Silicon Carbide Crystal Growth Apparatus, System and Method

Abstract

The present invention discloses a silicon carbide crystal growth device, which relates to the technical field of silicon carbide crystal growth. A cylindrical filtering component is arranged in a crucible component, and an annular raw material cavity for placing silicon carbide raw materials is formed between the outer wall of the filtering component and the inner wall of the crucible component; in the present invention, the annular raw material cavity is arranged close to the inner wall of the crucible component, ensuring the temperature uniformity of the raw material area and avoiding recrystallization of the silicon carbide raw materials during mass transfer; moreover, the filtering component can block graphitized particles, reducing the generation of carbon inclusions; the material of the flow guiding ring is graphite, and a planar blocking area is formed on its lower surface. When the silicon-rich gas phase component contacts the lower surface of the flow guiding ring at the initial stage of silicon carbide crystal growth, the gas phase component SiC is generated by reaction, reducing the adverse effects brought by the silicon-rich atmosphere. The present invention also discloses a silicon carbide crystal growth method, which pre-treats the silicon carbide raw materials by means of heating-holding-cooling to improve the quality of the generated silicon carbide crystals.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide crystal growth, and particularly to a silicon carbide crystal growth device, system and method. Background Art

[0002] As a stable compound of carbon and silicon, silicon carbide has become an excellent material for high-frequency, high-power, and high-temperature semiconductor devices due to its special physical structure properties and electrical and optical properties of different polytypes, thus promoting the technological development of the related equipment manufacturing industry. At present, the main preparation methods of silicon carbide are liquid phase epitaxy (LPE), chemical vapor deposition (CVD), and physical vapor transport (PVT). The most mature method for commercial silicon carbide growth is the PVT method. In this method, a carbon-silicon compound raw material is placed in the high-temperature zone of a crystal growth container. By controlling the temperature in the growth container, the carbon-silicon compound raw material is continuously heated to the sublimation temperature. The sublimated carbon-silicon compound raw material rises and condenses on a silicon carbide seed crystal with a lower temperature. Under continuous sublimation conditions, the reaction proceeds continuously, and crystals continuously accumulate and grow on the silicon carbide seed crystal to form a complete silicon carbide crystal.

[0003] As Figure 1 shown, in the existing crystal growth container, with the increase of the crucible diameter, the skin effect of induction heating (the maximum current density of induction heating appears on the surface layer of the cross-section of the heated body and decays towards the center with the law of an exponential function. This phenomenon is called the skin effect, manifested as a large amount of heat generation and high temperature on the surface, and less heat generation and low temperature in the center, resulting in a large regional temperature difference) will become more obvious. The temperature difference in the raw material area will be further amplified, making it very difficult to achieve uniform temperature in the raw material area. Similar problems also exist in the resistance heating method.

[0004] And the regional temperature difference will inevitably cause differences in the evaporation rate of the raw materials. As the crystal growth time progresses, the difference in the evaporation amount of the silicon carbide raw materials between the inner surface layer and the central area of the crucible continues to increase, manifested as the powder on the inner surface layer of the crucible tending to graphitize, and the powder in the central area tending to recrystallize (the volume density of silicon carbide increases after recrystallization). As Figure 2As shown in the figure. Due to the large difference in thermal conductivity between graphite and recrystallized silicon carbide, the temperature field is continuously redistributed. That is to say, during the crystal growth process, the temperature field distribution in the raw material area is in a dynamic change process, which increases the uncertainty of the decomposed gas components of silicon carbide in different regions and different crystal growth stages; in addition, there is a high probability that the recrystallization in the low-temperature area will block the transmission channels of the gas components of silicon carbide. All these undoubtedly make the gas components and diffusion fluxes out of control at different growth interfaces, greatly increasing the process difficulty and reducing the yield of crystal growth. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a silicon carbide crystal growth device, which can ensure the temperature uniformity in the raw material area, effectively avoid the recrystallization of silicon carbide raw materials during the mass transfer process, and can reduce the generation of carbon inclusions in silicon carbide crystals and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a silicon carbide crystal growth device, including a crucible assembly, and a seed crystal assembly is arranged in the crucible assembly; a cylindrical filtering assembly is further arranged in the crucible assembly, and an annular raw material cavity for placing silicon carbide raw materials is formed between the outer wall of the filtering assembly and the inner wall of the crucible assembly. A sealing assembly for preventing the leakage of silicon carbide gas components is arranged at the top of the annular raw material cavity; the filtering assembly can block the silicon carbide raw materials and allow the silicon carbide gas components generated after heating the silicon carbide raw materials to pass through; a diversion ring is arranged on the sealing assembly, the seed crystal assembly is arranged at the top of the diversion ring, and the bottom is lapped on the sealing assembly. The inner wall of the diversion ring protrudes inwards from the inner wall of the filtering assembly, and a flat blocking area is formed on the lower surface of the diversion ring, wherein the diversion ring is a graphite diversion ring.

[0008] Preferably, the filtering assembly is a cylindrical filter net, the crucible assembly is a cylindrical crucible assembly, the filter net is coaxially arranged with the crucible assembly, and the bottom of the filter net is in sealed contact with the bottom of the crucible assembly.

[0009] Preferably, the porosity of the filter net is 20%-80%, the aperture of the filter holes of the filter net is 1μm-1000μm, and the average aperture of the filter holes of the filter net is 40μm-60μm.

[0010] Preferably, the porosity of the filter net is 30%-60%, and the aperture of the filter holes of the filter net is 20μm-80μm.

[0011] Preferably, the material of the filter screen is high-temperature ceramic material, composite material or graphite material.

[0012] Preferably, the distance between the outer wall of the filter assembly and the inner wall of the crucible assembly is d, and d ≤ 1 / 3D; where D is the diameter of the crucible assembly.

[0013] Preferably, the sealing assembly is a radial heat-conducting ring, and a plurality of radial heat-conducting rings are arranged from top to bottom.

[0014] Preferably, a sealing coating is also coated at the position where the lower surface of the radial heat-conducting ring contacts the annular raw material cavity.

