Silicon carbide ultrafine powder purification process for semiconductor

Abstract

The invention provides a process for purifying silicon carbide ultrafine powder for semiconductors, which belongs to the technical field of semiconductor materials and comprises the following steps: carbonizing treated wood in flowing argon to form a carbon template; heating and stirring tetraethoxysilane, an ethanol water solution and oxalic acid, infiltrating the carbon template into the mixture, calcining under argon protection, carrying out vacuum heat treatment, and carrying out ball milling to obtain silicon carbide powder; the preparation method comprises the following steps: adding silicon carbide powder into water, mixing and stirring, adding polyethyleneimine and edible fatty acid base oil, stirring, separating, drying, putting into a NaOH solution, reacting at 50-80 DEG C, washing, drying, exposing in steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture, reacting, washing and drying to obtain the silicon carbide superfine powder. The method can reduce the production cost of silicon carbide and improve the purity of silicon carbide.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor materials, and in particular to a purification process of ultrafine silicon carbide powder for semiconductors. Background Art

[0002] With the development of electronic information technology, the working conditions that semiconductor devices need to adapt to are becoming more and more demanding. The application of devices based on the first and second generation semiconductor materials has limitations. The third generation semiconductor materials represented by silicon carbide have unique advantages when facing working conditions such as high temperature, high frequency, corrosion, and strong radiation.

[0003] Silicon carbide is an important artificially synthesized inorganic non-metallic material. No natural silicon carbide ore has been found in the earth's crust. At present, most of the silicon carbide single crystal materials used in semiconductor devices are prepared by physical vapor transport and high-temperature chemical deposition. Physical vapor transport technology is the most widely used method for growing silicon carbide single crystals, and the growth conditions of silicon carbide single crystals grown by physical vapor transport are simple and easy to industrialize. However, during the production process, due to the incomplete reaction of the raw materials and the influence of processing equipment and the external environment, the processed silicon carbide powder contains many impurities. These impurities mainly include amorphous carbon, silicon and silicon dioxide, as well as metal elements such as Fe, Al and their oxides. Their presence seriously affects the physical and chemical properties and scope of use of silicon carbide. Therefore, the purification of silicon carbide has become an important research topic at present.

[0004] The patent application document with the announcement number CN106744964A discloses a process for recovering silicon carbide from silicon carbide waste. First, the silicon carbide waste is crushed and washed to recover the metal zinc therein, then the trace aluminum and lead in the waste are recovered by alkali washing, and finally the silicon dioxide impurities are removed by hydrofluoric acid washing to obtain the finished silicon carbide product, and the purity of the silicon carbide reaches more than 97%, but the purification process has no significant removal effect on amorphous carbon impurities.

[0005] Therefore, it is necessary to provide a purification process for ultrafine silicon carbide powder for semiconductors to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0006] In view of this, the present invention provides a process for purifying ultrafine silicon carbide powder for semiconductors, which can reduce the production cost of silicon carbide and improve the purity of silicon carbide.

[0007] To achieve the above object, the present invention provides a process for purifying ultrafine silicon carbide powder for semiconductors, comprising the following steps: S1, carbonizing the treated wood in flowing argon to form a carbon template; S2, heating and stirring tetraethoxysilane, ethanol aqueous solution and oxalic acid, impregnating the carbon template therein, calcining under argon protection, vacuum heat treatment, and ball milling to obtain silicon carbide powder; S3. Add silicon carbide powder into water and mix and stir, then add polyethyleneimine and edible fatty acid-based oil and stir, separate, dry, place in NaOH solution, react at 50-80°C, wash, dry, expose to the steam of hydrofluoric acid-hydrochloric acid-nitric acid mixture to react, wash, and dry to obtain silicon carbide ultrafine powder.

[0008] The present invention uses treated wood as raw material, carbonizes it in an argon atmosphere to form a carbon template, uses tetraethoxysilane as a silicon source, hydrolyzes and condenses it under heating and acidic conditions to generate SiO2 gel. The gel decomposes into SiO2 particles at high temperature, and then reacts with carbon in the carbon template through heat treatment to form silicon carbide. Finally, through a ball milling process, collision and friction between particles cause the material to be broken and refined, thereby grinding large particles of silicon carbide into ultrafine particles, and realizing low-cost preparation of silicon carbide powder.

