Silicon carbide powder synthesis method and device

Abstract

The embodiment of the present invention provides a method and device for synthesizing silicon carbide powder, which relates to the technical field of silicon carbide powder synthesis. The method for synthesizing silicon carbide powder can be applied to a device for synthesizing silicon carbide powder. In the process of synthesizing silicon carbide powder, raw material powder and silicon crystal raw material are placed in a crucible, and the silicon crystal raw material includes a plurality of silicon rods, and the plurality of silicon rods are arranged at intervals, and the silicon rods are placed in the raw material powder. In the process of synthesizing silicon carbide powder, when the temperature in the crucible rises to a certain temperature, the silicon rods begin to melt and diffuse into the carbon powder. The carbon powder can penetrate with the silicon melt to form a large silicon-carbon mixture, which can then react at high temperature to generate silicon carbide powder. Each silicon rod can form a nucleation point of the silicon-carbon mixture, so as to react at high temperature to form silicon carbide powder, thereby improving the yield of large-sized silicon carbide powder.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide powder synthesis, and in particular to a method and device for synthesizing silicon carbide powder. Background Art

[0002] With the advancement of silicon carbide crystal growth technology, downstream epitaxial manufacturers have increasingly stringent requirements for substrate quality. Currently, most companies still use commercially available 8-20 mesh silicon carbide powder for crystal growth. Most existing silicon carbide powder synthesis adopts chemical vapor deposition. The powder decomposes into Si, Si2C, SiC2, SiC and other gases at high temperature. The gas is transported under the drive of temperature gradient and then recrystallized on SiC seed crystals to achieve crystal growth. The particles of this synthesized silicon carbide powder are fine, and a large number of carbon particles are produced during high-temperature decomposition. The finer particles are mixed in the high-temperature atmosphere and easily form defects such as carbon inclusions and microtubes in the crystal, seriously affecting the quality of the substrate.

[0003] In order to reduce defects such as carbon inclusions, some companies have begun to use large-size silicon carbide powder for crystal growth in recent years, and the inclusion defects have been greatly reduced.

[0004] In related technologies, the particle size of silicon carbide powder produced by chemical vapor deposition is mostly less than 6 mm. Silicon carbide powder synthesized by solid phase method can produce silicon carbide powder with some particle size reaching 15 mm, but the yield is lower than that of vapor deposition method. Summary of the Invention

[0005] The present invention aims to provide a method and apparatus for synthesizing silicon carbide powder, which can improve the yield of silicon carbide powder with large particle size, for example, 15 mm particle size.

[0006] The embodiments of the present invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for synthesizing silicon carbide powder, the method comprising:

[0008] Filling the crucible with raw material powder, wherein the raw material powder includes carbon powder;

[0009] The crucible is filled with silicon crystal raw materials, wherein the silicon crystal raw materials include a plurality of silicon rods, the plurality of silicon rods are arranged at intervals, and the silicon rods are accommodated in the raw material powder;

[0010] The silicon crystal raw material is melted in the carbon powder, and the silicon crystal raw material and the carbon powder are reacted together at a first preset temperature to generate silicon carbide powder.

[0011] In an optional embodiment, the raw material powder further includes a crystal stabilizer, which is used to reduce the interfacial energy of the silicon carbide particles.

[0012] In an optional embodiment, the crystal stabilizer accounts for 0.5-1.2% of the raw material powder charge.

[0013] In an optional embodiment, the crystal stabilizer is any one of magnesium borate, cerium oxide or cerium silicide.

[0014] In an optional embodiment, the first preset temperature is 2000-2400°C.

[0015] In an optional embodiment, before allowing the silicon crystal raw material and the carbon powder to react together at the first preset temperature to generate silicon carbide powder, the process further includes:

[0016] Evacuating the crucible to a first preset pressure;

[0017] An inert gas is filled into the crucible and the pressure in the crucible is set to a second preset pressure, wherein the inert gas includes argon.

[0018] In an optional embodiment, the crucible is further provided with a silicon carbide wafer, which separates the crucible into a first chamber and a second chamber. The first chamber is located on the side of the silicon carbide wafer away from the raw material powder. The silicon carbide wafer is used to deposit silicon carbide powder at a first preset temperature.

[0019] In an optional embodiment, the inner wall of the first chamber is coated with a thermal insulation coating.

