CN116803951B

CN116803951B - High-purity high-resistivity silicon carbide workpiece and forming process thereof

Info

Publication number: CN116803951B
Application number: CN202310891238.7A
Authority: CN
Inventors: 李靖晗; 张慧; 王力; 李华民; 包根平
Original assignee: Beijing Yisheng Precision Semiconductor Co ltd
Current assignee: Beijing Yisheng Precision Semiconductor Co ltd
Priority date: 2023-07-19
Filing date: 2023-07-19
Publication date: 2024-03-05
Anticipated expiration: 2043-07-19
Also published as: CN116803951A

Abstract

The application relates to the technical field of ceramic materials, and particularly discloses a high-purity high-resistivity silicon carbide workpiece and a forming process thereof. The process is as follows: slicing the digital model, respectively performing chemical vapor deposition on high-purity high-resistivity silicon carbide slices in the slice shape, and assembling and sintering the deposited high-purity high-resistivity silicon carbide slices to obtain the target product. By controlling slicing parameters, the whole part is 'integrated into zero', and the parts are respectively deposited, so that the preparation efficiency of chemical vapor deposition is greatly improved on the basis of precisely controlling the molding. The high purity high resistivity silicon carbide manufactured by the molding process has high purity (more than 99.98 percent) and high density (more than 3.204 g/cm) ³ ) Low machining reduction (0.4-1%), high hardness (3405 HV), high resistivity (more than 4.32X10) ⁶ Omega cm), and the like, and has the intrinsic characteristics of wear resistance, corrosion resistance, high temperature resistance and the like of the silicon carbide material.

Description

High-purity high-resistivity silicon carbide workpiece and forming process thereof

Technical Field

The application relates to the technical field of ceramic materials, in particular to a high-purity high-resistivity silicon carbide workpiece and a forming process thereof.

Background

Silicon carbide has the advantages of high hardness, high strength, high temperature resistance, corrosion resistance, wear resistance and the like due to the strong covalent bond property of Si-C bond, and has proper electrical characteristics. The advantages can make the high-purity silicon carbide products (bracket, flange, clamp, guide rail, etc.) work for a long time in special environments of high radiation, high temperature, high corrosiveness, etc., and have high demands in high added value industries of chip etching, aerospace, nuclear industry, etc.

The existing sintering technology mainly based on the Chinese invention patent CN104098335A can solve the problem of low resistivity of the silicon carbide ceramic parts to a certain extent by hybridization of amorphous phase, but has the following obvious defects due to process limitation: the sintering process still adds a large amount of sintering auxiliary agents, so that the purity of the silicon carbide is greatly reduced, and the excessive elements such as Al, O, er and the like have great influence on the environment in the clean cavity; the compactness caused by the sintering process is difficult to ensure, so that the corrosion resistance is to be verified.

Based on journal Journal of Crystal Growth,1978,43 (2): 209-212, the existing technology is based on the physical vapor transmission mode based on Chinese patent No. CN109234805A, which can produce high purity, high resistivity and high density silicon carbide bulk material, but has the following obvious disadvantages due to the technology limitation: the process technology can only produce column/cake-shaped monocrystalline silicon carbide, and the silicon carbide material must be mechanically processed under the application condition; the extremely high hardness of the silicon carbide makes the machine-added type finished product extremely difficult, and the yield is difficult to ensure; the massive high-purity high-resistivity high-density silicon carbide material has high manufacturing cost, and the large cutting amount causes great waste.

The conventional molding powder sintering process can mold and produce silicon carbide parts of simple shape to some extent, but has the following significant drawbacks due to process limitations: because of the characteristic that silicon carbide is not easy to sinter, a large amount of C, B sintering aids are required to be added, and the purity, density and resistivity performance of the finished product are usually insufficient; for long and branched workpieces with complex shapes, the problems of demolding damage, workpiece blank deformation and the like can be faced during mold opening, and particularly, the mold with complex structure in multi-side core pulling and multi-parting directions is difficult to design and difficult to form under high pressure. Therefore, when preparing multi-lug and long-extension silicon carbide products (brackets, flanges, clamps, guide rails and the like), the traditional molding powder sintering process is difficult to mold, and the purity, density and resistivity of the products are difficult to ensure.

The prior art mainly based on the Chinese invention patent CN108409330B is a 3D printing process for direct ink writing, which can form a product with higher purity (99 percent) and higher density (3.168 g/cm) ³ ) But because of process limitations, the following disadvantages exist: the direct ink writing 3D printing process is difficult to print a supporting structure in the forming process, and is difficult to maintain the shape when forming the long and branched structure such as a bracket; the silicon carbide complex product prepared by the process contains a large amount of SiO inside ₂ The particles are introduced with a large amount of oxygen element impurities, so that the high-temperature application effect of the particles is greatly limited; the purity (99%) of the silicon carbide product prepared by the process still cannot meet the requirements of high-grade clean rooms.

In summary, the preparation of the high-purity, high-density, high-resistivity multi-bump, long-extension silicon carbide effective product is difficult to solve due to the process limitations of the sintering nature of silicon carbide and the intrinsic too high hardness value of the material. At present, no related technical report on the preparation of high-purity, high-density and high-resistivity silicon carbide relatively complex parts (brackets, special flanges, clamps, guide rails and the like) exists.

