SiC efficient polishing solution based on core-shell structure functional abrasive and preparation method

Abstract

The invention relates to an efficient SiC polishing solution based on a core-shell structure functionalized abrasive, which is prepared from the following raw materials in percentage by mass: 1 to 10 percent of core-shell structure functionalized abrasive, 1 to 5 percent of potassium permanganate, 0.01 to 5 percent of dispersing agent, 0.01 to 5 percent of buffering agent and the balance of deionized water, the pH value of the SiC efficient polishing solution is 3-6. According to the invention, the functional abrasive material taking the hard abrasive material as the core and the catalytic metal oxide as the shell is constructed, and the catalytic active component is loaded on the surface of the abrasive material in a chemical bonding manner, so that the interface synergistic efficiency of mechanical grinding and chemical catalysis is obviously enhanced; the technical bottlenecks of insufficient synergistic effect and low material removal efficiency caused by separation of an abrasive and a catalyst in the prior art are solved, efficient material removal without increasing the concentration of an oxidizing agent or external field auxiliary conditions is realized, and excellent surface quality is ensured while the material removal efficiency is improved; therefore, the urgent demand of SiC substrate industrialization on high-quality and high-efficiency planarization processing is met.

Description

Technical Field

[0001] This invention belongs to the field of precision processing technology of semiconductor materials, specifically relating to a high-efficiency SiC polishing slurry based on core-shell structure functionalized abrasive and its preparation method. Background Technology

[0002] Single-crystal silicon carbide (SiC), as a third-generation semiconductor material with excellent comprehensive performance, possesses outstanding physicochemical properties such as a large bandgap, high breakdown electric field, strong radiation resistance, and good chemical stability. This makes it a preferred material for high-frequency, high-temperature, high-power, and radiation-resistant electronic devices and sensors, with important applications in aerospace, nuclear energy development, radar, photovoltaic new energy, and communications. However, the extremely high hardness and chemical inertness of single-crystal SiC pose numerous challenges to its polishing process. Therefore, overcoming the current processing bottlenecks of SiC wafers and achieving ultra-smooth, low-damage, and defect-free surface processing is crucial for ensuring the high performance and high reliability of semiconductor devices.

[0003] Chemical mechanical polishing (CMP) technology combines the chemical corrosion of polishing slurry with the mechanical abrasive action of abrasive particles and polishing pads, making it a key process for achieving global planarization of SiC wafers and obtaining ultra-smooth, damage-free surfaces. However, existing SiC CMP processes still face the core technological bottleneck of insufficient material removal efficiency (MRR), failing to meet the urgent industrial demand for efficient planarization processing.

[0004] As a core element of the CMP process, the polishing slurry is typically composed of high-hardness abrasives (such as diamond and alumina) and strong oxidants (such as permanganates and hypochlorites). Its component design and ratio directly determine the synergistic efficiency of chemical etching and mechanical polishing, making it a key factor affecting the removal efficiency of SiC materials. In existing technologies, methods commonly used to improve material removal efficiency include: increasing the concentration of abrasives and oxidants to enhance the intensity of mechanical and chemical interactions; adjusting the pH of the polishing slurry to optimize the reaction environment; or introducing auxiliary oxidation methods such as Fenton reactions and photocatalysis to improve overall oxidation efficiency. However, these improved methods still have significant limitations in practical applications: increasing the content of abrasives and oxidants in the system can improve material removal efficiency to some extent, but it easily induces component failure, leads to abrasive agglomeration, exacerbates surface scratches, and increases costs; while oxidation methods relying on external fields (such as photocatalysis) face problems such as complex processes, high equipment requirements, and the potential introduction of metal ion contamination, making them unsuitable for large-scale production.

[0005] In addition to the above methods, existing studies have also introduced nano-catalysts (such as MnO2, Fe3O4, etc.) into the polishing slurry system through physical mixing, aiming to enhance the chemical action of the polishing process and improve the material removal efficiency. However, this method also has the following defects: (1) Insufficient effective catalytic activity: Due to their large specific surface area and high surface energy, nano-catalysts are prone to agglomeration in the polishing slurry, resulting in a large number of active sites being buried and unable to fully participate in the surface oxidation reaction, thus affecting the improvement of material removal efficiency; (2) Low mechanical-chemical synergistic efficiency: Nano-catalyst particles and abrasives are randomly distributed at the polishing interface, making it impossible to achieve simultaneous mechanical grinding and chemical catalysis, resulting in significantly insufficient synergistic efficiency.

