Silicon carbide single crystal growth method capable of reducing carbon inclusion
By using a low-inclusion silicon carbide single crystal growth crucible and a TaC-coated graphite component, the source crystal distance is controlled, solving the problem of carbon inclusions in silicon carbide single crystal growth and achieving efficient and high-quality silicon carbide single crystal growth.
Patent Information
- Application Number
- CN202511150639.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-11-14
AI Technical Summary
In the existing silicon carbide single crystal growth process, the graphite crucible is easily corroded, introducing carbon inclusions, which leads to defects and reduced yield, and the utilization rate of raw materials is low.
A low-inclusion silicon carbide single crystal growth crucible is used, along with a TaC-coated graphite component. By controlling the source crystal distance and growth parameters, a closed system is formed, reducing the contact between the silicon carbide single crystal and the graphite material.
It significantly reduces carbon inclusions, improves the quality and purity of silicon carbide single crystals, enhances the utilization rate of raw materials, and reduces production costs.
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Abstract
Description
Technical Field
[0001] This invention relates to a method for growing silicon carbide single crystals with low-carbon inclusions, belonging to the field of crystal growth technology. Background Technology
[0002] Silicon carbide (SiC), as an important third-generation semiconductor material, possesses many excellent physicochemical properties, performance characteristics, and application advantages. SiC exhibits superior thermal conductivity, wide bandgap, high breakdown voltage, high electron saturation drift velocity, good high-temperature resistance, radiation resistance, and corrosion resistance. These properties make it outstanding in high-temperature, high-power, and high-frequency electronic devices, enabling stable operation under high-voltage environments, high-speed switching, and stable operation in high-temperature, radioactive, and corrosive environments. SiC has broad application potential in rail transportation, electric vehicles, high-voltage power transmission and transformation, 5G communications, and photovoltaics. Its excellent physicochemical properties and performance make it one of the most studied semiconductor materials currently under intense research.
[0003] TaC (TaC) has a very high melting point and remains stable at high temperatures, making it suitable for the high-temperature environment of PVT (Polymer Transformation) silicon carbide single crystal growth. TaC's excellent corrosion resistance protects the reaction vessel from the erosion of the silicon carbide source gas phase components, facilitating long-term crystal growth, maintaining the stability of the reaction environment, and preventing the introduction of impurities. TaC has become a promising auxiliary material in the PVT process for growing silicon carbide single crystals, contributing to high-quality growth.
[0004] Physical vapor transport (PVT) is currently a relatively mature method for growing silicon carbide single crystals. In PVT, a silicon carbide seed crystal is placed at the top of the crucible, and the silicon carbide source material for crystal growth is placed at the bottom. Under the influence of a temperature gradient, the source material is heated and sublimated into a gas phase, transported upwards along the crucible wall, and deposited at the seed crystal to grow the silicon carbide single crystal. Most of the excess carbon remains on the surface of the source material, forming a graphite layer. Traditional graphite crucibles are entirely made of graphite. During the source material transport reaction, the graphite material is corroded by the Si component and introduces C to participate in the reaction, significantly reducing the lifespan of ordinary graphite components. Furthermore, carbon particles inside the graphite and residual carbon particles in the source material flow with the gas components to the crystal growth interface and are encapsulated as the crystal grows, forming carbon inclusions inside the single crystal. These inclusions can induce defects such as microtubules, dislocations, and stacking faults, severely affecting the quality of the silicon carbide. In addition, excessive residual carbon significantly reduces the utilization rate of raw materials and may introduce defects, increasing the cost of silicon carbide single crystal growth and reducing the yield. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a method for growing silicon carbide single crystals with low-carbon inclusions.
[0006] Terminology Explanation: Near-equilibrium state: In this invention, it refers to a growth state in which the sublimation amount of silicon carbide source material is approximately 1:1 with the crystallization amount of the crystal, and the components in the growth system are relatively uniformly distributed with temperature.
[0007] Source-to-crystal distance: In this invention, it refers to the distance between the surface of the silicon carbide source material and the lower surface of the silicon carbide seed crystal. A small source-to-crystal distance of 3-10 mm is used in this invention.
[0008] Raw material utilization rate per unit time: In this invention, this refers to the ratio of silicon carbide raw material mass to silicon carbide single crystal mass per unit time during silicon carbide single crystal growth. From the perspective of silicon carbide single crystal preparation cost, a higher raw material utilization rate per unit time indicates higher crystal growth efficiency.
