is formed between the SiC substrate body 10 and the SiC material 40, and the SiC substrate body 10 can be etched using the temperature gradient as a driving force, and the strain layer 12 can be moved to the surface side of the SiC substrate body 10.

[0071] 〈Strain layer removal process〉 The warped layer removal step S2 is a step of removing the warped layer 12 thinned by the warped layer thinning step S1. Specifically, it is a step of removing the warped layer 12 that has moved to the surface side rather than the reference depth 20 which is the depth of the warped layer 12 before the warped layer thinning step S1, and is a step of removing at least a part on the surface side rather than the reference depth 20 (Figs. 1(a) to 1(c)).

[0072] Examples of the method used in this warped layer removal step S2 include the CMP method, the SiVE method, the hydrogen etching method, and the etching methods described in the above-mentioned [warped layer thinning step S1 involving etching].

[0073] In addition, the warped layer removal step S2 in the conventional method generally goes through a rough grinding step using abrasive grains such as diamond, a finish grinding step using abrasive grains with a smaller particle size than the abrasive grains used in the rough grinding step, and a CMP step of performing polishing by combining the mechanical action of the polishing pad and the chemical action of the slurry. In this conventional method, it was normal to remove all of the warped layer 12 introduced into the SiC substrate body 10 (see Fig. 1(d)).

[0074] In the warped layer removal step S2 according to the present invention, the warped layer 12 after the warped layer thinning step S1 is removed. Therefore, the warped layer 12 can be removed with an amount of removal smaller than the conventionally introduced warped layer depth (reference depth 20). Thereby, the amount of removal of the SiC substrate body 10 in the warped layer removal step S2 of the present invention can be made smaller than that of the conventional method.

[0075] According to the method for manufacturing an SiC substrate of the present invention, it includes a warped layer thinning step S1 of thinning the warped layer 12 by moving the warped layer 12 of the SiC substrate body 10 to the surface side. Thereby, the amount of material loss L in the warped layer removal step S2 can be reduced. Also, the cost and processing time in the warped layer removal step S2 can be reduced.

[0076] For example, consider a case where the depth of the strain layer 12 (reference depth 20) of the SiC substrate body 10 before the strain layer thinning process S1 is 5 μm, and the depth of the strain layer 12 becomes 1 μm by the strain layer thinning process S1. At this time, in the strain layer removal process S2, it is only necessary to remove 1 μm of the SiC substrate body 10. That is, in the conventional method, it was necessary to remove 5 μm of the SiC substrate body 10, but by including the strain layer thinning process S1, it is possible to reduce the material loss L by 4 μm. In addition, it is possible to reduce consumables (grinding stones, blades, abrasive grains, etc.) and processing time involved in processing. Therefore, the cost in the strain layer removal process S2 can be significantly reduced.

[0077] According to the method for manufacturing a SiC substrate according to the present embodiment, by adopting chemical mechanical polishing (CMP) in the strain layer removal process S2, it is possible to manufacture a SiC substrate 30 having an epitaxial surface while reducing the material loss L, cost, and processing time. The present invention can reduce the burden of CMP, which is the finishing process of the conventional method, by thinning the strain layer 12.

[0078] According to the method for manufacturing a SiC substrate according to the present embodiment, by adopting the strain layer thinning process S1 involving crystal growth, it is possible to adjust to a desired substrate thickness.

[0079] According to the method for manufacturing a SiC substrate according to the present embodiment, by adopting the strain layer thinning process S1 involving etching, the strain layer thinning process S1 and the strain layer removal process S2 can be performed simultaneously. Thereby, it is possible to reduce the introduction cost and outsourcing cost of the process and equipment, and reduce the cost.

[0080] According to the method for manufacturing a SiC substrate according to the present embodiment, the heating temperature of the strain layer thinning process S1 is 1400 °C or higher and 1600 °C or lower. By heating in such a temperature range, the burden on the equipment can be reduced. In addition, a lower temperature heat treatment device can be more easily introduced.