[0006] In summary, existing SiC polishing slurry technologies still face technical bottlenecks in improving material removal efficiency: traditional formulations, which increase component concentration, have an efficiency ceiling and are prone to surface damage and cost issues; external field-assisted oxidation methods suffer from high process complexity and difficulty in scaling up; and physically mixed catalysts struggle to achieve efficiency breakthroughs due to insufficient dispersion and synergistic mechanisms. The fundamental reason for this is that the aforementioned techniques cannot achieve precise synergy between mechanical grinding and chemical action at the polishing interface. Based on this, this application was developed. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of existing technologies and provide a high-efficiency SiC polishing slurry based on core-shell structured functionalized abrasives and its preparation method. By constructing a functionalized abrasive with a hard abrasive as the core and a catalytic metal oxide as the shell, the catalytically active components are loaded onto the abrasive surface through chemical bonding, which significantly enhances the interfacial synergistic efficiency of mechanical polishing and chemical catalysis. This solves the technical bottleneck of insufficient synergy and low material removal efficiency caused by the separation of abrasive and catalyst in existing technologies. It achieves high-efficiency material removal without increasing the oxidant concentration or external field assistance conditions, and ensures excellent surface quality while improving material removal efficiency, thereby meeting the urgent need for high-quality and high-efficiency planarization processing in the SiC substrate industrialization.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A high-efficiency SiC polishing slurry based on core-shell structure functionalized abrasive, wherein the raw materials of the high-efficiency SiC polishing slurry are composed of the following by mass percentage: 1-10% core-shell structure functionalized abrasive, 1-5% potassium permanganate, 0.01-5% dispersant, 0.01-5% buffer, and the balance being deionized water; the pH of the high-efficiency SiC polishing slurry is 3-6.

[0009] Specifically, the dispersant can be one or more of sodium silicate, sodium hexametaphosphate, sodium polyacrylate, sodium tripolyphosphate, sodium dodecylbenzenesulfonate, etc.; the buffer can be at least one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, etc.

[0010] Furthermore, the pH is adjusted to 3-6 using a pH adjuster, which can be at least one of HCl, HNO3, etc.

[0011] In this invention, a catalytic shell is grown in situ, using MnO2 as the catalytically active shell, and deposited in situ on the surface of activated alumina abrasive through a redox reaction to form a core-shell structured functionalized composite abrasive. Furthermore, in the above-mentioned high-efficiency SiC polishing slurry based on the core-shell structured functionalized abrasive, the core-shell structured functionalized abrasive is prepared through the following steps: a) Preparation of precursor solution: Using potassium permanganate (KMnO4) as manganese source and oxidant, and urea (CO(NH2)2) as precipitant, dissolve potassium permanganate and urea in deionized water at a molar ratio of 1:1-10, stir and mix well to prepare a precursor solution with a concentration of 0.05-0.5 mol / L, calculated as KMnO4; b) In-situ growth of the shell: The activated alumina abrasive suspension is placed in a water bath at 60-90℃. Under continuous stirring, after the temperature stabilizes, the precursor solution prepared in step a) above is added dropwise. After the addition is completed, the reaction is continued at a constant temperature and stirred for 1-3 hours to complete the in-situ growth of the shell. c) Abrasive post-processing: After the reaction is completed, the system is naturally cooled to room temperature, and then subjected to solid-liquid separation, washing, drying, and air jet pulverization to obtain core-shell structured functionalized abrasive Al2O3 / MnO2.

[0012] Specifically, in step b), the mass of KMnO4 is 10-50 wt% of the mass of the activated alumina abrasive; the stirring speed is set to 400-600 rpm; and the precursor solution prepared in step a) is slowly and uniformly added dropwise over 1-3 hours. The dropwise addition time of the precursor solution (1-3 hours) and the isothermal stirring reaction time (1-3 hours) are the core process parameters for controlling the crystallinity, density, and thickness of the MnO2 shell.

[0013] Specifically, in step c), solid-liquid separation is performed by high-speed centrifugation at 5000-12000 rpm to collect solid abrasive materials, with a centrifugation time of 5-15 min; the washing process involves repeatedly washing the solid abrasive materials twice with deionized water, and then washing them once with anhydrous ethanol (ethanol washing can reduce surface tension and reduce agglomeration); the drying process involves placing the material in a freeze dryer and freeze-drying it at -50 ~ -20℃ for 12-48 hours.

[0014] Further preferably, the activated alumina abrasive suspension in step b) is obtained through the following surface activation treatment: Alumina abrasive is mixed with deionized water at a solid-liquid ratio of 1:10-20 g / mL, a dispersant is added, and the mixture is continuously stirred with an electric stirrer for 10-60 min at room temperature to obtain an alumina dispersion suspension; then nitric acid is added to adjust the pH to 3-4, and the system is placed in a water bath at 40-90℃. After the system temperature stabilizes, stirring continues for 30-90 min to obtain the surface-treated activated alumina abrasive. Further, the alumina abrasive is nano-sized alumina polishing powder with a particle size range of 100-500 nm; the dispersant can be one or more of sodium hexametaphosphate, sodium silicate, sodium pyrophosphate, sodium tripolyphosphate, etc., and its addition amount is 0.1-1.0 wt% of the alumina abrasive mass. The speed of the electric stirrer is set to 400-600 rpm. The room temperature condition is 25±5℃. This step uses acid activation to make the surface of the alumina abrasive positively charged, providing active sites for the subsequent heterogeneous nucleation of the metal oxide shell.

