A device and preparation process for preparing silicon carbide by the PVT method

Abstract

The present invention discloses a device and a process for preparing silicon carbide by a PVT method, which relates to the technical field of silicon carbide production, and mainly includes a furnace body, a thermal insulation layer, a growth crucible, a raw material crucible and a porous gas permeable layer; the furnace body is provided with a thermal insulation layer, a growth crucible is provided in the thermal insulation layer, the raw material crucible is located in the growth crucible, and the porous gas permeable layer is provided at the top opening of the raw material crucible; the furnace body is connected to a furnace body vacuum system, and the bottom of the growth crucible is connected to a crucible vacuum system. The crucible is completely sealed to ensure that the silicon-rich atmosphere will not etch the crucible and external thermal insulation materials, to ensure that foreign impurities will not enter the growth crucible, and to reduce the generation of defects such as microtubes and carbon wrapping; to extend the service life while reducing the cost; a porous gas permeable layer is placed on the upper part of the raw material crucible, and the raw material crucible is placed on the upper part of the growth crucible, while absorbing the silicon-rich atmosphere, ensuring that the intake air is uniformly diffused from both sides of the growth crucible to the upper part of the raw material crucible, thereby ensuring the doping stability and the uniformity of the resistivity distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide production, and particularly to a device and a preparation process for preparing silicon carbide by the PVT method. Background Art

[0002] As a third-generation semiconductor material, compared with the first-generation and second-generation semiconductor materials, the third-generation semiconductor materials such as silicon carbide have a wider bandgap width, a higher breakdown field strength, a higher thermal conductivity, a higher electron saturation rate, and a higher radiation resistance, and are more suitable for manufacturing high-temperature, high-frequency, large-frequency, and radiation-resistant devices, and can be widely used in fields such as high voltage, high frequency, high temperature, and high reliability, including radio frequency communication, radar, satellite, power management, automotive electronics, industrial power electronics, etc.

[0003] The main methods for preparing silicon carbide are physical vapor transport method (PVT), liquid phase method (LPE), high-temperature chemical vapor deposition (HTCVD), etc. Among them, the most mature and commonly used method is PVT. In a typical PVT process for preparing silicon carbide, the crucible is made of graphite, and the required temperature gradient is established and controlled by induction or resistance heating and by placing appropriate coils and heat-insulating materials. The raw material powder is silicon carbide, and the seed crystal is also silicon carbide. The crucible is vertically placed below the seed crystal. As the temperature rises, the silicon carbide powder sublimates, and the gas-phase components condense at the seed crystal, and finally grow into silicon carbide crystals.

[0004] At present, there are still some defects in the structure of silicon carbide single crystal substrates prepared by the PVT method, including microtubes, carbon inclusions, polytypes, hexagonal voids, etc. These defects will affect the performance stability and long-term working performance of the later device manufacturing process. How to solve these defects and obtain high-quality silicon carbide ingots is an urgent problem to be solved at present.

[0005] Chinese Patent CN212610986U discloses a crucible for reducing carbon inclusion in silicon carbide crystals. By arranging an air flow homogenizing member and a cover plate above the silicon carbide polycrystalline material in the crucible, the air flow transmission mode is changed from mainly convection to mainly diffusion, and carbon particles are deposited, thereby reducing the carbon inclusions in the silicon carbide crystals. However, this method cannot guarantee the carbon inclusions caused by the carbon source introduced from the outside.

[0006] Chinese Patent CN214300468U discloses a crucible and a device for growing silicon carbide single crystals. The side wall of the crucible is made of a breathable graphite material, and by infiltrating nitrogen gas into the side wall of the crucible, the nitrogen doping stability and the resistivity uniformity of large-size N-type silicon carbide single crystals are improved.