Disclosure of Invention

The silicon carbide manufactured by the traditional process usually adopts a die pressing powder sintering process, but the density of the manufactured part is insufficient due to the low sintering diffusion characteristic of the silicon carbide, and the purity is insufficient due to the addition of a large amount of sintering aids, so that the resistivity is low, and the corrosion resistance and the high temperature resistance are poor. The silicon carbide product with high purity and high resistivity can also be prepared by a physical vapor transmission method, and a simple product is formed by a mechanical processing mode. However, the silicon carbide has the advantages of complex manufacturing process and high cost, the process is limited to be incapable of preparing the special-shaped structure, the machining is extremely difficult due to the extremely high hardness of the silicon carbide, the yield is difficult to ensure, and the large cutting amount causes extremely waste.

Aiming at the situation, in order to overcome the defects that the purity, density and resistivity of the silicon carbide workpiece prepared by the existing sintering technology are insufficient, and the multi-lug and long-extension type workpiece is difficult to prepare, the forming and the preparation of the high-purity high-resistivity silicon carbide workpiece are realized, the application creatively provides the high-purity high-resistivity silicon carbide workpiece and the forming process thereof, and the difficult problem that the workpiece cannot be effectively prepared is solved.

In a first aspect, the present application provides a process for forming a high purity high resistivity silicon carbide part, which adopts the following technical scheme:

a molding process of a high-purity high-resistivity silicon carbide workpiece specifically comprises the following steps (note: impurity ions and small-particle-size particles cannot be introduced in the whole process):

step 1: establishing a silicon carbide part digital model by using 3D modeling software;

step 2: performing slicing operation on the silicon carbide workpiece digital model for a plurality of times in the direction vertical to the z-axis direction of the silicon carbide workpiece digital model, and projecting in the vertical direction of slicing to obtain a two-dimensional graph of slicing;

step 3: preparing a substrate mould for chemical vapor deposition with a corresponding shape according to the two-dimensional pattern of the slice;

step 4: chemical vapor deposition of a high-purity silicon carbide sheet on the substrate die, and controlling the deposition thickness of the high-purity silicon carbide sheet obtained by deposition to be consistent with the thickness of the slice;

step 5: taking out the high-purity silicon carbide sheet and the substrate die obtained by deposition in the step 4, and placing the high-purity silicon carbide sheet and the substrate die in a muffle furnace for uniform heating until the substrate die is completely oxidized and removed, so as to obtain the high-purity silicon carbide sheet;

step 6: double-sided grinding and polishing are carried out on the high-purity silicon carbide sheet obtained in the step 5, and an oxide layer of tens of microns on the surface of the silicon carbide is removed, so that the high-purity silicon carbide sheet after grinding and polishing is obtained;

step 7: preparing a high-purity carbon layer on one single surface of the polished high-purity silicon carbide sheet;

step 8: preparing a high-purity silicon layer on the other single side of the high-purity silicon carbide sheet obtained in the step 7;

step 9: assembling the high-purity silicon carbide sheet obtained in the step 8 according to the slicing sequence of the digital model of the silicon carbide workpiece to obtain a silicon carbide assembly, and ensuring that both sides of all contact areas are respectively a high-purity silicon layer and a high-purity carbon layer;

step 10: placing the silicon carbide assembly in an atmosphere furnace for sintering to bond and mold the high-purity silicon carbide sheet, thus obtaining a molded part;

step 11: and (3) carrying out finish machining on the molded part to obtain the high-purity high-resistivity silicon carbide part.

The application innovatively provides a forming process, which comprises the following steps: slicing the digital model, respectively performing chemical vapor deposition on high-purity high-resistivity silicon carbide slices in the slice shape, and assembling and sintering the deposited high-purity high-resistivity silicon carbide slices to obtain the target product. By controlling slicing parameters, the whole part is 'integrated into zero', and the parts are respectively deposited, so that the preparation efficiency of chemical vapor deposition is greatly improved on the basis of precisely controlling the molding. By precisely controlling the thickness and the components of the contact surface high-purity silicon layer/high-purity carbon layer and the multi-stage sintering temperature gradient, the assembly sintering is feasible, the bonding is firm, and the product is stable. The high purity high resistivity silicon carbide manufactured by the molding process has high purity (more than 99.98 percent) and high density (more than 3.204 g/cm) ³ ) Low machining reduction (0.4-1%), high hardness (3405 HV), high resistivity (more than 4.32X10) ⁶ Omega cm), and the like, and has the intrinsic characteristics of wear resistance, corrosion resistance, high temperature resistance and the like of the silicon carbide material.

The 3D modeling software mentioned in step 1 of the present application is used to build a digital model of a silicon carbide part, and 3D modeling software that can achieve this objective in the prior art can be used in the present application.

Preferably, in the step 1, the z-axis direction dimension of the digital model is multiplied by a factor of 1.02-1.05.

Preferably, in the step 2, the slice thickness and the slice height are selected according to the actual size and the actual characteristics of the digital model of the silicon carbide workpiece.

Preferably, the lateral expansion of the silicon carbide part digital model is selected as a slice edge position.

Preferably, the slice thickness is 0.5-5mm.

Preferably, in the step 3, the x-axis and y-axis direction dimensions of the silicon carbide workpiece digital model are multiplied by 1.05-1.1 coefficients.

Preferably, the substrate mold is a high purity graphite mold.

Preferably, the thickness of the base mold is 1-2mm.