[0015] This invention provides a method for preparing the above-mentioned high-efficiency SiC polishing slurry based on core-shell structure functionalized abrasive, as detailed below: Core-shell structured functionalized abrasives are added to a certain amount of deionized water to prepare an abrasive suspension with a certain mass fraction. Under stirring conditions, potassium permanganate aqueous solution is slowly added, followed by dispersant, buffer and the remaining deionized water. Stirring is continued (about 20-40 minutes) until the mixture is uniform. Finally, the pH value is adjusted to the required range to obtain silicon carbide polishing slurry based on core-shell structured functionalized abrasives.

[0016] Furthermore, the mass fraction of the abrasive suspension is 10-40 wt%; the mass fraction of the potassium permanganate aqueous solution is 1-10 wt%; and the stirring speed is 400-600 rpm.

[0017] To achieve high material removal efficiency in silicon carbide polishing slurries, this invention provides a method for preparing silicon carbide polishing slurries based on core-shell structured functionalized abrasives. This method employs an in-situ growth process to firmly load a catalytically active component—MnO2 nanolayers—on the surface of alumina abrasives, thus preparing core-shell structured Al2O3 / MnO2 functionalized abrasives. These functionalized abrasives are then used as the grinding component, and the system formulation is designed in conjunction with oxidants, dispersants, and other components to ultimately form a polishing slurry system with high polishing performance.

[0018] This invention constructs a stable composite structure of "catalytic component shell - hard abrasive core" by preparing core-shell structured Al2O3 / MnO2 functionalized abrasives, achieving precise synergy between mechanical polishing and chemical catalysis. This structure, through in-situ growth of the MnO2 nanolayer, is tightly bonded to the Al2O3 abrasive surface via chemical bonding, effectively avoiding the problems of few active sites and low mechanical-chemical synergy efficiency commonly found in traditional physical mixing methods for nanocatalysts, thus significantly improving catalytic activity and stability. During the polishing process, when the functionalized abrasive comes into contact with the SiC surface, the MnO2 shell on the abrasive surface can form a catalytic cycle system with the oxidant component in the polishing solution (potassium permanganate is used as the oxidant component in this invention). MnO2, as a highly efficient electron transfer medium, can promote the decomposition of KMnO4 to generate highly oxidizing intermediate-valence manganese ions (such as MnO4). 3+ These active manganese components can rapidly act on the SiC surface, forming a softening layer by oxidatively breaking C-Si bonds. Simultaneously, under the mechanical grinding action of the system, the softening layer is promptly removed, exposing a new reaction interface, thus achieving continuous and efficient material removal. In this process, chemical oxidation and mechanical grinding occur simultaneously in the same area, forming a localized high-concentration active reaction zone. This achieves precise nanoscale synergy between "mechanical grinding and chemical oxidation," thereby significantly improving material removal efficiency and reliably ensuring the quality of the processed surface without significantly increasing the oxidant concentration or relying on external field assistance.

[0019] This invention, based on abrasive structure design, constructs functionalized abrasives with a core-shell structure, loading catalytically active components onto the abrasive surface via chemical bonding. This achieves precise synergy between mechanical abrasion and chemical catalysis at the nanoscale, thereby significantly improving material removal efficiency. Compared with existing technologies, the beneficial effects of this invention are as follows: 1) The silicon carbide polishing slurry of the present invention uses an in-situ growth process to load a MnO2 catalytically active shell layer on the surface of alumina abrasive, forming a core-shell structure Al2O3 / MnO2 functionalized abrasive, so that mechanical grinding and chemical catalysis can be carried out simultaneously on the same abrasive particle surface, significantly improving the material removal efficiency.

[0020] 2) The silicon carbide polishing slurry of the present invention optimizes the in-situ growth process parameters to ensure the integrity and stability of the catalytic shell, effectively ensuring efficient electron mass transfer during the polishing process and avoiding surface damage caused by shell peeling or breakage. Thus, while efficiently removing materials, the surface quality of the processed material is also reliably guaranteed.

[0021] 3) The silicon carbide polishing slurry of the present invention has a catalytic enhancement function. It can achieve a high removal rate without significantly increasing the concentration of oxidant (KMnO4 is used as oxidant in the present invention), effectively reducing the amount of chemicals used, reducing the waste liquid treatment load, and reducing production costs, which is in line with the trend of green manufacturing development.