[0015] Preferably, a closing protrusion protruding inward from the inner wall of the diversion ring is provided at the top of the diversion ring, and the closing protrusion forms a bearing ring for bearing the seed crystal assembly. The seed crystal assembly includes:

[0016] A seed crystal support ring placed on the bearing ring;

[0017] A silicon carbide seed crystal placed on the seed crystal support ring;

[0018] A graphite ring gasket placed on the silicon carbide seed crystal;

[0019] An upper pressing cover threadedly connected to the diversion ring, and the upper pressing cover presses the graphite ring gasket, the silicon carbide seed crystal and the seed crystal support ring on the bearing ring.

[0020] Preferably, the sealing assembly includes a first radial heat-conducting ring and a second radial heat-conducting ring arranged from top to bottom, and an isolation cavity is formed between the outer wall of the diversion ring, the inner wall of the second radial heat-conducting ring and the upper pressing cover.

[0021] Preferably, the thickness of the sealing assembly is c, c > 2a, where a is the thickness of the isolation cavity, 3 mm ≤ a ≤ 12 mm; the wall thickness of the diversion ring is b, 3 mm ≤ b ≤ 10 mm.

[0022] Preferably, a protective coating is also coated on the silicon carbide seed crystal.

[0023] Preferably, a graphite paper is also provided above the seed crystal assembly, and the graphite paper covers the cross-section of the cavity of the crucible assembly.

[0024] Preferably, the outer edge of the graphite paper is clamped and fixed by carbon felts, and the carbon felts include an upper carbon felt and a lower carbon felt, and the upper carbon felt and the lower carbon felt are respectively located above and below the graphite paper.

[0025] Preferably, a temperature-measuring blind hole is also provided on the crucible assembly, a temperature-measuring tube is installed on the temperature-measuring blind hole, and the inner cavity of the temperature-measuring tube is isolated from the outside.

[0026] Another object of the present invention is to provide a silicon carbide crystal growth system, which can ensure the temperature uniformity in the raw material area, effectively avoid recrystallization of the silicon carbide raw material during the mass transfer process, and can reduce the generation of carbon inclusions in the silicon carbide crystal and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth.

[0027] To achieve the above object, the present invention provides the following solutions:

[0028] A silicon carbide crystal growth system includes a heating furnace and the above-mentioned silicon carbide crystal growth device, and the silicon carbide crystal growth device is installed in the heating furnace.

[0029] Another object of the present invention is to provide a silicon carbide crystal growth method, which can ensure the temperature uniformity in the raw material area, effectively avoid recrystallization of the silicon carbide raw material during the mass transfer process, and can reduce the generation of carbon inclusions in the silicon carbide crystal and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth; and the silicon carbide raw material is pretreated by a method of heating-up - heat preservation - cooling-down, which can remove trace impurities in the silicon carbide raw material, eliminate the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth, stabilize the crystal form of the silicon carbide raw material, and strengthen and stabilize the mass transfer channel.

[0030] To achieve the above object, the present invention provides the following solutions:

[0031] A silicon carbide crystal growth method includes a raw material pretreatment process and a silicon carbide crystal growth process in the above-mentioned silicon carbide crystal growth device, wherein,

[0032] The raw material pretreatment process includes the following steps:

[0033] S1. Put the silicon carbide raw material into the annular raw material chamber, and then replace the seed crystal assembly with a recyclable temporary growth piece;

[0034] S2. Heat the silicon carbide raw material to a predetermined temperature and keep it warm for a preset time;

[0035] S3. Cool the silicon carbide raw material that has completed heat preservation to room temperature;

[0036] The silicon carbide crystal growth process includes the following steps:

[0037] S4. Replace the flow guiding ring in the silicon carbide crystal growth device used in the raw material pretreatment process with a new flow guiding ring, and replace the temporary growth piece with the seed crystal assembly again, and then carry out silicon carbide crystal growth.

[0038] Preferably, in step S2, the predetermined temperature is 1500°C to 2200°C, the preset time is 3 to 10 hours, and when heating the silicon carbide raw material, the partial pressure in the crucible assembly is ≤ 3 mbar.

[0039] Preferably, the predetermined temperature is 1700°C to 2000°C.

[0040] Preferably, the temporary growth piece includes:

[0041] A seed crystal support ring placed on the top of the flow guide ring, and a graphite paper is placed on the seed crystal support ring;

[0042] A graphite ring gasket placed on the graphite paper;

[0043] An upper pressing cover threadedly connected to the flow guide ring, and the upper pressing cover presses the graphite ring gasket, the graphite paper and the seed crystal support ring against the top of the flow guide ring.

[0044] The present invention has achieved the following beneficial technical effects compared with the prior art:

[0045] The silicon carbide crystal growth device proposed by the present invention is provided with a cylindrical filtering component in the crucible assembly. An annular raw material cavity for placing silicon carbide raw materials is formed between the outer wall of the filtering component and the inner wall of the crucible assembly. The annular raw material cavity is located in a region at a certain distance from the inner wall of the crucible assembly, so that the silicon carbide raw materials are distributed as much as possible near the inner wall of the crucible assembly, reducing the temperature non-uniformity caused by the skin effect, ensuring the temperature uniformity in the raw material region, and effectively avoiding recrystallization during the mass transfer of the silicon carbide raw materials; moreover, the filtering component can block the graphitized particles in the silicon carbide raw materials, reducing the generation of carbon inclusions in the silicon carbide crystal.

[0046] Furthermore, in the present invention, the inner wall of the flow guide ring protrudes inwards from the inner wall of the filtering component, a planar blocking area is formed on the lower surface of the flow guide ring, and the flow guide ring is a graphite flow guide ring; in the initial stage of silicon carbide crystal growth, the gas-phase components generated after heating the silicon carbide raw materials are too rich in silicon. Some of the silicon-rich gas-phase components contact the lower surface of the flow guide ring during movement. At this time, the silicon in the gas-phase components can react with the lower surface of the flow guide ring to generate the gas-phase component SiC, reducing the silicon-carbon ratio in the gas-phase components, thereby reducing the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth; moreover, the lower surface of the flow guide ring can also block the upward transmission of larger particles of C.