Preferably, in the step 4, the deposition time and the gas pressure of the chemical vapor deposition are controlled so that the deposition thickness of the high-purity silicon carbide sheet obtained by deposition is consistent with the thickness of the slice in the step 2.

Preferably, the high purity silicon carbide is deposited to a thickness of 0.5-5mm.

Preferably, the reaction gas of the chemical vapor deposition adopts CH ₃ SiCl ₃ 、C ₇ H ₂₀ Si ₂ 、SiH ₄ 、SiH ₃ Cl、SiH ₂ Cl ₂ 、SiHCl ₃ 、SiCl ₄ One or more of methane, ethane, propane and butane.

Preferably, the reaction gas is high purity CH ₃ SiCl ₃ 。

Preferably, the carrier gas component of the chemical vapor deposition is high-purity H ₂ 。

Preferably, the flow ratio of carrier gas to reactant gas for the chemical vapor deposition is 6-10.

Preferably, the reaction temperature of the chemical vapor deposition is 1000-1350 ℃.

Preferably, the reaction temperature rise and fall speed of the chemical vapor deposition is 1-5 ℃/min.

Preferably, the dispersed gas component of the chemical vapor deposition is high-purity Ar gas.

Preferably, the dispersed gas is 40-90% of the whole.

Preferably, the pressure in the chemical vapor deposition chamber is 100-1500Pa.

Preferably, the temperature in the muffle furnace is 700-800 ℃.

Preferably, in the step 6, the polishing process is a conventional high-purity material polishing process.

Preferably, the surface roughness of the polished high-purity silicon carbide sheet is Ra0.25-1.6.

Preferably, the preparation method of the high-purity carbon layer comprises, but is not limited to, low-pressure chemical vapor deposition and vacuum evaporation.

Preferably, the high purity carbon layer has a thickness of 0.6 to 5 μm.

Preferably, the surface roughness of the high purity carbon layer is greater than Ra 0.4.

Preferably, masking measures are taken to avoid deposition on the surface of the non-contact area.

Preferably, the preparation method of the high-purity silicon layer comprises, but is not limited to, a thin film preparation method such as plasma enhanced chemical vapor deposition, low-pressure chemical vapor deposition, vacuum evaporation and the like.

Preferably, the high purity silicon layer has a thickness of 0.5-5 μm.

Preferably, the high purity silicon layer is an amorphous phase or a fine crystalline phase.

Preferably, in the step 9, the high purity silicon layer of each contact surface is placed on the high purity carbon layer during assembly.

Preferably, continuous pressure is applied in the direction perpendicular to the slice after assembly.

Preferably, the applied pressure is 0.05-3MPa.

Preferably, in the step 10, the sintering process is as follows: two-stage sintering curves under Ar gas protection are adopted, namely medium-temperature reaction sintering and high-temperature diffusion sintering.

Preferably, the sintering curve of the sintering is: heating to 1450-1600 deg.C at a heating rate of 1-5 deg.C/min, maintaining for 1-3h, heating to 2100-2200 deg.C at a heating rate of 0.5-3 deg.C, maintaining for 0.5-3h, and cooling to room temperature at a cooling rate of 3-10 deg.C/min.

Preferably, in the step 11, the finishing is to round corners at the sintering transition of the slices.

In a second aspect, the present application provides a high purity, high resistivity silicon carbide article made using the above-described molding process.

In summary, the present application has the following beneficial effects:

the application provides a brand new preparation thought for preparing the silicon carbide workpiece. The method comprises the steps of adopting a digital model for slicing, respectively carrying out chemical vapor deposition on high-purity high-resistivity silicon carbide slices in the slice shape, and assembling and sintering the deposited high-purity high-resistivity silicon carbide slices to obtain the innovative process of the target product. Compared with the process for preparing the silicon carbide workpiece in the prior art, the method has the following advantages:

1. the method can prepare high-purity high-resistivity silicon carbide workpieces (brackets, flanges, clamps, guide rails and the like) with complex structures, can avoid the problems of die opening damage, blank deformation and the like of the existing die pressing powder sintering process, and can form longer stretching workpieces.

2. The forming thought of the high-purity high-resistivity silicon carbide workpiece which is integrated into zero and integrated into one avoids the powder metallurgy process for preparing the relatively complex workpiece, thereby avoiding the problem of adding a large amount of auxiliary agents and greatly improving the purity and density of the workpiece. The silicon carbide products of the present application have high purity (> 99.99%), high density (> 3.204 g/cm) ³ ) Is excellent in performance.

3. For the high-purity high-resistivity silicon carbide manufactured by the method, the product can be manufactured by only about 0.4-1% of machining reduction after assembly and sintering molding, so that the problem of mass cutting processing of column/cake-shaped high-purity silicon carbide materials prepared by a physical gas phase transmission mode is avoided, the difficult problem of difficult processing of high-purity silicon carbide with high hardness is avoided to a great extent, the yield is improved greatly, and the method is suitable for industrial mass production.

4. The high-purity high-resistivity silicon carbide manufactured piece prepared by the method has high hardness (3405 HV) and high resistivity (more than 4.32X10) ⁶ Omega cm), etcThe silicon carbide material has the advantages of wear resistance, corrosion resistance, high temperature resistance and other intrinsic characteristics.

Drawings

FIG. 1 is a flow chart of a process for forming a high purity high resistivity silicon carbide article provided herein.

Fig. 2 is a schematic diagram of a digital model of a silicon carbide article in example 1.