[0022] 4) The silicon carbide polishing slurry of the present invention has low cost of raw materials and manufacturing equipment, mild in-situ growth process conditions, and simple steps, making it suitable for mass production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a simplified process flow diagram of the present invention; Figure 2 This is a schematic diagram of the structure of the core-shell Al2O3 / MnO2 functionalized abrasive prepared according to the present invention; Figure 3 XRF spectrum of commercially available nano-sized alumina polishing powder; Figure 4 The XRF spectrum of the core-shell structured Al2O3 / MnO2 functionalized abrasive prepared for this invention is shown in the figure, where the red box marks the characteristic peak of MnO2. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] In the following examples, all raw materials used are common commercially available products that can be purchased directly, or can be prepared using conventional techniques in the art.

[0027] Example 1 A silicon carbide polishing slurry based on core-shell structured functionalized abrasives, comprising the following raw materials by mass percentage: The polishing solution contains 4.5% core-shell functionalized abrasive, 4.5% potassium permanganate (KMnO4), 0.25% sodium tripolyphosphate, 0.5% sodium dihydrogen phosphate, and the balance is deionized water; the pH of the polishing solution is 4.0.

[0028] Specifically, the preparation of the silicon carbide polishing slurry in this embodiment includes the following steps (process flow diagram as shown). Figure 1 (as shown) S1. Surface activation treatment of core-layer abrasive: Weigh 150g of commercially available nano-sized alumina polishing powder with a particle size of 200nm, mix with 1.5L of deionized water (solid-liquid ratio of 1:10 g / mL), add 0.75g of sodium hexametaphosphate (0.5% of the alumina abrasive mass), and stir continuously at 500rpm for 30min at room temperature (25℃) to obtain an alumina dispersion suspension. Then, add 1.0mol / L nitric acid solution dropwise to the suspension to adjust the pH to 3.5, and place the system in a 60℃ water bath environment and stir at a constant temperature for 60min to complete the surface activation treatment and obtain an activated alumina suspension.

[0029] S2, in-situ growth of catalytic shell: A. Preparation of precursor solution: Weigh 30g potassium permanganate (KMnO4, accounting for 20% of the mass of alumina abrasive in step S1) and 34.2g urea (CO(NH2)2, molar ratio KMnO4:urea is 1:3), dissolve them together in 500mL of deionized water, stir evenly, and prepare a 0.38 mol / L (calculated as KMnO4) precursor solution; B. In-situ shell growth: The activated alumina suspension obtained in S1 was placed in a 70°C water bath. Under continuous stirring at 500 rpm with an electric stirrer, the precursor solution prepared in step A was slowly and uniformly added dropwise to the system over 2 hours. After the addition was complete, the reaction was continued at a constant temperature and stirred for another 2 hours to complete the in-situ shell growth. C. Post-processing of abrasive: After the reaction in step B is completed, the system is cooled to room temperature, and the solid abrasive is collected by centrifugation at 8000 rpm for 10 min using a high-speed centrifuge. It is then washed twice with deionized water and once with anhydrous ethanol. After filtration, the filter cake is freeze-dried at -35℃ for 24 h. The dried powder is then subjected to air jet milling to obtain well-dispersed core-shell structured Al2O3 / MnO2 functionalized abrasive (see structural schematic diagram). Figure 2 ).

[0030] S3. Preparation of Polishing Slurry: Weigh 90g of the core-shell structured Al2O3 / MnO2 functionalized abrasive prepared in step S2, add it to 210g of deionized water, and prepare an abrasive suspension with a mass fraction of 30wt%. Simultaneously, weigh 90g of potassium permanganate and dissolve it in 1410g of deionized water to prepare 1500g of potassium permanganate aqueous solution with a mass fraction of 6wt%. Under continuous stirring at 500rpm using an electric stirrer, slowly add the potassium permanganate aqueous solution to the abrasive suspension system, then add 5g of sodium tripolyphosphate (0.25%) and 10g of sodium dihydrogen phosphate (0.5%) sequentially, and add deionized water until the total mass is 2000g. Continue stirring for 30min until uniformly mixed, then slowly add 1.0mol / L HNO3 solution to adjust the pH to 4.0, thus obtaining the silicon carbide polishing slurry based on the core-shell structured functionalized abrasive.

[0031] Figure 3 XRF spectra of commercially available nano-sized alumina polishing powder are presented. Figure 4 The XRF spectrum of the core-shell Al2O3 / MnO2 functionalized abrasive prepared in this embodiment is shown. Comparing the two figures, it can be seen that the XRF spectrum of the core-shell Al2O3 / MnO2 functionalized abrasive prepared in this embodiment shows obvious MnO2 characteristic peaks (located in the red box in the figure), indicating the successful loading of MnO2.