[0009] Porosity: In this invention, porosity refers to the ratio of the total pore volume inside the silicon carbide source material to the total volume of the source material. If the grown silicon carbide source material undergoes sublimation, a large amount of Si component sublimates, resulting in more residual carbon in the source material and increasing porosity. Decreased porosity indicates that the sublimated gaseous components were not effectively transported to the growth chamber, leading to secondary crystallization within the source material. After growth, uniform and relatively large porosity in each region reflects high source material utilization. The porosity can be assessed by evaluating the shape of the source material after single-crystal growth to determine the state of the silicon carbide source material.
[0010] Graphitization degree of the source material: In this invention, graphitization refers to the process where, after the source material participates in single crystal growth, the Si component preferentially escapes, and the remaining C component transforms into graphite in the source region. The degree of graphitization refers to the ratio of the volume of fully graphitized source material to the total volume of the source material when growing the same mass of silicon carbide single crystals. From the perspective of source material utilization, under the same single crystal growth quality conditions, a higher degree of graphitization indicates a higher source material utilization rate.
[0011] Mass transfer process: In this invention, it refers to the process in which the source material is decomposed into gaseous substances such as Si, Si2C, and SiC2 by heat during the growth of silicon carbide single crystals and then sublimated and transported to the crystal surface.
[0012] Source material radial temperature gradient: In this invention, this refers to the temperature difference per unit length between the center and edge of the silicon carbide source material surface. A large radial temperature gradient causes the source material at the edges to agglomerate towards the center, which is detrimental to the transport of growth components to the growth cavity. A smaller radial temperature gradient is beneficial for crystal growth.
[0013] Axial temperature gradient of the source material: In this invention, it refers to the temperature difference between the center of the surface and the center of the bottom of the silicon carbide source material per unit length. A large axial temperature gradient causes the sublimated components to crystallize on the surface of the material, which is not conducive to the transport of growth components to the growth chamber. A smaller axial temperature gradient is conducive to the development of the grown crystals.
[0014] This invention is achieved through the following technical solution: A method for growing silicon carbide single crystals with low carbon inclusions, wherein the method uses a low-inclusion silicon carbide single crystal growth crucible, the low-inclusion silicon carbide single crystal growth crucible includes a crucible body and a crucible cover that are connected in a sealed manner, a graphite bottom plate is provided at the bottom of the crucible body, a graphite side ring is provided on the side wall of the crucible body, and a graphite ring is provided on the crucible cover. The growth method includes the following steps: 1) Spread the silicon carbide polycrystalline block, which serves as the source material for silicon carbide single crystal growth, evenly on the graphite substrate, and fix the silicon carbide seed crystal inside the graphite ring of the crucible lid. 2) Seal the low-inclusion silicon carbide single crystal growth crucible, place it in the growth equipment, seal the growth equipment, and evacuate the inside of the growth equipment. 3) Heat the single crystal growth equipment, fill the growth chamber of the growth equipment with carrier gas, and adjust the temperature and pressure inside the single crystal growth equipment to the preset values; 4) After the crystal growth is completed, the inside of the single crystal growth equipment is cooled down, and the carrier gas is introduced to the preset cooling pressure. After cooling to room temperature, silicon carbide single crystal is obtained.
[0015] According to a preferred embodiment of the present invention, the thickness of the graphite substrate is 2-10 mm, and the surface is coated with a TaC coating with a thickness of 10-40 μm.
[0016] According to a preferred embodiment of the present invention, the thickness of the graphite side ring is 2-10 mm, and the surface is coated with a TaC coating with a thickness of 10-40 μm.
[0017] According to a preferred embodiment of the invention, the height of the graphite side ring extends from the top to the bottom of the crucible body.
[0018] According to a preferred embodiment of the present invention, the surface of the graphite ring is coated with a TaC coating, the thickness of which is 10-40 μm.
[0019] According to a preferred embodiment of the present invention, the inner diameter of the graphite ring is 150-300 mm.
[0020] According to a preferred embodiment of the present invention, when the crucible body and the crucible lid are connected, the graphite ring is in close contact with the side wall of the crucible body and abuts against the graphite side ring. This arrangement is used to isolate the silicon carbide polycrystalline block, the silicon carbide single crystal growth region, and the inner wall of the crucible.