FIG. 3 is a two-dimensional graph of a slice of a digital model of a silicon carbide article of example 1.

Fig. 4 is a schematic representation of a digital model of a silicon carbide article in example 2.

FIG. 5 is a two-dimensional graph of a slice of a digital model of a silicon carbide article of example 2.

Detailed Description

The forming process of the high-purity high-resistivity silicon carbide workpiece provided by the application specifically comprises the following steps:

step 1: a digital model of the silicon carbide part is built using 3D modeling software. In order to counteract the defect of the silicon carbide workpiece in the z-axis direction caused by the polishing operation, the z-axis direction dimension of the digital model is multiplied by an error coefficient. Preferably, the z-axis dimension of the digital model is multiplied by a factor of 1.02-1.05.

Step 2: and (3) on the basis of the digital model of the silicon carbide workpiece obtained in the step (1), carrying out slicing operation on the digital model of the silicon carbide workpiece for a plurality of times in the direction vertical to the z-axis of the digital model of the silicon carbide workpiece, and carrying out projection in the vertical direction of slicing to obtain a two-dimensional graph of slicing. The slice thickness and slice height are selected based on the actual dimensions of the silicon carbide article, the actual characteristics. Preferably, the slice thickness is 0.5-5mm.

Step 3: preparing a substrate mold for chemical vapor deposition with a corresponding shape according to the two-dimensional pattern of the slice obtained in the step 2. And (5) reserving a margin for the subsequent small machine tool, and multiplying the dimension of the digital model in the x-axis direction and the y-axis direction by an error coefficient. Preferably, the x-axis and y-axis dimensions of the digital model of the silicon carbide workpiece are multiplied by a factor of 1.05-1.1. Preferably, the thickness of the base mold is 1-2mm.

Step 4: and (3) performing chemical vapor deposition on the high-purity silicon carbide sheet on the substrate die obtained in the step (3), and controlling the deposition time and the gas pressure of the chemical vapor deposition to ensure that the deposition thickness of the high-purity silicon carbide sheet obtained by deposition is consistent with the slice thickness in the step (2). Preferably, the high purity silicon carbide is deposited to a thickness of 0.5-5mm.

Step 5: and (3) taking out the high-purity silicon carbide sheet and the substrate die obtained by deposition in the step (4), and placing the high-purity silicon carbide sheet and the substrate die in a muffle furnace for uniform heating until the substrate die is completely oxidized and removed, thus obtaining the high-purity silicon carbide sheet.

Step 6: and (3) carrying out proper double-sided grinding and polishing processing on the high-purity silicon carbide sheet obtained in the step (5), removing an oxide layer of tens of microns on the surface of the silicon carbide, obtaining the high-purity silicon carbide sheet after grinding and polishing processing, and retaining certain roughness. Preferably, the surface roughness of the polished high-purity silicon carbide sheet is Ra0.25-1.6.

Step 7: and (3) preparing a high-purity carbon layer on one side of the polished high-purity silicon carbide sheet obtained in the step (6). The preparation method comprises, but is not limited to, film preparation methods such as high molecular precursor film pyrolysis, low-pressure chemical vapor deposition, vacuum evaporation and the like. The high purity carbon layer prepared by the step should be as thin as possible and have a certain surface roughness. Masking measures may be taken to avoid deposition on the surface of the non-contact area. Preferably, the high purity carbon layer has a thickness of 0.6 to 5 μm. Preferably, the surface roughness of the high purity carbon layer is greater than Ra 0.4;

step 8: and 7, preparing a high-purity silicon layer on the other single side of the high-purity silicon carbide sheet obtained in the step 7. The preparation method comprises the preparation methods of films such as plasma enhanced chemical vapor deposition, low-pressure chemical vapor deposition, vacuum evaporation and the like. When the high-purity silicon layer is in an amorphous phase or a fine crystalline phase, the silicon-carbon film is more fully sintered in a reaction mode, and the impurity phases are fewer. The high-purity silicon layer prepared by the step should be as thin as possible, and the atomic molar ratio of the high-purity silicon layer to the carbon layer with the same area should be close to 1:1. Masking measures may be taken to avoid deposition on the surface of the non-contact area. Preferably, the high purity silicon layer has a thickness of 0.5-5 μm. Preferably, the high purity silicon layer is amorphous or fine crystalline;

step 9: and (3) assembling the high-purity silicon carbide sheet obtained in the step (8) according to the slicing sequence of the digital model of the silicon carbide workpiece in the step (2) to obtain a silicon carbide assembly, and ensuring that both sides of all contact areas are respectively a high-purity silicon layer and a high-purity carbon layer. For each contact surface, a high-purity silicon layer is arranged on the high-purity carbon layer, so that silicon can be fully dissolved, infiltrated and diffused and fully reacted in the liquefying process of reaction sintering. Continuous pressure can be applied in the z-axis direction (slice perpendicular direction) after assembly. Preferably, the applied pressure is 0.05-3MPa.

Step 10: and (3) placing the silicon carbide assembly obtained in the step (9) in an atmosphere furnace for sintering to bond and mold the high-purity silicon carbide sheet, and obtaining a molded product. The sintering process adopts a two-stage sintering curve (medium-temperature reaction sintering and high-temperature diffusion sintering) under Ar gas protection: the reaction sintering can lead the silicon layer to react with the rough carbon layer to generate silicon carbide, the high-temperature diffusion sintering plays a role in shaping, reduces the internal stress of the reaction layer and the thin sheet part, ensures that the crystal forms are uniform, and further ensures that the reaction is complete, thus obtaining the high-purity silicon carbide part. The higher the temperature, the larger the volume of the silicon carbide piece, and the corresponding temperature rise and fall speed is selected towards a low value interval. Continuous pressure can be applied during sintering, which is related to the number of slices, with greater applied pressure for greater numbers of slices.