[0032] Example 2 A silicon carbide polishing slurry based on core-shell structured functionalized abrasives, comprising the following raw materials by mass percentage: The polishing solution contains 6.0% core-shell functionalized abrasive, 3.5% potassium permanganate (KMnO4), 0.5% sodium polyacrylate, 0.3% potassium dihydrogen phosphate, and the balance is deionized water. The pH of the polishing solution is 4.5.

[0033] Specifically, the preparation of the silicon carbide polishing slurry in this embodiment includes the following steps: S1. Surface activation treatment of core-layer abrasive: Weigh 150g of commercially available nano-sized alumina polishing powder with a particle size of 300nm, mix with 2.25L of deionized water (solid-liquid ratio of 1:15 g / mL), add 1.5g of sodium silicate (accounting for 1.0% of the mass of alumina abrasive), and stir continuously at 600rpm for 40min at room temperature (25℃) to obtain an alumina dispersion suspension. Then, add 1.0mol / L nitric acid solution dropwise to the suspension to adjust the pH to 3.0, and place the system in a 70℃ water bath environment and stir at a constant temperature for 45min to complete the surface activation treatment and obtain an activated alumina suspension.

[0034] S2, in-situ growth of catalytic shell: A. Preparation of precursor solution: Weigh 45g potassium permanganate (KMnO4, accounting for 30% of the mass of alumina abrasive in step S1) and 51.3g urea (CO(NH2)2, molar ratio KMnO4:urea = 1:3), dissolve them together in 650mL of deionized water, stir evenly, and prepare a 0.44mol / L precursor solution; B. In-situ shell growth: The activated alumina suspension obtained in S1 was placed in an 80°C water bath. Under continuous stirring at 600 rpm with an electric stirrer, the precursor solution prepared in step A was slowly and uniformly added dropwise to the system over 2.5 hours. After the addition was complete, the reaction was continued at a constant temperature and stirred for another 2.5 hours to complete the in-situ shell growth. C. Post-processing of the abrasive: After the reaction in step B is completed, the system is cooled to room temperature, and the solid abrasive is collected by centrifugation at 10,000 rpm for 10 min using a high-speed centrifuge. It is then washed twice with deionized water and once with anhydrous ethanol. After filtration, the filter cake is freeze-dried at -35℃ for 24 h. The dried powder is then subjected to air jet milling to obtain well-dispersed core-shell structured Al2O3 / MnO2 functionalized abrasive.

[0035] S3. Preparation of Polishing Slurry: Weigh 120g of the Al2O3 / MnO2 functionalized abrasive prepared in step S2 and add it to 280g of deionized water to prepare an abrasive suspension with a mass fraction of 30wt%. Simultaneously, weigh 70g of potassium permanganate and dissolve it in 1097g of deionized water to prepare a potassium permanganate aqueous solution with a mass fraction of 6wt%. Under continuous stirring at 600rpm using an electric stirrer, slowly add the potassium permanganate aqueous solution to the abrasive suspension system, then add 10g of sodium polyacrylate (0.5%) and 6g of potassium dihydrogen phosphate (0.3%) sequentially, and add deionized water until the total mass is 2000g. Continue stirring for 30min until uniformly mixed, then slowly add 1.0mol / L HCl solution to adjust the pH to 4.5, thus obtaining the silicon carbide polishing slurry based on core-shell structure functionalized abrasive.

[0036] Comparative Example 1 The difference between the silicon carbide polishing slurry prepared in Comparative Example 1 and that prepared in Example 1 is that in Comparative Example 1, commercially available nano-sized alumina polishing powder was directly used as the abrasive component of the polishing slurry (i.e., no surface activation treatment was performed), and its addition amount was the same as the content of functionalized abrasive in the polishing slurry of Example 1. Other formulations and processes were the same as in Example 1.

[0037] Comparative Example 2 The difference between the silicon carbide polishing slurry prepared in Comparative Example 2 and that prepared in Example 1 is as follows: In Comparative Example 2, commercially available nano-sized alumina polishing powder was used as the abrasive component of the polishing slurry (i.e., no surface activation treatment was performed), and its addition amount was the same as the content of functionalized abrasive in the polishing slurry of Example 1; at the same time, the mass fraction of potassium permanganate in the polishing slurry was increased from 4.5% in Example 1 to 5.5%. Other formulations and processes were the same as in Example 1.