[0021] According to a preferred embodiment of the present invention, in step 1), the silicon carbide polycrystalline block is a silicon carbide polycrystalline block with large particle size, high quality, and irregular shape.
[0022] According to a preferred embodiment of the present invention, in step 1), the particle size of the silicon carbide polycrystalline block is 5-20 mm.
[0023] According to a preferred embodiment of the present invention, in step 1), the distance between the silicon carbide polycrystalline block and the seed crystal is 3-10 mm.
[0024] According to a preferred embodiment of the present invention, in step 1), the thickness of the silicon carbide polycrystalline block is 40-60 mm.
[0025] According to a preferred embodiment of the present invention, in step 3), the single crystal growth temperature is 2000 ~ 2400℃, the growth pressure is 1 ~ 30 mbar, and the growth time is 100 ~ 200 h.
[0026] The distance between the silicon carbide polycrystalline block and the seed crystal in this invention is a small source-crystal distance of 3-10 mm. The effects achieved by this distance are: 1) to make the crystallization zone and the sublimation zone close to each other, ensuring that the sublimation amount of silicon carbide source material is approximately 1:1 with the crystallization amount of the crystal, and reducing defects caused by Si or C rich components, such as carbon inclusions, microtubes, etc.; 2) to shorten the growth mass transfer distance, making it easier and faster for components to be transported to the surface of the seed crystal for recrystallization, thereby increasing the growth rate.
[0027] This invention uses large-particle-size, high-quality, irregularly shaped silicon carbide polycrystalline blocks as growth source materials, achieving the following effects: 1) High purity of the source material, effectively preventing the introduction of surface-attached impurities; 2) Large particle size and high quality, making it difficult for large graphite particles after graphitization on the source material surface to be transported into the crystal by the growth gas flow, reducing carbon inclusions; 3) Large particle size, making it easy for the graphite layer after graphitization on the source material surface to fully react with the excess silicon component in the system, improving the effective utilization rate of the source material.
[0028] The overall effects achieved by the low-inclusion silicon carbide single crystal growth crucible of this invention are: 1) It blocks the growth components from contacting the graphite material, preventing graphite corrosion from introducing carbon inclusions; 2) The tantalum carbide coating will not be corroded and can be reused; 3) The growth system is in a closed state, improving the utilization rate of raw materials.
[0029] Technical features and advantages of the present invention: 1. The silicon carbide single crystal growth method of the present invention uses a low-inclusion silicon carbide single crystal growth crucible, and the obtained silicon carbide single crystal has very few carbon inclusions, which greatly reduces the carbon inclusions in the silicon carbide single crystal.
[0030] 2. The silicon carbide single crystal growth method of the present invention has a fast single crystal growth rate and obtains high-quality crystals with high efficiency.
[0031] 3. The silicon carbide single crystal growth method of the present invention uses a low-inclusion silicon carbide single crystal growth crucible, and the graphite parts coated with TaC coating have a high reusability rate, which can save costs.
[0032] 4. The silicon carbide single crystal growth method of the present invention has a high effective utilization rate of silicon carbide source material during the growth of silicon carbide single crystals, and the obtained silicon carbide crystals have high purity. Attached Figure Description
[0033] The accompanying drawings, which constitute a part of this invention, are used to provide a further understanding of the invention. The illustrative examples and descriptions of the invention are used to explain the invention and do not constitute an improper limitation of the invention.
[0034] Figure 1 This is a schematic diagram of the crucible structure in this invention.
[0035] Figure 1 In the diagram: 1. Silicon carbide seed crystal; 2. Silicon carbide single crystal growth region; 3. Silicon carbide polycrystalline block; 4. Graphite substrate; 5. Graphite crucible; 6. Graphite side ring; 7. Graphite ring.
[0036] Figure 2 This is a crystal image of the crystal without inclusions and microtubules grown in Example 1; Figure 3 This is a crystal image of Comparative Example 1, showing a large number of inclusions and microtubules.
[0037] Figure 4 This is a diagram of a crystal with numerous inclusions and microtubules grown in Comparative Example 2. Detailed Implementation
[0038] To further understand the content of this invention, a detailed description is provided in conjunction with the accompanying drawings.