[0009] The present invention does not need to use high temperature to remove amorphous carbon, thus avoiding the problem of reduced final silicon carbide yield due to excessive oxidation at high temperature. Amorphous carbon is removed by two components in a coordinated manner, wherein polyethyleneimine is used as a dispersant to disperse silicon carbide slurry to improve the flotation carbon removal rate, and edible fatty acid-based oil is used as a flotation agent. Since silicon carbide and carbon have different hydrophilicities, the hydrophobic molecules in the edible fatty acid-based oil are attached to the surface of amorphous carbon particles by physical adsorption to form a hydrophobic coating layer. When water molecules contact the hydrophobic amorphous carbon particles, they tend to stay away from the surface of the carbon particles. In order to reduce the interaction between the solid and liquid phases, the system tends to reduce energy, thereby making the hydrophobic amorphous carbon particles close to each other and agglomerate, and being coated in the edible fatty acid-based oil, thereby achieving the purpose of removing impurity carbon by flotation.

[0010] The present invention adopts an alkali dissolution method for impurities Si and SiO2, silicon dioxide reacts with hot concentrated strong alkali solution to generate silicate and water, silicon reacts with water to generate silicic acid attached to the surface of silicon, and then reacts with hot concentrated alkali solution to generate silicate. In addition, hydrochloric acid-hydrofluoric acid-nitric acid is used to remove metal impurities from silicon carbide powder. Hydrofluoric acid is selected as a silicon remover to further remove silicon impurities, and nitric acid is added as an oxidant to oxidize metal impurities such as iron, aluminum, copper, etc. on the surface of silicon carbide, and hydrochloric acid is added in coordination to remove trace impurities such as iron in silicon carbide powder; in addition, due to the excessive hardness of silicon carbide, metal element impurities will inevitably be introduced from the grinding tool during sample crushing and grinding, and acid vapor can also be used to remove them together; for the silicon impurities that are difficult to be further oxidized due to the oxide film produced by oxidation, nitric acid is added to remove the remaining trace silicon impurities by chemical reaction. Compared with the impregnation method, steam treatment can provide higher removal efficiency, uniformity and fewer side effects (such as residual sediment and secondary pollution), thereby obtaining higher purity silicon carbide ultrafine powder.

[0011] Optionally, the treated wood is obtained by cutting waste wood into a rectangular shape, washing with water and drying naturally, peeling off the bark, immersing in a hydrochloric acid solution for treatment, and then washing with water and drying.

[0012] In the process of treating the waste wood, the invention utilizes hydrochloric acid to remove minerals and inorganic impurities in the wood.

[0013] Optionally, the molar concentration of the hydrochloric acid solution is 1 mol / L; the treatment time is 20-30 min and the temperature is 30-50°C.

[0014] Optionally, the drying time is 2 to 6 hours and the temperature is 100°C.

[0015] Optionally, the carbon template is formed by carbonizing treated wood at 1000° C. in flowing argon for 1 to 2 hours.

[0016] The purpose of the present invention to carbonize wood in flowing argon is mainly to prevent the wood from undergoing oxidation reaction at high temperature.

[0017] Optionally, in step S2, tetraethoxysilane, ethanol aqueous solution and oxalic acid are mixed and stirred at 60°C, the carbon template is infiltrated therein, and then calcined at 1000°C for 1 to 4 hours under argon protection, and finally heat treated at 1600°C for 60 minutes under vacuum conditions, and then placed in a ball mill and ball-milled for 2 to 8 hours to obtain silicon carbide powder.

[0018] Optionally, the volume concentration of the ethanol aqueous solution is 80%.

[0019] Optionally, in step S3, hydroxypropyl-β-cyclodextrin is also added when polyethyleneimine and edible fatty acid-based oil are added and stirred.

[0020] Optionally, in step S3, after adding silicon carbide powder to water and mixing, polyethyleneimine is added and stirred for 30 minutes, nitric acid is added to adjust the pH to 4-5, edible fatty acid base oil and hydroxypropyl-β-cyclodextrin are added and stirred for 30-60 minutes, separated and dried, placed in a NaOH solution with a mass concentration of 15%-35%, reacted at 50-80°C for 1-3 hours, washed with deionized water 2-3 times, dried in a drying oven at 105°C for 30-60 minutes, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture for reaction for 40-70 minutes, washed with deionized water 2-3 times, and dried in a drying oven at 105°C for 30-60 minutes to obtain ultrafine silicon carbide powder.