Step 11: and (5) carrying out finish machining on the molded part obtained in the step (10) to obtain the high-purity high-resistivity silicon carbide part. The corner at the transition part of the cutting piece can be rounded during finish machining.

The application also provides a high-purity high-resistivity silicon carbide workpiece prepared by the molding process. The high purity high resistivity silicon carbide manufactured by the molding process has high purity (more than 99.98 percent) and high density (more than 3.204 g/cm) ³ ) Low machining reduction (0.4-1%), high hardness (3405 HV), high resistivity (more than 4.32X10) ⁶ Omega cm), and the like, and has the intrinsic characteristics of wear resistance, corrosion resistance, high temperature resistance and the like of the silicon carbide material.

For the purposes, technical solutions and advantages of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.

The present application will be described in further detail with reference to examples, drawings, comparative examples and performance test results.

Examples

Example 1

The embodiment provides a molding process of a high-purity high-resistivity silicon carbide workpiece.

The method specifically comprises the following steps:

step 1: a digital model of a silicon carbide part is established by using 3D modeling software, and in this embodiment, the digital model of the silicon carbide part is specifically shown in fig. 2. To counteract the undersize of the silicon carbide workpiece in the z-axis direction caused by the polishing operation, the z-axis dimension of the digital model is multiplied by a factor of 1.03.

Step 2: and (3) on the basis of the digital model of the silicon carbide workpiece obtained in the step (1), carrying out slicing operation on the digital model of the silicon carbide workpiece for 32 times in the direction vertical to the z-axis of the digital model of the silicon carbide workpiece, and carrying out projection in the vertical direction of slicing to obtain a two-dimensional graph of slicing. A two-dimensional graph of a slice of a digital model of a silicon carbide part in this example is shown in fig. 3. The sliced thickness of the silicon carbide article in this example was 2mm.

Step 3: and (3) preparing a high-purity graphite mold with a corresponding shape according to the two-dimensional pattern of the slice obtained in the step (2) (the high-purity graphite mold is used as a substrate for chemical vapor deposition). And (3) reserving a margin for the subsequent small machine tool, and multiplying the x-axis and y-axis direction dimensions of the digital model by a factor of 1.07. The thickness of the high-purity graphite mold is 1mm.

Step 4: and (3) chemically vapor depositing a high-purity silicon carbide sheet on the high-purity graphite mold obtained in the step (3), and controlling the deposition thickness of the high-purity silicon carbide sheet to be 2mm by controlling the deposition time. The reaction gas for deposition adopts high-purity CH ₃ SiCl ₃ The carrier gas component is high-purity H ₂ The gas flow ratio of carrier gas to reaction gas is 8, the deposition reaction temperature is 1100 ℃, the temperature rising and falling speed is 2 ℃/min, the dispersed gas component is high-purity Ar gas, the dispersed gas accounts for 70% of the whole, and the gas pressure in the chamber is 1000Pa.

Step 5: and (3) taking out the high-purity silicon carbide sheet and the high-purity graphite mold obtained by deposition in the step (4), placing the high-purity silicon carbide sheet and the high-purity graphite mold in a muffle furnace, and uniformly heating the high-purity silicon carbide sheet at the temperature of 750 ℃ in the muffle furnace until the high-purity graphite mold is completely oxidized and removed, thereby obtaining the high-purity silicon carbide sheet.

Step 6: and (3) carrying out double-sided grinding and polishing processing on the high-purity silicon carbide sheet obtained in the step (5), removing an oxide layer of tens of microns on the surface of the silicon carbide, and obtaining the high-purity silicon carbide sheet subjected to grinding and polishing processing, wherein the grinding and polishing surface roughness is Ra 0.5.

Step 7: and (3) preparing a high-purity carbon layer on one side of the polished high-purity silicon carbide sheet obtained in the step (6) by using propane as a reaction gas through chemical vapor deposition. The thickness of the high purity carbon layer was 2 μm. Masking measures are taken to avoid deposition on the surface of the non-contact area.

Step 8: and (3) preparing a high-purity silicon layer on the other side of the high-purity silicon carbide sheet (one side is a high-purity carbon layer) obtained in the step (7) by using a low-pressure chemical vapor deposition mode. The high purity silicon layer is a fine crystalline phase and has a thickness of 2 μm. Masking measures are taken to avoid deposition on the surface of the non-contact area.

Step 9: and (3) assembling the high-purity silicon carbide sheet (one surface is a high-purity carbon layer and the other surface is a high-purity silicon layer) obtained in the step (8) according to the slicing sequence of the digital model of the silicon carbide workpiece in the step (2) to obtain a silicon carbide assembly, ensuring that the high-purity silicon layers and the high-purity carbon layers are respectively arranged on the two surfaces of all contact areas, placing the high-purity silicon layer of each contact area on the high-purity carbon layer, and applying a continuous pressure of 0.5MPa in the z-axis direction (slice vertical direction) after assembling.

