Method for processing silicon carbide ingot and method for processing silicon carbide substrate
Through the cyclic reaction of chemical modifier treatment and mechanical grinding, the problem of easy cracking of silicon carbide ingots during the grinding process was solved, and a silicon carbide ingot with a smooth surface and no cracks was obtained, which improved the processing efficiency and yield rate and realized the preparation of high-quality silicon carbide substrates.
Patent Information
- Application Number
- CN202411783897.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2044-12-06
AI Technical Summary
Silicon carbide ingots are prone to cracking during the grinding process, especially due to stress concentration and microcrack propagation caused by the convex morphology and sharp edge morphology, which affects the production of high-quality silicon carbide substrates and devices.
A chemical modifier is prepared by mixing a monovalent solid base and a solid oxygen-containing salt type oxidant to form a molten mixed liquid, which is used to soak the surface of the silicon carbide ingot to be treated and then mechanically ground. The surface is made porous and loose and the hardness is softened through chemical reaction, thereby reducing mechanical stress. The reaction is cyclically reacted to obtain a flat and smooth surface.
It effectively reduces the risk of cracking of silicon carbide ingots, improves processing efficiency, and increases the subsequent slicing yield, thereby achieving the preparation of high-quality silicon carbide substrates and device manufacturing.
Smart Images
Figure CN119260483B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for processing a silicon carbide ingot and a method for processing a silicon carbide substrate. Background Art
[0002] Surface grinding and circumferential grinding of SiC ingots are crucial for fabricating SiC substrates and devices. However, SiC ingots currently grown via physical vapor transport (PVT) often exhibit a convex morphology that becomes more pronounced as their diameter increases. This convex surface stress of SiC ingots with this morphology is relatively high, making it susceptible to cracking due to stress concentration during the grinding process. Furthermore, the edges of SiC ingots often exhibit a sharper morphology due to their increased diameter. During growth, microcracks of a certain depth inevitably form at these edges, extending radially inward. Consequently, these microcracks easily expand under stress during the grinding process, leading to cracking of the SiC ingot. Therefore, cracking of SiC ingots during grinding severely limits the production of high-quality SiC substrates and devices. Summary of the Invention
[0003] Based on this, it is necessary to provide a method for processing silicon carbide ingots and a method for processing silicon carbide substrates to address the above problems. The processing method of the silicon carbide ingot can effectively reduce processing stress, reduce the risk of cracking of the silicon carbide ingot, and has extremely high processing efficiency.
[0004] A method for processing a silicon carbide ingot comprises the following steps:
[0005] Providing a chemical modifier, the chemical modifier comprising a monovalent solid base and a solid oxygen-containing acid salt-type oxidant;
[0006] heating the chemical modifier to form a molten mixed solution;
[0007] The surface to be processed of the silicon carbide crystal ingot is immersed in the molten mixed liquid, and then plane mechanical grinding is performed to process the surface to be processed of the silicon carbide crystal ingot into a plane.
[0008] In one embodiment, the monovalent solid base is at least one of KOH or NaOH.
[0009] In one embodiment, the solid oxygen-containing salt type oxidant is at least one of KMnO4 or KIO4.
[0010] In one embodiment, the molar ratio of the monovalent solid base to the solid oxyacid salt type oxidant is 2:1-4:1.
[0011] In one embodiment, the surface to be processed of the silicon carbide ingot is immersed in the molten mixed solution and maintained for 10 minutes to 60 minutes, and then the surface is mechanically ground.
[0012] In one embodiment, in the step of immersing the surface to be processed of the silicon carbide ingot into the molten mixed solution, the temperature of the molten mixed solution is maintained at 400°C-800°C.
[0013] In one embodiment, the plane mechanical grinding uses a grinding wheel, and the grinding wheel reciprocates on the surface to be processed of the silicon carbide ingot.
[0014] In one embodiment, the plane mechanical grinding uses a grinding wheel with a mesh size of 200-1000, and the non-grinding surface of the grinding wheel is coated with polytetrafluoroethylene.
[0015] In one embodiment, the silicon carbide ingot has a diameter of 2 inches to 12 inches.
[0016] The present invention also provides a method for processing a silicon carbide substrate, including the above-mentioned method for processing a silicon carbide ingot.