[0038] Comparative Example 3 The difference between the silicon carbide polishing slurry prepared in Comparative Example 3 and that prepared in Example 1 is that Comparative Example 3 uses a physical mixing method instead of an in-situ growth process to introduce the MnO2 catalytic component during the preparation of the polishing slurry. Specifically, MnO2 nanoparticles with a particle size similar to the MnO2 shell in Example 1 were independently prepared by co-precipitation under conditions without alumina abrasive. These nanoparticles were then physically mixed with commercially available nano-sized alumina polishing powder (the mass ratio of Al2O3 to MnO2 in the mixed system was the same as the core-shell abrasive ratio in Example 1). Other formulations and processes were the same as in Example 1.

[0039] Comparative Example 4 The difference between the silicon carbide polishing slurry prepared in Comparative Example 4 and that prepared in Example 1 is that, in Comparative Example 4, the dropwise addition time of the precursor solution in step S2-B is shortened to 0.5 h (lower than the preferred range of 1-3 h of this invention). All other formulations and processes are the same as in Example 1.

[0040] Comparative Example 5 The difference between the silicon carbide polishing slurry prepared in Comparative Example 5 and that prepared in Example 1 is that in Comparative Example 5, the dropwise addition time of the precursor solution in step S2-B is extended to 4 hours (higher than the preferred range of 1-3 hours of this invention). All other formulations and processes are the same as in Example 1.

[0041] Comparative Example 6 The difference between the silicon carbide polishing slurry prepared in Comparative Example 6 and that prepared in Example 1 is that, in Comparative Example 6, after the precursor solution is added dropwise in step S2-B, the constant temperature stirring reaction time is shortened to 0.5 h (lower than the preferred range of 1-3 h of this invention). All other formulations and processes are the same as in Example 1.

[0042] Comparative Example 7 The difference between the silicon carbide polishing slurry prepared in Comparative Example 7 and that prepared in Example 1 is that in Comparative Example 7, after the precursor solution is added dropwise in step S2-B, the constant temperature stirring reaction time is extended to 4 hours (higher than the preferred range of 1-3 hours of this invention). Other formulations and processes are the same as in Example 1.

[0043] Table 1 lists the core differences in abrasive structure and preparation process between the silicon carbide polishing slurries of Examples 1-2 and Comparative Examples 1-7.

[0044] Table 1. Comparison of core composition and process of silicon carbide polishing slurries in Examples 1-2 and Comparative Examples 1-7 The processing performance of the silicon carbide polishing slurries prepared in Examples 1-2 and Comparative Examples 1-7 of this invention was tested. A 6-inch SiC wafer (Si facet) was used as the processing object, and the tests were conducted on a ZYP-400 polishing machine using a Suba 800 polishing pad. Specific process parameters were set as follows: polishing disc speed 75 rpm, polishing head speed 60 rpm, polishing pressure 15 kg, polishing slurry supply flow rate 60 mL / min, and polishing time 60 min.

[0045] After polishing, key performance indicators such as material removal efficiency (MRR), surface roughness (Ra), and surface scratches were tested. Specifically, the material removal efficiency was calculated by measuring the wafer mass before and after polishing and converting it into the thickness removal amount per unit time; surface roughness was measured using atomic force microscopy (AFM) within a scanning range of 30 μm × 30 μm; and surface scratches were observed using an optical microscope. Table 2 shows the polishing test results for each polishing slurry.

[0046] Table 2. Polishing performance test results of silicon carbide polishing slurries in Examples 1-2 and Comparative Examples 1-7 According to the test results in Table 2, the core-shell structured functionalized abrasive polishing slurry prepared in this invention has significant advantages in both material removal efficiency (MRR) and surface finish (Ra and scratches). The specific analysis is as follows: Compared to Comparative Example 1, the silicon carbide polishing slurry prepared in Example 1 of this invention exhibits superior processing performance. Specifically, under the same processing conditions, Comparative Example 1 (pure Al2O3 system) showed an MRR of 0.81 μm / h and a Ra of 0.182 nm, and exhibited micro-scratches, significantly inferior to Example 1 in terms of material removal efficiency (MRR of 1.32 μm / h) and surface finish (Ra of 0.128 nm and no scratches). This indicates that in the absence of catalytic components, the polishing process in Comparative Example 1 is primarily based on pure mechanical grinding, resulting in low material removal efficiency and significant surface scratch defects after processing, thus failing to achieve efficient and high-quality processing.

[0047] Compared to Comparative Example 2, the silicon carbide polishing slurry prepared in Example 1 of this invention exhibits superior processing performance. Specifically, under the same processing conditions, Comparative Example 2 (pure Al2O3, high KMnO4 content system) achieved an MRR of 1.05 μm / h by increasing the potassium permanganate content, which is higher than the 0.81 μm / h of Comparative Example 1, but still significantly lower than the 1.32 μm / h of Example 1; simultaneously, its surface roughness also deteriorated to 0.205 nm. These results indicate that simply increasing the oxidant concentration has limited effect on improving efficiency and can lead to surface quality degradation; they also demonstrate that this invention, by constructing a core-shell structure to achieve precise synergy between mechanical polishing and chemical catalysis, can simultaneously achieve high material removal rates and excellent surface quality at conventional oxidant concentrations.