[0039] The present application will now be described in further detail with reference to the accompanying drawings. It is understood that the terms "graphite side ring," "graphite ring," and "graphite plate" used in the drawings are for the convenience of describing the technical solution of this application and have no specific limiting effect; they are all general terms and do not constitute a limitation on the technical solution of this application.
[0040] A method for growing silicon carbide single crystals with low carbon inclusions, wherein the method uses a low-inclusion silicon carbide single crystal growth crucible, the low-inclusion silicon carbide single crystal growth crucible includes a crucible body and a crucible cover that are connected in a sealed manner, a graphite bottom plate is provided at the bottom of the crucible body, a graphite side ring is provided on the side wall of the crucible body, and a graphite ring is provided on the crucible cover. The growth method includes the following steps: 1) Spread the silicon carbide polycrystalline block, which serves as the source material for silicon carbide single crystal growth, evenly on the graphite substrate, and fix the silicon carbide seed crystal inside the graphite ring of the crucible lid. 2) Seal the low-inclusion silicon carbide single crystal growth crucible, place it in the growth equipment, seal the single crystal growth equipment, and evacuate the inside of the growth equipment. 3) Heat the single crystal growth equipment, fill the growth chamber of the growth equipment with carrier gas, and adjust the temperature and pressure inside the single crystal growth equipment to reach the preset values; the single crystal growth temperature is 2000 ~ 2400℃, the growth pressure is 1 ~ 30mbar, and the growth time is 100 ~ 200 h; 4) After the crystal growth is completed, the inside of the single crystal growth equipment is cooled down, and the carrier gas is introduced to the preset cooling pressure. After cooling to room temperature, silicon carbide single crystal is obtained.
[0041] The thickness of silicon carbide single crystals is measured to evaluate the thickness growth rate of silicon carbide crystals.
[0042] The thickness of silicon carbide single crystal in this invention refers to the thickness at the center of the crystal, which can be measured by vernier calipers.
[0043] In some other embodiments, the method for evaluating the utilization rate of silicon carbide source material further includes: Weigh the prepared silicon carbide single crystal and the remaining silicon carbide source material in the crucible to evaluate the source material utilization rate per unit time.
[0044] The raw material utilization rate refers to the ratio of the mass of raw material converted into silicon carbide single crystals per unit time to the mass of raw material lost per unit time.
[0045] In some other embodiments, the method for evaluating silicon carbide carbon inclusions further includes: The distribution of carbon inclusions and black haze inside silicon carbide crystals can be directly observed with the aid of inclusion magnifying glasses, inclusion illumination lamps, etc.
[0046] Example 1: A method for growing silicon carbide single crystals with low carbon inclusions, wherein the method employs a low-inclusion silicon carbide single crystal growth crucible, the structure of which is as follows: Figure 1 As shown, the crucible includes a sealed crucible body and a crucible lid. A graphite base plate is provided at the bottom of the crucible body, and graphite side rings are provided on the side walls of the crucible body. A graphite ring is provided on the crucible lid. The graphite plate is 3 mm thick and coated with a TaC coating with a thickness of 30 μm. The graphite side rings are 57 mm high and 2 mm thick, and coated with a TaC coating with a thickness of 30 μm. The graphite rings are also coated with a TaC coating with a thickness of 30 μm.
[0047] The growth method steps are as follows: 1) Spread large-diameter, irregularly shaped silicon carbide polycrystalline blocks with a particle size of 5 mm evenly on a graphite plate coated with TaC, with a source crystal spacing of 3 mm and a spreading thickness of 48 mm. Adhere one silicon carbide seed crystal to the top of the crucible, cover the crucible with the lid, and form a graphite-free TaC closed system. 2) Place the crucible in the single crystal growth furnace and evacuate it. Fill the furnace with carrier gas to a growth pressure of 10 mbar, heat the graphite crucible to 2050℃ for crystal growth, hold for 100 h, and cool the system to room temperature after growth to obtain silicon carbide single crystals.
[0048] 3) In the TaC closed system, the small source crystal spacing causes the excessive Si component to corrode the C-type layer on the surface of the large SiC particles, which can reduce carbon inclusions and improve the utilization rate of the source material.
[0049] The crystal obtained by growth in this embodiment is as follows: Figure 2 As shown; from Figure 2 It can be seen that there are basically no carbon inclusions in the crystal; at the same time, the graphite parts of TaC are not corroded and can be reused.
