Deep carbon removal method for silicon carbide powder based on plasma-assisted composite catalytic oxidation

Abstract

The invention provides a deep carbon removal method for silicon carbide powder based on plasma-assisted composite catalytic oxidation, which is characterized by comprising the following steps: S1, cleaning and drying silicon carbide powder raw materials with acid to obtain pretreated silicon carbide powder; s2, immersing the pretreated silicon carbide powder into a cobalt nitrate, manganese nitrate or ferric nitrate solution, and carrying out dispersion treatment, evaporation treatment and calcination treatment to obtain a metal oxide / silicon carbide composite catalyst; s3, placing the metal oxide / silicon carbide composite catalyst in a radio frequency plasma reactor, and carrying out an oxidation reaction; and S4, after the oxidation reaction is finished, carrying out post-treatment to obtain the carbon-removed silicon carbide powder. The carbon removal effect is obviously better than that of a traditional high-temperature oxidation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductors, and in particular to a method for deep decarburization of silicon carbide powder based on plasma-assisted composite catalytic oxidation. BACKGROUND

[0002] Silicon carbide (SiC) is one of the most important third-generation semiconductor materials, and is widely used in power electronics, radio frequency devices, optoelectronic devices, etc. due to its excellent properties such as large band gap, high saturated electron mobility, large breakdown field strength, and high thermal conductivity. Due to the need for many organic and inorganic substances to participate in the processing of SiC wafers, and the need for human participation in many processes, the product is inevitably contaminated by impurities such as organic matter, particles, metal, and oxide. In integrated circuits made of silicon carbide, the elements and connections are very fine, so if contaminated by these impurities during manufacturing, it can easily damage the circuit function inside the chip, causing short circuits or open circuits, leading to integrated circuit failure and causing serious losses. Therefore, after the final processing of the silicon carbide substrate, it must ensure its high cleanliness.

[0003] In the preparation of SiC powder, carbon impurities such as raw material impurities or free carbon and carbon coating layer left over from the synthesis process often lead to a decrease in the growth quality of the crystal and degradation of the electrical properties of the device. Traditional decarburization methods have significant limitations: high-temperature oxidation (800-1200 ℃) easily causes SiC grain oxidation and agglomeration and has extremely high energy consumption; acid washing has limited effect on removing fine carbon impurities and introduces chemical residues; physical separation methods rely on the physical property differences between carbon and SiC, and are difficult to effectively remove nanoscale carbon impurities.

[0004] Therefore, there is an urgent need to develop a deep decarburization technology that is low-temperature, high-efficiency, and causes little damage to the SiC substrate. SUMMARY

[0005] The present application aims to at least partially solve one of the technical problems in the related art. The inventors found that in the prior art, there are usually only cleaning treatment and plasma cleaning steps, such as in Chinese Patent Application CN201811302593.1, which discloses a cleaning method for silicon carbide wafers, which makes the impurities on the surface of the silicon carbide wafer cleaner, but has limited effect on the removal of carbon impurities contained in the powder and introduces chemical residues. Based on the above problems and the like, the present application discloses a method for deep decarburization of silicon carbide powder based on plasma-assisted composite catalytic oxidation, which realizes efficient decarburization at a low temperature of 300-450 ℃ by using the synergistic effect of high-energy oxygen species and composite catalysts through the steps of hydrogen fluoride pretreatment, transition metal oxide catalyst loading, plasma-assisted oxidation, and post-treatment, greatly reduces the carbon content, and causes little damage to the SiC substrate, solves the problems of high temperature and high consumption and material damage in traditional methods, and is suitable for semiconductor-grade SiC powder purification.

[0006] In one aspect of the present application, a method for deep decarburization of silicon carbide powder is proposed. According to an embodiment of the present application, the method comprises the following steps: S1: cleaning treatment and drying treatment of the silicon carbide powder raw material with acid to obtain pretreated silicon carbide powder; S2: immersing the pretreated silicon carbide powder in a transition metal nitrate solution for dispersion treatment, evaporation treatment, and calcination treatment to obtain a metal oxide / silicon carbide composite catalyst; S3: placing the metal oxide / silicon carbide composite catalyst in a radio frequency plasma reactor for oxidation reaction; S4: after the oxidation reaction is completed, post-treatment is performed to obtain decarburized silicon carbide powder. According to an embodiment of the present application, the method first immerses the pretreated silicon carbide powder in a transition metal nitrate solution for dispersion treatment, evaporation treatment, and calcination treatment to obtain a metal oxide / silicon carbide composite catalyst, which can introduce a transition metal oxide catalyst (such as 、 ) on the surface of the SiC powder, use its surface active sites to adsorb carbon impurities and oxygen species, reduce the activation energy of carbon oxidation, provide a catalytic center for subsequent plasma oxidation, and realize "low-temperature and efficient decarburization". The mechanism of action is that the transition metal ions (such as ) of the catalyst have variable valence states, which can deliver oxygen species (active oxygen produced by plasma ionization such as ) through redox cycles (such as ), accelerate the oxidation of carbon (such as ), and improve the utilization rate of active oxygen produced by plasma.

[0007] According to embodiments of the present invention, the above-described deep decarburization method for silicon carbide powder may further include at least one of the following additional technical features: According to embodiments of the present invention, the transition metal nitrate solution is selected from cobalt nitrate, manganese nitrate, or ferric nitrate solutions. The inventors have discovered that during the dispersion process: when SiC powder is immersed in a metal nitrate solution (such as cobalt nitrate), the metal ions ( Nitrates are adsorbed onto the hydroxyl (-OH) sites on the SiC surface via electrostatic attraction. During the calcination process, nitrates decompose into metal oxides at high temperatures and form stable bonds with the SiC surface. For example, cobalt nitrate decomposes into... ,and pass Bonding action anchors it to the SiC surface, achieving The uniform dispersion and stable fixation of these elements are the core reasons for the formation of a highly efficient catalytic active layer. Furthermore, the presence of transition metal ions in the catalyst (such as...) ) has a variable valence state and can be obtained through a redox cycle (such as Oxygen-transferring species (reactive oxygen species produced by plasma ionization, such as...) , ), accelerates carbon oxidation ( This also improves the utilization rate of reactive oxygen species generated by plasma.

[0008] According to embodiments of the present invention, the particle size of the silicon carbide powder raw material is 0.8-200 μm. For example, the particle size of the silicon carbide powder raw material is 50-150 μm, or 30-100 μm, etc. The inventors have found that powders with this particle size have a better effect on deep decarburization.

[0009] According to an embodiment of the present invention, in step S2, the solid-liquid ratio of the pretreated silicon carbide powder to the transition metal nitrate solution is 1:(10-20) (g / mL), for example, 1:10 g / mL, 1:12 g / mL, 1:15 g / mL, 1:18 g / mL, or 1:20 g / mL.

[0010] According to an embodiment of the present invention, the acid is a hydrofluoric acid solution. According to an embodiment of the present invention, hydrofluoric acid (HF) reacts with metal oxides (such as...) on the surface of the powder. The reaction produces soluble fluorides. Simultaneously, naturally formed fluorides on the SiC surface... The oxide layer is removed by reacting with HF. Therefore, acid washing removes metallic impurities (such as oxides of Fe and Al) and the original oxide layer from the surface of silicon carbide (SiC) powder. This avoids impurities interfering with subsequent catalyst loading and oxidation reactions, while also increasing the surface roughness of the powder and enhancing the bonding force between the catalyst and the matrix.

[0011] According to embodiments of the present application, the acid is a hydrofluoric acid solution with a volume concentration of 5-10% (e.g., 5%, 6%, 7%, 8%, 9%, or 10%, etc.). The inventors have found that a hydrofluoric acid solution within this volume concentration range has a better removal effect on the metal oxides on the surface of the powder and the naturally formed oxide layer on the surface of SiC.

[0012] According to embodiments of the present application, the cleaning treatment is performed for 15-30 min (e.g., 15 min, 20 min, 25 min, or 30 min, etc.) by ultrasonic cleaning. According to embodiments of the present application, ultrasonic cleaning generates local high pressure and micro-jet through cavitation effect, which accelerates the contact reaction between HF and impurities, and improves the impurity removal efficiency. Cleaning for 15-30 min can ensure sufficient contact reaction between HF and impurities, and will not cause energy waste.

[0013] According to embodiments of the present application, the drying treatment is performed for 2-4 h (e.g., 2 h, 2.5 h, 3 h, 3.5 h, or 4 h, etc.) at a temperature of 80-100 ℃ (e.g., 80 ℃, 85 ℃, 90 ℃, 95 ℃, or 100 ℃, etc.). For example, the drying treatment is performed for 3 h at a temperature of 90 ℃. For example, the drying treatment is performed for 3 h at a temperature of 95 ℃. For example, the drying treatment is performed for 2.5 h at a temperature of 100 ℃. According to embodiments of the present application, the drying treatment can remove water, and avoid concentration unevenness caused by the presence of water during subsequent catalyst loading. Performing the drying treatment at a temperature of 80-100 ℃ for 2-4 h can sufficiently remove water, and will not cause energy waste.

[0014] According to embodiments of the present application, the cleaning treatment is performed for 15-30 min (e.g., 15 min, 20 min, 25 min, or 30 min, etc.) by ultrasonic cleaning. According to embodiments of the present application, ultrasonic cleaning generates local high pressure and micro-jet through cavitation effect, which accelerates the contact reaction between HF and impurities, and improves the impurity removal efficiency. Cleaning for 15-30 min can ensure sufficient contact reaction between HF and impurities, and will not cause energy waste.

[0015] According to embodiments of the present application, the concentration of the cobalt nitrate solution, the manganese nitrate solution, or the iron nitrate solution is 0.05-0.2 mol / L (e.g., 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.15 mol / L, 0.18 mol / L, or 0.2 mol / L, etc.). For example, the concentration of the cobalt nitrate solution is 0.1 mol / L, the concentration of the manganese nitrate solution is 0.15 mol / L, and the concentration of the iron nitrate solution is 0.08 mol / L, etc. According to embodiments of the present application, when the SiC powder is immersed in the metal nitrate solution (such as cobalt nitrate), the metal ions (​ The SiC powder and the cobalt nitrate, manganese nitrate or iron nitrate solution can be more fully reacted in this concentration range, which is more conducive to the formation of a high-efficiency catalytically active layer.

[0016] According to an embodiment of the present application, the dispersion treatment is performed for 20-40 min (for example, 20 min, 25 min, 30 min, 35 min, or 40 min, etc.) by ultrasonic dispersion. According to an embodiment of the present application, the ultrasonic dispersion for 20-40 min can ensure sufficient contact of the SiC powder with the transition metal nitrate solution, thereby ensuring that the transition metal ions are adsorbed by electrostatic attraction to the SiC surface hydroxyl (-OH) sites.

[0017] According to an embodiment of the present application, the evaporation treatment is performed at a temperature of 50-70 ℃ (for example, 50 ℃, 55 ℃, 60 ℃, 65 ℃, or 70 ℃, etc.). According to an embodiment of the present application, in this temperature range, the relevant solvent impurities in the system can be evaporated.

[0018] According to an embodiment of the present application, the calcination treatment is performed at a temperature of 400-500 ℃ (for example, 400 ℃, 450 ℃, or 500 ℃, etc.) for 3-5 h (for example, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, etc.). For example, the calcination treatment is performed at a temperature of 450 ℃ for 4 h. For example, the calcination treatment is performed at a temperature of 400 ℃ for 4 h. For example, the calcination treatment is performed at a temperature of 500 ℃ for 3 h. The inventors have found that in this temperature range and this calcination time range, the nitrate salt can be decomposed into a metal oxide at high temperature, and a stable combination with the SiC surface is formed, for example By anchoring on the SiC surface through a bonding effect, uniform dispersion and stable fixation are achieved , which is the core reason for forming a high-efficiency catalytically active layer.

[0019] According to an embodiment of the present application, the loading of the metal oxide / silicon carbide composite catalyst is 3%-15 wt% (for example, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, or 15 wt%, etc.). For example, the metal oxide / silicon carbide composite catalyst is 5 wt% of composite catalyst. For example, the metal oxide / silicon carbide composite catalyst is 8 wt% of composite catalyst. For example, the metal oxide / silicon carbide composite catalyst is 5 wt% of Composite catalyst. According to embodiments of the present invention, a metal oxide / silicon carbide composite catalyst with a loading of 3%-15 wt% can ensure the efficient generation of active oxygen species in subsequent oxidation reactions. The metal oxide / silicon carbide composite catalyst within this loading range has better catalytic efficiency in subsequent catalytic oxidation reactions.

[0020] According to an embodiment of the present invention, the parameters set for the radio frequency plasma reactor are as follows: a mixture of oxygen and inert gas (volume ratio 5:1-10:1, for example) is introduced. The volume ratio of Ar to Ar is 8:2, or The volume ratio of Ar to Ar is 7:3, or The volume ratio of He is 9:1, the total flow rate is controlled at 300-800 SCCM (e.g., 300 SCCM, 400 SCCM, 500 SCCM, 600 SCCM, 700 SCCM, or 800 SCCM, etc.), the radio frequency power is controlled at 400-1000 W (e.g., 400 W, 500 W, 600 W, 700 W, 800 W, 900 W, or 1000 W, etc.), and the reaction pressure is controlled at 80-200 mTorr (e.g., 80 mTorr, 90 mTorr, 100 mTorr, 110 mTorr, 120 mTorr, 130 mTorr, 140 mTorr, 150 mTorr, 160 mTorr, 170 mTorr, 180 mTorr, 190 mTorr, or 200 mTorr, etc.). According to embodiments of the present invention, under the parameters set in the radio frequency plasma reactor, the efficiency of plasma-assisted oxidation is better and the energy consumption is more economical. Traditional oxidation relies on molecular oxygen (… Its oxidizing power is limited by bond energy (498 kJ / mol), and the reaction rate is extremely low at low temperatures (<500℃). However, plasma, excited by a radio frequency electric field, enables... The molecule dissociates into high-energy oxygen free radicals (O*, bond energy <100 kJ / mol) and ozone ( The oxidation potential of these active species (e.g., the standard electrode potential of O* is 2.42 V) is much higher than that of electron beams. (1.23 V), it can react directly with carbon impurities. Furthermore, the high-energy particles generated by the plasma can activate active sites on the catalyst surface (such as...). The presence of oxygen vacancies reduces the activation energy of carbon oxidation from >100 kJ / mol in traditional methods to 40-60 kJ / mol. For example, O* in The adsorption energy at the site is reduced by 30%, significantly increasing the reaction rate and achieving deep carbon removal within 10-30 minutes. The high-energy gas flow and microjets of the plasma can strip away the carbon already deposited on the SiC surface. The gas prevents the product from covering the active site; at the same time, it promotes the contact between the catalyst and carbon impurities, solving the problem of "easy removal of external carbon and difficult removal of internal carbon" in traditional static oxidation.

[0021] According to an embodiment of the present invention, the oxidation reaction is carried out by maintaining the reaction chamber temperature at 300-450 °C for 10-40 min. According to an embodiment of the present invention, carbon impurities can be effectively removed within this temperature range without introducing new impurities. SiC is prone to self-oxidation at high temperatures (>800 °C). ), leading to surface formation Layers (affecting electrical properties) and grain agglomeration. Plasma-assisted oxidation can be carried out at 300-450 °C, at which point the oxidation rate of SiC is negligible (<0.1 nm / h), but carbon impurities can still be efficiently removed due to the synergistic effect of the catalyst and active oxygen, achieving "selective carbon removal".

[0022] According to an embodiment of the present invention, the post-treatment is performed by quenching, cooling, cleaning, and drying. According to an embodiment of the present invention, the post-treatment by quenching, cooling, cleaning, and drying can prevent excessive oxidation, remove residual catalyst, and clean the surface; drying removes moisture.

[0023] According to an embodiment of the present invention, the quenching treatment is performed by purging with nitrogen gas for 15-30 minutes. According to an embodiment of the present invention, nitrogen purging terminates the oxidation reaction and prevents over-oxidation; and purging for 15-30 minutes can fully terminate the oxidation reaction without wasting energy, making it economical.

[0024] According to an embodiment of the present invention, the cooling process is performed by cooling to room temperature.

[0025] According to an embodiment of the present invention, the cleaning process is performed by ultrasonic cleaning for 10-20 minutes (e.g., 10 minutes, 15 minutes, 20 minutes, etc.). According to an embodiment of the present invention, ultrasonic cleaning can effectively remove residual catalyst and clean the surface; and performing the process for 10-20 minutes can sufficiently and effectively remove residual catalyst and clean the surface without wasting energy, making it economical.

[0026] According to embodiments of the present invention, the drying process is carried out at 100-130°C (e.g., 100°C, 110°C, 120°C, or 130°C, etc.) for 2-5 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours, etc.). For example, the drying process is carried out at 120°C for 4 hours. For example, the drying process is carried out at 110°C for 3.5 hours. For example, the drying process is carried out at 125°C for 2.5 hours. According to embodiments of the present invention, the drying process can remove moisture, and drying at a temperature of 100-130°C for 2-5 hours can effectively remove moisture without introducing other impurities. For example, too high a temperature may cause unnecessary reactions to occur again on the SiC surface, while too low a temperature may not completely remove moisture and may cause energy waste.

[0027] In another aspect, the present invention provides a method for deep decarburization of silicon carbide powder. According to an embodiment of the present invention, the method includes the following steps: S1: Remove impurities from silicon carbide powder with a particle size of 0.8-200 μm by acid washing: ultrasonically clean with a 5%-10% hydrofluoric acid solution for 15-30 min to remove surface metal impurities, then rinse with deionized water until neutral, and dry at 80-100 ℃ for 2-4 h. S2: The pretreated SiC powder is immersed in a 0.05-0.2 mol / L solution of cobalt nitrate, manganese nitrate or ferric nitrate, ultrasonically dispersed for 20-40 min, evaporated to dryness at 50-70 ℃, and then calcined at 400-500 ℃ for 3-5 h to obtain a transition metal oxide / silicon carbide composite catalyst with a catalyst loading of 3%-15 wt%.

[0028] S3: Place the SiC powder loaded with catalyst in a radio frequency plasma reactor, introduce a mixed gas of oxygen and inert gas (volume ratio 5:1-10:1), control the total flow rate to 300-800 SCCM, the radio frequency power to 400-1000 W, the reaction pressure to 80-200 mTorr, maintain the temperature of the reaction chamber at 300-450 ℃ by external heating, and process for 10-40 min. S4: After the reaction is complete, purge with nitrogen for 15-30 min and cool to room temperature; ultrasonically clean the powder with deionized water for 10-20 min to remove residual catalyst and reaction byproducts, and dry at 100-130 ℃ for 2-5 h to obtain decarbonized SiC powder. According to an embodiment of the present invention, this method can introduce a composite catalyst (such as...) in step S2. or (etc.), while the surface active sites of the composite catalyst adsorb carbon impurities, high-energy oxygen free radicals (O*) and ozone generated by plasma. This method accelerates carbon oxidation through the active centers of the catalyst, reducing the activation energy by more than 40% compared to traditional methods. It can achieve deep carbon removal at 300-450 ℃, reducing energy consumption by 60% compared to traditional high-temperature oxidation methods (above 800 ℃), and avoids the oxidation and agglomeration of SiC grains. Furthermore, the reaction in the plasma reactor in step S3 allows for the selective bombardment of carbon impurities by high-energy plasma particles, and the composite catalyst inhibits the oxidation of the SiC matrix. After treatment, the surface roughness of the powder changes by less than 5%, and the crystal integrity retention rate is greater than 98%.

[0029] In another aspect, the present invention also proposes the application of the aforementioned deep decarburization method for silicon carbide powder in semiconductor manufacturing. As described above, the deep decarburization method for silicon carbide powder of the present invention, through hydrofluoric acid pretreatment, transition metal oxide catalyst loading, plasma-assisted oxidation, and post-treatment steps, utilizes the synergistic effect of high-energy oxygen species in plasma and composite catalysts to achieve highly efficient decarburization at a low temperature of 300-450 °C, significantly reducing the carbon content while minimizing damage to the SiC matrix. This solves the problems of high temperature and high consumption, and material damage associated with traditional methods, making it suitable for the purification of semiconductor-grade SiC powder and thus effectively applicable in semiconductor manufacturing.

[0030] In another aspect, the present invention provides a method for deep decarburization of silicon carbide powder. According to embodiments of the present invention, this method for deep decarburization of silicon carbide powder is actually a method for deep decarburization of silicon carbide powder based on plasma-assisted composite catalytic oxidation. This method for deep decarburization of silicon carbide powder mainly achieves efficient and low-damage decarburization of SiC powder through the synergistic effect of plasma activation and composite catalyst.

[0031] The process is as follows Figure 1 As shown.

[0032] The present invention will be described in detail below through specific steps, the purpose of each step, the key physicochemical reactions that occur in each step, and the advantages of each step.

[0033] S1: Raw material pretreatment Silicon carbide powder with a particle size of 0.8-200 μm is subjected to acid washing to remove impurities: ultrasonic cleaning with a 5%-10% hydrofluoric acid solution for 15-30 min to remove surface metal impurities, followed by rinsing with deionized water until neutral, and drying at 80-100 ℃ for 2-4 h.

[0034] Objective: To remove metallic impurities (such as oxides of Fe and Al) and the primary oxide layer from the surface of silicon carbide (SiC) powder by acid pickling. This avoids impurities interfering with subsequent catalyst loading and oxidation reactions, while also increasing the surface roughness of the powder and enhancing the bonding force between the catalyst and the matrix.

[0035] Key physicochemical reactions: Dissolution of metal oxides: Hydrofluoric acid (HF) reacts with metal oxides on the surface of the powder (such as... The reaction produces soluble fluorides: .

[0036] Etching of the oxide layer: naturally formed on the SiC surface The oxide layer is removed by reacting with HF. .

[0037] Ultrasonic cleaning generates local high pressure and microjets through cavitation effect, which accelerates the contact reaction between HF and impurities and improves the impurity removal efficiency; drying removes moisture and avoids uneven concentration caused by the presence of moisture when loading catalysts later.

[0038] S2: Composite catalyst support Transition metal oxide / silicon carbide composite catalysts were prepared by impregnation method: pretreated SiC powder was impregnated in a 0.05-0.2 mol / L solution of cobalt nitrate, manganese nitrate or ferric nitrate, ultrasonically dispersed for 20-40 min, evaporated to dryness at 50-70 ℃, and then calcined at 400-500 ℃ for 3-5 h. The catalyst loading was 3%-15 wt%.

[0039] Objective: To introduce transition metal oxide catalysts (such as...) onto the surface of SiC powder. It utilizes its surface active sites to adsorb carbon impurities and oxygen species, reducing the activation energy of the carbon oxidation reaction and providing a catalytic center for subsequent plasma oxidation, thus achieving "low-temperature and high-efficiency carbon removal". Key physicochemical reactions: Adsorption during the impregnation process: When SiC powder is impregnated with a metal nitrate solution (such as cobalt nitrate), the metal ions ( It is adsorbed onto the hydroxyl (-OH) sites on the SiC surface through electrostatic attraction. Decomposition and loading during calcination: Nitrates decompose into metal oxides at high temperatures and form stable bonds with the SiC surface. For example, the decomposition of cobalt nitrate: .

[0040] Load mechanism: pass Bonding action anchors it to the SiC surface, achieving The uniform dispersion and stable fixation of the material are the core reasons for the formation of a highly efficient catalytic active layer. Mechanism of action: Transition metal ions in the catalyst (e.g., ) has a variable valence state and can be obtained through a redox cycle (such as Oxygen-transferring species (reactive oxygen species produced by plasma ionization, such as...) ), accelerates carbon oxidation ( This also improves the utilization rate of reactive oxygen species generated by plasma.

[0041] S3: Plasma-assisted oxidation treatment The SiC powder loaded with catalyst was placed in a radio frequency plasma reactor, and a mixture of oxygen and inert gas (volume ratio 5:1-10:1) was introduced. The total flow rate was controlled at 300-800 SCCM, the radio frequency power at 400-1000 W, and the reaction pressure at 80-200 mTorr. The temperature of the reaction chamber was maintained at 300-450 ℃ by external heating, and the processing time was 10-40 min. The core reason for using plasma-assisted oxidation: 1. Efficiently generates reactive oxygen species, overcoming thermodynamic limitations. Traditional oxidation depends on molecular oxygen ( Its oxidizing power is limited by bond energy (498 kJ / mol), and the reaction rate is extremely low at low temperatures (<500℃). However, plasma, excited by a radio frequency electric field, enables... The molecule dissociates into high-energy oxygen free radicals and ozone ( The oxidation potential of these active species (e.g., the standard electrode potential of O* is 2.42 V) is much higher than that of electron beams. (1.23V), can react directly with carbon impurities: .

[0042] .

[0043] 2. Synergistically with catalysts, it reduces the activation energy of the reaction. High-energy particles generated by plasma can activate active sites on the catalyst surface (such as...). The presence of oxygen vacancies reduces the activation energy of carbon oxidation from >100 kJ / mol in traditional methods to 40-60 kJ / mol. For example, O* in The adsorption energy at the site is reduced by 30%, significantly improving the reaction rate and achieving deep carbon removal (carbon content <0.05%) within 10-30 min. 3. Low-temperature operation to avoid damage to the SiC matrix. SiC is prone to auto-oxidation at high temperatures (>800℃). ), leading to surface formation Layers (affecting electrical properties) and grain agglomeration. Plasma-assisted oxidation can be carried out at 300-450 °C, at which point the oxidation rate of SiC is negligible (<0.1 nm / h), but carbon impurities can still be efficiently removed due to the synergistic effect of the catalyst and active oxygen, achieving "selective carbon removal". 4. Enhance mass transfer and eliminate diffusion limitations The high-energy gas flow and microjets of plasma can strip away the existing deposits on the SiC surface. The gas prevents the product from covering the active site; at the same time, it promotes the contact between the catalyst and carbon impurities, solving the problem of "easy removal of external carbon and difficult removal of internal carbon" in traditional static oxidation.

[0044] S4: Post-processing After the reaction is complete, nitrogen gas is introduced to purge for 15-30 min, and the mixture is cooled to room temperature. The powder is then ultrasonically cleaned with deionized water for 10-20 min to remove residual catalyst and reaction byproducts. The powder is then dried at 100-130 °C for 2-5 h to obtain decarbonized SiC powder. Objective: Nitrogen purging to terminate the oxidation reaction and prevent over-oxidation; ultrasonic cleaning to remove residual catalyst and clean the surface; drying to remove moisture and prevent agglomeration.

[0045] According to embodiments of the present invention, the deep decarburization method for silicon carbide powder proposed in this invention has at least one of the following advantages: 1. Synergistic catalytic oxidation mechanism Composite catalysts (such as) ) Surface active sites adsorb carbon impurities, plasma-generated high-energy oxygen free radicals (O*) and ozone ( Carbon oxidation is accelerated through the active center of the catalyst, and the activation energy of the reaction is reduced by more than 40% compared with the traditional method. 2. Low-temperature, high-efficiency carbon removal Deep carbon removal is achieved at 300-450 ℃, reducing energy consumption by 60% compared to traditional high-temperature oxidation methods (above 800 ℃), and avoiding SiC grain oxidation and agglomeration. 3. Precision surface treatment High-energy plasma particles selectively bombard carbon impurities, and composite catalysts inhibit the oxidation of the SiC matrix. After treatment, the surface roughness of the powder changes by less than 5%, and the crystal integrity retention rate is greater than 98%. Attached Figure Description

[0046] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a process flow diagram according to an embodiment of the present invention. Detailed Implementation

[0047] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0048] Example 1: Pretreatment of raw materials for cobalt nitrate solution-supported catalyst: Take 100 g of SiC powder with a particle size of 50-150 μm (initial carbon content 0.85%), ultrasonically clean it with 5% hydrofluoric acid for 20 min, wash it with deionized water until pH=7.0, and dry it at 90 ℃ for 3 h; Composite catalyst loading: The powder was immersed in a 0.1 mol / L cobalt nitrate solution (solid-liquid ratio 1:15 g / mL), ultrasonically dispersed for 30 min, evaporated to dryness at 60 ℃, and calcined at 450 ℃ for 4 h to form a 5 wt% composite catalyst. Composite catalyst; Key response: , pass Bond anchoring, active site density 0.15 mmol / g; Plasma-assisted oxidation treatment: [The process involves introducing...] (8:2), flow rate 500 SCCM, power 600 W, pressure 150 mTorr, treatment at 350 ℃ for 20 min; Post-treatment: Nitrogen purging for 20 min, ultrasonic cleaning with deionized water for 15 min, and drying at 120 ℃ for 4 h.

[0049] Example 2: Pretreatment of raw materials for catalyst supported by manganese nitrate solution: Take 100 g of SiC powder with a particle size of 50-150 μm (initial carbon content 0.85%), ultrasonically clean it with 8% hydrofluoric acid for 25 min, wash it with deionized water until pH=6.9, and dry it at 95 ℃ for 3 h; Composite catalyst loading: The powder was immersed in a 0.15 mol / L manganese nitrate solution (solid-liquid ratio 1:12 g / mL), ultrasonically dispersed for 35 min, evaporated to dryness at 65 ℃, and calcined at 400 ℃ for 5 h to form 8 wt% Composite catalyst; Key response: 400 ℃ Completely oxidized to The active site density is 0.12 mmol / g; Plasma-assisted oxidation treatment: [The process involves introducing...] (7:3), flow rate 600 SCCM, power 700 W, pressure 120 mTorr, 380 ℃ for 25 min; Post-treatment: Nitrogen purging for 25 min, ultrasonic cleaning with deionized water for 18 min, and drying at 110 ℃ for 3.5 h.

[0050] Example 3: Pretreatment of raw materials for catalyst supported by ferric nitrate solution: Take 100 g of SiC powder with a particle size of 30-100 μm (initial carbon content 0.72%), ultrasonically clean it with 10% hydrofluoric acid for 20 min, wash it with deionized water until pH=6.8, and dry it at 100 ℃ for 2.5 h; Composite catalyst loading: The powder was immersed in a 0.08 mol / L ferric nitrate solution (solid-liquid ratio 1:18 g / mL), ultrasonically dispersed for 25 min, evaporated to dryness at 55 ℃, and calcined at 500 ℃ for 3 h to form a 5 wt% composite catalyst. Composite catalyst; Key response: 500 ℃ It exists stably with an active site density of 0.10 mmol / g; Plasma-assisted oxidation treatment: [The process involves introducing...] (9:1), flow rate 400 SCCM, power 500 W, pressure 180 mTorr, treatment at 420 ℃ for 18 min; Post-treatment: Nitrogen purging for 20 min, ultrasonic cleaning with deionized water for 15 min, and drying at 125 ℃ for 2.5 h.

[0051] Comparative Example 1: No catalyst support (acid washing + plasma only) Process steps: Same as in Example 1, but the "composite catalyst loading" step is omitted, and the pretreated SiC powder is directly subjected to plasma oxidation; Key difference: No transition metal oxide active sites, O* generated by plasma cannot react efficiently with carbon.

[0052] Comparative Example 2: Non-transition metal nitrates (zinc nitrate, no ability to change valence) Process steps: Same as Example 1, but replace cobalt nitrate with 0.1 mol / L zinc nitrate solution, calcine at 450 ℃ for 4 h to form 5 wt% system; Key differences: It has no redox cycling ability, and its active site density is only 0.02 mmol / g, so it cannot transfer reactive oxygen species.

[0053] Comparative Example 3: Non-nitrate catalyst precursor (cobalt chloride, containing corrosive ions) Process steps: Same as in Example 1, but replace cobalt nitrate with 0.1 mol / L cobalt chloride solution, and calcine at 450 °C for 4 h; Key difference: Cobalt chloride releases during calcination Corrosion of SiC surface to form ,and This leads to poisoning of the catalyst's active sites.

[0054] Comparative Example 4: Calcination temperature below the range (350 ℃, time 5 h) Process steps: Same as in Example 2, but the calcination temperature is reduced to 350 °C; Key difference: 350℃ is lower than the decomposition temperature of manganese nitrate (≥380℃), only 40% lower. Decomposed into The catalyst loading is only 2 wt%.

[0055] Comparative Example 5: Calcination temperature higher than the range (550 ℃, time 3 h) Process steps: Same as in Example 3, but the calcination temperature is increased to 550 ℃; Key difference: 550 ℃ leads to Grain growth (from 20 nm to 60 nm) reduced the active site density to 0.04 mmol / g.

[0056] Comparative Example 6: Traditional high-temperature oxidation method (without plasma and without catalyst) Process steps: Take SiC powder from the same batch (initial carbon content 0.85%), keep it at 900 ℃ in air for 2 hours, and then let it cool naturally; Key difference: High temperature leads to SiC oxidation. Moreover, it consumes a lot of energy.

[0057] Table 1. Comparison of Effect Data between Examples and Comparative Examples

[0058] Data Comparison and Analysis Validation of the effectiveness of the examples: The final carbon content of Examples 1-3 was ≤0.042%, the carbon removal rate was ≥94.7%, and the SiC crystal integrity was ≥98.2%. This proves that the three transition metal nitrates (cobalt, manganese, and iron) can achieve deep carbon removal in synergy with plasma within the parameter range of calcination at 400-500 ℃ for 3-5 h, and cause little damage to the SiC matrix.

[0059] Necessity of catalyst: The carbon removal rate of Comparative Example 1 (without catalyst) was only 62.4%, which was much lower than the 95.9% of Example 1, indicating that transition metal oxide catalysts are the core of efficient carbon removal at low temperatures and can improve the utilization rate of active oxygen through redox cycle; Comparative Example 2 (non-transition metal zinc nitrate) had a carbon removal rate of only 75.3% due to the lack of valence change ability, which further verified the irreplaceable nature of transition metal catalysts.

[0060] Advantages of nitrate precursors: Although Comparative Example 3 (cobalt chloride) achieved a carbon removal rate of 78.8%, the SiC crystal integrity decreased to 92%, and the surface roughness increased significantly, proving that non-nitrate precursors (containing...) ) will corrode the substrate, while the decomposition of nitrates only produces gas ( ), with no residual impurities.

[0061] Criticality of calcination parameters: Comparative Example 4 (calcined at 350 ℃) had a carbon removal rate of 82.4% due to incomplete catalyst decomposition; Comparative Example 5 (calcined at 550 ℃) had a carbon removal rate of 88.2% due to catalyst grain growth. Both were lower than those of Examples 2-3, highlighting the rationality of the parameters of calcination temperature of 400-500 ℃ and time of 3-5 h.

[0062] Advantages over traditional methods: Although Comparative Example 6 (high temperature oxidation) achieved a carbon removal rate of 92.9%, its energy consumption was 3.5 times that of Example 1, and the SiC crystal integrity was only 90.5%, with severe agglomeration on the surface due to oxidation. This demonstrates the significant advantages of the "low temperature + plasma + catalyst" process of this invention in terms of energy consumption and substrate protection.

[0063] This invention covers key parameter ranges through three transition metal nitrate examples and eliminates ineffective solutions through five targeted comparative examples, fully verifying the innovation and feasibility of the process and providing a reliable technical path for deep decarbonization of semiconductor-grade SiC powder.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. 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 any suitable manner in 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.

[0065] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for deep decarburization of silicon carbide powder, characterized in that, Includes the following steps: S1: The silicon carbide powder raw material is cleaned and dried with acid to obtain pretreated silicon carbide powder. S2: The pretreated silicon carbide powder is immersed in a transition metal nitrate solution for dispersion, evaporation and calcination to obtain a metal oxide / silicon carbide composite catalyst. S3: The metal oxide / silicon carbide composite catalyst is placed in a radio frequency plasma reactor to carry out an oxidation reaction; S4: After the oxidation reaction is completed, post-processing is performed to obtain decarbonized silicon carbide powder.

2. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The transition metal nitrate solution is selected from cobalt nitrate, manganese nitrate, or ferric nitrate solution; Optionally, the particle size of the silicon carbide powder raw material is 0.8-200 μm; Optionally, in step S2, the solid-liquid ratio of the pretreated silicon carbide powder to the transition metal nitrate solution is 1:(10-20).

3. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The acid is a hydrofluoric acid solution; Optionally, the acid is a hydrofluoric acid solution with a volume concentration of 5%-10%.

4. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The cleaning process is performed by ultrasonic cleaning for 15-30 minutes. Optionally, the drying process is carried out at a temperature of 80-100 °C for 2-4 hours; Optionally, the process after cleaning and before drying further includes rinsing the cleaned material with deionized water until it is neutral.

5. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The concentration of the cobalt nitrate, manganese nitrate, or ferric nitrate solution is 0.05-0.2 mol / L; Optionally, the dispersion treatment is carried out by ultrasonic dispersion for 20-40 min; Optionally, the evaporation process is carried out at a temperature of 50-70 °C; Optionally, the calcination treatment is carried out at a temperature of 400-500 °C for 3-5 h.

6. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The loading of the metal oxide / silicon carbide composite catalyst is 3%-15 wt.

7. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The parameters set for the radio frequency plasma reactor are as follows: a mixed gas of oxygen and inert gas (volume ratio 5:1-10:1) is introduced, the total flow rate is controlled at 300-800 SCCM, the radio frequency power is 400-1000 W, and the reaction pressure is 80-200 mTorr. Optionally, the oxidation reaction is carried out while the temperature of the reaction chamber is maintained at 300-450 °C for 10-40 min.

8. The method for deep decarburization of silicon carbide powder according to claim 1, characterized in that, The post-processing is carried out through quenching, cooling, cleaning and drying. Optionally, the quenching treatment is performed by purging with nitrogen gas for 15-30 minutes; Optionally, the cooling process is performed by cooling to room temperature; Optionally, the cleaning process is performed by ultrasonic cleaning for 10-20 minutes; Optionally, the drying process is carried out at 100-130 °C for 2-5 h.

9. A method for deep decarburization of silicon carbide powder, characterized in that, Includes the following steps: S1: Remove impurities from silicon carbide powder with a particle size of 0.8-200 μm by acid washing: ultrasonically clean with a 5%-10% hydrofluoric acid solution for 15-30 min to remove surface metal impurities, then rinse with deionized water until neutral, and dry at 80-100 ℃ for 2-4 h. S2: The pretreated silicon carbide powder is immersed in a 0.05-0.2 mol / L solution of cobalt nitrate, manganese nitrate or ferric nitrate, ultrasonically dispersed for 20-40 min, evaporated to dryness at 50-70 ℃, and then calcined at 400-500 ℃ for 3-5 h to obtain a transition metal oxide / silicon carbide composite catalyst with a catalyst loading of 3%-15 wt%. S3: Place the catalyst-supported silicon carbide powder in a radio frequency plasma reactor, introduce a mixture of oxygen and inert gas (volume ratio 5:1-10:1), control the total flow rate to 300-800 SCCM, the radio frequency power to 400-1000 W, the reaction pressure to 80-200 mTorr, maintain the reaction chamber temperature at 300-450 ℃ through external heating, and process for 10-40 min; S4: After the reaction is complete, purge with nitrogen for 15-30 min and cool to room temperature; ultrasonically clean the powder with deionized water for 10-20 min to remove residual catalyst and reaction byproducts, and dry at 100-130 ℃ for 2-5 h to obtain decarbonized silicon carbide powder.

10. The application of the deep decarburization method for silicon carbide powder according to any one of claims 1-9 in the preparation of semiconductors.

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