[0007] In currently published patents, the crucible is not completely sealed. The crucible is either thread-fitted or porous, which not only causes the escape of the silicon-rich atmosphere and etching of the crucible and insulation materials, but also introduces foreign impurities during crystal growth, resulting in growth defects such as microtubes and carbon encapsulation. Therefore, it is very important to provide a PVT silicon carbide preparation device and process that can prevent impurity introduction, extend the service life of raw materials, and reduce production costs. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a PVT method for preparing a silicon carbide device and a preparation process to ensure the stable and controllable sublimation of the atmosphere during crystal growth.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] The present invention provides a PVT method for preparing a silicon carbide device, including a furnace body, a heat-insulating layer, a growth crucible, a raw material crucible, and a porous breathable layer; the heat-insulating layer is arranged inside the furnace body, the growth crucible is arranged inside the heat-insulating layer, the raw material crucible is located inside the growth crucible, and the porous breathable layer is arranged at the top open end of the raw material crucible; the furnace body is connected to a furnace body vacuum system, and the bottom of the growth crucible is connected to a crucible vacuum system.

[0011] Optionally, the furnace body includes an upper furnace cover, a main furnace body, and a lower furnace cover; the main furnace body is a cavity structure that is vertically through; the upper furnace cover is arranged on the top of the main furnace body, and the lower furnace cover is arranged on the bottom of the main furnace body.

[0012] Optionally, the main furnace body is a quartz tube, or the main furnace body is made of stainless steel material, and both the upper furnace cover and the lower furnace cover are made of stainless steel.

[0013] Optionally, the growth crucible is made of ultra-high purity and high-density isostatic graphite, with a bulk density of 1.84 - 1.95 g / cm 3 , and an average particle size of 2 - 5 μm; the raw material crucible is made of ultra-high purity and high-density isostatic graphite or ultra-high purity breathable graphite, with a bulk density of less than or equal to 1.84 g / cm 3 , and an average particle size of 3 - 10 μm.

[0014] Optionally, the porous breathable layer is a porous graphite sheet and / or a porous metal carbide sheet or a porous graphite sheet with a metal carbide coating on its surface. When the porous breathable layer is a porous graphite sheet and a porous metal carbide sheet, the porous graphite sheet and the porous metal carbide sheet have the same shape, and the porous graphite sheet is located below the porous metal carbide sheet; the thickness of the porous breathable layer is 2 - 5 mm, the average porosity is 20 - 50%, and the average pore diameter is 2 - 5 μm.

[0015] Optionally, the metal carbide used for the porous metal carbide sheet or the porous graphite sheet with a metal carbide coating on the surface is one or more of tantalum carbide, hafnium carbide, and niobium carbide.

[0016] Optionally, the connection between the growth crucible and the crucible vacuum system and the connection between the furnace body and the furnace body vacuum system are connected by bolts and / or adhesives.

[0017] Optionally, the furnace body vacuum system maintains the vacuum degree of the furnace body at 1.0×10 -4 ~1.0×10 -5 pa, and the growth crucible vacuum system makes the vacuum degree of the crucible 1.0×10 -4 ~1.0×10 -5 pa.

[0018] Optionally, during the crystal growth process, the vacuum degree of the furnace body is 1.0×10 -3 ~1.0×10 -4 pa, and the vacuum degree of the growth crucible is 150 - 1500 pa.

[0019] The present invention also provides a preparation process based on the above PVT method for preparing a silicon carbide device. Charge the raw material crucible, place the raw material crucible into the growth crucible, and then put the raw material crucible, the growth crucible, and the thermal insulation material into the furnace body. Heat it. During the crystal growth stage, adjust the pressure difference inside and outside the crucible to ensure that the vacuum degree of the furnace body is 1.0×10 -4 ~1.0×10 - 5 pa, and the vacuum degree of the growth crucible is 150 - 1500 pa. Then take out the ingot and perform annealing treatment to obtain the silicon carbide crystal.

[0020] The present invention has achieved the following technical effects compared with the prior art:

[0021] 1. The crucible is completely sealed and completely separated from the thermal insulation material in the furnace body, ensuring that the silicon-rich atmosphere will not etch the crucible and the external thermal insulation material. At the same time, it ensures that foreign impurities, including impurities from the external environment and the thermal insulation material, will not enter the growth crucible, reducing the generation of defects such as microtubes and carbon inclusions.

[0022] 2. Use low-cost thermal insulation materials to replace ultra-high-purity thermal insulation materials, and the thermal insulation materials will not be contaminated, extending the service life while reducing costs.