[0021] The present invention adds hydroxypropyl-β-cyclodextrin and edible fatty acid base oil as flotation agents. As a water-soluble cyclic oligosaccharide, its molecular structure is a circular ring molecule, which can form an inclusion compound with hydrophobic amorphous carbon and cooperate with the edible fatty acid base oil to remove amorphous carbon particles. In addition, hydroxypropyl-β-cyclodextrin can cooperate with polyethyleneimine and help disperse silicon carbide particles to prevent particle aggregation. By improving particle dispersibility, more uniform and finer powders can be obtained.

[0022] Optionally, the volume ratio of hydrofluoric acid, hydrochloric acid and nitric acid is 0.5:1:2.

[0023] The above technical solution of the present invention includes at least the following beneficial effects: 1. The present invention uses treated wood as raw material, carbonizes it in an argon atmosphere to form a carbon template, uses tetraethoxysilane as a silicon source, forms silicon carbide through heat treatment, and finally uses a ball milling process. The collision and friction between particles cause the material to be broken and refined, thereby grinding large particles of silicon carbide powder into ultrafine particles, thereby achieving low-cost preparation of silicon carbide powder.

[0024] 2. The present invention adopts two components to synergistically remove amorphous carbon, avoiding the problem of reduced silicon carbide yield due to excessive oxidation at high temperature. Polyethyleneimine is used as a dispersant to disperse silicon carbide slurry to improve the flotation carbon removal rate, and edible fatty acid base oil is used as a flotation agent. Since silicon carbide and carbon have different hydrophilicity, the hydrophobic molecules in the edible fatty acid base oil are adsorbed on the surface of amorphous carbon particles by physical adsorption, and the hydrophobic amorphous carbon particles are close to each other and agglomerated and coated in the edible fatty acid base oil to remove impurity carbon by flotation.

[0025] 3. The present invention adopts an alkali dissolution method for impurities Si and SiO2. Silicon dioxide can react with hot concentrated strong alkali solution to generate silicate and water. Silicon reacts with water to generate silicic acid attached to the surface of silicon, and then reacts with hot concentrated alkali solution to generate silicate. In addition, hydrochloric acid-hydrofluoric acid-nitric acid are used to remove metal impurities from silicon carbide powder. Hydrofluoric acid is selected as a silicon remover, and nitric acid is added as an oxidant. Hydrochloric acid is added in combination to remove trace impurities such as iron in silicon carbide powder; and compared with the impregnation method, steam treatment can provide higher removal efficiency, uniformity and fewer side effects, thereby obtaining higher purity silicon carbide ultrafine powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the ultrafine silicon carbide powder prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in combination with the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0028] Example 1 1000g of waste wood was cut into a cuboid shape, washed with water and dried naturally, then the bark was peeled off and immersed in 1L of hydrochloric acid solution with a molar concentration of 1mol / L at 37℃ for 25min, then washed with water and dried in an oven at 100℃ for 5h to obtain the treated wood. The treated wood was carbonized for 2h in flowing argon at 1000℃ to form a carbon template; 41.6g of tetraethoxysilane, 200mL of ethanol aqueous solution with a volume concentration of 80% and 8mL of oxalic acid were stirred evenly at 60℃, 100g of the carbon template was infiltrated therein, and then calcined at 1000℃ for 3.5h under argon protection, and finally heat treated at 1600℃ for 60min under vacuum conditions, and then put into a ball mill and ball milled for 5h to obtain ultrafine silicon carbide powder.

[0029] 30 g of silicon carbide ultrafine powder was added to 70 mL of water and mixed and stirred, then 0.7 mL of polyethyleneimine was added and stirred for 30 min, nitric acid was added to adjust the pH to 4, 1.2 mL of edible fatty acid base oil and 0.3 g of hydroxypropyl-β-cyclodextrin were added and stirred for 40 min, separated, dried, placed in 70 ml of NaOH solution with a mass concentration of 20%, reacted at 70 ° C for 2.5 h, washed twice with deionized water, dried in a drying oven at 105 ° C for 50 min, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF: HNO3: HCl volume ratio of 0.5:1:2) for 60 min, washed twice with deionized water, and dried in a drying oven at 105 ° C for 45 min to obtain high-purity silicon carbide ultrafine powder.