[0047] The silicon carbide crystal growth system proposed by the present invention includes a heating furnace and the above-mentioned silicon carbide crystal growth device. The silicon carbide crystal growth device is installed in the heating furnace, which can ensure the temperature uniformity in the raw material area, effectively avoid recrystallization of the silicon carbide raw material during the mass transfer process, and can reduce the generation of carbon inclusions in the silicon carbide crystal and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth.

[0048] The silicon carbide crystal growth method proposed by the present invention includes a raw material pretreatment process and a silicon carbide crystal growth process. The silicon carbide raw material is pretreated by heating-holding-cooling, which can remove trace impurities in the silicon carbide raw material, eliminate the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth, stabilize the crystal form of the silicon carbide raw material, and strengthen and stabilize the mass transfer channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0050] Figure 1 is a schematic structural diagram of a silicon carbide crystal growth container in the prior art;

[0051] Figure 2 is a schematic diagram of the mass transfer path of silicon carbide gas components in the prior art;

[0052] Figures 1-2 In, 200 is the crucible body, 201 is the graphite support, 202 is the graphite paper, 203 is the silicon carbide seed crystal, 204 is the silicon carbide crystal, 205 is the radial heat conduction ring, 206 is the raw material, A is the raw material area, B is the recrystallization area, and G is the silicon carbide crystallization area;

[0053] Figure 3 is a schematic structural diagram of the silicon carbide crystal growth device in the embodiment of the present invention;

[0054] Figure 4 is a schematic diagram of the mass transfer path of silicon carbide gas components in the embodiment of the present invention;

[0055] Figure 5 is a schematic diagram of the inner wall of the crucible assembly, the inner wall of the filter assembly, the outer wall of the filter assembly, and the contact position between the second radial heat conduction ring and the annular raw material cavity of the silicon carbide crystal growth device in the embodiment of the present invention;

[0056] Figure 6 is Figure 5 the enlarged schematic diagram at position I in

[0057] Figure 7 It is a schematic diagram of the computer-simulated thermal field of a silicon carbide crystal growth container in the prior art;

[0058] Figure 8 It is a schematic diagram of the computer-simulated thermal field of a silicon carbide crystal growth device in an embodiment of the present invention;

[0059] Figures 3-6 In the figure, 1 is a crucible assembly, 2 is a first radial heat conduction ring, 3 is a second radial heat conduction ring, 4 is a carbon felt, 5 is a graphite paper, 6 is an upper pressing cover, 7 is a graphite ring gasket, 8 is a seed crystal support ring, 9 is a flow guiding ring, 10 is a silicon carbide seed crystal, 11 is a silicon carbide crystal, 12 is a filtering assembly, 13 is a silicon carbide raw material, 14 is a temperature measuring tube, 15 is a furnace cover, 16 is a threaded connection, 100 is the inner wall of the crucible assembly, 110 is the outer wall of the filtering assembly, 120 is the inner wall of the filtering assembly, 130 is the contact position between the second radial heat conduction ring and the annular raw material cavity, A1 is the annular raw material cavity, C is the filtering area, E is the isolation cavity, F is the planar blocking area, and G1 is the silicon carbide crystallization area. Detailed implementation manners

[0060] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0061] One of the purposes of the present invention is to provide a silicon carbide crystal growth device, which can ensure the temperature uniformity in the raw material area, effectively avoid recrystallization of the silicon carbide raw material during the mass transfer process, and can reduce the generation of carbon inclusions in the silicon carbide crystal and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth.

[0062] Another purpose of the present invention is to provide a silicon carbide crystal growth system, which can ensure the temperature uniformity in the raw material area, effectively avoid recrystallization of the silicon carbide raw material during the mass transfer process, and can reduce the generation of carbon inclusions in the silicon carbide crystal and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth.

[0063] Another object of the present invention is to provide a method for growing silicon carbide crystals, which can ensure the temperature uniformity in the raw material region, effectively avoid recrystallization of silicon carbide raw materials during mass transfer, and can reduce the generation of carbon inclusions in silicon carbide crystals and reduce the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth; moreover, the silicon carbide raw materials are pretreated by heating-holding-cooling, which can remove trace impurities in the silicon carbide raw materials, eliminate the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth, stabilize the crystal form of the silicon carbide raw materials, and strengthen and stabilize the mass transfer channel.

[0064] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1

[0066] As Figures 3-6 shown, this embodiment provides a silicon carbide crystal growth device, which includes a crucible assembly 1, and a seed crystal assembly is arranged in the crucible assembly 1; a cylindrical filtering assembly 12 is also arranged in the crucible assembly 1, and an annular raw material cavity A1 for placing silicon carbide raw materials 13 is formed between the outer wall of the filtering assembly 12 and the inner wall of the crucible assembly 1. A sealing assembly for preventing the leakage of silicon carbide gas-phase components is arranged at the top of the annular raw material cavity A1. The annular raw material cavity A1 is located in a region at a certain distance from the inner wall 100 of the crucible assembly. Since it is arranged as close as possible to the inner wall 100 of the crucible assembly, the radial temperature difference in the annular raw material cavity A1 can be reduced, the temperature uniformity in the annular raw material cavity A1 can be ensured, the influence caused by the skin effect can be reduced as much as possible, and at the same time, recrystallization of the silicon carbide raw materials 13 in the annular raw material cavity A1 at the filtering assembly 12 and in the raw material region during mass transfer can be avoided; wherein, the filtering assembly 12 can block the silicon carbide raw materials 13 and allow the silicon carbide gas-phase components generated after heating the silicon carbide raw materials 13 to pass through.