[0023] 3. A porous breathable layer is placed on the upper part of the raw material crucible, and the raw material crucible is placed on the upper part of the growth crucible. While adsorbing the silicon-rich atmosphere, it ensures that the intake air diffuses evenly from both sides of the growth crucible to the upper part of the raw material crucible, thereby ensuring doping stability and uniform resistivity distribution. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying 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 accompanying drawings can be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of the device for preparing silicon carbide by the PVT method of the present invention;

[0026] Figure 2 It is a diagram of a silicon carbide ingot prepared by the specific example one of the device and preparation process for preparing silicon carbide by the PVT method of the present invention;

[0027] Figure 3 It is a diagram of a silicon carbide wafer prepared by the specific example one of the device and preparation process for preparing silicon carbide by the PVT method of the present invention.

[0028] Figure 4 It is a diagram of the temperature measurement holes during the crystal growth process of the device and preparation process for preparing silicon carbide by the PVT method of the present invention;

[0029] Figure 5 It is a diagram of the temperature measurement holes during the crystal growth process of the prior art;

[0030] Figure 6 It is a diagram of the thermal field etching situation after the crystal growth of the device and preparation process for preparing silicon carbide by the PVT method of the present invention;

[0031] Figure 7 It is a diagram of the thermal field etching situation after the crystal growth of the prior art.

[0032] Explanation of the reference numerals: 1. Growth crucible cover; 2. Silicon carbide seed crystal; 3. Porous breathable layer; 4. Air inlet; 5. Furnace body vacuum system; 6. Thermal insulation material; 7. Growth crucible; 8. Raw material crucible; 9. Silicon carbide powder; 10. Furnace body; 11. Ventilation port; 12. Crucible vacuum system. Detailed implementation manners

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] Embodiment 1

[0035] As Figure 1As shown in the figure, this embodiment provides a device for preparing silicon carbide by the PVT method, which includes a furnace body 10, a heat-insulating layer, a growth crucible 7, a raw material crucible 8, and a porous breathable layer 3. A heat-insulating layer is arranged inside the furnace body 10, a growth crucible 7 is arranged inside the heat-insulating layer, the raw material crucible 8 is located inside the growth crucible 7, and the porous breathable layer 3 is arranged at the top opening of the raw material crucible 8. The furnace body 10 is connected to a furnace body 10 vacuum system 5, and the bottom of the growth crucible 7 is connected to a crucible vacuum system 12. The silicon carbide seed crystal 2 grows on the bottom of the growth crucible cover 1 at the top of the growth crucible 7.

[0036] In this embodiment, the furnace body 10 includes an upper furnace cover, a main furnace body 10, and a lower furnace cover. The main furnace body 10 is a cavity structure that penetrates up and down. The upper furnace cover is arranged at the top of the main furnace body 10, and the lower furnace cover is arranged at the bottom of the main furnace body 10. The main furnace body 10, the upper furnace cover, and the lower furnace cover are all made of stainless steel. The upper furnace cover and the lower furnace cover are connected to the main furnace body 10 by bolts.

[0037] The growth crucible 7 is made of ultra-high purity and high-density isostatic graphite, with a bulk density of 1.84 - 1.95 g / cm 3 , and an average particle size of 2 - 5 μm. The raw material crucible 8 is made of ultra-high purity and high-density isostatic graphite or ultra-high purity breathable graphite, with a bulk density of less than or equal to 1.84 g / cm 3 , and an average particle size of 3 - 10 μm.

[0038] The porous breathable layer 3 is used to filter the particulate matter in the silicon-rich gas generated by heating the silicon carbide powder 9 in the raw material crucible 8, ensuring the stable and controllable sublimation of the atmosphere during crystal growth, and greatly reducing crystal growth defects such as microtubes, carbon inclusions, hexagonal voids, and dislocation density.

[0039] The porous breathable layer 3 can be made of porous graphite sheets, or porous metal carbide sheets, or porous graphite sheets with a metal carbide coating on the surface, or porous graphite sheets and porous metal carbide sheets can be used simultaneously.