[0030] Example 2 1000g of waste wood was cut into a cuboid shape, washed with water and dried naturally, then the bark was peeled off, immersed in 1L of hydrochloric acid solution with a molar concentration of 1mol / L at 45℃ for 25min, then washed with water, and dried in an oven at 100℃ for 4h to obtain the treated wood. The treated wood was carbonized for 1.5h in flowing argon at 1000℃ to form a carbon template; 41.6g of tetraethoxysilane, 200mL of ethanol aqueous solution with a volume concentration of 80% and 8mL of oxalic acid were stirred evenly at 60℃, 100g of carbon template was infiltrated therein, and calcined at 1000℃ for 3.5h under argon protection, and finally heat treated at 1600℃ for 60min under vacuum conditions, and then put into a ball mill and ball milled for 7h to obtain silicon carbide ultrafine powder; wherein, the ethanol mixed solution was prepared by mixing 80mL of ethanol, 40mL of deionized water and 3mL of oxalic acid evenly.

[0031] 30 g of silicon carbide ultrafine powder was added to 70 mL of water and mixed and stirred, then 0.9 mL of polyethyleneimine was added and stirred for 30 min, nitric acid was added to adjust the pH to 4.5, 1.5 mL of edible fatty acid base oil and 0.2 g of hydroxypropyl-β-cyclodextrin were added and stirred for 50 min, separated, dried, placed in 60 ml of NaOH solution with a mass concentration of 30%, reacted at 70 ° C for 2 h, washed with deionized water 3 times, dried in a drying oven at 105 ° C for 50 min, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF: HNO3: HCl volume ratio of 0.5:1:2) for reaction for 55 min, washed with deionized water 3 times, and dried in a drying oven at 105 ° C for 40 min to obtain high-purity silicon carbide ultrafine powder.

[0032] Example 3 1000g of waste wood was cut into a cuboid shape, washed with water and dried naturally, then the bark was peeled off, immersed in 1L of hydrochloric acid solution with a molar concentration of 1mol / L at 40℃ for 25min, then washed with water, and dried in an oven at 100℃ for 5h to obtain the treated wood. The treated wood was carbonized for 1.5h in flowing argon at 1000℃ to form a carbon template; 41.6g of tetraethoxysilane, 200mL of ethanol aqueous solution with a volume concentration of 80% and 8mL of oxalic acid were stirred evenly at 60℃, 100g of carbon template was infiltrated therein, and calcined at 1000℃ for 3h under argon protection, and finally heat treated at 1600℃ for 60min under vacuum conditions, and then put into a ball mill and ball milled for 5h to obtain silicon carbide ultrafine powder; wherein, the ethanol mixed solution was prepared by mixing 80mL of ethanol, 40mL of deionized water and 3mL of oxalic acid evenly.

[0033] 30 g of silicon carbide ultrafine powder was added to 70 mL of water and mixed and stirred, then 0.7 mL of polyethyleneimine was added and stirred for 30 min, nitric acid was added to adjust the pH to 4, 1.2 mL of edible fatty acid base oil was added and stirred for 40 min, separated, dried, placed in 45 ml of NaOH solution with a mass concentration of 15%, reacted at 70 ° C for 2 h, washed with deionized water 3 times, dried in a drying oven at 105 ° C for 50 min, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF: HNO3: HCl volume ratio of 0.5:1:2) for reaction for 50 min, washed twice with deionized water, and dried in a drying oven at 105 ° C for 50 min to obtain high-purity silicon carbide ultrafine powder.

