Growth raw material of silicon carbide crystal, preparation method and application

Abstract

The invention discloses a growth raw material of a silicon carbide crystal, a preparation method and application, the growth raw material of the silicon carbide crystal comprises a core layer, a first wrapping layer on the outer side of the core layer and a second wrapping layer on the outer side of the first wrapping layer, the core layer is silicon carbide, the first wrapping layer is silicon, and the second wrapping layer is silicon carbide. The growth raw material of the silicon carbide crystal is designed into a three-layer structure, so that the carbon-rich phenomenon of raw material decomposition can be effectively improved, and the defect of carbon wrapping in a prepared silicon carbide single crystal product is overcome.

Description

Technical Field

[0001] The present application relates to the field of semiconductor materials, and specifically to a growth material, a preparation method and an application of silicon carbide crystals. Background Art

[0002] SiC has the characteristics of wide bandgap, high critical breakdown electric field, high thermal conductivity, high carrier saturation migration velocity, etc. It has great application potential in high temperature, high frequency, high power, microelectronic devices, etc. It is the most representative single crystal compound in the current third-generation semiconductor materials. Most of the silicon carbide crystal growth currently adopts PVT technology, that is, physical vapor transmission: solid silicon carbide powder is placed in a crucible made of graphite, and the top of the crucible is pasted with a seed crystal of the required crystal type. The entire crucible is wrapped with a certain amount of graphite felt for insulation and then heated by electromagnetic induction of the induction coil to form a specific temperature field. When the crystal grows, the solid SiC powder decomposes and sublimates to generate various forms of gas phase components. The gas phase components are transported to the crystal growth interface with a relatively low temperature under the drive of the axial temperature gradient, and recrystallized into SiC crystals on the growth interface.

[0003] During the entire growth process, the decomposition of silicon carbide is a non-stoichiometric sublimation. Si in the silicon carbide source evaporates preferentially. The gas phase material in the sublimation growth process is usually silicon-rich. Therefore, microscopic defects often appear in the early stage due to the high proportion of silicon. As the growth proceeds, the unevaporated growth raw material becomes more and more carbon-rich, making the carbon-silicon ratio in the later stage of growth higher and higher, deviating more and more from the stoichiometric ratio of silicon carbide. At the same time, the graphitization of the crucible in the later stage of growth causes carbon elements to be deposited on the growth interface along with the silicon carbide gas flow, resulting in "carbon encapsulation" defects.

[0004] These "carbon inclusion" defects will not only cause stress concentration inside the crystal, reduce the mechanical strength and electrical properties of the crystal, but may also cause leakage when the device is working, affecting the working performance of the device. In addition, the presence of carbon inclusions will induce defects such as micropipes, dislocations, and stacking faults, which will seriously deteriorate the quality of the crystal and increase the risk of device failure. Therefore, the presence of carbon inclusion defects greatly reduces the quality of SiC crystals and limits the excellent performance of SiC-based devices. In order to improve the crystal quality and performance of SiC-based devices, it is necessary to conduct in-depth research on the formation mechanism of these defects and reduce the generation of carbon inclusions. Summary of the invention

[0005] The purpose of this application is to reduce the "carbon encapsulation" defects of silicon carbide crystals.

[0006] To achieve the above objectives, the technical solution adopted in the present application is: to provide a growth material for silicon carbide crystal, including a core layer, a first wrapping layer outside the core layer, and a second wrapping layer outside the first wrapping layer, the core layer is silicon carbide, the first wrapping layer is silicon, and the second wrapping layer is silicon carbide.

[0007] Preferably, the thickness of the first wrapping layer is 700-900 µm, and the thickness of the second wrapping layer is 400-500 µm.

[0008] As another preference, the thickness of the first wrapping layer is 750±30 µm, and the thickness of the second wrapping layer is 450±30 µm.

[0009] The present application also provides a method for preparing a growth raw material for silicon carbide crystals, comprising the following preparation steps: S1: synthesizing silicon carbide powder from silicon powder and carbon powder as a core layer; S2: mixing trichlorosilane with a first carrier gas, and forming a first coating layer on the outside of the core layer after high-temperature calcination to obtain first particles; S3: mixing trichlorosilane with a second carrier gas, and forming a second coating layer on the outside of the first particles after high-temperature calcination to obtain the growth raw material for the silicon carbide crystals.

[0010] As another preference, the first carrier gas is an inorganic gas, and the second carrier gas is an organic gas.

[0011] As another preference, the first carrier gas is hydrogen, and the second carrier gas is methane.

[0012] As another preference, the mesh number of the core layer is 20-40 meshes, the mesh number of the first particles is 8-20 meshes, and the mesh number of the silicon carbide crystal growth raw material is 5-8 meshes.

[0013] The present application provides a method for growing a silicon carbide single crystal, providing a seed crystal and a raw material chamber, wherein a raw material decomposes and sublimates into the seed crystal in the raw material chamber, and recrystallizes and grows into the silicon carbide single crystal on the seed crystal, wherein the raw material includes the growth raw material of the silicon carbide crystal mentioned above, or the growth raw material of the silicon carbide crystal obtained by the above preparation method.

[0014] Further preferably, the raw material includes an upper layer close to the seed crystal and a lower layer close to the bottom of the crucible, the lower layer is any of the above-mentioned growth raw materials for silicon carbide crystals, or the raw material includes any of the above-mentioned preparation methods.

[0015] Further preferably, the mass ratio of the upper layer to the lower layer is 3:2.

[0016] Compared with the prior art, the beneficial effects of this application are: (1) The present application designs a three-layer structure of silicon carbide crystal growth raw material, and uses the growth raw material to decompose and prepare silicon carbide single crystal, which can effectively improve the "carbon-rich" phenomenon of raw material decomposition, thereby reducing the "carbon encapsulation" defects in the product; (2) The method for preparing the raw material for growing silicon carbide crystals provided in the present application has a simple preparation process, a high yield, and strong economy, and is suitable for mass production for growing silicon carbide crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the raw material structure for growing silicon carbide crystals of the present application.

[0018] Figure 2 The invention relates to a device for preparing growth raw materials for silicon carbide crystals of the present application.

[0019] Figure 3 The invention relates to an application device for growing raw materials of silicon carbide crystals of the present application.

[0020] In the figure: 1. Discharging area; 2. Heater; 3. Air inlet; 4. Buffer. DETAILED DESCRIPTION

[0021] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0022] In the description of the present application, it should be noted that directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of narrating the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of the present application.

[0023] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0024] The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0025] like Figure 1 The present application provides a growth raw material for silicon carbide crystals, which is used for growing silicon carbide crystals by a PVT method. The growth raw material of the present application is placed inside a crucible. After the raw material decomposes and sublimates, it recrystallizes at the seed crystal on the top of the crucible to generate a silicon carbide single crystal. Through the decomposition of the growth raw material of the present application, the "carbon-rich" phenomenon of raw material decomposition can be effectively improved, thereby reducing the "carbon encapsulation" defect of the silicon carbide single crystal.

[0026] The growth raw material of the silicon carbide crystal of the present application includes a core layer, a first encapsulation layer outside the core layer, and a second encapsulation layer outside the first encapsulation layer. The core layer material is silicon carbide, the first encapsulation layer material is silicon, and the second encapsulation layer material is silicon carbide.

[0027] By designing a multilayer structure of the core layer, the first wrapping layer and the second wrapping layer, during the decomposition process, the silicon carbide in the second wrapping layer is first heated and decomposed, and this process is also a non-chemically proportional decomposition and sublimation, mainly Si evaporating first. The second wrapping layer gradually decomposes to expose the first wrapping layer, which is a Si layer. The decomposition of the first wrapping layer can timely replenish the missing silicon source in the system, improve the "carbon-rich" phenomenon of the growth raw material, and thus reduce the "carbon-wrapped" defects of the generated silicon carbide single crystal.

[0028] In some embodiments, the thickness of the first encapsulation layer is 700-900 µm, and the thickness of the second encapsulation layer is 400-500 µm. The thickness of the first encapsulation layer and the second encapsulation layer is related to the decomposition rate. If the second encapsulation layer is too thin, it is easier to be quickly decomposed completely, which will result in the subsequent stage of the silicon layer being decomposed alone; and if the second encapsulation layer is too thick, the second encapsulation layer is continuously decomposed without timely replenishment of the silicon source, and the early silicon carbide single crystal still has the defect problem of "carbon encapsulation".

[0029] In some preferred embodiments, the thickness of the first encapsulation layer is 750±30 µm, and the thickness of the second encapsulation layer is 450±30 µm. The thickness of the second encapsulation layer is appropriate, and after the second encapsulation layer is decomposed, the silicon in the first encapsulation layer can be decomposed in time, thereby achieving the purpose of replenishing the silicon source. Alternatively, while the second encapsulation layer of a part of the growth raw material preferentially decomposes and begins to decompose the first encapsulation layer, the second encapsulation layer of another part of the growth raw material begins to decompose, thereby achieving the purpose of adjusting the silicon-carbon ratio of the silicon carbide growth raw material.

[0030] The present application also provides a method for preparing a raw material for growing silicon carbide crystals, comprising the following preparation steps: S1: Silicon carbide powder synthesized from silicon powder and carbon powder as the core layer; S2: trichlorosilane gas is mixed with the first carrier gas, and calcined at high temperature to form a first coating layer that wraps around the outside of the core layer, thereby obtaining first particles; S3: The trichlorosilane gas is mixed with the second carrier gas, and calcined at high temperature to form a second coating layer that coats the outside of the first particle, thereby obtaining the growth raw material of the silicon carbide crystal of the present application.

[0031] In some embodiments, the first encapsulating layer is silicon and the second encapsulating layer is silicon carbide. That is, the silicon carbide crystal growth raw material prepared by the preparation method of the present application forms a core layer of silicon carbide, a first encapsulating layer encapsulated outside the core layer, and a second encapsulating layer structure encapsulated outside the first encapsulating layer. The core layer material is silicon carbide, the first encapsulating layer material is silicon, and the second encapsulating layer material is silicon carbide.

[0032] In some embodiments, the temperature of high temperature calcination in step S2 and step S3 is above 1300° C. Under high temperature calcination, trichlorosilane and the first carrier gas, trichlorosilane and the second carrier gas decompose at high temperature to form silicon and silicon carbide, respectively.

[0033] In some embodiments, the first carrier gas is an inorganic gas and the second carrier gas is an organic gas. The decomposition products of pure trichlorosilane at high temperature generally include silicon, hydrogen chloride and chlorine. When the first carrier gas is an inorganic gas, trichlorosilane mixes and decomposes with the inorganic gas to form silicon wrapped around the outside of the core layer; when the second carrier gas is an organic gas, trichlorosilane mixes and decomposes with the organic gas to form silicon carbide wrapped around the outside of the first particle.

[0034] In some preferred embodiments, the first carrier gas is hydrogen, which is mixed with trichlorosilane gas and decomposed, which helps to reduce the generation of product chlorine and avoids the presence of toxic gases in the tail gas, which requires additional emission treatment. In some preferred implementations, the second carrier gas is methane, which decomposes at 1000°C under normal pressure, breaking the carbon-hydrogen bonds in methane, generating carbon and hydrogen, and decomposing together with trichlorosilane to obtain silicon carbide.

[0035] In some embodiments, the mixing ratio of trichlorosilane to the first carrier gas is 1:(5-20), and the mixing ratio of trichlorosilane to the second carrier gas is 1:(2-8).

[0036] In some embodiments, the silicon carbide powder or the synthesized material is screened by the following specific steps: S1: 6N high-purity silicon powder and 5N high-purity carbon powder are used for synthesis, the silicon powder D50 is 200-300 µm, the carbon powder D50 is 20-30 µm, the carbon powder and silicon powder are sent into a heating furnace for heating at a temperature of 2000-2500 °C to synthesize silicon carbide powder, the synthesized silicon carbide powder is sieved, washed and dried, and 20-40 mesh silicon carbide powder is selected as the core layer; S2: Trichlorosilane is mixed with the first carrier gas and calcined at a high temperature above 1300°C to form a first coating layer that wraps around the outside of the core layer to obtain first particles. The first particles are washed and dried, and then sieved to obtain first particles of 8-20 mesh; S3: Trichlorosilane is mixed with a second carrier gas and calcined at a high temperature above 1300°C to form a second coating layer that wraps around the outside of the first particle. The product is washed and dried, and then sieved to obtain a 5-8 mesh product for use as a raw material for the growth of silicon carbide crystals.

[0037] The present application also provides a device for preparing raw materials for growing silicon carbide crystals, such as Figure 2 As shown, the layered deposition tower includes a discharge zone 1, a heater 2, an air inlet 3 and a buffer chamber 4, the heater 2 is arranged on both sides of the area from the air inlet 3 to the discharge zone 1, the air inlet 3 is arranged below the discharge zone 1, and the buffer chamber 4 is arranged above the discharge zone 1. The gas enters from the air inlet 3 below the discharge zone 1, is thermally decomposed in the discharge zone 1 and contacts with the raw materials in the discharge zone 1, and the tail gas is collected or discharged after passing through the buffer chamber 4.

[0038] The discharge area 1 includes a plurality of layered plates, which are graphite gas-permeable disks suitable for gas to pass through. The plates are used to place raw materials, such as the core layer or the first particle to be coated. After trichlorosilane is mixed with the first carrier gas, or trichlorosilane is mixed with the second carrier gas, it starts to be heated after entering from the air inlet 3, and contacts with the raw materials through the discharge area 1 to form a package. The tail gas is stabilized in the buffer chamber 4.

[0039] Through the preparation device of the present application, the growth raw material of silicon carbide crystal with a three-layer structure of a core layer, a first wrapping layer and a second wrapping layer can be easily prepared. The preparation method is mature and stable, consumes less manpower and resources, and reduces production costs.

[0040] The present application also provides an application device for growing raw materials for silicon carbide crystals, such as Figure 3As shown, it includes a graphite crucible, an insulation layer and a heating component. The graphite crucible is provided with a crucible cover, a silicon carbide seed crystal, and the growth raw material of the silicon carbide crystal is placed under the silicon carbide seed crystal. Usually, a medium-frequency induction coil is used as a heat source, so that the high-density graphite heating element is heated under the action of eddy currents, and the silicon carbide growth raw material is placed at the bottom of the graphite crucible. The silicon carbide seed crystal is bonded to the inside of the graphite crucible cover at a certain distance from the surface of the growth raw material. The graphite crucible is placed in the heating component as a whole, and the external insulation layer is adjusted so that the growth raw material is placed in the high-temperature zone and the silicon carbide seed crystal is in the corresponding low-temperature zone, so that the silicon carbide growth raw material in the high-temperature zone is decomposed and sublimated, and the gas phase components such as Si, Si2C and SiC2 are transported to the low-temperature zone under the drive of the temperature gradient, and nucleate and crystallize on the C surface of the SiC seed crystal to grow into a silicon carbide single crystal.

[0041] The growth raw material includes an upper layer and a lower layer, wherein the upper layer is defined as the growth raw material relatively closer to the silicon carbide seed crystal, and the lower layer is defined as the growth raw material relatively closer to the bottom of the graphite crucible. In some embodiments, the growth raw material of the silicon carbide crystal prepared in the present application is placed in the graphite crucible instead of the conventional growth raw material, and for cost considerations, the growth raw material of the silicon carbide crystal prepared in the present application can be placed in the lower layer, and the upper layer is placed with 5-8 mesh silicon carbide raw material that has not been coated.

[0042] In some embodiments, the mass ratio of the growth raw material of the silicon carbide crystal prepared in the present application to the silicon carbide raw material that has not been coated is 3:2.

[0043] In the growth raw material of the silicon carbide crystal of the present application, in the middle and late stages of the growth process of the silicon carbide crystal, the silicon atoms in the first encapsulation layer decompose and are supplemented into the growth raw material as a silicon source, so that the silicon-carbon ratio in the decomposed growth raw material is closer to 1:1, thereby reducing the "carbon encapsulation" phenomenon of the silicon carbide crystal.

[0044] The present application also provides a method for growing a silicon carbide single crystal, providing a seed crystal and a raw material chamber, wherein the raw material chamber is arranged below the seed crystal, and the raw material decomposes and sublimates to the seed crystal in the raw material chamber, and recrystallizes and grows into a silicon carbide single crystal on the seed crystal. The raw material includes the growth raw material of the silicon carbide crystal prepared by the above-mentioned present application, or the growth raw material of the silicon carbide crystal prepared by the above-mentioned preparation method.

[0045] In some embodiments, the raw material includes an upper layer relatively close to the seed crystal and a lower layer relatively close to the bottom of the crucible. The raw material of the lower layer is the growth raw material of the silicon carbide crystal prepared in the present application, and the raw material of the upper layer can be set to conventional silicon carbide raw material without coating treatment to achieve the purpose of cost saving.

[0046] In some preferred embodiments, the mass ratio of the upper layer raw material to the lower layer raw material is 3:2.

[0047] Example 1 A method for preparing a growth material for a silicon carbide crystal comprises the following steps: S1: 6N high-purity silicon powder and 5N high-purity carbon powder are used for synthesis, silicon powder D50 = 200~300 µm, carbon powder D50 = 20~30 µm, silicon powder manufacturer is Germany Wacker, model PCL-NCS-FA, carbon powder manufacturer is Germany SGL, model V598, carbon powder and silicon powder are sent to a heating furnace for heating at a temperature of 2200 °C to synthesize silicon carbide powder, the synthesized silicon carbide powder is sieved, washed and dried, and 20~40 mesh silicon carbide powder is selected as the core layer; S2: Trichlorosilane and hydrogen are mixed in a ratio of 1:8, and calcined at a high temperature above 1300°C to form a first coating layer on the outside of the core layer. The first coating layer is silicon, and first particles are obtained. After the first particles are washed and dried, they are sieved to obtain first particles of 8-20 mesh; S3: Trichlorosilane is mixed with methane in a ratio of 1:3, and calcined at a high temperature above 1300°C to form a second coating layer on the outside of the first particle. The second coating layer is silicon carbide. After the product is washed and dried, it is sieved to take 5-8 mesh products for the growth of silicon carbide crystals.

[0048] Provided is a growth material for silicon carbide crystal prepared in the present application, comprising a core layer, a first wrapping layer outside the core layer, and a second wrapping layer outside the first wrapping layer, wherein the core layer is silicon carbide, the first wrapping layer is silicon, and the second wrapping layer is silicon carbide.

[0049] Take 2 kg of the growth raw material of the silicon carbide crystal prepared in this application with a mesh size of 5-8 and place it in the lower layer of the graphite crucible, and take 3 kg of the silicon carbide raw material with a mesh size of 5-8 and not wrapped and place it in the upper layer of the graphite crucible. Place the graphite crucible in a hot field for heating, set the growth conditions of 300 Pa, 2150 ° C, and argon gas flow rate of 150 sccm, and grow the crystal for 120 h.

[0050] Example 2 3 kg of raw material of silicon carbide crystals prepared in this application with a mesh size of 5 to 8 was placed in the lower layer of the graphite crucible, and 2 kg of raw material of silicon carbide without wrapping treatment with a mesh size of 5 to 8 was placed in the upper layer of the graphite crucible. The rest of the preparation method was consistent with the preparation method in Example 1.

[0051] Example 3 Take 3 kg of 5-8 mesh unwrapped silicon carbide raw material and put it into the lower layer of the graphite crucible, take 2 kg of 5-8 mesh growth raw material of silicon carbide crystal prepared in this application and place it in the upper layer of the graphite crucible, and the rest of the preparation method is consistent with the preparation method in Example 1.

[0052] Example 4 5 kg of 5-8 mesh silicon carbide crystal growth raw material prepared in this application was placed in a graphite crucible to grow silicon carbide crystals. The rest of the preparation method was consistent with the preparation method in Example 1.

[0053] Comparative Example 1 5 kg of 8-40 mesh silicon carbide crystal growth raw material prepared in this application was placed in a graphite crucible to grow silicon carbide crystals. The rest of the preparation method was consistent with the preparation method in Example 1.

[0054] Comparative Example 2 5 kg of 5-8 mesh uncoated silicon carbide raw material was placed in a graphite crucible to grow silicon carbide crystals. The rest of the preparation method was consistent with the preparation method in Example 4.

[0055] Comparative Example 3 5 kg of 8-40 mesh uncoated silicon carbide raw material was placed in a graphite crucible to grow silicon carbide crystals. The rest of the preparation method was consistent with the preparation method in Example 5.

[0056] Comparative Example 4 5 kg of 5-8 mesh SiC powder and Si powder were mixed and placed in a graphite crucible for silicon carbide crystal growth. The rest of the preparation method was consistent with the preparation method in Example 4.

[0057] Performance Testing 1. Analysis of carbon content in the residual material: The high-temperature carbon removal method is used to perform carbon removal analysis on the residual material of the growth raw material in the middle and late stages of silicon carbide crystal growth, and the weight loss of the residual material is obtained. The weight loss ratio is calculated, which is the carbon atomic content in the residual material. Then, according to the atomic molar ratio of Si to C in the SiC molecular formula of 1:1, the silicon-carbon molar ratio in the residual material is calculated. The analysis of different residual materials at different crystal growth times is recorded in the following Table 1.

[0058] Table 1 Analysis of growth raw material residues at different crystal growth times

[0059] 2. Carbon encapsulation ratio: After the silicon carbide crystals prepared according to the embodiments and comparative examples are processed into substrate sheets, the number of "carbon encapsulation" appearing on the substrate sheets is detected. The number of "carbon encapsulated" substrates is divided by the total number of sheets to obtain the carbon encapsulation ratio.

[0060] The silicon carbide single crystals prepared in each embodiment and each comparative example were subjected to residual carbon content detection and “carbon encapsulation” calculation, and the test results are recorded in Table 2 below.

[0061] Table 2 Performance test results of various embodiments and comparative examples

[0062] Analyzing the "carbon encapsulation" data in Table 2, the "carbon encapsulation" ratio of the silicon carbide crystals prepared by the embodiments of the present application is lower than the "carbon encapsulation" ratio of the silicon carbide crystals prepared by the conventional method in the comparative example. Therefore, the growth raw materials of the silicon carbide crystals of the present application can significantly improve the "carbon encapsulation" phenomenon in the single crystal products, which is helpful to obtain more high-quality silicon carbide single crystals and enhance the performance of SiC-based devices.

[0063] From the analysis of the "carbon encapsulation" ratio of the embodiments, the best quality silicon carbide single crystal is obtained in embodiment 4, and its "carbon encapsulation" ratio is less than 1%. The scheme of embodiment 4 is to use the growth raw material of the present application as the only silicon carbide single crystal growth raw material, that is, the minimum "carbon encapsulation" ratio can be obtained, but due to processing costs and processing time considerations, all growth raw materials cannot be replaced. The present application also explores the upper layer of growth raw materials and the lower layer of growth raw materials, as well as the proportional relationship. From the "carbon encapsulation" ratio analysis in Table 2, it can be seen that the growth raw material prepared in the present application is placed in the lower layer, and the silicon carbide raw material that has not been encapsulated is placed in the upper layer, and the mass ratio of the upper and lower raw materials is 3:2, which can obtain a better silicon carbide crystal, and its "carbon encapsulation" ratio is about 1.29%.

[0064] Analyzing the performance test results of Example 4 and Comparative Example 4, in Comparative Example 4, conventional silicon carbide powder and silicon powder that have not been coated are mixed, and the multi-layer core-shell structure is not formed by simple physical mixing. The "carbon coating" problem cannot be well solved. Simply adding silicon source to the system causes the silicon source to decompose from the beginning, breaking the initial carbon-silicon ratio balance, and it is impossible to supplement silicon in the imbalance stage. This solution is obviously substantially different from the technical solution of the present application.

[0065] In summary, the present application provides a raw material for growing silicon carbide crystals, which is used for growing silicon carbide single crystals by a PVT method, and includes a core layer, a first wrapping layer outside the core layer, and a second wrapping layer outside the first wrapping layer, wherein the core layer is silicon carbide, the first wrapping layer is silicon, and the second wrapping layer is silicon carbide. The raw material for growing silicon carbide crystals of the present application can effectively solve the "carbon wrapping" phenomenon of silicon carbide single crystals and improve the quality of the product silicon carbide single crystals.

[0066] The above describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and the specification only describe the principles of the present application. The present application may have various changes and improvements without departing from the spirit and scope of the present application, and these changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the attached claims and their equivalents.

Claims

1. A raw material for growing silicon carbide crystals, characterized in that: It comprises a core layer, a first wrapping layer outside the core layer, and a second wrapping layer outside the first wrapping layer. The core layer is silicon carbide, the first wrapping layer is silicon, and the second wrapping layer is silicon carbide.

2. The raw material for growing silicon carbide crystal according to claim 1, characterized in that: The thickness of the first wrapping layer is 700-900 μm, and the thickness of the second wrapping layer is 400-500 μm.

3. The raw material for growing silicon carbide crystal according to claim 2, characterized in that: The thickness of the first wrapping layer is 750±30 µm, and the thickness of the second wrapping layer is 450±30 µm.

4. A method for preparing a raw material for growing silicon carbide crystal according to any one of claims 1 to 3, characterized in that: The method comprises the following preparation steps: S1: Silicon carbide powder synthesized from silicon powder and carbon powder as the core layer; S2: trichlorosilane is mixed with a first carrier gas, and after high-temperature calcination, a first coating layer is formed outside the core layer to obtain first particles; S3: Trichlorosilane is mixed with a second carrier gas, and after high-temperature calcination, a second coating layer is formed on the outside of the first particles to obtain the growth raw material of the silicon carbide crystal.

5. The preparation method according to claim 4, characterized in that: The first carrier gas is an inorganic gas, and the second carrier gas is an organic gas.

6. The preparation method according to claim 5, characterized in that: The first carrier gas is hydrogen, and the second carrier gas is methane.

7. The preparation method according to claim 4, characterized in that: The mesh number of the core layer is 20-40 meshes, the mesh number of the first particles is 8-20 meshes, and the mesh number of the silicon carbide crystal growth raw material is 5-8 meshes.

8. A method for growing a silicon carbide single crystal, characterized in that: A seed crystal and a raw material chamber are provided, wherein a raw material decomposes and sublimates into the seed crystal in the raw material chamber, and recrystallizes and grows into the silicon carbide single crystal on the seed crystal, wherein the raw material comprises the growth raw material of the silicon carbide crystal as described in any one of claims 1 to 3, or the raw material comprises the growth raw material of the silicon carbide crystal obtained by the preparation method as described in any one of claims 4 to 7.

9. The growth method according to claim 8, characterized in that The raw material includes an upper layer close to the seed crystal and a lower layer close to the bottom of the crucible, the lower layer is the growth raw material of the silicon carbide crystal according to any one of claims 1 to 3, and the upper layer is silicon carbide.

10. The growth method according to claim 9, characterized in that The mass ratio of the upper layer to the lower layer is 3:2.

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