[0040] When the porous breathable layer 3 is made of porous graphite sheets, high-quality graphite materials that do not powderize need to be used to prevent the graphite sheets from generating dust and affecting the crystallization quality. For porous graphite sheets made of ordinary graphite materials, a metal carbide coating can be added to the surface. A porous sheet made of metal carbide can also be covered above the porous graphite sheet made of ordinary graphite to filter the graphite powder. At this time, a porous sheet made of metal carbide with a thickness of only 50 μm can meet the requirements. If only a porous sheet made of metal carbide is used, the thickness of the porous sheet needs to be increased to 1 mm to meet the strength requirements of the porous sheet.

[0041] The metal carbide used for the porous metal carbide sheet or the porous graphite sheet with a metal carbide coating on the surface is one or more of tantalum carbide, hafnium carbide, and niobium carbide.

[0042] The connection between the growth crucible 7 and the crucible vacuum system 12 and the connection between the furnace body 10 and the furnace body 10 vacuum system 5 are bolted and connected with adhesives such as epoxy glue, phenolic resin, and graphite glue to enhance the sealing effect of the connection.

[0043] The furnace body 10 vacuum system 5 maintains the vacuum degree of the furnace body 10 at 1.0×10 -4 ~1.0×10 -5 pa, and the crucible vacuum system 12 makes the vacuum degree of the growth crucible 7 1.0×10 -4 ~1.0×10 -5 pa. Preferably, during the crystal growth process, the vacuum degree of the furnace body 10 is 1.0×10 -4 ~1.0×10 -5 pa, and the vacuum degree of the growth crucible 7 is 150 - 1500 pa.

[0044] Another object of the present invention is to extend the service life of the material, use ordinary thermal insulation material 6 instead of expensive ultra-high purity thermal insulation material 6, reduce the crystal growth cost, and obtain low-cost and high-quality silicon carbide crystals. The thermal insulation material 6 is graphite, graphite soft felt, or graphite hard felt.

[0045] Figure 2 and Figure 3 are diagrams of conductive silicon carbide ingots and wafers prepared by the PVT method and preparation process of the present invention.

[0046] The steps for preparing conductive silicon carbide crystals using the device in this embodiment are as follows:

[0047] 1. Add self-made high-purity silicon carbide powder 9 with a particle size range of 5 - 200 mesh, a purity greater than 99.9999%, and a bulk density of 1.2 g / cm 3 to the raw material crucible 8. After loading, place a 2-mm-thick graphite sheet with a tantalum carbide coating on top of the powder.

[0048] 2. Place the raw material crucible 8 inside the growth crucible 7, and the growth crucible 7 is sealed with bolts and glue;

[0049] 3. Place the thermal field composed of the growth crucible 7 and the thermal insulation material 6 into the furnace body 10, and connect and seal the bottom of the growth crucible 7 to the inlet and outlet gas pipelines. The sealing method is bolts with graphite paper.

[0050] 4. Close the upper and lower furnace lids and seal them through the flange;

[0051] 5. Turn on the vacuum system to ensure that the vacuum inside the furnace body 10 and the crucible reaches 9×10 -5 Pa.

[0052] 6. Pass a mixed gas of argon and nitrogen into the growth crucible 7 through the air inlet 4 and the vent 11, with a ratio of 100:1. The argon flow rate is 1200 sccm, so that the vacuum inside the growth crucible 7 is 1300 Pa and the vacuum inside the furnace body 10 is 5×10 -3 Pa. At the same time, raise the furnace temperature from room temperature to 2000 °C. After reaching the established pressure and temperature, maintain stable growth at this pressure for 120 h to complete the crystal growth stage.

[0053] 7. After the crystal growth is completed, slowly increase the pressure inside the crucible and the pressure inside the furnace body 10 to atmospheric pressure, and at the same time lower the temperature and slowly cool it to room temperature. Finally, a 22-mm-thick silicon carbide ingot is obtained, with an average growth rate of 183 μm / h. There are no defects such as carbon inclusions and polytypes when observed from the front, and the utilization rate can reach over 98%.