[0017] In the processing method of the present invention, the surface to be processed of the silicon carbide ingot is first immersed in a molten mixed liquid of a specific composition to react with the molten mixed liquid, so that the surface to be processed of the silicon carbide ingot becomes porous and loose and the hardness becomes softer, thereby reducing the mechanical stress in the subsequent mechanical grinding process and avoiding the risk of cracking; at the same time, during the mechanical grinding process, a new surface will be exposed, and the new surface will continue to react with the molten mixed liquid to reduce the mechanical stress in the mechanical grinding process. Such a cycle can eventually obtain a relatively flat silicon carbide ingot with a smooth surface, no cracks, and low stress. Not only is the processing efficiency extremely high, but the yield of subsequent slicing can also be effectively improved, thereby realizing the preparation of high-quality silicon carbide substrates and the manufacture of devices. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0019] Figure 1 Schematic diagram of the process of the silicon carbide ingot processing method of the present invention;
[0020] Figure 2 Schematic diagram of the process of plane and circumference processing of silicon carbide ingots according to the present invention;
[0021] Figure 3 This is a photo of the silicon carbide ingot after processing in Example 1 of the present invention;
[0022] Figure 4 This is a photo of the silicon carbide ingot after processing according to Example 2 of the present invention.
[0023] In the figure: 1. Silicon carbide ingot; 2. Container; 3. Carrier; 4. Molten mixed liquid; 5. Grinding wheel. DETAILED DESCRIPTION
[0024] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.
[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or the combination of all related listed items.
[0026] In the present invention, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Furthermore, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.
[0027] like Figure 1 As shown, the method for processing silicon carbide ingot provided by the present invention comprises the following steps:
[0028] S1, providing a chemical modifier, wherein the chemical modifier comprises a monovalent solid base and a solid oxygen-containing acid salt type oxidant;
[0029] S2, heating the chemical modifier to form a molten mixed liquid;
[0030] S3, immersing the surface to be processed of the silicon carbide crystal ingot into the molten mixed liquid, and then performing plane mechanical grinding to process the surface to be processed of the silicon carbide crystal ingot into a flat surface.
[0031] Silicon carbide crystals have high hardness, high brittleness, good wear resistance, and extremely stable chemical properties, making precision machining of silicon carbide ingots very difficult. In the processing method of silicon carbide ingots provided by the present invention, a chemical modifier is first prepared using a monovalent solid base and a solid oxyacid-type oxidant, and heated to form a molten mixed liquid. The surface to be processed of the silicon carbide ingot is then immersed in the molten mixed liquid of this specific component. The surface to be processed of the silicon carbide ingot reacts with the molten mixed liquid. During the reaction, thanks to the synergistic effect of the base and the oxyacid-type oxidant in the molten mixed liquid, the surface to be processed of the silicon carbide ingot becomes porous and loose, and the hardness softens, thereby reducing the mechanical stress during the subsequent mechanical grinding process and avoiding the risk of cracking.
[0032] At the same time, during the mechanical grinding process, the surface to be processed of the silicon carbide ingot will expose a new surface, which will continue to react with the molten mixture to reduce the mechanical stress during the mechanical grinding process. This cycle will eventually result in a relatively flat silicon carbide ingot with a smooth surface, no cracks, and low stress. This not only has extremely high processing efficiency, but can also effectively improve the yield of subsequent slicing, thereby realizing the preparation of high-quality silicon carbide substrates and the manufacture of devices.
[0033] In order to enable the alkali and oxygen-containing salt type oxidant in the molten mixed liquid to play a better synergistic role, so that the to-be-treated surface of the silicon carbide ingot becomes more porous and loose, and the hardness becomes softer, in step S1, the molar amount of the monovalent solid base in the chemical modifier is greater than the molar amount of the solid oxygen-containing salt type oxidant. Preferably, the molar ratio of the monovalent solid base to the solid oxygen-containing salt type oxidant is 2:1-4:1, including but not limited to 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, or a range consisting of any two of these values, and the present invention is not limited to this.
[0034] Among them, the specific selection of the monovalent solid base and the solid oxyacid salt type oxidant may not be limited. Preferably, the monovalent solid base is selected from at least one of KOH or NaOH, and the solid oxyacid salt type oxidant is at least one of KMnO4 or KIO4. For example, the chemical modifier includes KOH and KMnO4, or the chemical modifier includes KOH and KIO4, or the chemical modifier includes NaOH and KMnO4, or the chemical modifier includes NaOH and KIO4, or the chemical modifier includes KOH, NaOH and KMnO4, or the chemical modifier includes KOH, NaOH and KIO4, or the chemical modifier includes KOH, KMnO4 and KIO4, or the chemical modifier includes NaOH, KMnO4 and KIO4, or the chemical modifier includes KOH, NaOH, KMnO4 and KIO4, or the chemical modifier includes KOH, NaOH, KMnO4 and KIO4.