[0081] [Slice thickness in the slicing process] Table 1 summarizes an example of manufacturing a SiC substrate 30 with a substrate thickness of 350 μm in the manufacturing methods of the SiC substrates according to the present embodiment and the conventional method, respectively.

[0082]

Table 1

[0083] As shown in Table 1, a total material loss L of 100 μm occurs in the conventional method. In particular, in the conventional method, in order to surely remove the strain layer 12 introduced in each process, it is common to remove 100 μm or more per SiC substrate body 10. On the other hand, the amount of material loss L in the manufacturing method of the SiC substrate according to the present embodiment is 50 μm as shown in Table 1. As such, according to the present embodiment, it is possible to significantly reduce the amount of material loss L in the manufacturing of the SiC substrate.

[0084] Also, the substrate thickness D1 of the SiC substrate body 10 cut out from the ingot I in the slicing step S3 is set with the amount of this material loss L as an index. That is, the thickness obtained by adding the amount of material loss L to the substrate thickness D (the thickness of the SiC substrate 30 at the end of the surface processing) of the SiC substrate 30 that is finally desired to be obtained is set as the substrate thickness D1 at the time of slicing.

[0085] As such, the amount of material loss L is added to the thickness of the SiC substrate 30 after the completion of the surface processing to determine the substrate thickness D1 at the time of slicing. Here, the “surface processing” refers to processing that reduces the thickness of the SiC substrate body 10, such as the etching step S4 and the strain layer removal step S2. That is, the amount of material loss L is added to the thickness of the SiC substrate 30 when it reaches the point where the thickness does not decrease any further due to subsequent processes, and the substrate thickness D1 at the time of slicing is set.

[0086] Therefore, it is preferable to set, as the substrate thickness D1 at the time of slicing, the value obtained by adding a thickness of 37 μm or more, more preferably 40 μm or more, as a lower limit to the substrate thickness D of the SiC substrate 30.

[0087] Further, it is preferable to set the substrate thickness D1 at the time of slicing to be the substrate thickness D of the SiC substrate 30 added with a thickness of 100 μm or less, more preferably 90 μm or less, still more preferably 80 μm or less, still more preferably 70 μm or less, still more preferably 60 μm or less, and still more preferably 50 μm or less as an upper limit. Thereby, more SiC substrates 30 can be manufactured from one ingot I.

[0088] Also, as described above, in the conventional method, it is common to remove 100 μm or more per SiC substrate 30. Therefore, it is preferable to set the substrate thickness D1 at the time of slicing to be the substrate thickness D of the SiC substrate 30 added with a thickness of 100 μm or less, more preferably less than 100 μm as an upper limit. Thereby, more SiC substrates 30 can be manufactured as compared with the case of using the generally performed conventional method.

[0089] Note that the substrate thickness D of the SiC substrate 30 that has gone through the slicing step S3 to the strain layer removing step S2 can typically be exemplified as 100 to 600 μm, more typically 150 to 550 μm, still more typically 200 to 500 μm, still more typically 250 to 450 μm, and still more typically 300 to 400 μm. That is, it is preferable to add the amount of material loss L of the SiC substrate manufacturing method of the present invention to these typical substrate thicknesses of the SiC substrate 30 and set the substrate thickness D1 at the time of slicing.

[0090] Specifically, when it is desired to obtain a SiC substrate 30 having a substrate thickness D of 350 μm as a final product by the manufacturing method of the SiC substrate of the present invention, it is preferable to obtain, in the slicing step S3, a SiC substrate 30 having a substrate thickness D1 of 387 μm or more, more preferably 390 μm or more, and still more preferably 400 μm or more as a lower limit. Also, in this case, it is preferable to obtain the SiC substrate 30 in the slicing step S3, where the substrate thickness D1 during slicing is 450 μm or less, more preferably 440 μm or less, still more preferably 430 μm or less, still more preferably 420 μm or less, still more preferably 410 μm or less, and still more preferably 400 μm or less as the upper limit.