[0054] 8. Anneal the obtained ingot for 60 h. The annealing temperature is 2200 °C. After annealing, the ingot is cut, ground, polished and cleaned to obtain the Figure 3 wafer as shown.

[0055] The microtube density of the 4H silicon carbide wafer prepared by using the present invention can reach 0.2 / cm 2 , without polytypes, hexagonal cavity defects, and the carbon inclusion is ≤0.05%, and the resistivity is 0.02 Ω·cm.

[0056] Example 2

[0057] Use the device in Example 1 to prepare semi-insulating silicon carbide crystals, and the steps are as follows:

[0058] 1. Put the self-made high-purity silicon carbide powder 9 into the raw material crucible 8. The particle size range of the silicon carbide powder 9 is 5 - 200 mesh, the purity is greater than 99.9999%, and the bulk density is 1.2 g / cm 3 . After loading, place a 2-mm-thick graphite sheet with a tantalum carbide coating on top of the powder.

[0059] 2. Place the raw material crucible 8 inside the growth crucible 7, and the growth crucible 7 is sealed with bolts and glue;

[0060] 3. Put the thermal field composed of the growth crucible 7 and the thermal insulation material 6 into the furnace body 10. The bottom of the growth crucible 7 is connected and sealed with the air inlet and outlet pipes, and the sealing method is bolts with graphite paper.

[0061] 4. Close the upper and lower furnace lids and seal them through the flange;

[0062] 5. Turn on the vacuum system to ensure that the vacuum inside the furnace body 10 and the crucible reaches 9×10 -5 Pa.

[0063] 6. Pass a mixed gas of argon and hydrogen into the growth crucible 7 through the gas inlet 4 and the vent 11. The concentrations of nitrogen and hydrogen are <1 ppb, the volume ratio is 2:1, and the argon flow rate is 800 sccm, so that the vacuum inside the growth crucible 7 is 1400 Pa and the vacuum inside the furnace body 10 is 5×10 -3 Pa. At the same time, raise the furnace temperature from room temperature to 2100 °C. After reaching the established pressure and temperature, maintain stable growth for 120 h at this pressure to complete the crystal growth stage.

[0064] 7. After the crystal growth is completed, slowly increase the pressure inside the crucible and the pressure inside the furnace body 10 to atmospheric pressure, and at the same time lower the temperature and slowly cool it to room temperature. Finally, a 20-mm-thick silicon carbide ingot is obtained, and the average growth rate is 166 μm / h. There are no defects such as carbon inclusions and polymorphs when observed from the front, and the utilization rate can reach more than 98%.

[0065] 8. Anneal the obtained ingot for 60 h. The annealing temperature is 2200 °C. After annealing, the ingot is subjected to cutting, grinding, polishing and cleaning treatments.

[0066] The microtube density of the 4H silicon carbide wafer prepared by using the present invention can reach 0.2 / cm 2 , without polymorphs, hexagonal cavity defects, and the carbon inclusion is ≤0.05%, and the resistivity is 8.29×10 10 Ω·cm.

[0067] By using Embodiment 1 and Embodiment 2 of the device of the present invention, silicon carbide crystals with a small microtube density, no polymorphs, hexagonal cavity defects, and small carbon inclusions can be prepared. Compared with the silicon carbide crystals prepared by a single set of vacuum systems, the macroscopic defects are greatly reduced, indicating that the present invention can reduce crystal defects and prepare high-quality silicon carbide single crystals.

[0068] Figure 4 And Figure 5 are pictures of the temperature measurement holes during the growth process of Embodiment 1 and the prior art. It is found that there are black flaky substances on the temperature measurement holes in the prior art, blocking the temperature measurement holes and affecting the temperature measurement accuracy. There is no blockage in the temperature measurement holes of Embodiment 1, indicating that the present invention can prevent gas from escaping and blocking the temperature measurement holes, and the temperature measurement data is stable and reliable, which has a beneficial effect on the process stability.

[0069] Figure 6 And Figure 7 are pictures of the thermal field after the growth of Embodiment 1 and the prior art. It is found that there is gas volatilization outside the thermal field in the prior art, and there is no gas volatilization outside the thermal field in Embodiment 1, indicating that the present invention can prevent gas from escaping and etching the external thermal insulation material, prolonging the life of the thermal insulation material, which has a beneficial effect on reducing the process cost.

