A method of synthesizing silicon carbide powder

Abstract

The application provides a method for synthesizing silicon carbide powder, comprising the following steps: S1: selecting a silicon raw material to crush to obtain silicon particles; S2: carrying out etching treatment on the silicon particles obtained in the step S1 to obtain porous silicon particles; S3: mixing the porous silicon particles obtained in the step S2 with carbon powder at a molar ratio of (1.2-1):1, and then placing the mixture into a graphite crucible; S4: carrying out secondary temperature increasing and heating treatment on the graphite crucible treated in the step S3, heating to 1000-1300 DEG C for the first time to carry out reaction, and then heating to 1800-2100 DEG C for the second time to carry out reaction; and S5: obtaining a silicon carbide synthesis block after the graphite crucible is cooled, and completing the treatment. Through the method, the problems of small particle size, low yield, low raw material utilization rate and instability in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of silicon carbide powder synthesis, in particular, to a method for synthesizing silicon carbide powder. BACKGROUND

[0002] Silicon carbide (SiC) is a typical representative of the third generation of semiconductor materials, which has excellent comprehensive performance such as high thermal conductivity, wide band gap, high chemical stability, and strong radiation resistance compared with the first generation of Si and the second generation of GaAs semiconductor materials. This makes SiC semiconductor materials be used for preparing high-power power electronic devices and microwave devices, and has been widely used in high-voltage power transmission, 5G communication, electric vehicles, etc. SiC semiconductor materials and devices have become an industry that countries strive to develop.

[0003] At present, silicon carbide wafers are mainly prepared by sublimation method, which mainly includes three steps: sublimation of silicon carbide powder, transportation of sublimation product, and surface reaction and crystallization. In order to ensure the quality of silicon carbide, it is necessary to ensure the stable mass transfer in the sublimation process. In the sublimation process of silicon carbide powder, the purity of raw materials, the carbon-silicon ratio and the particle size affect the stability of mass transfer, among which the carbon-silicon ratio of raw materials is the most important factor, and silicon carbide powder with balanced carbon-silicon ratio needs to be used.

[0004] The prior art mainly uses solid phase synthesis method to prepare silicon carbide powder, carbon powder and silicon powder are uniformly mixed in a certain proportion, the mixed raw materials are transferred to a graphite crucible by a quartz beaker, the upper cover is covered, and then put into a raw material synthesis furnace for solid phase reaction to generate silicon carbide polycrystalline particles.

[0005] In the prior art, silicon powder starts to melt at 1410℃ or above, and gradually reacts with carbon powder in the process of temperature rising. The reaction is basically complete when the temperature reaches 2000℃ or above. Due to the existence of temperature gradient in the longitudinal direction of graphite crucible, silicon will volatilize to reduce the silicon content at the bottom of raw materials before reaching the reaction temperature of 2000℃ or above, forming a carbon-rich layer at the bottom and a silicon-rich layer at the top. After reaching the reaction temperature, the bottom cannot crystallize, and the carbon-silicon ratio of the top crystalline body is unbalanced, resulting in small particle size and low yield of silicon carbide powder meeting the requirements of sublimation method. The effective utilization rate of silicon carbide prepared by solid phase synthesis method is low.

[0006] Compared to large-particle-size silicon carbide powder, small-particle-size silicon carbide powder has a higher packing density in the crucible. During sublimation, the channels for sublimation gas are smaller, resulting in a lower gas production and a slower sublimation rate. Furthermore, the sublimation gas tends to remain trapped within the silicon carbide powder, and as the sublimation reaction proceeds, sintering occurs between the powder particles, ultimately leading to a gradually decreasing sublimation rate and an inability to maintain a stable rate. Therefore, small-particle-size silicon carbide powder exhibits a low and unstable sublimation rate during the sublimation process for preparing silicon carbide crystals. Simultaneously, after complete graphitization, the lighter weight of small-particle-size silicon carbide powder makes it easier for the sublimation gas to carry it to the crystal surface, resulting in graphite inclusions within the crystal. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for synthesizing silicon carbide powder, so as to solve the problems of low effective utilization rate of silicon carbide, small particle size of synthesized silicon carbide and low yield in the prior art when synthesizing silicon carbide powder.

[0008] To overcome the shortcomings of the prior art, this invention provides a method for synthesizing silicon carbide powder, comprising the following steps:

[0009] S1: Select silicon raw materials and crush them to obtain silicon particles;

[0010] S2: The silicon particles obtained in step S1 are processed to obtain porous silicon particles.