[0091] 《Manufacturing Apparatus for SiC Substrate》 Hereinafter, a manufacturing apparatus for realizing the manufacturing method of the SiC substrate according to the present invention will be described in detail. In this embodiment, components that are basically the same as those shown in the previous manufacturing method are denoted by the same reference numerals, and the description thereof will be simplified.

[0092] As shown in FIG. 6, the manufacturing apparatus for the SiC substrate according to this embodiment includes a main body container 50 capable of accommodating the SiC substrate body 10, and a heating furnace 60 capable of heating so as to form a temperature gradient between the SiC substrate body 10 and the SiC material 40.

[0093] (Main Body Container) The main body container 50 is a fitting container including an upper container 51 and a lower container 52 that can be fitted to each other. A minute gap 53 is formed at the fitting portion between the upper container 51 and the lower container 52, and the main body container 50 is configured to be evacuated (vacuumed) from this gap 53.

[0094] The upper container 51 and the lower container 52 according to this embodiment are made of polycrystalline SiC. Therefore, the main body container 50 itself may be used as the SiC material 40. Alternatively, only the portion of the main body container 50 facing the SiC substrate body 10 may be made of the SiC material 40. In that case, a high melting point material (the same material as the high melting point container 70 described later) can be adopted for the portion other than the SiC material 40.

[0095] Alternatively, as shown in FIGS. 3 to 5, a configuration in which the substrate-like SiC material 40 is separately accommodated may be adopted. In that case, a spacer (such as the substrate holder 54) may be disposed between the substrate-like SiC material 40 and the SiC substrate body 10 to form a crystal growth space X or an etching space Y. The substrate holder 54 is preferably made of a high melting point material similar to the high melting point container 70.

[0096] That is, the main body container 50 is configured to generate an atmosphere containing Si element and C element in the internal space when heated with the SiC substrate body 10 accommodated therein. In the present embodiment, by heating the SiC material 40 made of polycrystalline SiC, an atmosphere containing Si element and C element is formed in the internal space.

[0097] Further, the space in the heated main body container 50 is preferably a vapor pressure environment of a mixed system of gas-phase species containing Si element and gas-phase species containing C element. Examples of the gas-phase species containing Si element include Si, Si2, Si3, Si2C, SiC2, and SiC. Examples of the gas-phase species containing C element include Si2C, SiC2, SiC, and C. That is, it is preferable that the SiC-based gas exists in a quasi-closed space.

[0098] The crystal growth space X or the etching space Y is a space for transporting raw materials from the SiC substrate body 10 to the SiC material 40 and from the SiC material 40 to the SiC substrate body 10, with the temperature gradient provided between the SiC substrate body 10 and the SiC material 40 as the driving force.

[0099] For example, consider a case where the SiC substrate body 10 is arranged such that when comparing the temperature of the surface of the SiC substrate body 10 with the temperature of the SiC material 40 facing this surface, the temperature on the SiC substrate body 10 side is lower and the temperature of the SiC material 40 is higher (see Fig. 4). Thus, when the SiC substrate body 10 and the SiC material 40 are arranged opposite to each other and heated such that the SiC substrate body 10 is on the low-temperature side and the SiC material 40 is on the high-temperature side, raw materials are transported from the SiC material 40 to the SiC substrate body 10, and single-crystalline SiC grows on the SiC substrate body 10. That is, a crystal growth space X is formed between the SiC material 40 and the SiC substrate body 10.

[0100] On the other hand, consider a case where the SiC substrate body 10 is arranged such that when comparing the temperature of the surface of the SiC substrate body 10 with the temperature of the SiC material 40 facing this surface, the temperature on the SiC substrate body 10 side is higher and the temperature of the SiC material 40 is lower (see Fig. 5). Thus, when the SiC substrate body 10 and the SiC material 40 are arranged opposite to each other and heated such that the SiC substrate body 10 is on the high-temperature side and the SiC material 40 is on the low-temperature side, raw materials are transported from the SiC substrate body 10 to the SiC material 40, and the SiC substrate body 10 is etched. That is, an etching space Y is formed between the SiC material 40 and the SiC substrate body 10.