[0070] Table 1 shows the SIMS results of B and N elements and the crystal resistivity measured in Example 1 and Example 2 carried out using the device of the present invention.

[0071]

[0072] In Table 1, the number of atoms per cubic centimeter of the crystal has reached the requirements of high purity. The higher content of N atoms in Example 1 is because the N element was doped into the crystal. According to the resistivity of high-purity conductive silicon carbide in the industry of 15 - 30 mΩ·cm, the resistivity of the semi-insulating silicon carbide crystal for minimizing the device insulation back-gate effect is greater than 1x10 5 Ω·cm. The product in Example 1 meets the requirements of conductivity, and the product in Example 2 meets the requirements of semi-insulation. Therefore, the present invention has successfully prepared high-purity conductive and semi-insulating silicon carbide single crystals.

[0073] It should be noted that for those skilled in the art, obviously the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. 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.

[0074] Specific examples are used in this specification to elaborate on the principles and implementation manners 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, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A device for preparing silicon carbide by PVT method, characterized in that: The invention comprises a furnace body, a heat-insulating layer, a growth crucible, a raw material crucible and a porous air-permeable layer; the heat-insulating layer is arranged in the furnace body, the growth crucible is arranged in the heat-insulating layer, the raw material crucible is located in the growth crucible, and the porous air-permeable layer is arranged at the top opening of the raw material crucible; the furnace body is connected to a furnace body vacuum system, and the bottom of the growth crucible is connected to a crucible vacuum system; The growth crucible is made of ultra-high purity high-density isostatic graphite with a bulk density of 1.84-1.95 g / cm 3 , with an average particle size of 2 to 5 mm; the raw material crucible is made of ultra-high purity high-density isostatic graphite or ultra-high purity breathable graphite, with a bulk density of less than or equal to 1.84 g / cm 3 , the average particle size is 3~10mm; The porous air-permeable layer is a porous graphite sheet and a porous metal carbide sheet or a porous graphite sheet with a metal carbide coating on the surface. When the porous air-permeable layer is a porous graphite sheet and a porous metal carbide sheet, the porous graphite sheet and the porous metal carbide sheet have the same shape, and the porous graphite sheet is located below the porous metal carbide sheet; the porous air-permeable layer has a thickness of 2-5 mm, an average porosity of 20-50%, and an average pore size of 2-5 mm.

2. The device for preparing silicon carbide by the PVT method according to claim 1, characterized in that: The furnace body comprises an upper furnace cover, a main furnace body and a lower furnace cover; the main furnace body is a cavity structure that penetrates from top to bottom; the upper furnace cover is arranged on the top of the main furnace body, and the lower furnace cover is arranged on the bottom of the main furnace body.

3. The device for preparing silicon carbide by the PVT method according to claim 2, characterized in that: The main furnace body is a quartz tube, or the main furnace body is made of stainless steel, and the upper furnace cover and the lower furnace cover are both made of stainless steel.

4. The device for preparing silicon carbide by the PVT method according to claim 1, characterized in that: The metal carbide used in the porous metal carbide sheet or the porous graphite sheet with a metal carbide coating on the surface is one or more of tantalum carbide, hafnium carbide and niobium carbide.

5. The device for preparing silicon carbide by the PVT method according to claim 1, characterized in that: The connection between the growth crucible and the crucible vacuum system and the connection between the furnace body and the furnace body vacuum system are connected by bolts and / or adhesives.

6. The device for preparing silicon carbide by PVT method according to claim 1, characterized in that: The furnace vacuum system keeps the furnace vacuum degree at 1.0×10 -4 ~1.0×10 -5 pa, the crucible vacuum system makes the crucible vacuum degree 1.0×10 -4 ~1.0×10 -5 pa.

7. The device for preparing silicon carbide by the PVT method according to claim 6, characterized in that: During the crystal growth process, the furnace vacuum degree is 1.0×10 -3 ~1.0×10 -4 pa, and the vacuum degree of the growth crucible is 150~1500 pa.

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