[0048] Compared to Comparative Example 3, the silicon carbide polishing slurry prepared in Example 1 of this invention exhibits superior processing performance. Specifically, under the same processing conditions, Comparative Example 3 (physical mixing of Al2O3 and MnO2) showed an MRR of 0.93 μm / h and a Ra of 0.165 nm, demonstrating better polishing performance than Comparative Example 1 but worse performance than Example 1. These results indicate that physical mixing can uniformly disperse the catalytic components in the polishing slurry system, thereby improving material removal efficiency to some extent. However, the preparation of the polishing slurry through physical mixing is prone to problems such as agglomeration and deactivation of the catalytic components, as well as low synergistic efficiency of mechanical and chemical interactions, resulting in significantly lower catalytic capacity and ultimately failing to achieve a significant improvement in material removal efficiency.

[0049] Compared to Comparative Examples 4 and 6, the silicon carbide polishing slurry prepared in Example 1 of this invention exhibits superior processing performance. Specifically, the MRR of Comparative Example 4 (precursor drop time 0.5 h) and Comparative Example 6 (isothermal reaction time 0.5 h) were 1.10 μm / h and 1.07 μm / h, respectively, and both showed micro-scratches, indicating significantly lower performance than Example 1. These results suggest that an excessively short in-situ growth time is insufficient to form a complete, dense catalytic shell that is firmly bonded to the abrasive core, leading to insufficient exposure of catalytic active sites and poor shell mechanical stability. Consequently, during polishing, the weak shell is prone to localized peeling: on the one hand, this reduces the number of catalytic active sites, decreasing material removal efficiency; on the other hand, the hard particles generated by peeling become scratch sources, deteriorating surface processing quality.

[0050] Compared to Comparative Examples 5 and 7, the silicon carbide polishing slurry prepared in Example 1 of this invention exhibits superior processing performance. Specifically, the MRR of Comparative Example 5 (precursor drop time 4 h) and Comparative Example 7 (isothermal reaction time 4 h) were 1.02 μm / h and 1.01 μm / h, respectively, and scratch defects were observed on the polished surfaces of both examples, indicating significantly lower performance than Example 1. These results suggest that excessively long in-situ growth time may lead to overgrowth of the MnO2 shell and changes in its structure: on the one hand, an excessively thick shell may hinder electron mass transfer and reduce the catalytic efficiency per unit mass of abrasive, thereby limiting a significant improvement in material removal rate; on the other hand, the structural integrity and mechanical properties of an overgrown shell may deteriorate, making it more prone to peeling or breakage during polishing, thus acting as hard particles that cause surface scratches and damage the surface processing quality.

[0051] The above comparative results show that the silicon carbide polishing slurry of the present invention has successfully achieved a highly efficient synergistic effect between mechanical polishing and chemical catalysis through the design of core-shell structured Al2O3 / MnO2 functionalized abrasives and the precise control of in-situ growth process. Compared to the pure Al2O3 abrasive system (Comparative Example 1), the introduction of MnO2 catalytic components in the core-shell structure significantly enhanced the chemical corrosion-assisted removal effect, greatly improving the material removal efficiency. Compared to the physically mixed MnO2 system (Comparative Example 3), the in-situ growth process enabled the MnO2 shell to form a firm bond with the Al2O3 core, avoiding the agglomeration and deactivation of the catalytic components. At the same time, it optimized the spatial matching between mechanical action and chemical catalysis, significantly improving the synergistic efficiency. The optimization of the in-situ growth process parameters (including precursor drop time of 1-3 h and isothermal reaction time of 1-3 h) ensured the integrity, density, and stable bonding of the shell. On the one hand, too short a growth time (Comparative Example 4, Comparative Example 6) would result in an incomplete shell, insufficient exposure of catalytic active sites, and easy peeling, leading to decreased efficiency and scratches. On the other hand, too long a growth time (Comparative Example 5, Comparative Example 7) would cause mass transfer obstruction and structural deterioration due to excessive shell growth, which would also reduce efficiency and increase the risk of scratches.

[0052] In summary, the silicon carbide polishing slurry and its preparation method based on core-shell structure functionalized abrasives of this invention can simultaneously achieve a significant improvement in material removal efficiency and a reliable guarantee of processed surface quality without significantly increasing the oxidant concentration or relying on external field assistance.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A SiC high-efficiency polishing liquid based on a core-shell structure functionalized abrasive, characterized in that, The SiC high-efficiency polishing liquid is prepared by mixing the following raw materials in percentage by mass: 1-10% of the core-shell structure functional abrasive, 1-5% of potassium permanganate, 0.01-5% of the dispersant, 0.01-5% of the buffer, and the rest of deionized water; and the pH of the SiC high-efficiency polishing liquid is 3-6.

2. The SiC high-efficiency polishing liquid based on the core-shell structure functionalized abrasive according to claim 1, wherein, The dispersant is one or more of sodium silicate, sodium hexametaphosphate, sodium polyacrylate, sodium tripolyphosphate, and sodium dodecylbenzenesulfonate; and the buffer is at least one of sodium dihydrogen phosphate and potassium dihydrogen phosphate.

3. The SiC high-efficiency polishing liquid based on the core-shell structure functionalized abrasive according to claim 1, wherein the core-shell structure functionalized abrasive is a core-shell structure functionalized abrasive in which a core material is SiC, and a shell material is SiO2. The pH is adjusted to 3-6 by using a pH regulator, which is at least one of HCl and HNO3.

4. The SiC high-efficiency polishing liquid based on the core-shell structure functionalized abrasive according to claim 1, wherein the core-shell structure functionalized abrasive is a core-shell structure functionalized abrasive in which a core material is SiC, and a shell material is SiO2. The core-shell structure functional abrasive is prepared by the following steps: a) preparing a precursor solution: dissolving potassium permanganate and urea in deionized water at a molar ratio of 1:1-10, mixing uniformly, and preparing a precursor solution with a concentration of 0.05-0.5 mol / L, calculated based on KMnO4; b) in-situ shell growth: placing the activated alumina abrasive suspension in a water bath environment at 60-90°C, uniformly adding the precursor solution prepared in step a) under continuous stirring, continuing to stir at constant temperature for 1-3 h after the addition is completed, and completing the in-situ shell growth; c) abrasive post-treatment: after the reaction is completed, naturally cooling the system to room temperature, performing solid-liquid separation, washing, drying, and airflow crushing, and obtaining the core-shell structure functional abrasive Al2O3 / MnO2.

5. The SiC high-efficiency polishing liquid based on the core-shell structure functionalized abrasive according to claim 1, wherein the core-shell structure functionalized abrasive is a core-shell structure functionalized abrasive in which a core material is SiC, and a shell material is SiO2. In step b), the mass of KMnO4 is 10-50 wt% of the mass of the activated alumina abrasive; the stirring speed is set to 400-600 rpm; and the precursor solution prepared in step a) is added uniformly within 1-3 h.

6. The SiC high-efficiency polishing liquid based on the functionalized abrasives of core-shell structure according to claim 1, wherein, In step c), the solid-liquid separation is performed by high-speed centrifugation at 5000-12000 rpm; and the drying is performed by placing the material in a freeze dryer and freeze-drying at -50~ -20°C for 12-48 h.

7. The SiC high-efficiency polishing liquid based on the functionalized abrasives of core-shell structure according to claim 4, characterized in that, In step b), the activated alumina abrasive suspension is obtained by the following surface activation treatment: mixing alumina abrasive and deionized water at a solid-liquid ratio of 1:10-20 g / mL, adding a dispersant, stirring at room temperature, obtaining an alumina dispersion suspension, then adjusting the pH to 3-4, and placing the system in a water bath environment at 40-90°C and continuing to stir for 30-90 min.

8. The SiC high-efficiency polishing liquid based on the functionalized abrasives of core-shell structure according to claim 7, characterized in that, The alumina abrasive is a nano-level alumina polishing powder with a particle size range of 100-500 nm; and the dispersant is one or more of sodium hexametaphosphate, sodium silicate, sodium pyrophosphate, or sodium tripolyphosphate, which is added in an amount of 0.1-1.0 wt% of the mass of the alumina abrasive.

9. The method for preparing the SiC high-efficiency polishing liquid based on the core-shell structure functionalized abrasives according to any one of claims 1 to 8, characterized in that, The core-shell structure functional abrasive is added to a certain amount of deionized water to prepare an abrasive suspension with a certain mass fraction, and then the following steps are performed under stirring: adding a potassium permanganate aqueous solution, and then adding a dispersant, a buffer, and the rest of deionized water in sequence, mixing uniformly, and finally adjusting the pH value to the required range.

10. The method for preparing the SiC high-efficiency polishing slurry based on core-shell structure functionalized abrasive as described in claim 9, characterized in that, The mass fraction of the abrasive suspension is 10-40 wt%; the mass fraction of the potassium permanganate aqueous solution is 1-10 wt%; and the stirring speed is 400-600 rpm.

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