[0067] Further, a flow guiding ring 9 is provided on the sealing assembly. A seed crystal assembly is provided at the top of the flow guiding ring 9 and is lapped on the sealing assembly at the bottom. The inner wall of the flow guiding ring 9 protrudes inwards from the inner wall of the filtering assembly 12. A planar blocking area F is formed on the lower surface of the flow guiding ring 9, and the flow guiding ring 9 is a graphite flow guiding ring made of graphite material. In the initial stage of silicon carbide crystal growth, the silicon carbide gas-phase components generated after heating the silicon carbide raw material 13 are overly rich in silicon. Some of the silicon-rich gas-phase components contact the lower surface of the flow guiding ring 9 during movement. At this time, the silicon in the gas-phase components can react with the lower surface of the flow guiding ring 9 to generate the gas-phase component SiC, reducing the silicon-carbon ratio in the gas-phase components, thereby reducing the adverse effects brought by the silicon-rich atmosphere in the initial stage of silicon carbide crystal growth. Moreover, the lower surface of the flow guiding ring 9 can also block the upward transmission of larger particles of C. Among them, the thickness e of the planar blocking area F is selected according to specific working requirements, and the thickness of the planar blocking area F is the horizontal distance between the inner wall of the flow guiding ring 9 and the inner wall of the filtering assembly 12.

[0068] It should be noted that the crucible assembly 1 is a mature and existing technology in the art and will not be elaborated in this embodiment. It mainly includes a crucible body, and a crucible top cover that can be opened is provided at the top of the crucible body. Among them, the filtering assembly 12, the flow guiding ring 9, and the seed crystal assembly are all located inside the crucible body, and the inner wall of the crucible assembly 1 is the inner wall of the crucible body. Further, the material of the crucible assembly 1 is preferably graphite material, or other materials are selected according to working requirements, and the wall thickness f of the crucible body is set according to specific working requirements.

[0069] In the present invention, the "inward" in the inward protrusion specifically refers to the central position of the crucible assembly 1.

[0070] In this embodiment, the shape of the filtering assembly 12 matches the shape of the crucible assembly 1 and is selected according to specific working requirements, and can be a square tube shape, a cylindrical shape, or other polygonal tube shapes. In this embodiment, the filtering assembly 12 is preferably a cylindrical filter net, and the crucible assembly 1 correspondingly is a cylindrical crucible assembly 1. The filter net is coaxially arranged with the crucible assembly 1, and the bottom of the filter net is in sealing contact with the bottom of the crucible assembly 1. Or, an annular mounting seat can be provided inside the crucible assembly 1, and the bottom of the filter net is in sealing contact with the annular mounting seat.

[0071] In this embodiment, in order to further ensure the temperature uniformity in the annular raw material cavity A1, the distance between the outer wall of the filter net and the inner wall of the crucible assembly 1 (the thickness of the annular raw material cavity A1) is d, and d ≤ 1 / 3D. Further preferably, d ≤ (1 / 6 - 1 / 9)D. Among them, D is the diameter of the crucible assembly 1. In this embodiment, the annular raw material cavity A1 with the above smaller thickness is adopted, which can avoid the influence of the heating device position, different thermal insulation materials, and the crucible assembly 1 structure design on the temperature field in the annular raw material cavity A1 from being aggravated as the inner diameter of the crucible assembly 1 increases.

[0072] Furthermore, in this embodiment, the silicon carbide raw material 13 is in the highest temperature region of the entire crucible assembly 1. Under the condition of the same heating power, the overall temperature of the silicon carbide raw material 13 is high, or a high material temperature can be obtained under the minimum heating power, which can reduce the power loss by 10% - 20%. Moreover, a cylindrical filter screen is adopted, and the filter screen is close to the inner wall of the crucible assembly 1, ensuring a large surface area of the filter screen, thereby increasing the evaporation area of the silicon carbide raw material 13 and improving the growth rate of the silicon carbide crystal 11.

[0073] In this embodiment, the thermal conductivity of the material of the filter screen is preferably less than or equal to 20 w / (m·k) to avoid forming a supercooled wall at the filter screen.

[0074] In this embodiment, the filter screen is a porous filter material, which can not only filter out the graphitized fine particles, but also serve as a diffusion channel for the gas-phase components of silicon carbide to ensure uniform, continuous, and stable gas-phase transmission; and the porosity of the porous filter material will affect the diffusion flux of the gas-phase components of silicon carbide. Therefore, porous filter materials with different porosities can be selected to adjust the growth rate of the silicon carbide crystal 11. In this embodiment, the material of the filter screen is preferably a high-temperature ceramic material, a composite material, a graphite material with a relatively high strength (bending strength greater than 2.5 Mpa, compressive strength greater than 4 Mpa), etc.; among them, the high-temperature ceramic material refers to a ceramic material with a melting temperature higher than 3000 °C, such as TaC (tantalum carbide) ceramic, ZrC (zirconium carbide) ceramic, NbC (niobium carbide) ceramic, etc., and the composite material is a graphite-ceramic composite material, a graphite material with a coating, etc.; further, the graphite-ceramic composite material specifically includes one or more of C-TaC, C-ZrC, C-NbC, etc., and the coating in the graphite material with a coating is a TaC coating.

[0075] In this embodiment, the porosity of the filter screen is 20% - 80%, preferably 30% - 60%; the pore size distribution of the filter holes of the filter screen is required to be between 1 μm and 1000 μm. For example, it can be 1 μm, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 500 μm, 510 μm, 980 μm, 1000 μm, etc. The pore size of the filter holes of the filter screen is preferably 20 μm - 80 μm, and further preferably 40 μm - 60 μm; the average pore size of the filter holes of the filter screen is between 40 μm and 60 μm.

[0076] In this embodiment, the filter screen can filter out fine graphitized particles. Through the isolation and shielding of the filter screen, common carbon inclusions that appear in the middle and late stages of the growth of silicon carbide crystal 11 are avoided. Under such conditions, a lower growth pressure (such as 1 mbar) can also be achieved. The lower growth pressure is beneficial to the stability of the 4H-SiC crystal form. At the same time, by adjusting the diameters and axial dimensions of the filter screen and the crucible assembly 1, the growth rate of silicon carbide crystal 11 can be changed, which also brings greater flexibility to the adjustment of the growth rate of silicon carbide crystal 11.

[0077] In this embodiment, the upper side wall of the crucible assembly 1 bulges outward (i.e., bulges in the direction away from the center position of the crucible assembly 1), forming an annular mounting platform on the inner wall of the crucible assembly 1. The outer bottom of the sealing assembly is lapped on this mounting platform. The inner bottom of the sealing assembly is provided with an annular lapping platform that protrudes inward from its inner wall. The bottom of the lapping platform is lapped on the top of the filter screen, and the bottom of the diversion ring 9 is lapped on the top of the lapping platform.