[0011] S3: The porous silicon particles obtained in step S2 are mixed with carbon powder at a molar ratio of (1.2-1):1 and then placed in a graphite crucible;

[0012] S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1000-1300℃ for reaction, and then the second heating is carried out at 1800-2100℃ for reaction.

[0013] S5: After the graphite crucible cools down, silicon carbide synthesis blocks are obtained, and the process is completed.

[0014] This invention proposes a method for synthesizing silicon carbide powder. By porousening the surface of large-diameter silicon particles, silicon particles with surface micropores are obtained. During the solid-phase reaction with carbon powder, the high specific surface area of ​​the silicon particles provides more reaction sites, resulting in large-sized silicon carbide particles. These particles are used as raw materials to provide a stable silicon / carbon ratio during silicon carbide crystal growth, reducing defects during crystal growth. The methods for preparing porous silicon particles include electrochemical etching, metal-assisted chemical etching, laser etching, and etchant methods. The surface-treated porous silicon particles have high surface area and activity, which is crucial for the efficiency of subsequent high-temperature synthesis reactions. In the first stage of high-temperature synthesis (1000–1300℃), the main purpose is to activate the initial reaction between silicon and carbon. Because the surface of the silicon particles has been treated into a porous structure, their contact area with the carbon powder is increased, leading to a more complete reaction and improved reaction efficiency. This allows the silicon particles to fully react with the carbon particles before volatilization to form silicon carbide particles. Within a temperature range of 1000 to 1300 °C, silicon and carbon in the mixture react to form the low-temperature phase α-SiC. Further heating in the second stage (1800–2100 °C) on top of the low-temperature silicon carbide phase formed in the first stage can further improve the crystal quality of silicon carbide and increase the overall purity of the material. The high temperature in this stage can promote the complete conversion of more unreacted silicon and carbon, and gradually transform the low-temperature α-SiC phase into the thermodynamically more stable high-temperature phase β-SiC.

[0015] In one possible implementation, in step S1, the silicon raw material is either polycrystalline silicon or monocrystalline silicon.

[0016] In one possible implementation, in step S1, the silicon particles have a particle size of 300-1000 μm. If the particle size is too small, it is difficult to obtain large-sized silicon carbide particles during the synthesis process. If the particle size is too large, the synthesis reaction is difficult to diffuse into the interior of the silicon particles, preventing the silicon particles from completely transforming into silicon carbide.

[0017] In one possible implementation, in step S2, the surface treatment method is one of electrochemical etching, metal-assisted chemical etching, laser etching, and etchant method, which forms a microporous morphology on the surface of silicon particles.

[0018] In one possible implementation, in step S2, the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g, so that silicon particles and carbon powder can form sufficient reaction sites during the high-temperature synthesis reaction.

[0019] In one possible implementation, in step S3, the particle size of the toner is in the range of 10-100 μm, so that the toner can form a good surface coating with the silicon particles.

[0020] In one possible implementation, in step S4, the first heating reaction time is 5-10 hours, causing the silicon particles and carbon powder to undergo a synthesis reaction and transform into low-temperature phase silicon carbide particles. The second heating reaction time is 15-30 hours, causing the low-temperature phase silicon carbide particles to grow and transform into high-temperature phase silicon carbide particles.

[0021] In one possible implementation, step S5, after obtaining the silicon carbide synthesis block, further includes crushing, screening, washing, and drying the synthesis block to obtain finished silicon carbide powder. Attached Figure Description

[0022] Figure 1 This refers to the porous silicon surface morphology formed by metal-assisted chemical etching of silicon particles in this invention.

[0023] Figure 2 The morphology of silicon carbide particles prepared in Example 1 of this invention;

[0024] Figure 3 This is the morphology of silicon carbide particles prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0025] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0026] This invention provides a method for synthesizing silicon carbide powder, comprising the following steps:

[0027] S1: Select silicon raw materials and crush them to obtain silicon particles;

[0028] S2: The silicon particles obtained in step S1 are etched to obtain porous silicon particles;

[0029] S3: The porous silicon particles obtained in step S2 are mixed with carbon powder at a molar ratio of (1.2-1):1 and then placed in a graphite crucible;

[0030] S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1000-1300℃ for reaction, and then the second heating is carried out at 1800-2100℃ for reaction.

[0031] S5: After the graphite crucible cools down, silicon carbide synthesis blocks are obtained, and the process is completed.