Step 10: and (3) placing the silicon carbide assembly obtained in the step (9) in an atmosphere furnace for sintering to bond and mold the high-purity silicon carbide sheet, and obtaining a molded product. The sintering process adopts a two-stage sintering curve (medium-temperature reaction sintering and high-temperature diffusion sintering) under the protection of Ar gas. The sintering curve is: heating to 1500 ℃ at a heating rate of 4 ℃/min, preserving heat for 2h, heating to 2100 ℃ at a heating rate of 1 ℃ and preserving heat for 2h, and cooling to room temperature at a cooling rate of 10 ℃/min.

Step 11: and (3) carrying out finish machining (carrying out rounding treatment on the edges and corners of the sintering transition part of the slice) on the molded part obtained in the step (10) to obtain the high-purity high-resistivity silicon carbide part.

Example 2

The embodiment provides a molding process of a high-purity high-resistivity silicon carbide workpiece. This embodiment differs from embodiment 1 in that: the shape and size of the product; parameters of each step.

The method specifically comprises the following steps:

step 1: a digital model of a silicon carbide part is established by using 3D modeling software, and in this embodiment, the digital model of the silicon carbide part is shown in fig. 4. To counteract the undersize of the silicon carbide workpiece in the z-axis direction caused by the polishing operation, the z-axis dimension of the digital model is multiplied by a factor of 1.05.

Step 2: and (3) on the basis of the digital model of the silicon carbide workpiece obtained in the step (1), carrying out slicing operation on the digital model of the silicon carbide workpiece in the direction vertical to the z axis of the digital model of the silicon carbide workpiece for 29 times, and carrying out projection in the vertical direction of slicing to obtain a two-dimensional graph of slicing. A two-dimensional plot of a slice of a digital model of a silicon carbide part in this example is shown in fig. 5. The sliced thickness of the silicon carbide article in this example was 2.2mm.

Step 3: and (3) preparing a high-purity graphite mold with a corresponding shape according to the two-dimensional pattern of the slice obtained in the step (2). And (3) leaving a margin for the subsequent few machine tools, and multiplying the x-axis and y-axis direction dimensions of the digital model by 1.09 coefficients. The thickness of the high-purity graphite mold is 1mm.

Step 4: and (3) chemically vapor depositing a high-purity silicon carbide sheet on the high-purity graphite mold obtained in the step (3), and controlling the deposition thickness of the high-purity silicon carbide sheet to be 2.2mm by controlling the deposition time. The reaction gas for deposition adopts high-purity CH ₃ SiCl ₃ The carrier gas component is high-purity H ₂ The gas flow ratio of carrier gas and reaction gas is 6, the deposition reaction temperature is 1150 ℃, the temperature rising and falling speed is 2 ℃/min, the dispersed gas component is high-purity Ar gas, the dispersed gas accounts for 60% of the whole, and the gas pressure in the chamber is 800Pa.

Step 5: and (3) taking out the high-purity silicon carbide sheet and the high-purity graphite mold obtained by deposition in the step (4), placing the high-purity silicon carbide sheet and the high-purity graphite mold in a muffle furnace, and uniformly heating the high-purity silicon carbide sheet at the temperature of 800 ℃ in the muffle furnace until the high-purity graphite mold is completely oxidized and removed, thereby obtaining the high-purity silicon carbide sheet.

Step 6: and (3) carrying out double-sided grinding and polishing processing on the high-purity silicon carbide sheet obtained in the step (5), removing an oxide layer of tens of microns on the surface of the silicon carbide, and obtaining the high-purity silicon carbide sheet subjected to grinding and polishing processing, wherein the grinding and polishing surface roughness is Ra 1.6.

Step 7: and (3) preparing a high-purity carbon layer on one side of the polished high-purity silicon carbide sheet obtained in the step (6) by using a vacuum evaporation mode. Specifically, the high-purity carbon layer is prepared by sublimating the nanoscale graphene film material by a laser source in a vacuum chamber, and a covering measure is adopted for the surface of the non-contact area to avoid deposition.

Step 8: and (3) preparing a high-purity silicon layer on the other side of the high-purity silicon carbide sheet (one side is a high-purity carbon layer) obtained in the step (7) by using a low-pressure chemical vapor deposition mode. The high purity silicon layer is amorphous and has a thickness of 1 μm. Masking measures are taken to avoid deposition on the surface of the non-contact area.

Step 9: and (3) assembling the high-purity silicon carbide sheet (one surface is a high-purity carbon layer and the other surface is a high-purity silicon layer) obtained in the step (8) according to the slicing sequence of the digital model of the silicon carbide workpiece in the step (2) to obtain a silicon carbide assembly, ensuring that the high-purity silicon layers and the high-purity carbon layers are respectively arranged on the two surfaces of all contact areas, placing the high-purity silicon layer of each contact area on the high-purity carbon layer, and applying a continuous pressure of 0.1MPa in the z-axis direction (slice vertical direction) after assembling.

Step 10: and (3) placing the silicon carbide assembly obtained in the step (9) in an atmosphere furnace for sintering to bond and mold the high-purity silicon carbide sheet, and obtaining a molded product. The sintering process adopts a two-stage sintering curve (medium-temperature reaction sintering and high-temperature diffusion sintering) under the protection of Ar gas. The sintering curve is: heating to 1500 ℃ at a heating rate of 5 ℃/min, preserving heat for 2h, heating to 2100 ℃ at a heating rate of 1 ℃ and preserving heat for 0.5h, and cooling to room temperature at a cooling rate of 10 ℃/min.

Example 3

The embodiment provides a molding process of a high-purity high-resistivity silicon carbide workpiece. This embodiment differs from embodiment 1 in that: sintering curve of step 10.

The sintering curve of step 10 in this example is: heating to 1500 ℃ at a heating rate of 10 ℃/min, preserving heat for 1h, heating to 2100 ℃ at a heating rate of 1 ℃, gradually heating the pressure to 30MPa, preserving heat for 2h, and cooling to room temperature at a cooling rate of 10 ℃/min.

Comparative example

Comparative example 1

Comparative example 1 provides a compression molding process for a silicon carbide article. The process is the prior art and specifically comprises the following steps:

step 1: the commercial product silicon carbide granulated powder (containing high purity silicon carbide particles 95%, 3% sintering aid and 2% phenolic filler) is used as raw material for subsequent operation.

Step 2: filling the granulated powder into a die, and isostatic pressing for 2min under 200 MPa.

Step 3: setting degumming and sintering heating curve, at maximum 2100 deg.c, and maintaining for 3 hr.

Comparative example 2

Comparative example 2 provides a sintering process for high resistivity silicon carbide articles. The process of this comparative example is based on the application published under number CN104098335a, and comprises in particular the following steps:

step 1: silicon carbide powder and sintering aid (Al ₂ O ₃ 1.54wt％，Er ₂ O ₃ 3.46 wt%) was added to 100g of the total, and 3 kinds of powders were prepared into a slurry having a solid content of 50wt% using 100g of alcohol as a solvent.

Step 2: 200g of silicon carbide balls are used as ball milling media, the slurry is ball milled for 4 hours in a planetary way, and then the slurry is dried in a constant temperature box at 60 ℃.

Step 3: grinding and crushing the obtained block, sieving by a 100-mesh sieve, and sintering in a discharge plasma sintering furnace under vacuum after debonding, wherein the sintering temperature is 1700 ℃, and the heat preservation time is 10min.

Comparative example 3

Comparative example 3 provides a process for forming a high purity silicon carbide article. The process of this comparative example is based on the physical vapor transport technology of the patent application of application publication number CN109234805 a.

Comparative example 4

Comparative example 4 provides a process for forming a high purity high resistivity silicon carbide article. This comparative example differs from example 1 in that: the operation of preparing the high-purity carbon layer in the step 7 and the operation of preparing the high-purity silicon layer in the step 8 are not performed, and the step 9 is to assemble the polished high-purity silicon carbide sheet obtained in the step 6.

Performance test results

The following tests were carried out on the silicon carbide articles obtained in examples 1 to 3 and comparative examples 1 to 3.

The hardness of the silicon carbide articles prepared in examples 1-2 was measured by the Vickers hardness test method. The resistivity of the resulting silicon carbide article was measured by a four-probe method at high pressure. The density of the resulting silicon carbide article was measured by archimedes method. The purity of the resulting silicon carbide article was checked by Glow Discharge Mass Spectrometry (GDMS). And the corresponding amounts of machine addition and subtraction of comparative examples 1 to 3 were calculated from the shape of the silicon carbide article of example 1.

The test results are shown in Table 1.

TABLE 1 detection results for examples 1-3 and comparative examples 1-3

As can be seen from Table 1, the hardness of the silicon carbide product prepared in example 1 is 3385HV, the hardness of the silicon carbide product prepared in example 1 is 3405HV, and the hardness is high, so that the silicon carbide product can meet the requirements of various application scenes. According to the detection result, the silicon carbide workpiece manufactured by the forming process provided by the application is high in hardness, and the requirements of various application scenes can be met.

The resistivity of the silicon carbide article obtained in comparative example 1 was only 134. Omega. Cm, whereas the high purity high resistivity silicon carbide article obtained by the molding process of the present application had a high resistivity (> 4.32X10) ⁶ Omega cm). Therefore, the forming thought of the preparation of the high-purity high-resistivity silicon carbide workpiece avoids the problem of low resistivity of the silicon carbide workpiece prepared by the traditional compression molding process represented by the comparative example 1, and greatly reduces the constraint of the low resistivity caused by the preparation process on the electrical condition of the silicon carbide workpiece.

The forming thought of the preparation of the high-purity silicon carbide workpiece which is integrated into zero and is integrated into one piece avoids the powder metallurgy process of preparing the more complex workpiece, thereby avoiding the addition problem of a large amount of auxiliary agents. The molding process of the present application greatly improved the purity of the silicon carbide article compared to comparative example 1 (94.5% purity) and comparative example 2 (95% purity). The silicon carbide manufactured piece prepared by the molding process has high purity (more than 99.98 percent) and high density (more than 3.204 g/cm) ³ ) Is excellent in performance.

In addition, for the high-purity high-resistivity silicon carbide relatively complex structural parts prepared by the method, the parts can be prepared only by machining reduction of about 0.4-1% after assembly, sintering and molding. The method solves the problem of large-scale cutting processing (machining reduction of 68%) of the column/cake-shaped high-purity silicon carbide material prepared by physical vapor transmission mainly in comparative example 3, thereby greatly avoiding the difficult problem of high hardness and difficult processing of the high-purity silicon carbide, greatly improving the yield and being suitable for industrial batch production.