[0078] In this embodiment, the sealing assembly is preferably a radially heat-conducting ring. While sealing the top of the annular raw material chamber A1, the radially heat-conducting ring can conduct heat. The material of the radially heat-conducting ring is preferably a highly dense graphite material. The so-called highly dense graphite material means that the porosity of the graphite material is ≤10% to prevent the leakage of silicon carbide gas-phase components through the radially heat-conducting ring.

[0079] In this embodiment, there are multiple radially heat-conducting rings arranged from top to bottom, and the specific number can be selected according to the working needs. Preferably, two radially heat-conducting rings are provided, including a first radially heat-conducting ring 2 and a second radially heat-conducting ring 3 arranged in sequence from top to bottom. Among them, the lower surface of the second radially heat-conducting ring 3 seals the top of the annular raw material chamber A1. Further, as Figure 5 shown, a sealing coating is also applied at the contact position 130 between the second radially heat-conducting ring and the annular raw material chamber to further reduce the permeability of the interface at the contact position 130 between the second radially heat-conducting ring and the annular raw material chamber to the silicon carbide gas-phase components. Among them, the sealing coating is preferably a TaC coating. In this embodiment, the radially heat-conducting ring includes a first radially heat-conducting ring 2 and a second radially heat-conducting ring 3 that are separately arranged, and there is a gap between the first radially heat-conducting ring 2 and the second radially heat-conducting ring 3. Combining with the gas path design, it is convenient for the discharge of some impurities and silicon-rich gas-phase components in the initial stage of silicon carbide crystal growth.

[0080] As Figure 4 shown, the mass transfer process of the silicon carbide gas-phase components in this embodiment is as follows: In the annular raw material chamber A1, it travels along the radial direction through a very short distance from the inner wall 100 of the crucible assembly to the outer wall 110 of the filter assembly at a slightly lower temperature, then passes through the filter assembly 12 to the inner wall 120 of the filter assembly, and finally, under the driving force of the axial temperature gradient, it flows unobstructedly to the silicon carbide crystallization region G1.

[0081] In this embodiment, the temperature difference in the raw material region is very small, and the diffusion rate of the silicon carbide gas-phase components is fast, which can effectively avoid the recrystallization of the silicon carbide raw material 13, ensuring the stability and persistence of mass transfer. The main advantages are as follows:

[0082] 1. As the evaporation of the silicon carbide raw material 13 proceeds, the change trends of the silicon carbide raw material 13 in different regions are the same, ensuring that during the entire growth process of the silicon carbide crystal 11, the silicon carbide gas-phase components are always in a uniform and stable transport state, improving the growth quality of the silicon carbide crystal 11 and the stability of the process;

[0083] 2. The temperature gradient in the raw material region is very small, avoiding the recrystallization of the silicon carbide gas-phase components in the raw material region and achieving directional crystallization only at the silicon carbide seed crystal 10, which is beneficial to the improvement of the growth rate of the silicon carbide crystal 11;

[0084] 3. It is beneficial to the use of silicon carbide fine powder (the mesh number of the silicon carbide powder ≤ 40) to increase the evaporation area of the silicon carbide powder, which can further improve the growth rate of the silicon carbide crystal;

[0085] 4. There is no recrystallization of the silicon carbide powder during the mass transfer process, improving the stability of mass transfer, and thus the utilization rate of the silicon carbide raw material 13 can be greatly increased, which is especially significant for breaking through the growth thickness of the silicon carbide crystal 11 and can easily reach a growth thickness of more than 35 mm.

[0086] In this embodiment, a cylindrical filter screen with a certain thickness is used as a barrier, and the silicon carbide raw material 13 is distributed within a certain thickness range on the inner surface layer of the crucible assembly 1. The upper part of the annular raw material chamber A1 is sealed with a sealing component, and it can also be used for the growth of large-size silicon carbide crystals 11; specifically, for the growth of silicon carbide crystals 11 with a size of more than 8 inches, only the loading depth needs to be increased, that is, the height of the annular raw material chamber A1 is increased, and the growth of large-size silicon carbide crystals 11 can be achieved; as Figure 7 and Figure 8 shown, through the silicon carbide crystal 11 growth practice and computer thermal field simulation demonstration, in this embodiment, the axial temperature difference and the radial temperature difference at most positions in the raw material region are greatly reduced, ensuring the consistency of the decomposed gas-phase components of the silicon carbide raw material 13 and greatly weakening or avoiding the recrystallization problem of the silicon carbide raw material, thereby ensuring uniform and stable mass transfer; moreover, by increasing the diameter and height of the filter screen simultaneously, the evaporation area can be increased in two dimensions, further improving the growth rate of the silicon carbide crystal 11.

[0087] Figure 7 and Figure 8 both take the cylindrical crucible assembly (the whole is cylindrical) as an example, and T represents temperature; among them, Figure 7Among them, the temperature at the top of the central axis position in the raw material area is 2259.7 °C, the temperature at the bottom of the central axis position is 2356.9 °C, and the axial temperature difference at the central axis position is: 97.2 °C. The temperature at the top of the outer side of the raw material area (the side close to the inner wall of the crucible assembly) is 2305.9 °C, the temperature at the bottom of the outer side of the raw material area is 2373 °C, and the axial temperature difference on the outer side of the raw material area is: 67.1 °C. The radial temperature difference from the top of the outer side of the raw material area to the top of the central axis position is: 46.2 °C, and the radial temperature difference from the bottom of the outer side of the raw material area to the bottom of the central axis position is: 16.1 °C; and Figure 8 Among them, the temperature at the top of the inner side of the raw material area (the side close to the central axis position of the crucible assembly) is 2292.2 °C, the temperature at the bottom of the inner side of the raw material area is 2304.3 °C, and the axial temperature difference on the inner side of the raw material area is: 12.1 °C. The temperature at the top of the outer side of the raw material area is 2314 °C, the temperature at the bottom of the outer side of the raw material area is 2335 °C, and the axial temperature difference on the outer side of the raw material area is: 21 °C. The radial temperature difference from the top of the outer side of the raw material area to the top of the inner side of the raw material area is 21.8 °C, and the radial temperature difference from the bottom of the outer side of the raw material area to the bottom of the inner side of the raw material area is 30.7 °C.