[0101] (Heating furnace) As shown in Fig. 6, the heating furnace 60 includes a main heating chamber 61 capable of heating an object to be processed (such as the SiC substrate body 10, etc.) to a temperature of 1000°C or higher and 2300°C or lower, a preheating chamber 62 capable of preheating the object to be processed to a temperature of 500°C or higher, a high-melting-point container 70 capable of accommodating the main body container 50, and a moving means 63 (a moving table) capable of moving the high-melting-point container 70 from the preheating chamber 62 to the main heating chamber 61.

[0102] The main heating chamber 61 is formed in a regular hexagon shape in a planar cross-sectional view, and the high-melting-point container 70 is arranged inside thereof. Inside this heating chamber 61, a heating heater 64 (mesh heater) is provided. Further, multilayer heat-reflective metal plates are fixed to the side walls and ceiling of this heating chamber 61 (not shown in the figure). This multilayer heat-reflective metal plate is configured to reflect the heat of the heating heater 64 toward the substantially central part of the heating chamber 61.

[0103] As a result, inside the heating chamber 61, the heating heater 64 is arranged so as to surround the high melting point container 70 in which the object to be processed is accommodated, and further, a multilayer heat-reflective metal plate is arranged outside thereof, so that the temperature can be raised to a temperature of 1000 °C or higher and 2300 °C or lower. As the heating heater 64, for example, a resistance heating type heater or a high frequency induction heating type heater can be used.

[0104] Further, the heating heater 64 may adopt a configuration capable of forming a temperature gradient inside the high melting point container 70. For example, the heating heater 64 may be configured such that many heaters are arranged on the upper side. Further, the heating heater 64 may be configured such that the width increases as it goes upward. Alternatively, the heating heater 64 may be configured such that the power supplied can be increased as it goes upward.

[0105] Further, connected to this heating chamber 61 are a vacuum forming valve 65 for exhausting the inside of the heating chamber 61, an inert gas injection valve 66 for introducing an inert gas into the heating chamber 61, and a vacuum gauge 67 for measuring the degree of vacuum inside the heating chamber 61.

[0106] The vacuum forming valve 65 is connected to a vacuum pumping pump for evacuating the inside of the heating chamber 61 and creating a vacuum (not shown in the figure). By this vacuum forming valve 65 and the vacuum pumping pump, the degree of vacuum inside the heating chamber 61 can be adjusted to, for example, 10 Pa or less, more preferably 1 Pa or less, and even more preferably 10 -3 Pa or less. As this vacuum pumping pump, a turbo molecular pump can be exemplified.

[0107] The inert gas injection valve 66 is connected to an inert gas supply source (not shown). With this inert gas injection valve 66 and the inert gas supply source, inert gas can be introduced into the main heating chamber 61 in the range of 10 -5 ~10000 Pa. As this inert gas, Ar, He, N2, etc. can be selected.

[0108] Further, the inert gas injection valve 66 is a dopant gas supply means capable of supplying a dopant gas into the main body container 50. That is, by selecting a dopant gas (for example, N2, etc.) in the inert gas, the doping concentration of the growth layer can be adjusted.

[0109] The preheating chamber 62 is connected to the main heating chamber 61 and is configured such that the high melting point container 70 can be moved by the moving means 63. Note that the preheating chamber 62 of the present embodiment is configured to be able to be heated up by the residual heat of the heater 64 of the main heating chamber 61. For example, when the main heating chamber 61 is heated up to 2000°C, the preheating chamber 62 is heated up to about 1000°C, and degassing treatment of the object to be processed (SiC substrate body 10, main body container 50, high melting point container 70, etc.) can be performed.

[0110] The moving means 63 is configured to place the high melting point container 70 and move the main heating chamber 61 and the preheating chamber 62. Since the conveyance between the main heating chamber 61 and the preheating chamber 62 by this moving means 63 is completed in about the shortest 1 minute, temperature increase and decrease at 1~1000°C / min can be realized. Since rapid temperature increase and rapid temperature decrease can be performed in this way, it is possible to observe the surface shape having no low temperature growth history during temperature increase and temperature decrease, which was difficult with conventional devices. Also, in FIG. 6, the preheating chamber 62 is arranged below the main heating chamber 61, but it is not limited to this, and it may be arranged in any direction.

[0111] Moreover, the moving means 63 according to this embodiment is a moving table on which the high melting point container 70 is placed. A minute amount of heat is dissipated from the contact portion between this moving table and the high melting point container 70. Thereby, a temperature gradient can be formed in the high melting point container 70 (and in the main body container 50). That is, in the heating furnace 60 of this embodiment, since the bottom of the high melting point container 70 is in contact with the moving table, a temperature gradient is provided such that the temperature decreases from the upper container 71 to the lower container 72 of the high melting point container 70. This temperature gradient is preferably formed along the front and back directions of the SiC substrate body 10. Also, as described above, a temperature gradient may be formed by the configuration of the heating heater 64. Further, the temperature gradient may be configured to be reversible by this heating heater 64.

[0112] (High melting point container) The heating furnace 60 preferably forms an atmosphere containing Si element and can heat the main body container 50 within this atmosphere. The atmosphere containing Si element in the heating furnace 60 according to this embodiment is formed using the high melting point container 70 and the Si vapor supply source 74. In addition, any method that can form an atmosphere containing Si element around the main body container 50 can of course be adopted.

[0113] The high melting point container 70 is composed of a high melting point material. For example, C which is a general-purpose heat-resistant member, W, Re, Os, Ta, Mo which are high melting point metals, Ta9C8, HfC, TaC, NbC, ZrC, Ta2C, TiC, WC, MoC which are carbides, HfN, TaN, BN, Ta2N, ZrN, TiN which are nitrides, HfB2, TaB2, ZrB2, NB2, TiB2 which are borides, polycrystalline SiC, etc. can be exemplified.

[0114] This high melting point container 70 is a fitting container including an upper container 71 and a lower container 72 that can be fitted to each other, similar to the main body container 50, and is configured to be able to accommodate the main body container 50. A minute gap 73 is formed at the fitting portion between the upper container 71 and the lower container 72, and the high melting point container 70 is configured to be able to exhaust (vacuum) the inside through this gap 73.

[0115] The high melting point container 70 preferably has a Si vapor supply source 55 capable of supplying the vapor pressure of the gas phase species containing Si element into the high melting point container 70. The Si vapor supply source 55 may have a configuration that generates Si vapor into the high melting point container 70 during heating. For example, solid Si (Si pellets such as single crystal Si wafers and Si powders) or Si compounds can be exemplified.

[0116] The manufacturing apparatus of the SiC substrate according to this embodiment employs TaC as the material of the high melting point container 70 and tantalum silicide as the Si vapor supply source 55. That is, as shown in FIGS. 4 and 5, a tantalum silicide layer is formed inside the high melting point container 70, and the Si vapor pressure environment is configured to be formed by supplying Si vapor from the tantalum silicide layer into the container during heating. In addition to this, any configuration can be adopted as long as the vapor pressure of the gas phase species containing Si element is formed inside the high melting point container 70 during heating.

[0117] Hereinafter, the present invention will be described more specifically with reference to Example 1.

Example

[0118] 〈Example 1: Movement of the strain layer〉 The SiC substrate body 10 after the slicing step S3 was accommodated in the main body container 50 and the high melting point container 70 (see FIG. 7) and heat-treated under the following heat treatment conditions. In this Example 1, the main body container 50 is formed of polycrystalline SiC so that the main body container 50 itself functions as the SiC material 40 (Si element supply source and C element supply source).

[0119] [SiC substrate body 10] Polytype: 4H-SiC Substrate size: width 10 mm × length 10 mm × thickness 0.45 mm Off direction and off angle: 4° off in the <11-20> direction Heat treatment surface: (0001) plane Depth of the strain layer 12: 3.5 μm

[0120] Note that the depth of the strained layer 12 was confirmed by the SEM-EBSD method. In addition, this strained layer 12 can also be confirmed by TEM, μXRD, or Raman spectroscopy.

[0121] [Main body container 50] Material: Polycrystalline SiC Container size: Diameter 60 mm × Height 4 mm Material of the substrate holder 54: Single-crystalline SiC Distance between the SiC substrate body 10 and the bottom surface of the main body container 50: 2 mm

[0122] [High melting point container 70] Material: TaC Container size: Diameter 160 mm × Height 60 mm Si vapor source 74 (Si compound): TaSi2

[0123] [Heat treatment conditions] The SiC substrate body 10 arranged under the above-mentioned conditions was heat-treated under the following conditions. Heating temperature: 1500 °C Heating time: 10 h Etching amount: 40 nm Temperature gradient: 1 °C / mm Vacuum degree of the main heating chamber: 10 -5 Pa

[0124] [Measurement of the strained layer by the SEM-EBSD method] The lattice strain of the SiC substrate body 10 can be obtained by comparing it with a reference crystal lattice as a reference. As a means of measuring this lattice strain, for example, the SEM-EBSD method can be used. The SEM-EBSD method is a technique (Electron Back Scattering Diffraction: EBSD) capable of measuring the strain in a micro-region based on the Kikuchi line diffraction pattern obtained by electron backscattering in a scanning electron microscope (SEM). In this technique, the lattice strain amount can be obtained by comparing the diffraction pattern of the reference crystal lattice as a reference with the diffraction pattern of the measured crystal lattice.

[0125] As the reference crystal lattice, for example, reference points are set in a region where it is considered that no lattice strain occurs. That is, it is desirable to arrange reference points in the region of the bulk layer 11. Usually, it is a generally accepted theory that the depth of the strained layer 12 is about 10 μm. Therefore, reference points may be set at positions about 20 to 35 μm deep, which are considered to be sufficiently deeper than the strained layer 12.

[0126] Next, the diffraction pattern of the crystal lattice at this reference point is compared with the diffraction patterns of the crystal lattices in each measurement region measured at a pitch on the nanometer order. Thereby, the amount of lattice strain in each measurement region with respect to the reference point can be calculated.

[0127] In addition, although the case of setting a reference point where it is considered that no lattice strain occurs as the reference crystal lattice has been shown, it is of course also possible to use the ideal crystal lattice of single-crystalline SiC as a reference, or to use the crystal lattice that occupies the majority (for example, more than a majority) within the measurement region plane as a reference.

[0128] By measuring whether or not lattice strain exists by this SEM-EBSD method, the presence or absence of the strained layer 12 can be determined. That is, when strain is introduced due to processing damage, lattice strain occurs in the SiC substrate body 10, so stress is observed by the SEM-EBSD method.

[0129] The strained layer 12 existing in the SiC substrate body 10 of Example 1 before and after the strained layer thinning step S1 was observed by the SEM-EBSD method. The results are shown in FIGS. 8(a) and 8(b).

[0130] In this measurement, regarding the cross-section obtained by cleaving the SiC substrate body 10 before and after the strained layer thinning step S1 of Example 1, measurement was performed using a scanning electron microscope under the following conditions. SEM apparatus: Merline manufactured by Zeiss EBSD analysis: OIM crystal orientation analysis apparatus manufactured by TSL Solutions Accelerating voltage: 15 kV Probe current: 15 nA Step size: 200 nm Reference point R depth: 20 μm

[0131] Fig. 8(a) is a cross-sectional SEM-EBSD imaging image of the SiC substrate body 10 before the strain layer thinning step S1 in Example 1. As shown in this Fig. 8(a), before the strain layer thinning step S1, lattice strain of 3.5 μm in depth was observed in the SiC substrate body 10. This is the lattice strain introduced during the slicing step S3, and it can be seen that it has a strain layer 12. Note that compressive stress is observed in this Fig. 8(a).

[0132] Fig. 8(b) is a cross-sectional SEM-EBSD imaging image of the SiC substrate body 10 after the strain layer thinning step S1 in Example 1. As shown in this Fig. 8(b), after the strain layer thinning step S1, lattice strain of 1.3 μm in depth was observed in the SiC substrate body 10. Since the etching amount during heat treatment is 40 nm, it can be seen that the strain layer 12 has moved and concentrated about 2.2 μm toward the surface side. Also, by increasing the heating time, the strain layer 12 can be further moved toward the surface side. In this way, by heat-treating the SiC substrate body 10 in a quasi-closed space containing a Si element supply source and a C element supply source, the strain layer 12 can be moved and concentrated on the surface side of the SiC substrate body 10.

[0133] According to the present invention, by including the strain layer thinning step S1, it is possible to reduce and minimize the region that has been removed as material loss in the conventional method.

Explanation of reference numerals

[0134] 10 SiC substrate body 11 Bulk layer 12 Strain layer 20 Reference depth 30 SiC substrate 40 SiC material 50 Main body container 51 Upper container 52 Lower container 53 Gap 54 Substrate holder 55 Si vapor supply source 60 Heating furnace 61 Main heating chamber 62 Preheating chamber 63 Moving means 64 Heating heater 65 Valve for vacuum formation 66 Valve for inert gas injection 67 Vacuum gauge 70 High melting point container 71 Upper container 72 Lower container 73 Gap 74 Si vapor supply source X Crystal growth space Y Etching space S1 Strained layer thinning process S2 Strained layer removal process S3 Slicing process S4 Etching process I Ingot

Claims

1. A method for manufacturing a SiC substrate, comprising a strain layer thinning step of thermally etching a SiC substrate body within a main body container made of a SiC material to move a strain layer of the SiC substrate body to the surface side and thinning the strain layer, and a strain layer removing step of removing the strain layer.

2. The strain layer thinning step is a step of moving the strain layer after the strain layer thinning step to the surface side with respect to a reference depth which is the depth of the strain layer before the strain layer thinning step, and the strain layer removing step is a step of removing at least a part on the surface side with respect to the reference depth. The method for manufacturing a SiC substrate according to Claim 1.

3. The strain layer removing step is chemical mechanical polishing. The method for manufacturing a SiC substrate according to Claim 2.

4. The strain layer removing step is the step of performing the thermal etching, and is performed simultaneously with the strain layer thinning step. The method for manufacturing a SiC substrate according to Claim 2.

5. Further comprising a slicing step of slicing an ingot to obtain a SiC substrate body, wherein the slicing step is a step of obtaining a SiC substrate body having a thickness obtained by adding a thickness of 100 μm or less to the thickness of the SiC substrate body after the strain layer removing step. The method for manufacturing a SiC substrate according to any one of Claims 2 to 4.

6. The slicing step is a step of obtaining a SiC substrate body having a thickness obtained by adding a thickness of 50 μm or less to the thickness of the SiC substrate body after the strain layer removing step. The method for manufacturing a SiC substrate according to Claim 5.

7. Further comprising an etching step of etching the surface of the SiC substrate body, wherein the etching step is wet etching. The method for manufacturing a SiC substrate according to any one of Claims 1 to 6.

8. The etching step includes, as an etching solution, one or more selected from the group consisting of a potassium hydroxide melt, a chemical solution containing hydrofluoric acid, a potassium permanganate-based chemical solution, and tetramethylammonium hydroxide. The method for manufacturing a SiC substrate according to Claim 7.

9. Comprising a slicing step of slicing an ingot to obtain a SiC substrate body, wherein the slicing step, the etching step, and the strain layer thinning step are included in this order. The method for manufacturing a SiC substrate according to Claim 8.

10. The warped layer thinning process is a process of arranging the SiC substrate body and the main body container or other SiC materials relative to each other, heating them so that a temperature gradient is formed between the SiC substrate body and the main body container or other SiC materials, and performing thermal etching. The method for manufacturing a SiC substrate according to any one of claims 1 to 9.

11. The heating temperature in the warped layer thinning process is 1400°C or higher and 1600°C or lower. The method for manufacturing a SiC substrate according to any one of claims 1 to 10.

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