[0020] In an optional embodiment, the silicon crystal raw material further includes a silicon plate, and a plurality of silicon rods are spaced apart and arranged on the silicon plate;

[0021] The method for filling the raw material powder into the crucible comprises:

[0022] Lay a preset thickness of raw material powder on the bottom of the crucible;

[0023] Placing silicon crystal raw materials in a crucible, and placing a silicon plate on the surface of raw material powder of a preset thickness;

[0024] Continue to pour raw material powder into the crucible and make the raw material powder submerge the silicon crystal raw material.

[0025] In a second aspect, the present invention provides a silicon carbide powder synthesis device for preparing silicon carbide powder by the silicon carbide powder synthesis method of any of the aforementioned embodiments, comprising:

[0026] Crucible;

[0027] Raw material powder, the raw material powder includes carbon powder and is contained in a crucible;

[0028] Silicon crystal raw material, the silicon crystal raw material includes a plurality of silicon rods, the plurality of silicon rods are arranged at intervals, and the silicon rods are contained in the raw material powder.

[0029] An embodiment of the present invention provides a method and device for synthesizing silicon carbide powder. The method for synthesizing silicon carbide powder is applied to a silicon carbide powder synthesis device. During the synthesis of silicon carbide powder, since silicon rods are embedded in raw material powder, at a certain temperature, the silicon rods begin to melt and diffuse into the carbon powder. Since the carbon powder has high porosity and good adsorption properties, the carbon powder can penetrate with the silicon melt to form a large silicon-carbon mixture, which can then react at high temperature to generate silicon carbide powder. Moreover, each silicon rod can form a nucleation point for the silicon-carbon mixture, so that under the action of multiple silicon rods, a large silicon-carbon mixture can be formed to react at high temperature to form silicon carbide powder, thereby improving the yield of large-size silicon carbide powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic structural diagram of the silicon carbide powder synthesis device provided in this embodiment;

[0032] Figure 2 This is a schematic structural diagram of the crucible body provided in this embodiment.

[0033] Icons: 1-Silicon carbide powder synthesis device; 100-Crucible; 110-Crucible body; 1110-Mounting slot; 1111-Connecting inner wall; 1112-Connecting end wall; 120-Crucible cover; 101-First chamber; 102-Second chamber; 130-Silicon carbide wafer; 140-Thermal insulation coating; 200-Raw material powder; 300-Silicon crystal raw material; 310-Silicon plate; 320-Silicon rod. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0037] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0038] In addition, the terms "first", "second", etc., if used, are merely used to distinguish and describe, and should not be understood as indicating or implying relative importance.

[0039] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0040] At present, most companies are still using commercially available 8~20 mesh silicon carbide powder for crystal growth. Most of the existing silicon carbide powder synthesized adopt chemical vapor deposition method. The powder decomposes into Si, Si2C, SiC2, SiC and other gases at high temperature. The gas is transported under the drive of temperature gradient and then recrystallized on SiC seed crystal to achieve crystal growth. The obtained silicon carbide powder has a particle size of less than 6mm. The particles of this synthetic silicon carbide powder are finer and a large amount of carbon particles are generated when decomposed at high temperature. The finer particles are mixed in the high temperature atmosphere, which easily forms defects such as carbon inclusions and microtubes in the crystal, seriously affecting the quality of the substrate.

[0041] In order to reduce defects such as carbon inclusions, some companies have begun to use large-size silicon carbide powder for crystal growth in recent years. The particle size of the obtained silicon carbide powder can be 15mm, but its yield is low, only about 50%.

[0042] An embodiment of the present invention provides a method for synthesizing silicon carbide powder, which includes:

[0043] First, the raw material powder 200 is filled into the crucible 100 . It should be noted that the raw material powder 200 includes carbon powder.

[0044] The crucible 100 is filled with silicon crystal raw material 300 , which includes a plurality of silicon rods 320 . The plurality of silicon rods 320 are spaced apart and are contained in the raw material powder 200 .

[0045] The silicon crystal raw material 300 is melted in the carbon powder, and the silicon crystal raw material and the carbon powder are reacted at a first preset temperature to generate silicon carbide powder.

[0046] It is understandable that since the silicon rod 320 is embedded in the raw material powder 200, at a certain temperature, generally around 1414°C, the silicon rod 320 begins to melt and diffuse into the carbon powder. Since the carbon powder has a high porosity and good adsorption properties, the carbon powder can penetrate the silicon melt to form a large silicon-carbon mixture, which can then react at high temperature to form silicon carbide powder.

[0047] In this embodiment, multiple silicon rods 320 are arranged at intervals, and each silicon rod 320 diffuses into the carbon powder after melting, and each silicon rod 320 can form a nucleation point for the silicon-carbon mixture. Under the action of multiple silicon rods 320, a large silicon-carbon mixture can be formed to react at high temperature to form silicon carbide powder. After cooling, the silicon carbide powder can be taken out, crushed with a hammer, and filtered through a screen. The silicon carbide powder on the screen can be the powder of the target particle size.

[0048] Since each silicon rod 320 can form a nucleation point for the silicon-carbon mixture, each silicon rod 320 can form a large silicon-carbon mixture with carbon powder after melting. Therefore, it is easy to react at high temperature to form silicon carbide powder. The yield of synthesized silicon carbide powder larger than 15 mm can reach 85%, thereby improving the yield of large-sized silicon carbide powder.

[0049] Optionally, the first preset temperature is 2000-2400°C, for example, the first preset temperature may be 2000°C, 2050°C, 2100°C, 2200°C, 2300°C or 2400°C, so that the silicon crystal raw material 300 fully reacts with the carbon powder to form silicon carbide powder.

[0050] Optionally, in some embodiments, in order to facilitate the stable placement of the silicon rods 320 in the raw material powder 200 , the silicon crystal raw material 300 further includes a silicon plate 310 , and a plurality of silicon rods 320 are spaced apart and arranged on the silicon plate 310 .

[0051] Therefore, when loading raw material powder 200 and silicon crystal raw material 300, a predetermined thickness of raw material powder 200, which may be 10 to 15 mm, is first laid on the bottom of crucible 100. Raw material powder 200 may include a mixed powder comprising carbon powder and a crystal stabilizer. It is understood that the mixed powder of raw material powder 200 and the crystal stabilizer can provide support for silicon plate 310.

[0052] It can be understood that in the process of synthesizing silicon carbide powder, the crucible 100 is heated to a certain temperature, approximately 1414°C, and the silicon rod 320 and the silicon plate 310 begin to melt and diffuse into the carbon powder. Since the carbon powder has a high porosity and good adsorption properties, the silicon plate 310 and each silicon rod 320 can form a nucleation point for the silicon-carbon mixture. The carbon powder can penetrate the silicon melt to form a large silicon-carbon mixture, which can then react at high temperature to generate silicon carbide powder.

[0053] It should be noted that before laying a preset thickness of raw material powder 200 on the bottom of crucible 100, raw material powder 200 may be prepared in advance. The step of preparing raw material powder 200 includes weighing a certain mass of carbon powder according to a certain molar ratio, adding a crystal stabilizer, and mixing on a roller mixer for a certain time to obtain raw material powder 200, so as to ensure that the crystal stabilizer in raw material powder 200 is evenly mixed with carbon powder.

[0054] Then, the silicon crystal raw material 300 is placed in the crucible 100 , and the silicon plate 310 is placed on the surface of the raw material powder 200 of a preset thickness.

[0055] Then, the raw material powder 200 may be continuously poured into the crucible 100 , and the raw material powder 200 may be made to submerge the silicon crystal raw material 300 .

[0056] It should be noted that the mixed raw material powder can be prepared by weighing a certain mass of C powder according to a certain molar ratio, adding a crystal stabilizer, wherein the crystal stabilizer accounts for 0.5-1.2% of the charge of the raw material powder 200 to ensure the proportion of carbon powder in the raw material powder 200 and provide a sufficient carbon source for the synthesis of silicon carbide powder. The charge amount can be understood as the sum of the crystal stabilizer and the raw material powder 200. Mixing is carried out on a roller mixer for 2 hours to obtain a mixed raw material powder.

[0057] The crystal stabilizer can be magnesium borate, cerium oxide or cerium silicide. In this embodiment, the crystal stabilizer is magnesium borate to promote the formation of α-SiC crystal. The powder synthesis temperature can be reduced from 2300°C to about 2100°C, which can effectively reduce energy consumption.

[0058] Optionally, in some embodiments, a silicon carbide wafer 130 is further provided in the crucible 100, and the silicon carbide wafer 130 divides the crucible 100 into a first chamber 101 and a second chamber 102, wherein the silicon crystal raw material 300 and the raw material powder 200 are accommodated in the second chamber 102, and the first chamber 101 is located on the side of the silicon carbide wafer 130 away from the raw material powder 200, and the silicon carbide wafer 130 is used to deposit silicon carbide powder at a first preset temperature.

[0059] That is, the sublimated gas of the silicon crystal raw material 300 and the raw material powder 200 is used to crystallize on the silicon carbide wafer 130 , thereby forming silicon carbide powder on the silicon carbide wafer 130 .

[0060] It can be understood that the waste silicon carbide wafer 130 in the upper part of the crucible 100 can act as a seed crystal, inducing the Si-containing component gas volatilized at high temperature to recrystallize and grow silicon carbide powder on its surface, fully recovering part of the vaporized raw materials, improving the raw material utilization rate, and thus increasing the output of the silicon carbide powder synthesis.

[0061] Before allowing the silicon crystal raw material and the carbon powder to react together at the first preset temperature to generate silicon carbide powder, the method further includes:

[0062] The crucible 100 is then evacuated to make the pressure inside the crucible 100 at a first preset pressure.

[0063] It is understood that during vacuuming, the gas in the crucible 100 can be extracted to provide a relatively clean environment for the subsequent synthesis of silicon carbide powder. Optionally, the first preset pressure can be 3-10 Pa, for example, the first preset pressure is 3 Pa, 4 Pa, 5 Pa, 6 Pa, 8 Pa, or 10 Pa.

[0064] Then, an inert gas may be filled into the crucible 100 and the pressure in the crucible 100 is set to a second preset pressure.

[0065] It should be noted that the inert gas can be argon. It is understandable that when the powder is synthesized, the Ar gas diffuses into the first chamber 101 through the wall of the crucible 100 to form an Ar gas layer. It is understandable that the Ar gas has poor thermal conductivity and can form an insulation layer in the first chamber 101 to improve the heat utilization rate during powder synthesis.

[0066] Optionally, in order to further improve heat utilization, the inner wall of the first chamber 101 may be coated with a heat-insulating coating 140. The heat-insulating coating 140 may be a tantalum carbide coating or a niobium carbide coating. Of course, the heat-insulating coating 140 may also be a coating formed of other materials capable of achieving heat insulation.

[0067] Optionally, the second preset pressure may be 5500~6500Pa. In this embodiment, the second preset pressure is 6000Pa. Of course, in some other embodiments, the second preset pressure may be 5500Pa, 5800Pa, 6200Pa or 6500Pa.

[0068] The crucible 100 is heated to a first preset temperature within a first preset time, and maintained at the first preset temperature for a second preset time. Alternatively, in this embodiment, the assembled crucible 100 containing the raw material powder 200 and the silicon crystal raw material 300 can be placed in a resistance furnace and heated to a temperature within a range of 2050-2100°C within two hours. The temperature is then maintained within the range of 2050-2100°C for 20-25 hours to allow the silicon crystal raw material and the carbon powder to react to form silicon carbide powder.

[0069] Then, the crucible 100 is cooled to the second preset temperature within the second preset time. Optionally, in this embodiment, the temperature can be reduced to room temperature within 1 hour, and the room temperature is generally 20-25°C.

[0070] Finally, the synthesized cylindrical bulk SiC can be poured out from the crucible 100, crushed with a hammer, and then passed through a sieve. The silicon carbide powder on the sieve can be powder of the target particle size.

[0071] The specific structure of a silicon carbide powder synthesis device provided by an embodiment of the present invention and the corresponding technical effects brought about by it are described in detail below with reference to the patent drawings.

[0072] Please refer to Figure 1-Figure 2 The present invention also provides a silicon carbide powder synthesis device 1, which is primarily used to prepare silicon carbide powder using the above-described synthesis method. The silicon carbide powder synthesis device 1 includes a crucible 100, a raw material powder 200, and a silicon crystal raw material 300. The raw material powder 200 includes carbon powder and is contained in the crucible 100. The silicon crystal raw material 300 includes a plurality of silicon rods 320, which are spaced apart and contained in the raw material powder 200.

[0073] It can be understood that in order to facilitate the stable accommodation of the silicon rods 320 in the raw material powder 200, the silicon crystal raw material 300 also includes a silicon plate 310, and multiple silicon plates 310 are arranged at intervals on the silicon plate 310. The silicon plates 310 and the silicon rods 320 are accommodated in the raw material powder 200.

[0074] It should be noted that the silicon rod 320 and the silicon plate 310 are accommodated in the raw material powder 200, which can be understood as the raw material powder 200 in the crucible 100 completely covering the silicon rod 320 and the silicon plate 310, and the axial dimension of the material surface of the raw material powder 200 is higher than the upper side dimension of the silicon rod 320.

[0075] Therefore, in this embodiment, the crucible 100 containing the raw material powder 200 and the silicon crystal raw material 300 is heated to achieve the synthesis of silicon carbide powder. Since the silicon rods 320 and the silicon plates 310 are embedded in the raw material powder 200, at a certain temperature, generally around 1414°C, the silicon rods 320 and the silicon plates 310 begin to melt and diffuse into the carbon powder. Since the carbon powder has a high porosity and good adsorption properties, the carbon powder can penetrate into the silicon melt to form a large silicon-carbon mixture, which can then react at high temperature to generate silicon carbide powder.

[0076] In this embodiment, a plurality of silicon rods 320 are provided on the silicon plate 310 at intervals. Each silicon rod 320 diffuses into the carbon powder after melting, and each silicon rod 320 can form a nucleation point for the silicon-carbon mixture. Thus, under the action of the silicon plate 310 and the plurality of silicon rods 320, a large silicon-carbon mixture can be formed, so as to react at high temperature to form silicon carbide powder, thereby improving the yield of large-size silicon carbide powder.

[0077] In this embodiment, the silicon plate 310 is spaced apart from the bottom surface of the crucible 100, and raw material powder 200 is provided on both the upper and lower sides of the silicon plate 310, so that a silicon-carbon mixture is formed on the lower side of the silicon plate 310 and the raw material powder 200 below the silicon plate 310, thereby reacting at a high temperature to form silicon carbide powder.

[0078] In this embodiment, the silicon rods 320 are arranged on the upper side of the silicon plate 310. It can be understood that the silicon plate 310 can support the silicon rods 320. Under the support of the silicon plate 310, the silicon rods 320 are stably placed in the raw material powder 200, so as to ensure that each silicon rod 320 can diffuse relatively stably into the surrounding carbon powder when melted, thereby ensuring the smooth formation of a large silicon-carbon mixture.

[0079] It should be noted that the silicon plate 310 in this embodiment may be circular, and the silicon plate 310 and the crucible 100 are coaxial, and the radial dimension of the silicon plate 310 is smaller than the radial dimension of the inner wall of the crucible 100 .

[0080] For example, in some embodiments, the difference between the radial dimension of the inner wall of the crucible 100 and the radial dimension of the silicon plate 310 can be in the range of 10~15 mm, the thickness of the silicon plate 310 can be 10 mm, the radial dimension of the silicon rod 320 can also be 10 mm, the spacing between any two adjacent silicon rods 320 can be 20~25 mm, and the axial dimension of the silicon rod 320 can be 10~12 mm.

[0081] Of course, in some other embodiments, the difference in radial dimensions between the two can also be within other ranges, or the difference in radial dimension between the inner wall of the crucible 100 and the radial dimension of the silicon plate 310 can be greater than 15 mm, and the difference in radial dimension between the inner wall of the crucible and the radial dimension of the silicon plate 310 can be less than 10 mm. Of course, the thickness of the silicon plate 310 can also be less than or greater than 10 mm, and the diameter of the silicon rod 320 is not limited to 10 mm. Similarly, the axial dimension of the silicon rod 320 is not limited to 10~12 mm. The spacing between any two adjacent silicon rods 320 can also be less than 20 mm or greater than 25 mm. There is no restriction on the dimensions of the silicon plate 310 and silicon rods 320 of the silicon crystal raw material 300.

[0082] It should be noted that, in this embodiment, there is a gap between the upper surface of the raw material powder 200 and the upper side of the silicon rod 320 to ensure that there is sufficient raw material powder 200 on the upper side of the silicon rod 320 to form a silicon-carbon mixture with the molten silicon rod 320, which serves as the basis for the subsequent reaction to form silicon carbide powder.

[0083] Optionally, the silicon plate 310 in this embodiment is provided with a plurality of mounting holes, and the plurality of silicon rods 320 are plugged into the plurality of mounting holes in a one-to-one correspondence. It is understood that the silicon rods 320 and the silicon plate 310 can be provided in a separate manner to facilitate assembly. During the transportation of the silicon crystal raw material 300, the silicon rods 320 and the silicon plate 310 can be separated to facilitate the transportation of the silicon crystal raw material 300. Of course, in other embodiments, the silicon plate 310 and the silicon rods 320 can also be provided as an integral whole.

[0084] Optionally, to better form silicon carbide powder, the raw powder 200 also includes a crystal stabilizer to reduce the interfacial energy of the silicon carbide particles. The crystal stabilizer can be magnesium borate, cerium oxide, or cerium silicide. In this embodiment, magnesium borate is used to promote the formation of the α-SiC crystal form. The powder synthesis temperature can be reduced from 2300°C to approximately 2100°C, effectively reducing energy consumption.

[0085] In this embodiment, the crystal stabilizer accounts for 0.5-1.2% of the total charge. It should be noted that the total charge can be understood as the sum of the carbon powder and the crystal stabilizer.

[0086] Optionally, in this embodiment, the molar ratio of silicon to carbon in the raw material powder 200 and the silicon crystal raw material 300 is 1-1.05, so as to ensure the utilization rate of the raw material powder 200 and the silicon crystal raw material 300 when synthesizing silicon carbide powder.

[0087] Optionally, to further improve the utilization rate of raw materials for silicon carbide powder synthesis, the silicon carbide powder synthesis device 1 further includes a silicon carbide wafer 130, wherein the silicon carbide wafer 130 can be a discarded silicon carbide wafer 130, which can save the cost of silicon carbide powder synthesis. The silicon carbide wafer 130 is installed in the crucible 100 and is spaced apart from the raw material powder 200. That is, there is a gap between the silicon carbide wafer 130 and the upper surface of the raw material powder 200. The silicon crystal raw material 300 and the sublimated gas phase of the raw material powder 200 are used to crystallize on the silicon carbide wafer 130, forming silicon carbide powder on the silicon carbide wafer 130.

[0088] That is to say, the waste silicon carbide wafer 130 in the upper part of the crucible 100 can act as a seed crystal, inducing the Si-containing component gas volatilized at high temperature to recrystallize and grow silicon carbide powder on its surface, fully recovering part of the vaporized raw materials, improving the utilization rate of the raw materials, and thus effectively improving the yield of the synthesized silicon carbide powder.

[0089] In detail, in this embodiment, the silicon carbide wafer 130 divides the crucible 100 into a first chamber 101 and a second chamber 102 which are separately arranged. The first chamber 101 is located on the side of the silicon carbide wafer 130 away from the raw material powder 200 , and the inner side of the first chamber 101 is coated with a thermal insulation coating 140 .

[0090] Since the first chamber 101 and the second chamber 102 in this embodiment are separated, the flow of the sublimated gas phase of the raw material powder 200 and the sublimated gas phase of the silicon crystal raw material 300 to the first chamber 101 can be reduced, thereby ensuring the utilization rate of the raw material powder 200 and the silicon crystal raw material 300 when synthesizing silicon carbide powder.

[0091] It is understandable that by applying the thermal insulation coating 140 on the inner side of the first chamber 101 , the heat dissipation in the crucible 100 can be reduced, the first chamber 101 can play a certain role in thermal insulation, and improve the thermal utilization rate of the crucible 100 when synthesizing powder.

[0092] Optionally, the thermal insulation coating 140 may be a tantalum carbide coating or a niobium carbide coating. Of course, the thermal insulation coating 140 may also be a coating formed of other materials capable of achieving thermal insulation.

[0093] In detail, in this embodiment, the crucible 100 includes a crucible body 110 and a crucible cover 120. The crucible body 110 is provided with an annular mounting groove 1110. The mounting groove 1110 includes a connecting inner wall 1111 and a connecting end wall 1112 at an angle. The connecting inner wall 1111 is provided with an internal thread, and the crucible cover 120 is provided with an external thread threadedly connected to the crucible body 110, thereby ensuring the connection strength between the crucible cover 120 and the crucible body 110.

[0094] In this embodiment, the silicon carbide wafer 130 overlaps the connecting end wall 1112, and the crucible cover 120 is pressed against the side of the silicon carbide wafer 130 away from the connecting end wall 1112, thereby effectively ensuring the installation strength of the silicon carbide wafer 130 in the crucible 100. In other words, in this embodiment, the thermal insulation coating 140 is applied to the inner wall of the crucible cover 120.

[0095] The silicon carbide powder synthesis apparatus 1 further includes a heating assembly, which optionally includes a resistance furnace. The crucible 100 is placed in the resistance furnace, which is used to heat the crucible 100. It is understood that heating in a resistance furnace provides relatively small radial and axial temperature gradients, which facilitates in-situ reaction of the raw materials to form silicon carbide powder.

[0096] Of course, in some other embodiments, the crucible 100 may be heated in other ways.

[0097] In summary, an embodiment of the present invention provides a method and device for synthesizing silicon carbide powder. The method for synthesizing silicon carbide powder is applied to a silicon carbide powder synthesis device 1. During the synthesis of silicon carbide powder, at a certain temperature, the silicon rod 320 begins to melt and diffuse into the carbon powder. Since the carbon powder has high porosity and good adsorption properties, the carbon powder can penetrate with the silicon melt to form a large silicon-carbon mixture, which can then react at high temperature to generate silicon carbide powder. Moreover, each silicon rod 320 can form a nucleation point for the silicon-carbon mixture. Under the action of multiple silicon rods 320, a large silicon-carbon mixture can be formed to react at high temperature to form silicon carbide powder, thereby improving the yield of large-size silicon carbide powder.

[0098] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for synthesizing silicon carbide powder, characterized in that: The method comprises: Filling a raw material powder (200) into a crucible (100), wherein the raw material powder (200) includes carbon powder and further includes a crystal stabilizer, wherein the crystal stabilizer is used to reduce the interfacial energy of silicon carbide particles; A silicon crystal raw material (300) is filled into the crucible (100), wherein the silicon crystal raw material (300) comprises a plurality of silicon rods (320), the plurality of silicon rods (320) are arranged at intervals, and the silicon rods (320) are accommodated in the raw material powder (200); The silicon crystal raw material (300) is melted in the carbon powder, and the silicon crystal raw material and the carbon powder are reacted together at a first preset temperature to generate silicon carbide powder; The crucible (100) is further provided with a silicon carbide wafer (130), and the silicon carbide wafer (130) separates the crucible (100) into a first chamber (101) and a second chamber (102), wherein the first chamber (101) is located on a side of the silicon carbide wafer (130) away from the raw material powder (200), and the silicon carbide wafer (130) is used to deposit silicon carbide powder at the first preset temperature.

2. The method for synthesizing silicon carbide powder according to claim 1, wherein: The crystal stabilizer accounts for 0.5-1.2% of the charge amount of the raw material powder (200).

3. The method for synthesizing silicon carbide powder according to claim 1, wherein: The crystal stabilizer is any one of magnesium borate, cerium oxide or cerium silicide.

4. The method for synthesizing silicon carbide powder according to claim 1, wherein: The first preset temperature is 2000~2400℃.

5. The method for synthesizing silicon carbide powder according to claim 1, wherein: Before causing the silicon crystal raw material and the carbon powder to react together at the first preset temperature to generate silicon carbide powder, the method further includes: Evacuating the crucible (100) so that the pressure inside the crucible (100) is at a first preset pressure; An inert gas is filled into the crucible (100) and the pressure in the crucible (100) is set to a second preset pressure, wherein the inert gas includes argon.

6. The method for synthesizing silicon carbide powder according to claim 1, wherein: The inner wall of the first chamber (101) is coated with a thermal insulation coating (140).

7. The method for synthesizing silicon carbide powder according to claim 1, wherein: The silicon crystal raw material (300) further includes a silicon plate (310), and a plurality of silicon rods (320) are arranged at intervals on the silicon plate (310); The method for filling the raw material powder (200) into the crucible (100) comprises: Laying a raw material powder (200) of a preset thickness on the bottom of the crucible (100); Placing the silicon crystal raw material (300) in a crucible (100), and placing the silicon plate (310) on the surface of the raw material powder (200) of the preset thickness; The raw material powder (200) is continuously poured into the crucible (100), and the raw material powder (200) is made to submerge the silicon crystal raw material (300).

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