The high-purity high-resistivity silicon carbide manufactured piece prepared by the method has high hardness (3405 HV) and high resistivity (more than 4.32X10) ⁶ Omega cm), and the like, and has the intrinsic characteristics of wear resistance, corrosion resistance, high temperature resistance and the like of the silicon carbide material.

As can be seen from the comparison between the example 1 and the comparative example 4, the operations of preparing the high-purity carbon layer in the step 7 and preparing the high-purity silicon layer in the step 8 can greatly improve the interfacial bonding force between the layers, so that the mechanical properties of the product are higher, and the practical application requirements are met.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting thereof; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims

1. The molding process of the high-purity high-resistivity silicon carbide workpiece is characterized by comprising the following steps of:

step 10: placing the silicon carbide assembly in an atmosphere furnace for sintering to bond and mold the high-purity silicon carbide sheet, thus obtaining a molded part; adopting two-section sintering curves under Ar gas protection, which are medium temperature reaction sintering and high temperature diffusion sintering respectively;

the sintering curve of the sintering is as follows: heating to 1450-1600 ℃ at a heating rate of 1-5 ℃/min, preserving heat for 1-3h, heating to 2100-2200 ℃ at a heating rate of 0.5-3 ℃ and preserving heat for 0.5-3h, and cooling to room temperature at a cooling rate of 3-10 ℃/min;

2. The process of claim 1, wherein in step 1, the z-axis dimension of the digital model is multiplied by a factor of 1.02-1.05.

3. The process of claim 1, wherein in step 2, the slice thickness and slice height are selected according to the actual dimensions and the actual characteristics of the digital model of the silicon carbide part.

4. The process of claim 1, wherein the lateral expansion of the digital model of the silicon carbide part is selected to be the slice edge position.

5. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein said cut sheet has a thickness of 0.5 to 5mm.

6. The process of claim 1, wherein in step 3, the x-axis and y-axis dimensions of the digital model of the silicon carbide are multiplied by a factor of 1.05-1.1.

7. The process of claim 1, wherein the base mold is a high purity graphite mold.

8. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the base mold has a thickness of 1-2mm.

9. The process of claim 1, wherein in step 4, the deposition time and gas pressure of the chemical vapor deposition are controlled so that the deposition thickness of the high-purity silicon carbide sheet obtained by the deposition is consistent with the thickness of the slice in step 2.

10. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the high purity silicon carbide has a deposition thickness of 0.5 to 5mm.

11. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein said chemical vapor deposited reactant gas is CH ₃ SiCl ₃ 、C ₇ H ₂₀ Si ₂ 、SiH ₄ 、SiH ₃ Cl、SiH ₂ Cl ₂ 、SiHCl ₃ 、SiCl ₄ One or more of methane, ethane, propane and butane.

12. The process for forming a high purity high resistivity silicon carbide article according to claim 11, wherein the reactant gas is high purity CH ₃ SiCl ₃ 。

13. The process of claim 1, wherein the carrier gas component of the chemical vapor deposition is high purity H ₂ 。

14. The process of claim 1, wherein the flow ratio of carrier gas to reactant gas for chemical vapor deposition is from 6 to 10.

15. The process of claim 1, wherein the chemical vapor deposition reaction temperature is 1000-1350 ℃.

16. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the chemical vapor deposition reaction ramp down and ramp down rate is 1-5 ℃/min.

17. The process of claim 1, wherein the chemical vapor deposited dispersed gas is high purity Ar gas.

18. The process for forming a high purity high resistivity silicon carbide article according to claim 17, wherein the dispersed gas is present in an amount of 40 to 90 percent of the total mass.

19. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the pressure in the chemical vapor deposition chamber is between 100 Pa and 1500Pa.

20. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the temperature in the muffle furnace is 700-800 ℃.

21. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein in step 6, the polishing process is a conventional high purity material polishing process.

22. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the polished high purity silicon carbide sheet has a surface roughness of from about Ra0.25 to about 1.6.

23. The process of claim 1, wherein the high purity carbon layer is prepared by a method including, but not limited to, high molecular precursor film pyrolysis, low pressure chemical vapor deposition, and vacuum evaporation.

24. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the high purity carbon layer has a thickness of 0.6 to 5 μm.

25. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the high purity carbon layer has a surface roughness greater than Ra 0.4.

26. The process for forming a high purity high resistivity silicon carbide article according to claim 1 wherein masking is applied to the surface of the non-contact surface area to avoid deposition.

27. The process of claim 1, wherein the high purity silicon layer is prepared by a method including, but not limited to, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, vacuum evaporation.

28. The process for forming a high purity high resistivity silicon carbide article according to claim 1, wherein the high purity silicon layer has a thickness of 0.5 to 5 μm.

29. The process of claim 1, wherein the high purity silicon layer is amorphous or fine crystalline.

30. The process of claim 1, wherein in step 9, the high purity silicon layer of each contact surface is disposed on the high purity carbon layer during assembly.

31. The process of forming a high purity high resistivity silicon carbide article according to claim 1, wherein continuous pressure is applied in a direction perpendicular to the cut pieces after assembly.

32. The process for forming a high purity high resistivity silicon carbide article according to claim 31, wherein the applied pressure is between 0.05 MPa and 3MPa.

33. The process of claim 1, wherein in step 11, the finishing is a rounding of the corners at the sintering transition of the slices.

34. A high purity high resistivity silicon carbide article made by the molding process of any one of claims 1-33.