[0034] Example 4 1000g of waste wood was cut into a cuboid shape, washed with water and dried naturally, then the bark was peeled off, immersed in 1L of hydrochloric acid solution with a molar concentration of 1mol / L at 50℃ for 30min, then washed with water, and dried in an oven at 100℃ for 6h to obtain the treated wood. The treated wood was carbonized for 2h in flowing argon at 1000℃ to form a carbon template; 41.6g of tetraethoxysilane, 200mL of ethanol aqueous solution with a volume concentration of 80% and 8mL of oxalic acid were stirred evenly at 60℃, 100g of carbon template was infiltrated therein, and calcined at 1000℃ for 4h under argon protection, and finally heat treated at 1600℃ for 60min under vacuum conditions, and then put into a ball mill and ball milled for 8h to obtain silicon carbide ultrafine powder; wherein, the ethanol mixed solution was prepared by mixing 80mL of ethanol, 40mL of deionized water and 5mL of oxalic acid evenly.

[0035] 30 g of silicon carbide ultrafine powder was added to 70 mL of water and mixed and stirred, then 2 mL of polyethyleneimine was added and stirred for 30 min, nitric acid was added to adjust the pH to 5, 1.5 mL of edible fatty acid base oil and 0.3 g of hydroxypropyl-β-cyclodextrin were added and stirred for 60 min, separated, dried, placed in 90 ml of NaOH solution with a mass concentration of 35%, reacted at 80 ° C for 3 h, washed with deionized water 3 times, dried in a drying oven at 105 ° C for 60 min, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF: HNO3: HCl volume ratio of 0.5:1:2) for 70 min, washed with deionized water 3 times, and dried in a drying oven at 105 ° C for 60 min to obtain high-purity silicon carbide ultrafine powder.

[0036] Example 5 1000g of waste wood was cut into a cuboid shape, washed with water and dried naturally, then the bark was peeled off, immersed in 1L of hydrochloric acid solution with a molar concentration of 1mol / L at 30℃ for 20min, then washed with water, and dried in an oven at 100℃ for 2h to obtain the treated wood. The treated wood was carbonized for 1h in flowing argon at 1000℃ to form a carbon template; 41.6g of tetraethoxysilane, 200mL of ethanol aqueous solution with a volume concentration of 80% and 8mL of oxalic acid were stirred evenly at 60℃, 100g of carbon template was infiltrated therein, and calcined at 1000℃ for 1h under argon protection, and finally heat treated at 1600℃ for 60min under vacuum conditions, and then put into a ball mill and ball milled for 2h to obtain silicon carbide powder; wherein, the ethanol mixed solution was prepared by mixing 80mL of ethanol, 40mL of deionized water and 2mL of oxalic acid evenly.

[0037] 30 g of silicon carbide ultrafine powder was added to 70 mL of water and mixed and stirred, then 0.5 mL of polyethyleneimine was added and stirred for 30 min, nitric acid was added to adjust the pH to 4, 0.5 mL of edible fatty acid base oil was added and stirred for 30 min, separated, dried, placed in 45 ml of NaOH solution with a mass concentration of 35%, reacted at 50 ° C for 1 h, washed twice with deionized water, dried in a drying oven at 105 ° C for 30 min, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF: HNO3: HCl volume ratio of 0.5:1:2) for reaction for 40 min, washed twice with deionized water, and dried in a drying oven at 105 ° C for 30 min to obtain silicon carbide ultrafine powder.

[0038] Example 6 1000g of waste wood was cut into a cuboid shape, washed with water and dried naturally, then the bark was peeled off and immersed in 1L of hydrochloric acid solution with a molar concentration of 1mol / L at 40℃ for 30min, then washed with water and dried in an oven at 100℃ for 5h to obtain the treated wood. The treated wood was carbonized for 1.5h in flowing argon at 1000℃ to form a carbon template; 41.6g of tetraethoxysilane, 200mL of ethanol aqueous solution with a volume concentration of 80% and 8mL of oxalic acid were stirred evenly at 60℃, 100g of the carbon template was infiltrated therein, and then calcined at 1000℃ for 3h under argon protection, and finally heat treated at 1600℃ for 60min under vacuum conditions, and then put into a ball mill and ball milled for 6h to obtain silicon carbide powder.

[0039] 30 g of silicon carbide powder was added to 70 mL of water and mixed and stirred, and then 1 mL of polyethyleneimine was added and stirred for 30 min. Nitric acid was added to adjust the pH to 4.5, and 0.9 mL of edible fatty acid base oil and 0.6 g of hydroxypropyl-β-cyclodextrin were added and stirred for 50 min. After separation and drying, it was placed in 90 ml of NaOH solution with a mass concentration of 25%, reacted at 70 ° C for 2 h, washed with deionized water 3 times, dried in a drying oven at 105 ° C for 60 min, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF: HNO3: HCl volume ratio of 0.5:1:2) for 60 min, washed twice with deionized water, and dried in a drying oven at 105 ° C for 60 min to obtain silicon carbide ultrafine powder.

[0040] The present invention also carries out comparative examples and related tests.

[0041] Comparative Example 1 Compared with Example 6, the difference is that polyethyleneimine is not added, and the other components and preparation steps are completely the same, and finally silicon carbide ultrafine powder is obtained.

[0042] Comparative Example 2 Compared with Example 6, the difference is that polyethyleneimine and edible fatty acid base oil are not added, high temperature is used to remove amorphous carbon, and the other components and preparation steps are exactly the same, that is: 30g of silicon carbide powder is calcined at 650°C for 5h, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture (HF:HNO3:HCl volume ratio of 0.5:1:2) for reaction for 60min, washed twice with deionized water, and dried in a drying oven at 105°C for 60min to finally obtain silicon carbide ultrafine powder.

[0043] Comparative Example 3 Compared with Example 6, the difference is that hydrochloric acid and nitric acid are not added, and the other components and preparation steps are exactly the same, that is, 30g of silicon carbide powder is added to 70mL of water and mixed and stirred, 1mL of polyethyleneimine is added and stirred for 30min, nitric acid is added to adjust the pH to 4.5, 0.9mL of edible fatty acid base oil and 0.6g of hydroxypropyl-β-cyclodextrin are added and stirred for 50min, separated, dried, placed in 90ml of NaOH solution with a mass concentration of 25%, reacted at 70°C for 2h, washed with deionized water 3 times, dried in a drying oven at 105°C for 60min, exposed to hydrofluoric acid vapor for reaction for 60min, washed twice with deionized water, and dried in a drying oven at 105°C for 60min to obtain ultrafine silicon carbide powder.

[0044] Comparative Example 4 Compared with Example 6, the difference is that the steam of the hydrofluoric acid-hydrochloric acid-nitric acid mixture is not used, but the hydrofluoric acid-hydrochloric acid-nitric acid combination is used as the impregnating agent, and the other components and preparation steps are exactly the same, that is, 30g of silicon carbide powder is added to 70mL of water and mixed and stirred, 1mL of polyethyleneimine is added and stirred for 30min, nitric acid is added to adjust the pH to 4.5, 0.9mL of edible fatty acid base oil and 0.6g of hydroxypropyl-β-cyclodextrin are added and stirred for 50min, separated, dried, placed in 90ml of NaOH solution with a mass concentration of 25%, reacted at 70°C for 2h, washed with deionized water 3 times, dried in a drying oven at 105°C for 60min, placed in a hydrofluoric acid-hydrochloric acid-nitric acid impregnation solution (HF:HNO3:HCl volume ratio of 0.5:1:2) for 60min, washed twice with deionized water, and dried in a drying oven at 105°C for 60min to obtain ultrafine silicon carbide powder.

[0045] Performance testing The silicon carbide powder (unpurified) prepared in Example 6 was used as a blank group and the silicon carbide ultrafine powder purified in Examples 1 to 6 and Comparative Examples 1 to 4 was tested for chemical composition according to the national standard GB / T2480-2022 ordinary abrasive silicon carbide, including the mass fraction content of SiC, C, Si, SiO2 and metal impurities. The results are shown in Table 1.

[0046] Table 1

[0047] As can be seen from Table 1, Examples 1 to 6 all meet the national standards. Among them, the purity of the silicon carbide ultrafine powder after multi-stage purification is significantly higher than the purity of the unpurified silicon carbide powder in the blank group; in addition, the overall carbon removal rate in Example 6 is significantly improved due to the addition of polyethyleneimine; in Comparative Example 2, polyethyleneimine and edible fatty acid-based oil are not used, but high-temperature calcination is used to remove amorphous carbon, and the removal rate is worse than that in Example 6, and the impurity SiO2 increases; Comparative Example 3 does not add hydrochloric acid and nitric acid, which significantly reduces the removal rate of metal impurities, and also has a certain impact on the removal rate of Si and SiO2; In Comparative Example 4, the last step using conventional impregnation methods has a lower removal effect on impurities than Example 6. The removal rate of amorphous carbon in Examples 2 and 5 is reduced due to the lack of hydroxypropyl-β-cyclodextrin. In addition, Figure 1 The SEM image of the sample prepared in Example 6 shows that the surface of the prepared ultrafine silicon carbide powder is relatively smooth without obvious impurities and is nano-sized particles. In summary, the ultrafine silicon carbide powder for semiconductors prepared by the purification process of Examples 1 to 6 of the present invention has a high purity.

[0048] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A process for purifying ultrafine silicon carbide powder for semiconductors, characterized in that: The steps include: S1, carbonizing the treated wood in flowing argon to form a carbon template; S2, heating and stirring tetraethoxysilane, ethanol aqueous solution and oxalic acid, impregnating the carbon template therein, calcining under argon protection, vacuum heat treatment, and ball milling to obtain silicon carbide powder; S3. Add silicon carbide powder into water and mix and stir, then add polyethyleneimine and edible fatty acid-based oil and stir, separate, dry, place in NaOH solution, react at 50-80°C, wash, dry, expose to the steam of hydrofluoric acid-hydrochloric acid-nitric acid mixture to react, wash, and dry to obtain silicon carbide ultrafine powder.

2. A process for purifying ultrafine silicon carbide powder for semiconductors according to claim 1, characterized in that: The treated wood is obtained by cutting waste wood into a rectangular shape, washing with water and drying naturally, peeling off the bark, immersing in a hydrochloric acid solution for treatment, and then washing with water and drying.

3. A process for purifying ultrafine silicon carbide powder for semiconductors according to claim 2, characterized in that: The molar concentration of the hydrochloric acid solution is 1 mol / L; the treatment time is 20-30 min and the temperature is 30-50° C.

4. A process for purifying ultrafine silicon carbide powder for semiconductors according to claim 2, characterized in that: The drying time is 2-6 hours and the temperature is 100°C.

5. The process for purifying ultrafine silicon carbide powder for semiconductor according to claim 1, characterized in that: The carbon template is formed by carbonizing the treated wood at 1000° C. in flowing argon for 1 to 2 hours.

6. A process for purifying ultrafine silicon carbide powder for semiconductor use according to claim 1, characterized in that: In the step S2, tetraethoxysilane, ethanol aqueous solution and oxalic acid are mixed and stirred at 60°C, the carbon template is impregnated therein, and then calcined at 1000°C for 1-4 hours under argon protection, and finally heat treated at 1600°C for 60 minutes under vacuum conditions, and then placed in a ball mill and ball-milled for 2-8 hours to obtain silicon carbide powder.

7. A process for purifying ultrafine silicon carbide powder for semiconductor use according to claim 1, characterized in that: The volume concentration of the ethanol aqueous solution is 80%.

8. The process for purifying ultrafine silicon carbide powder for semiconductor according to claim 1, characterized in that: In the step S3, hydroxypropyl-β-cyclodextrin is also added when polyethyleneimine and edible fatty acid-based oil are added and stirred.

9. A process for purifying ultrafine silicon carbide powder for semiconductor use according to claim 1, characterized in that: In the step S3, after adding silicon carbide powder to water and mixing, polyethyleneimine is added and stirred for 30 minutes, nitric acid is added to adjust the pH to 4-5, edible fatty acid base oil and hydroxypropyl-β-cyclodextrin are added and stirred for 30-60 minutes, separated, dried, placed in a NaOH solution with a mass concentration of 15%-35%, reacted at 50-80° C. for 1-3 hours, washed with deionized water 2-3 times, dried in a drying oven at 105° C. for 30-60 minutes, exposed to the steam of a hydrofluoric acid-hydrochloric acid-nitric acid mixture for reaction for 40-70 minutes, washed with deionized water 2-3 times, and dried in a drying oven at 105° C. for 30-60 minutes to obtain ultrafine silicon carbide powder.

10. A process for purifying ultrafine silicon carbide powder for semiconductor use according to claim 1, characterized in that: The volume ratio of the hydrofluoric acid, hydrochloric acid and nitric acid is 0.5:1:2.

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