[0088] It can be seen that overall, in this embodiment, the axial temperature difference and the radial temperature difference at most positions in the raw material area have decreased significantly.

[0089] In this embodiment, a closing protrusion protruding inward from the inner wall of the flow guiding ring 9 is provided at the top of the flow guiding ring 9. The closing protrusion constitutes a bearing ring for bearing the seed crystal assembly. The seed crystal assembly mainly includes a seed crystal support ring 8, a silicon carbide seed crystal 10, a graphite ring gasket 7, and an upper pressing cover 6. Among them, the seed crystal support ring 8 is placed on the bearing ring, the silicon carbide seed crystal 10 is placed on the seed crystal support ring 8, the graphite ring gasket 7 is placed on the silicon carbide seed crystal 10, and the upper pressing cover 6 is threadedly connected to the flow guiding ring 9 and can press the seed crystal support ring 8, the silicon carbide seed crystal 10, and the graphite ring gasket 7. Specifically, the upper pressing cover 6 can be tightened on the top of the flow guiding ring 9 by a torque wrench, and its tightening torque value is determined by the fixed torque set by the torque wrench. The tightening torque value is preferably 13 N·m ≤ P ≤ 20 N·m. Further, a protective coating is also coated on the surface of the silicon carbide seed crystal 10, which can prevent the back sublimation of the silicon carbide seed crystal. Among them, the protective coating is preferably a carbon coating or a ceramic coating, and the thickness of the protective coating is preferably within 100 μm.

[0090] In this embodiment, the seed crystal assembly with the above structure is adopted, which can reduce the stress caused by seed crystal pasting in the traditional process. This is of great significance for problems such as phase change, dislocation, and crystal edge cracking, thereby greatly improving the quality of silicon carbide crystal growth.

[0091] In this embodiment, a graphite paper 5 is further provided above the seed crystal assembly. The graphite paper 5 should be able to cover the cross-section of the cavity of the crucible assembly 1. By utilizing the great heat conduction effect of the graphite paper 5 in the horizontal direction, the radial temperature distribution of the silicon carbide seed crystal 10 is finely adjusted. Among them, the outer edge of the graphite paper 5 is clamped and fixed by a carbon felt 4, and the carbon felt 4 can also adjust the radial temperature distribution of the silicon carbide seed crystal. The carbon felt 4 includes an upper carbon felt and a lower carbon felt, and the upper carbon felt and the lower carbon felt are respectively located above and below the graphite paper 5.

[0092] Further, an isolation cavity E is formed between the outer wall of the flow guiding ring 9, the inner wall of the second radial heat conducting ring 3, and the upper pressing cover 6. By adjusting the thickness of the isolation cavity E, the radial temperature distribution of the silicon carbide seed crystal 10 in the flow guiding ring 9 can be further finely adjusted. The thickness of the isolation cavity E is a, and preferably 3 mm ≤ a ≤ 12 mm; the thickness of the radial heat conducting ring is c, and c > 2a; among them, the thickness of the isolation cavity E and the thickness of the radial heat conducting ring are both the thicknesses in the radial direction. Considering the influence of the flow guiding ring 9 on the stress of the silicon carbide crystal 11, the wall thickness b of the flow guiding ring 9 is preferably 3 mm ≤ b ≤ 10 mm.

[0093] In this embodiment, a temperature measuring blind hole is further provided on the crucible assembly 1. Specifically, a temperature measuring blind hole is provided in the middle of the crucible top cover of the crucible assembly 1, and a temperature measuring tube 14 is installed on the temperature measuring blind hole; one end of the temperature measuring tube 14 is connected to the crucible top cover, and the other end is connected to the furnace cover 15 of the heating furnace. The internal cavity of the temperature measuring tube 14 is isolated from the outside to ensure that the volatile substances in the heating furnace cannot enter the temperature measuring surface of the temperature measuring tube 14, thereby ensuring the accuracy of temperature measurement; further, a small amount of protective gas is filled inside the temperature measuring tube 14 to make the internal pressure of the temperature measuring tube 14 greater than the external pressure, and a pressure difference is generated between the inside and the outside of the temperature measuring tube 14, which can further prevent the internal device of the temperature measuring tube 14 from being contaminated; among them, the amount of the protective gas filled is selected according to specific working requirements, as long as a pressure difference can be generated between the inside and the outside of the temperature measuring tube 14, and the protective gas is preferably an inert gas. In addition, the graphite paper 5 provided above the seed crystal assembly can effectively prevent the condensation of silicon carbide vapor on the outer wall of the temperature measuring tube 14 and the upper inner wall of the crucible body, and further ensure the long-term stability of the temperature measuring tube 14.

[0094] Embodiment 2

[0095] This embodiment provides a silicon carbide crystal growth system, which includes a heating furnace and the silicon carbide crystal growth device in Embodiment 1. The silicon carbide crystal growth device is installed in the heating furnace; among them, the heating furnace is a mature and existing technology in the art, and will not be elaborated in this embodiment. The heating furnace mainly includes a furnace shell, a furnace cover 15 is provided at the top of the furnace shell, a heating device is provided inside the furnace shell for heating the crucible assembly 1, and an insulating and heat-preserving layer for heat preservation is also provided inside the furnace shell.

[0096] Further, the furnace shell can be a quartz shell or a metal shell, the heating device can be an induction coil or a graphite heating rod, and the insulation and heat preservation layer can be a graphite soft felt or a graphite hard felt; wherein, the heating device can cover the entire crucible assembly 1 in the axial direction to reduce the axial temperature difference in the crucible assembly 1.

[0097] Embodiment III

[0098] This embodiment provides a method for growing silicon carbide crystals, which mainly includes: performing a raw material pretreatment process and a silicon carbide crystal growth process in the silicon carbide crystal growth device in Embodiment I.