[0035] In step S2, in the step of heating the chemical modifier to form a molten mixed solution, the heating temperature is preferably 400°C-800°C, including but not limited to 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, or a range consisting of any two of these values, and the present invention is not limited thereto. In actual operation, the mixed chemical modifier is first placed in a container such as a crucible that can hold the molten mixed solution, wherein the crucible and other containers are preferably made of materials such as nickel, platinum, gold, etc., which are not only resistant to high temperatures but also chemically stable and will not react with the molten mixed solution of the present invention.
[0036] Thus, in step S3, in the step of immersing the surface to be processed of the silicon carbide ingot into the molten mixed liquid, the temperature of the molten mixed liquid is maintained at 400°C-800°C, and preferably the temperature is kept constant. Similarly, during the mechanical surface grinding process, the temperature is preferably kept constant, which is beneficial to the stability and uniformity of the reaction.
[0037] Optionally, the surface to be treated of the silicon carbide ingot is immersed in the molten mixed liquid, first held for a certain time, and then subjected to plane mechanical grinding. Preferably, the holding time is 10min-60min, including but not limited to 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min, or a range consisting of any two of these values. The present invention is not limited to this. The surface to be treated of the silicon carbide ingot can be fully chemically reacted in the molten mixed liquid first, so that the surface to be treated of the silicon carbide ingot has a porous structure and the hardness becomes lower, which is beneficial to reduce the stress in mechanical grinding and avoid cracking of the silicon carbide ingot during processing.
[0038] It should be noted that during the mechanical surface grinding process, the molten mixed liquid can still contact and react with the surface in the grinding process, making the surface porous and loose and softening the hardness. Optionally, when the present invention performs plane mechanical grinding, it is preferred to use a grinding wheel. Further, it is preferred that the grinding wheel reciprocates on the surface to be treated of the silicon carbide ingot, so that the new surface exposed by the grinding process can be fully contacted and reacted with the molten mixed liquid again, re-forming a porous and loose structure, while reducing the hardness, which is conducive to improving the processing effect and processing efficiency.
[0039] Preferably, the plane mechanical grinding uses a grinding wheel with a mesh size of 200-1000, including but not limited to 200 mesh, 400 mesh, 600 mesh, 800 mesh or 1000 mesh, or a range consisting of any two of these values. The present invention is not limited to this. By adjusting the mesh size of the grinding wheel, a relatively flat, smooth surface and crack-free silicon carbide ingot can be obtained. Furthermore, it is preferred that the non-grinding surface of the grinding wheel is coated with polytetrafluoroethylene. Since neither polytetrafluoroethylene nor the diamond on the grinding surface reacts with the molten mixed solution of the present invention, the grinding wheel can be prevented from reacting with the molten mixed solution, affecting the processing effect.
[0040] In the processing method of the present invention, the processed silicon carbide ingots include the currently mainstream n-type ingots, p-type ingots and semi-insulating ingots with diameters of 2 inches to 12 inches. However, it should be noted that the processing method of the present invention is applicable to all silicon carbide ingots and is not limited by the type and size of the silicon carbide ingots.
[0041] For example, refer to Figure 2 As shown, for the silicon carbide ingot 1 with a convex plane and sharp edges currently grown by physical vapor transport (PVT), the processing process generally includes planar processing and circular processing. It can be understood that there is no special requirement for the order of planar processing and circular processing. Circular processing can be performed first and then planar processing, or planar processing can be performed first and then circular processing.
[0042] Specifically, in the actual processing process, a chemical modifier composed of a monovalent solid base and a solid oxygen-containing acid salt type oxidant is first placed in a container 2 such as a crucible, heated to form a molten mixed liquid 4, and then a carrier 3 such as nickel, platinum, gold, etc. that is resistant to high temperatures and does not react with the molten mixed liquid 4 of the present invention is used to support the silicon carbide ingot 1. The raised surface of the silicon carbide ingot 1 is first immersed in the molten mixed liquid 4 as the surface to be treated and maintained for 10 minutes to 60 minutes, so that the surface to be treated reacts with the molten mixed liquid 4 to become porous and loose and the hardness becomes soft, and then the grinding wheel 5 is started for mechanical surface grinding. During grinding, the grinding wheel 5 reciprocates on the surface to be treated of the silicon carbide ingot 1 until a relatively flat surface is obtained.