[0050] Example 2: A method for growing silicon carbide single crystals with low carbon inclusions, wherein the method employs a low-inclusion silicon carbide single crystal growth crucible, the structure of which is as follows: Figure 1 As shown, the crucible includes a sealed crucible body and a crucible lid. A graphite base plate is provided at the bottom of the crucible body, and graphite side rings are provided on the side walls of the crucible body. A graphite ring is provided on the crucible lid. The graphite plate is 3 mm thick and coated with a TaC coating with a thickness of 30 μm. The graphite side rings are 52 mm high and 2 mm thick, and coated with a TaC coating with a thickness of 30 μm. The graphite rings are also coated with a TaC coating with a thickness of 30 μm.
[0051] The growth method steps are as follows: 1) Spread large-diameter, irregularly shaped silicon carbide polycrystalline blocks with a particle size of 10 mm evenly on a graphite plate coated with TaC, with a source crystal spacing of 5 mm and a spreading thickness of 48 mm. Attach one silicon carbide seed crystal to the top of the crucible and cover it with the crucible lid to form a graphite-free TaC closed system.
[0052] 2) Place the crucible in the single crystal growth furnace and evacuate it. Fill the furnace with carrier gas to a growth pressure of 5 mbar, heat the graphite crucible to 2150℃ for crystal growth, hold for 100 h, and then cool the system to room temperature to obtain silicon carbide single crystals.
[0053] 3) In the TaC closed system, the small source crystal spacing causes the excessive Si component to corrode the C-type layer on the surface of the large SiC particles, which can reduce carbon inclusions and improve the utilization rate of the source material.
[0054] In this embodiment, the crystal obtained by growth has no carbon inclusions; the TaC-plated graphite part is not corroded and can be reused.
[0055] Example 3: A method for growing silicon carbide single crystals with low carbon inclusions, wherein the method employs a low-inclusion silicon carbide single crystal growth crucible, the structure of which is as follows: Figure 1 As shown, the crucible includes a sealed crucible body and a crucible lid. A graphite base plate is provided at the bottom of the crucible body, and graphite side rings are provided on the side walls of the crucible body. A graphite ring is provided on the crucible lid. The graphite plate is 3 mm thick and coated with a TaC coating with a thickness of 30 μm. The graphite side ring is 57 mm high and 2 mm thick, and coated with a TaC coating with a thickness of 30 μm. The graphite ring is coated with a TaC coating with a thickness of 30 μm.
[0056] The growth method steps are as follows: 1) Spread large-diameter, irregularly shaped silicon carbide polycrystalline blocks with a particle size of 20 mm evenly on a graphite plate coated with TaC, with a source crystal distance of 10 mm and a spreading thickness of 48 mm. Attach one silicon carbide seed crystal to the top of the crucible and cover it with the crucible lid to form a graphite-free TaC closed system.
[0057] 2) Place the crucible in the single crystal growth furnace and evacuate it. Fill the furnace with carrier gas to a growth pressure of 2 mbar, heat the graphite crucible to 2400℃ for crystal growth, hold for 60 hours, and then cool the system to room temperature to obtain silicon carbide single crystals.
[0058] 3) In the TaC closed system, the small source crystal spacing allows the excess Si component to corrode the C-type layer on the surface of the large SiC source material, which can reduce carbon inclusions and improve the source material utilization rate. In this embodiment, the crystals obtained by growth have no carbon inclusions; the TaC-plated graphite parts are not corroded and can be reused.
[0059] Comparative Example 1 The method for growing silicon carbide single crystals with low-carbon inclusions as described in Example 1 differs in that: The graphite parts were not coated with TaC, and the other growth conditions were exactly the same as in Example 1.
[0060] In a closed system, the small source intergrowth distance causes excessive Si components to corrode the C-type layer on the surface of large SiC particles. However, because the graphite parts are not coated with TaC, the crucible walls and graphite parts are severely corroded. Although Comparative Example 1 has a higher source material utilization rate, compared with the crystals grown in Example 1, the crystals of Comparative Example 1 introduce a large number of carbon inclusions, such as... Figure 3 .
[0061] Comparative Example 2 The method for growing silicon carbide single crystals with low-carbon inclusions as described in Example 1 differs in that: The particle size of the silicon carbide source material was 2 mm, and other growth conditions were exactly the same as in Example 1.
[0062] In a TaC closed system, small-particle source materials more easily release excess Si components and corrode the carbide layer on the surface of the small SiC particles, which can improve the source material utilization rate. The TaC-plated graphite parts are not corroded and can be reused. However, the fine carbon particles formed by the small-particle source materials easily participate in crystal growth along with component transport. In this comparative example, the crystals obtained produced more carbon inclusions and formed a black haze, such as... Figure 4 As shown.
[0063] Comparative Example 3 The method for growing silicon carbide single crystals with low-carbon inclusions as described in Example 1 differs in that: The source-to-crystal distance was 60 mm, and other growth conditions were exactly the same as in Example 1.
[0064] In the TaC enclosed system, the larger source-to-crystal distance causes excessive Si components to concentrate in the upper region, making it impossible to corrode the C-coating layer on the surface of the large SiC particles. This results in a lower source material utilization rate in Comparative Example 3 compared to Example 1. At the same time, the larger source-to-crystal distance increases the axial temperature gradient, causing C powder particles in the source material to be transported to the crystal growth region by the airflow, resulting in carbon inclusions in the crystals grown in Comparative Example 3. The TaC-coated graphite parts did not show any corrosion and can be reused.
Claims
1. A method for growing silicon carbide single crystals with low carbon inclusions, the method using a low-inclusion silicon carbide single crystal growth crucible, the low-inclusion silicon carbide single crystal growth crucible comprising a crucible body and a crucible cover connected in a sealed manner, a graphite base plate being provided at the bottom of the crucible body, a graphite side ring being provided on the side wall of the crucible body, and a graphite ring being provided on the crucible cover. The growth method includes the following steps: 1) Spread the silicon carbide polycrystalline block, which serves as the source material for silicon carbide single crystal growth, evenly on the graphite substrate, and fix the silicon carbide seed crystal inside the graphite ring of the crucible lid. 2) Seal the low-inclusion silicon carbide single crystal growth crucible, place it in the growth equipment, seal the growth equipment, and evacuate the inside of the growth equipment. 3) Heat the single crystal growth equipment, fill the growth chamber of the growth equipment with carrier gas, and adjust the temperature and pressure inside the single crystal growth equipment to the preset values; 4) After the crystal growth is completed, the inside of the single crystal growth equipment is cooled down, and the carrier gas is introduced to the preset cooling pressure. After cooling to room temperature, silicon carbide single crystal is obtained.
2. The silicon carbide single crystal growth method according to claim 1, characterized in that, The graphite substrate is 2-10 mm thick and has a TaC coating with a thickness of 10-40 μm.
3. The silicon carbide single crystal growth method according to claim 1, characterized in that, The thickness of the graphite side ring is 2-10 mm, and the surface is coated with a TaC coating with a thickness of 10-40 μm.
4. The silicon carbide single crystal growth method according to claim 1, characterized in that, The height of the graphite side ring extends from the top to the bottom of the crucible body.
5. The silicon carbide single crystal growth method according to claim 1, characterized in that, The surface of the graphite ring is coated with a TaC coating with a thickness of 10-40 μm.
6. The silicon carbide single crystal growth method according to claim 1, characterized in that, The inner diameter of the graphite ring is 150-300 mm.
7. The silicon carbide single crystal growth method according to claim 1, characterized in that, When the crucible body and the crucible lid are connected, the graphite ring is in close contact with the side wall of the crucible body and is aligned with the graphite side ring.
8. The method for growing silicon carbide single crystals according to claim 1, characterized in that, In step 1), the silicon carbide polycrystalline block is a large-particle-size, high-quality, irregularly shaped silicon carbide polycrystalline block with a particle size of 5-20 mm.
9. The method for growing silicon carbide single crystals according to claim 1, characterized in that, In step 1), the distance between the silicon carbide polycrystalline block and the seed crystal is 3-10 mm, and the thickness of the silicon carbide polycrystalline block is 40-60 mm.
10. The method for growing silicon carbide single crystals according to claim 1, characterized in that, In step 3), the single crystal growth temperature is 2000 ~ 2400℃, the growth pressure is 1 ~ 30 mbar, and the growth time is 100 ~ 200 h.