[0032] As a preferred embodiment, in step S1, the silicon raw material is either polycrystalline silicon or monocrystalline silicon.

[0033] As a preferred embodiment, in step S1, the particle size of the silicon particles is 300-500 μm.

[0034] As a preferred embodiment, in step S2, the corrosion treatment method is one of electrochemical corrosion, wet chemical corrosion, or hydrothermal corrosion.

[0035] As a preferred embodiment, in step S2, the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g.

[0036] As a preferred embodiment, in step S3, the particle size range of the toner is 10-100 μm.

[0037] As a preferred embodiment, in step S4, the reaction time for the first heating is 5-10 hours, and the reaction time for the second heating is 15-30 hours.

[0038] As a preferred embodiment, in step S5, after obtaining the silicon carbide synthesis block, the synthesis block is further subjected to crushing, screening, washing, and drying processes to obtain finished silicon carbide powder.

[0039] The following section further elaborates on the present invention in conjunction with the above preparation method and data range:

[0040] Example 1:

[0041] This embodiment provides a method for synthesizing silicon carbide powder, including the following steps:

[0042] S1: Select polycrystalline silicon material and crush it to obtain silicon particles with a particle size of 300-500um;

[0043] S2: The silicon particles obtained in step S1 are subjected to metal-assisted chemical etching to obtain porous silicon particles, wherein the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g;

[0044] S3: The porous silicon particles obtained in step S2 are mixed with carbon powder with a particle size range of 10-100um at a molar ratio of 1.1:1 and then placed in a graphite crucible;

[0045] S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1000-1300°C for 7.5 hours. Then, the second heating is carried out at 1950°C for 22.5 hours.

[0046] S5: After the graphite crucible cools down, a silicon carbide synthesis block is obtained. The synthesis block is then crushed, sieved, washed, and dried to obtain finished silicon carbide powder, thus completing the process.

[0047] In Example 1, the silicon carbide synthesis yield was 97.6%, and the proportion of silicon carbide particles with a particle size >500 μm in the prepared finished silicon carbide powder was 85.5%.

[0048] Example 2:

[0049] This embodiment provides a method for synthesizing silicon carbide powder, including the following steps:

[0050] S1: Select polycrystalline silicon material and crush it to obtain silicon particles with a particle size of 500-800um;

[0051] S2: The silicon particles obtained in step S1 are subjected to electrochemical etching to obtain porous silicon particles, wherein the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g;

[0052] S3: The porous silicon particles obtained in step S2 are mixed with carbon powder with a particle size range of 10-100um in a 1:1 molar ratio and then placed in a graphite crucible.

[0053] S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1000°C for 5 hours, and the second heating is carried out at 1800°C for 15 hours.

[0054] S5: After the graphite crucible cools down, a silicon carbide synthesis block is obtained. The synthesis block is then crushed, sieved, washed, and dried to obtain finished silicon carbide powder, thus completing the process.

[0055] In Example 2, the silicon carbide synthesis yield was 95.3%, and the proportion of silicon carbide particles with a particle size >500 μm in the prepared finished silicon carbide powder was 83.2%.

[0056] Example 3:

[0057] This embodiment provides a method for synthesizing silicon carbide powder, including the following steps:

[0058] S1: Select polycrystalline silicon material and crush it to obtain silicon particles with a particle size of 300-500um;

[0059] S2: The silicon particles obtained in step S1 are subjected to electrochemical etching to obtain porous silicon particles, wherein the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g;

[0060] S3: The porous silicon particles obtained in step S2 are mixed with carbon powder with a particle size range of 10-100um at a molar ratio of 1.2:1 and then placed in a graphite crucible;

[0061] S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1300°C for 10 hours, and the second heating is carried out at 2100°C for 30 hours.

[0062] S5: After the graphite crucible cools down, a silicon carbide synthesis block is obtained. The synthesis block is then crushed, sieved, washed, and dried to obtain finished silicon carbide powder, thus completing the process.

[0063] In Example 3, the silicon carbide synthesis yield was 96.5%, and the proportion of silicon carbide particles with a particle size >500 μm in the prepared finished silicon carbide powder was 84.7%.

[0064] Comparative Example 1:

[0065] This comparative example provides a method for synthesizing silicon carbide powder, including the following steps:

[0066] S1: Select polycrystalline silicon material and crush it to obtain silicon particles with a particle size of 100-300um;

[0067] S2: The silicon particles obtained in step S1 are subjected to metal-assisted chemical etching to obtain porous silicon particles, wherein the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g;

[0068] S3: The porous silicon particles obtained in step S2 are mixed with carbon powder with a particle size range of 10-100um at a molar ratio of 1.1:1 and then placed in a graphite crucible;

[0069] S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1000-1300°C for 7.5 hours. Then, the second heating is carried out at 1950°C for 22.5 hours.

[0070] S5: After the graphite crucible cools down, a silicon carbide synthesis block is obtained. The synthesis block is then crushed, sieved, washed, and dried to obtain finished silicon carbide powder, thus completing the process.

[0071] In Comparative Example 1, the silicon carbide synthesis yield was 92.1%, and the proportion of silicon carbide particles with a particle size >500 μm in the prepared finished silicon carbide powder was 63.6%.

[0072] Comparative Example 2:

[0073] This comparative example provides a method for synthesizing silicon carbide powder, including the following steps:

[0074] S1: Select polycrystalline silicon material and crush it to obtain silicon particles with a particle size of 300-500um;

[0075] S2: The silicon particles obtained in step S1 are mixed with carbon powder with a particle size range of 10-100um at a molar ratio of 1.1:1 and then placed in a graphite crucible;

[0076] S4: The graphite crucible processed in step S2 is subjected to a second heating treatment. The first heating is carried out at 1000-1300°C for 7.5 hours. Then, the second heating is carried out at 1950°C for 22.5 hours.

[0077] S5: After the graphite crucible cools down, a silicon carbide synthesis block is obtained. The synthesis block is then crushed, sieved, washed, and dried to obtain finished silicon carbide powder, thus completing the process.

[0078] In Comparative Example 2, the silicon carbide synthesis yield was 89.6%, and the proportion of silicon carbide particles with a particle size >500 μm in the prepared finished silicon carbide powder was 56.8%.

[0079] like Figures 1-3 As shown, Figure 1 It refers to the porous silicon surface morphology formed after silicon particles are chemically etched with metal assistance; Figure 2 The morphology of silicon carbide particles prepared in Example 1 of this invention; Figure 3 The morphology of the silicon carbide particles prepared in Comparative Example 1 can be seen from... Figure 2 / 3 comparison and Figure 1 The morphology diagrams show that the proportion of large-diameter silicon carbide particles prepared in Example 1 of this invention is higher, and the synthesis yield of silicon carbide is also improved. The yield of silicon carbide powder is the ratio of the mass of the final silicon carbide powder to the mass of the raw material.

[0080] The test and analysis of the results of Examples 1-3 and Comparative Examples 1-2 proved that the method for synthesizing silicon carbide powder provided by the present invention has high synthesis efficiency, a higher proportion of large-diameter silicon carbide particles, and significantly improved preparation yield, and has high commercialization and promotion value.

[0081] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0082] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0083] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for synthesizing silicon carbide powder, characterized in that, Includes the following steps: S1: Select silicon raw materials and crush them to obtain silicon particles; S2: The silicon particles obtained in step S1 are etched to obtain porous silicon particles; S3: The porous silicon particles obtained in step S2 are mixed with carbon powder at a molar ratio of (1.2-1):1 and then placed in a graphite crucible; S4: The graphite crucible processed in step S3 is subjected to a second heating treatment. The first heating is carried out at 1000-1300℃ for reaction, and then the second heating is carried out at 1800-2100℃ for reaction. S5: After the graphite crucible cools down, silicon carbide synthesis blocks are obtained, and the process is completed; In step S1, the particle size of the silicon particles is 300-1000 μm; In step S2, the specific surface area of ​​the porous silicon particles is >200 cm². 2 / g; In step S3, the particle size range of the toner is 10-100 μm.

2. The method for synthesizing silicon carbide powder according to claim 1, characterized in that, In step S1, the silicon raw material is either polycrystalline silicon or monocrystalline silicon.

3. The method for synthesizing silicon carbide powder according to claim 1, characterized in that, In step S2, the corrosion treatment method is one of electrochemical etching, metal-assisted chemical etching, laser etching, and etchant method.

4. The method for synthesizing silicon carbide powder according to claim 1, characterized in that, In step S4, the reaction time for the first heating is 5-10 hours, and the reaction time for the second heating is 15-30 hours.

5. The method for synthesizing silicon carbide powder according to claim 1, characterized in that, In step S5, after obtaining the silicon carbide synthesis block, the process further includes crushing, screening, washing, and drying the synthesis block to obtain finished silicon carbide powder.

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