[0043] Then, the silicon carbide ingot 1 after surface grinding is subjected to circumferential processing, and the carrier 3 is used to carry the silicon carbide ingot 1. The edge of the silicon carbide ingot 1 with a sharp morphology is used as a new surface to be processed. It is first immersed in the molten mixed liquid 4 and kept for 10min-60min, so that the surface to be processed reacts with the molten mixed liquid 4 to become porous and loose and the hardness becomes soft. Then the grinding wheel 5 is started to perform mechanical surface grinding. During grinding, the grinding wheel 5 reciprocates on the surface to be processed of the silicon carbide ingot 1 until a relatively flat circumferential surface is obtained, and finally a relatively flat, smooth surface without cracks and low stress silicon carbide ingot is obtained. Preferably, during the processing, the container 2 such as the crucible can be sealed to reduce the volatilization of the molten mixed liquid 4.
[0044] Therefore, based on the processing method of the present invention, a relatively flat silicon carbide ingot with a smooth surface without cracks and low stress can be obtained, and the processing efficiency is extremely high.
[0045] The present invention also provides a method for processing a silicon carbide substrate, including the above-mentioned method for processing a silicon carbide ingot. Since the method for processing a silicon carbide ingot of the present invention can obtain a relatively flat silicon carbide ingot with a smooth surface, no cracks, and low stress, it can effectively improve the yield of subsequent slicing and realize the preparation of high-quality silicon carbide substrates.
[0046] Hereinafter, the processing method of the silicon carbide ingot and the processing method of the silicon carbide substrate will be further described through the following specific embodiments.
[0047] Example 1
[0048] First, solid sodium hydroxide (NaOH) and potassium permanganate (KMnO4) with a molar ratio of 3:1 are mixed into a crucible and heated to 500°C to prepare a molten mixed solution.
[0049] The raised surface of a 6-inch diameter silicon carbide ingot was immersed in the molten mixture. After 30 minutes, the surface was mechanically ground using an 800-mesh grinding wheel. During grinding, the grinding wheel reciprocated on the surface to be processed until a relatively flat surface was obtained.
[0050] The sharp edge of the silicon carbide ingot after plane grinding is used as the new surface to be processed. It is immersed in the molten mixture so that the irregular edge of the silicon carbide ingot contacts the molten mixture. After 25 minutes, it is subjected to circumferential mechanical grinding using an 800-mesh grinding wheel. During grinding, the grinding wheel reciprocates on the surface to be processed until a relatively flat circumferential surface is obtained, completing the entire processing process. The results are as follows: Figure 3 As shown, the silicon carbide ingot did not crack and no new cracks were introduced.
[0051] Example 2
[0052] First, solid sodium hydroxide (NaOH) and potassium periodate (KIO4) with a molar ratio of 3:1 are mixed into a crucible and heated to 600°C to prepare a molten mixed solution.
[0053] The raised surface of an 8-inch diameter silicon carbide ingot was immersed in the molten mixture. After 20 minutes, the surface was mechanically ground using a 600-mesh grinding wheel. During grinding, the grinding wheel reciprocated on the surface to be processed until a relatively flat surface was obtained.
[0054] The edge of the silicon carbide ingot with a sharp morphology after surface grinding is used as the new surface to be processed. It is immersed in the molten mixture so that the irregular edge of the silicon carbide ingot contacts the molten mixture. After 10 minutes, a 600-mesh grinding wheel is used for circular mechanical grinding. During grinding, the grinding wheel reciprocates on the surface to be processed until a relatively flat circular surface is obtained. The entire processing process is completed. The results are as follows. Figure 4 As shown, the silicon carbide ingot did not crack and no new cracks were introduced.
[0055] Example 3
[0056] First, solid potassium hydroxide (KOH) and potassium periodate (KIO4) with a molar ratio of 3:1 are mixed into a crucible and heated to 550°C to prepare a molten mixed solution.
[0057] The raised surface of a 12-inch diameter silicon carbide ingot was immersed in the molten mixture. After 40 minutes, the surface was mechanically ground using an 800-mesh grinding wheel. During grinding, the grinding wheel reciprocated on the surface to be processed until a relatively flat surface was obtained.
[0058] The sharp edge of the silicon carbide ingot after surface grinding is used as the new surface to be processed and immersed in the molten mixture so that the irregular edge of the silicon carbide ingot contacts the molten mixture. After 20 minutes, circular mechanical grinding is performed using an 800-mesh grinding wheel. During grinding, the grinding wheel reciprocates on the surface to be processed until a relatively flat circular surface is obtained, completing the entire processing process. During the entire processing process, the silicon carbide ingot does not crack and no new cracks are introduced.
[0059] Example 4
[0060] First, solid sodium hydroxide (NaOH) and potassium permanganate (KMnO4) with a molar ratio of 2:1 are mixed into a crucible and heated to 800°C to prepare a molten mixed solution.
[0061] The raised surface of a 12-inch-diameter silicon carbide ingot was immersed in the molten mixture. After 15 minutes, the surface was mechanically ground using a 400-mesh grinding wheel. During grinding, the grinding wheel reciprocated on the surface to be processed until a relatively flat surface was obtained.