[0099] Most of the growth defects of the silicon carbide crystal 11 occur in the initial stage of the growth of the silicon carbide crystal 11. Therefore, a raw material pretreatment process is added; wherein, the raw material pretreatment process mainly includes the following steps:

[0100] S1. Put the silicon carbide raw material 13 into the annular raw material cavity A1 of the crucible assembly 1. Specifically, first place the filter screen at the designated position in the crucible assembly 1, then add the silicon carbide raw material 13. The particle size of the silicon carbide raw material 13 is preferably 20 mesh - 40 mesh, and then assemble the sealing component, the flow guiding ring 9, the temporary growth piece, etc. in sequence;

[0101] S2. Heat the silicon carbide raw material 13 to a predetermined temperature and keep it warm for a preset time;

[0102] S3. Cool the silicon carbide raw material 13 that has completed heat preservation to room temperature; wherein, the silicon carbide raw material 13 can be naturally cooled to room temperature in an inert gas atmosphere;

[0103] The silicon carbide crystal growth process mainly includes the following steps:

[0104] S4. Install a new flow guiding ring 9 in the original crucible assembly 1, reinstall the seed crystal assembly on the top of the new flow guiding ring 9, and then grow the silicon carbide crystal.

[0105] In this embodiment, in step S2, the predetermined temperature is 1500°C to 2200°C, preferably 1700°C to 2000°C, and the preset time is 3 to 10 hours; when heating the silicon carbide raw material 13, the partial pressure in the crucible assembly 1 ≤ 3 mbar, where the partial pressure in the crucible assembly 1 refers to the internal environmental pressure value in the crucible assembly 1.

[0106] In this embodiment, during the raw material pretreatment process, a temporary growth piece is placed on the top of the diversion ring 9. The temporary growth piece mainly includes a seed crystal support ring 8, graphite paper, a graphite ring gasket 7, and an upper gland 6. Among them, the seed crystal support ring 8 is placed on the top of the diversion ring 9, the graphite paper is placed on the seed crystal support ring 8, and the graphite paper covers the cross-section of the inner cavity of the diversion ring 9. The graphite ring gasket 7 is placed on the graphite paper, and the upper gland 6 is threadedly connected to the diversion ring 9 and can press the seed crystal support ring 8, the graphite paper, and the graphite ring gasket 7. In this embodiment, in the temporary growth piece, the graphite paper replaces the silicon carbide seed crystal 10. The graphite paper has good flatness and can seal the top of the diversion ring 9. When the silicon carbide crystal growth process is carried out, a brand-new seed crystal assembly is used to replace the temporary growth piece.

[0107] In this embodiment, the above raw material pretreatment process is used to pretreat the silicon carbide raw material 13, which mainly has the following functions:

[0108] 1. Remove trace impurities in the silicon carbide raw material 13, such as nitrogen, phosphorus, boron, aluminum, etc., which is particularly important for the growth of semi-insulating silicon carbide crystals 11.

[0109] 2. Eliminate the silicon-rich atmosphere at the initial stage of the growth of silicon carbide crystals 11: The silicon-carbon ratio of the silicon carbide gas phase component increases as the particle size of the silicon carbide decreases. For example, when the particle size decreases from 2 mm to 3 mm to 0.06 mm, the silicon-carbon ratio increases from 1.3 to 4. When the particle size is small to a certain extent, the Si partial pressure increases, and a layer of Si film is formed on the surface of the growing crystal, inducing VLS (vapor-liquid-solid) growth, which has an impact on the polytype, point defects, and line defects of the silicon carbide crystals 11. Especially when the silicon carbide raw material 13 powder is finer or the powder adheres to more ultrafine powder, pretreating the silicon carbide raw material 13 can eliminate the adverse effects caused by the silicon-rich atmosphere at the initial stage of crystal growth.

[0110] 3. Stabilize the crystal form of the silicon carbide raw material 13: Theoretical calculations show that when using 6H-SiC raw materials, Si / C = 1.2 in the adsorption layer, and the gas phase above the β-SiC raw material is richer in silicon, Si / C≈5.5. Therefore, in the early stage of the growth of silicon carbide crystals 11, Si / C in the adsorption layer > 1.2. As the growth of silicon carbide crystals 11 proceeds, the raw material undergoes a β→α phase transformation, and the Si / C ratio in the growth chamber decreases, causing the Si / C ratio in the adsorption layer to drop back and approach the stoichiometric ratio. Therefore, pre-burning the silicon carbide raw material 13 to convert some of the residual β-SiC in the silicon carbide raw material 13 into α-SiC can eliminate the silicon-rich atmosphere caused by the improper crystal form of the silicon carbide raw material in the early stage of growth.

[0111] 4. Through heating - holding - cooling, slight sintering and bonding occur between the silicon carbide raw material powders, forming a porous network structure. This heat treatment process can play a role in strengthening and stabilizing the mass transfer channel.

[0112] In this embodiment, the silicon carbide crystal growth process is carried out using the silicon carbide crystal growth device in Embodiment 1, and specifically includes: after the raw material pretreatment process is completed, the temporary growth part, the flow guiding ring 9 and the sealing component are disassembled and cleaned in sequence. At the same time, a small amount of silicon carbide crystals adhering to the inner wall of the filter screen are cleaned up; the sealing component and the flow guiding ring 9 are reinstalled. At this time, a silicon carbide seed crystal 10 coated with a protective coating is placed on the seed crystal support ring 8 of the seed crystal component, and it is reinstalled in the crucible component 1 to grow the silicon carbide crystal 11; the growth conditions are as follows: the temperature of the silicon carbide seed crystal 10 is 2100°C to 2150°C, the temperature gradient is 30 to 40°C / cm, the Ar pressure in the crucible component 1 is 0.5 mbar to 2 mbar, and the Ar flow rate is 0.1 to 0.2 L / min.

[0113] Among them, the silicon carbide crystal growth process is a mature existing technology in the art (PVT method), which is selected according to specific working needs and will not be elaborated in this embodiment. Preferably, the silicon carbide crystal growth is carried out according to the 4H-SiC crystal growth process.

[0114] It should be noted that for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0115] Specific examples are used in the present invention to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A silicon carbide crystal growth device, comprising a crucible assembly (1), wherein a seed crystal assembly is arranged inside the crucible assembly (1); characterized in that: A cylindrical filtering component (12) is further arranged inside the crucible component (1). An annular raw material chamber (A1) for placing silicon carbide raw material (13) is formed between the outer wall of the filtering component (12) and the inner wall of the crucible component (1). A sealing component for preventing leakage of silicon carbide gas-phase components is arranged at the top of the annular raw material chamber (A1); the filtering component (12) can block the silicon carbide raw material (13) and allow the silicon carbide gas-phase components generated after heating the silicon carbide raw material (13) to pass through; a diversion ring (9) is arranged on the sealing component. The seed crystal component is arranged at the top of the diversion ring (9), and the bottom is lapped on the sealing component. The inner wall of the diversion ring (9) protrudes inwards from the inner wall of the filtering component (12), and a planar blocking area (F) is formed on the lower surface of the diversion ring (9). Among them, the diversion ring (9) is a graphite diversion ring; The filtering component (12) is a cylindrical filter screen, and the crucible component (1) is a cylindrical crucible component (1). The filter screen is coaxially arranged with the crucible component (1), and the bottom of the filter screen is in sealed abutment with the bottom of the crucible component (1); A closing protrusion protruding inwards from the inner wall of the diversion ring (9) is arranged at the top of the diversion ring (9). The closing protrusion constitutes a bearing ring for bearing the seed crystal component. The seed crystal component includes: A seed crystal support ring (8) placed on the bearing ring; A silicon carbide seed crystal (10) placed on the seed crystal support ring (8); A graphite ring gasket (7) placed on the silicon carbide seed crystal (10); An upper pressing cover (6) threadedly connected to the diversion ring (9). The upper pressing cover (6) presses the graphite ring gasket (7), the silicon carbide seed crystal (10) and the seed crystal support ring (8) on the bearing ring.

2. The silicon carbide crystal growth device according to claim 1, characterized in that: The porosity of the filter screen is 20%-80%, the aperture of the filtering holes of the filter screen is 1μm-1000μm, and the average aperture of the filtering holes of the filter screen is 40μm-60μm.

3. The silicon carbide crystal growth device according to claim 1 or 2, characterized in that: The material of the filter screen is a high-temperature ceramic material, a composite material or a graphite material.

4. The silicon carbide crystal growth device according to claim 1, characterized in that: The distance between the outer wall of the filtering component (12) and the inner wall of the crucible component (1) is d, and d≤1 / 3D; where D is the diameter of the crucible component (1).

5. The silicon carbide crystal growth device according to claim 1, characterized in that: The sealing component is a radial heat-conducting ring, and a plurality of radial heat-conducting rings are arranged from top to bottom.

6. The silicon carbide crystal growth device according to claim 5, characterized in that: A sealing coating is further coated at the position where the lower surface of the radial heat-conducting ring contacts the annular raw material chamber (A1).

7. The silicon carbide crystal growth device according to claim 1, characterized in that: The sealing component includes a first radial heat-conducting ring (2) and a second radial heat-conducting ring (3) arranged from top to bottom. An isolation chamber is formed between the outer wall of the diversion ring (9), the inner wall of the second radial heat-conducting ring (3) and the upper pressing cover (6).

8. The silicon carbide crystal growth device according to claim 7, characterized in that: The thickness of the sealing component is c, and c>2a, where a is the thickness of the isolation chamber, and 3mm≤a≤12mm; the wall thickness of the diversion ring (9) is b, and 3mm≤b≤10mm.

9. The silicon carbide crystal growth device according to claim 1, characterized in that: A protective coating is further coated on the silicon carbide seed crystal (10).

10. The silicon carbide crystal growth device according to claim 1, characterized in that: Above the seed crystal assembly, there is also a graphite paper (5) which covers the cross-section of the cavity of the crucible assembly (1).

11. The silicon carbide crystal growth device according to claim 10, characterized in that: The outer edge of the graphite paper (5) is clamped and fixed by a carbon felt (4), and the carbon felt (4) includes an upper carbon felt and a lower carbon felt, and the upper carbon felt and the lower carbon felt are respectively located above and below the graphite paper (5).

12. The silicon carbide crystal growth device according to claim 1, characterized in that: The crucible assembly (1) is also provided with a temperature measurement blind hole, and a temperature measurement tube (14) is installed on the temperature measurement blind hole, and the inner cavity of the temperature measurement tube (14) is isolated from the outside.

13. A silicon carbide crystal growth system, characterized in that: It includes a heating furnace and a silicon carbide crystal growth device according to any one of claims 1-12, and the silicon carbide crystal growth device is installed in the heating furnace.

14. A silicon carbide crystal growth method, characterized in that: In the silicon carbide crystal growth device according to any one of claims 1-12, a raw material pretreatment process and a silicon carbide crystal growth process are carried out, wherein, The raw material pretreatment process includes the following steps: S1. Put the silicon carbide raw material (13) into the annular raw material cavity (A1), and then replace the seed crystal assembly with a recyclable temporary growth piece; S2. Heat the silicon carbide raw material (13) to a predetermined temperature and keep it warm for a preset time; S3. Cool the silicon carbide raw material (13) that has completed heat preservation to room temperature; The silicon carbide crystal growth process includes the following steps: S4. Replace the flow guide ring (9) in the silicon carbide crystal growth device used in the raw material pretreatment process with a new flow guide ring (9), and replace the temporary growth piece with the seed crystal assembly again, and then carry out silicon carbide crystal growth.

15. The silicon carbide crystal growth method according to claim 14, wherein: In step S2, the predetermined temperature is 1500°C to 2200°C, the preset time is 3 to 10 hours, and when heating the silicon carbide raw material (13), the partial pressure in the crucible assembly (1) is ≤ 3 mbar.

16. The silicon carbide crystal growth method according to claim 14, wherein: The temporary growth piece includes: A seed crystal support ring (8) placed on the top of the flow guide ring (9), and a graphite paper is placed on the seed crystal support ring (8); A graphite ring gasket (7) placed on the graphite paper; An upper pressing cover (6) threadedly connected to the flow guide ring (9), and the upper pressing cover (6) presses the graphite ring gasket (7), the graphite paper and the seed crystal support ring (8) against the top of the flow guide ring (9).

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