[0062] The sharp edge of the silicon carbide ingot after surface grinding is used as the new surface to be processed and immersed in the molten mixture so that the irregular edge of the silicon carbide ingot contacts the molten mixture. After 10 minutes, circular mechanical grinding is performed using a 400-mesh grinding wheel. During grinding, the grinding wheel reciprocates on the surface to be processed until a relatively flat circular surface is obtained, completing the entire processing process. During the entire processing process, the silicon carbide ingot does not crack and no new cracks are introduced.
[0063] Example 5
[0064] First, solid sodium hydroxide (NaOH) and potassium permanganate (KMnO4) with a molar ratio of 4:1 are mixed into a crucible and heated to 400°C to prepare a molten mixed solution.
[0065] The raised surface of a 12-inch diameter silicon carbide ingot was immersed in the molten mixture. After 60 minutes, the surface was mechanically ground using a 1000-mesh grinding wheel. During grinding, the grinding wheel reciprocated on the surface to be processed until a relatively flat surface was obtained.
[0066] The sharp edge of the silicon carbide ingot after surface grinding is used as the new surface to be processed and immersed in the molten mixture so that the irregular edge of the silicon carbide ingot contacts the molten mixture. After 40 minutes, circular mechanical grinding is performed using a 1000-mesh grinding wheel. During grinding, the grinding wheel reciprocates on the surface to be processed until a relatively flat circular surface is obtained, completing the entire processing process. During the entire processing process, the silicon carbide ingot does not crack and no new cracks are introduced.
[0067] It can be seen from the above Examples 1-5 that the processing method of the present invention can effectively reduce the mechanical stress during mechanical grinding and avoid the risk of cracking of the silicon carbide ingot. Moreover, the processing efficiency is extremely high, and a relatively flat, smooth surface, crack-free, and low-stress silicon carbide ingot can be obtained, which effectively improves the yield of subsequent slicing and realizes the preparation of high-quality silicon carbide substrates and the manufacture of devices.
[0068] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0069] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.
Claims
1. A method for processing a silicon carbide ingot, characterized in that: The following steps are involved: Providing a chemical modifier, the chemical modifier comprising a monovalent solid base and a solid oxygen-containing salt type oxidant; heating the chemical modifier to form a molten mixed liquid; The surface to be processed of the silicon carbide crystal ingot is immersed in the molten mixed liquid, and then plane mechanical grinding is performed to process the surface to be processed of the silicon carbide crystal ingot into a plane, wherein the surface to be processed of the silicon carbide crystal ingot includes the edge of the silicon carbide crystal ingot and the convex end of the silicon carbide crystal ingot. During the plane mechanical grinding process, the surface to be processed of the silicon carbide crystal ingot contacts and reacts with the molten mixed liquid, so that the surface to be processed of the silicon carbide crystal ingot becomes porous and loose and its hardness becomes softer.
2. The method for processing a silicon carbide ingot according to claim 1, wherein: The monovalent solid base is at least one of KOH and NaOH.
3. The method for processing a silicon carbide ingot according to claim 1, wherein: The solid oxygen-containing salt type oxidant is at least one of KMnO4 or KIO4.
4. The method for processing a silicon carbide ingot according to claim 1, wherein: The molar ratio of the monovalent solid base to the solid oxyacid salt type oxidant is 2:1-4:
1.
5. The method for processing a silicon carbide ingot according to claim 1, wherein: The surface to be processed of the silicon carbide ingot is immersed in the molten mixed solution and maintained for 10 minutes to 60 minutes, and then subjected to plane mechanical grinding.
6. The method for processing a silicon carbide ingot according to claim 1, wherein: In the step of immersing the surface to be processed of the silicon carbide ingot into the molten mixed solution, the temperature of the molten mixed solution is maintained at 400°C-800°C.
7. The method for processing a silicon carbide ingot according to claim 1, wherein: The plane mechanical grinding adopts a grinding wheel, and the grinding wheel reciprocates on the surface to be processed of the silicon carbide ingot.
8. The method for processing a silicon carbide ingot according to claim 7, wherein: The plane mechanical grinding adopts a grinding wheel with mesh sizes of 200-1000, and the non-grinding surface of the grinding wheel is coated with polytetrafluoroethylene.
9. The method for processing a silicon carbide ingot according to claim 1, wherein: The silicon carbide ingot has a diameter of 2 inches to 12 inches.
10. A method for processing a silicon carbide substrate, characterized in that: A method for processing a silicon carbide ingot comprising the steps of: