Chemical mechanical polishing composition and polishing method

Abstract

The present invention belongs to the technical field of chemical engineering, and specifically provides a chemical mechanical polishing (CMP) composition and CMP method for a silicon carbide substrate. The composition includes abrasive alumina particles, an oxidizing agent and clay, wherein in the composition, the abrasive particles have a negative zeta potential at a pH of 7.5 to 9.5, and the clay has a z-average size of 1 nm to 20 μm measured by dynamic light scattering. The CMP composition provided by the present invention can improve the polishing effect on the silicon carbide substrate, and can achieve good recirculation performance and a low number of surface defects while obtaining a high material removal rate and low surface roughness.

Description

Chemical mechanical polishing composition and polishing method thereof Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and relates to a chemical mechanical polishing composition and a polishing method for a silicon carbide substrate. Background Art

[0002] Chemical Mechanical Polishing (CMP) is a common process for achieving global planarization in integrated circuit manufacturing and other fields. This process is primarily used to create a smooth surface that is both flat and free of scratches and impurities. This process polishes various target substrates through a combination of chemical and mechanical forces, with chemical mechanical polishing (CMP) compositions playing a crucial role in this process. These compositions are typically aqueous solutions containing a uniform dispersion of various chemical additives and abrasive particles. CMP compositions are also known as polishing slurries, polishing solutions, or polishing compositions.

[0003] After decades of development, first-generation silicon semiconductors have become near-perfect crystals. Despite extensive research on silicon materials, the potential for performance improvements in silicon-based devices is shrinking. Against this backdrop, third-generation semiconductors, such as gallium nitride and silicon carbide, offer greater potential for further improving the performance of electronic devices due to their superior material physical properties.

[0004] Silicon carbide (SiC) is a typical representative of the third-generation semiconductor materials and is also one of the wide-bandgap semiconductor materials with the most mature and widely used crystal production technology and device manufacturing levels. The devices made with it have the characteristics of high temperature resistance, high voltage resistance, high frequency, high power, and radiation resistance. It has the advantages of fast switching speed and high efficiency, which can greatly reduce product power consumption, improve energy conversion efficiency and reduce product size. It is mainly used in radio frequency fields represented by 5G communications, national defense and military industry, aerospace, and power electronics fields represented by new energy vehicles and "new infrastructure". It has clear and considerable market prospects in both civilian and military fields.

[0005] Polishing silicon carbide wafers primarily involves two steps: rough polishing and fine polishing. Rough polishing focuses on rapid removal, while fine polishing emphasizes achieving good flatness and smoothness. During rough polishing, achieving high removal rates on silicon carbide is challenging due to its extremely hard substrate. CMP compositions containing colloidal silica abrasives, commonly used for polishing silicon substrates, do not achieve sufficiently high removal rates. While CMP compositions containing aluminum oxide abrasives are typically used for polishing, they achieve high removal rates. However, the use of large aluminum oxide abrasives can easily scratch silicon carbide wafers. Furthermore, due to the extremely hard nature of silicon carbide, polishing times are also very long. Rough polishing slurries are typically recycled to reduce manufacturing costs, waste, and environmental impact. Good recyclability (i.e., long recycle times combined with a stable removal rate during recycle) is crucial for slurry recycling. Therefore, there is still a need for a CMP composition comprising small-size aluminum oxide abrasive particles suitable for rough polishing of silicon carbide that can achieve higher removal rates, good recycling performance, low surface roughness, and low surface defect counts.

[0006] Summary of the Invention

[0007] One object of the present invention is to overcome the aforementioned problems existing in the prior art. Specifically, embodiments of the present invention provide a chemical mechanical polishing composition suitable for rough polishing of silicon carbide, which, on the one hand, exhibits a high material removal rate and low surface roughness, and, on the other hand, can achieve good recyclability while simultaneously achieving a low number of surface defects.

[0008] Specifically, an embodiment of the present invention provides a chemical mechanical polishing composition comprising aluminum oxide abrasive particles, an oxidizing agent, and clay, wherein the abrasive particles have a negative zeta potential at a pH of 7.5 to 9.5 in the composition, wherein the clay has a z-average particle size of 1 nm to 20 μm as measured by dynamic light scattering.

[0009] Another object of an embodiment of the present invention is to provide a polishing method for a silicon carbide substrate, preferably a rough polishing method for a silicon carbide substrate, wherein the method is implemented using the above composition.

[0010] The CMP composition provided by the present invention not only achieves a high removal rate for silicon carbide substrates, but also ensures a low number of surface defects on the silicon carbide substrates, achieves a long recycling time, and maintains a stable removal rate during recycling, making it environmentally friendly and economically efficient. Products polished with the CMP composition of the present invention have low surface roughness and a low number of surface defects. DETAILED DESCRIPTION

[0011] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0012] Chemical mechanical polishing compositions typically comprise abrasive particles dispersed in an aqueous carrier. The abrasive particles can aid in the removal of material from the substrate surface during the polishing process. Preferably, the abrasive particles are metal oxide abrasive particles selected from the group consisting of cerium oxide (ceria), aluminum oxide (aluminum oxide), silicon oxide (silicon dioxide), zirconium oxide (zirconium oxide), titanium oxide (titania), germanium oxide (germania), magnesium oxide (magnesium oxide), nickel oxide, gallium oxide (gallium oxide), yttrium oxide (yttrium oxide), and combinations thereof. Preferably, the abrasive particles comprise at least 67 wt% (weight percent), more preferably at least 74 wt%, more preferably at least 81 wt%, more preferably at least 88 wt%, and most preferably at least 93 wt% aluminum oxide. In particularly preferred embodiments, the abrasive particles are entirely aluminum oxide abrasive particles.

[0013] At the time of use, the composition preferably comprises at least 0.02 wt%, more preferably at least 0.10 wt%, more preferably at least 0.20 wt%, more preferably at least 0.40 wt%, and most preferably at least 0.50 wt% of abrasive particles. As used herein, the term "at the time of use" refers to the moment when the composition is applied to the surface of the substrate during chemical mechanical polishing. If the concentration of abrasive particles is too high, the composition may cause undesirable surface defects, such as scratches on the substrate, during polishing. Therefore, at the time of use, the composition preferably comprises at most 24.0 wt%, more preferably at most 20.0 wt%, more preferably at most 16.0 wt%, more preferably at most 12.0 wt%, and most preferably at most 8.0 wt% of abrasive particles. In a preferred embodiment, the composition comprises 0.02 wt% to 24.0 wt%, more preferably 0.10 wt% to 20.0 wt%, more preferably 0.20 wt% to 16.0 wt%, more preferably 0.40 wt% to 12.0 wt%, most preferably 0.50 wt% to 8.0 wt% abrasive particles.

[0014] As known to those skilled in the art, the aluminum oxide abrasive grains may be fumed aluminum oxide or aluminum oxide with different crystalline phases, such as α-alumina, β-alumina, γ-alumina, δ-alumina, θ-alumina, σ-alumina, κ-alumina, η-alumina, χ-alumina, β-alumina, and combinations thereof. Preferably, the aluminum oxide abrasive grains are selected from α-alumina, β-alumina, γ-alumina, δ-alumina, σ-alumina, θ-alumina, and combinations thereof.

[0015] Experiments have shown that α-alumina can exhibit higher substrate material removal rates during chemical mechanical polishing compared to alumina abrasive grains having other crystal phases. Therefore, the alumina abrasive grains preferably contain at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90%, and most preferably at least 99 wt% of α-alumina. As known to those skilled in the art, the amount of α-alumina can be determined by X-ray diffraction (XRD), for example, using a D8 X-ray diffractometer (Bruker Corp) based on the integrated intensity ratio of the (113) plane. In a particularly preferred embodiment, the alumina abrasive grains in the composition of the present invention are all α-alumina.

[0016] The abrasive particles may be present in the composition as individual particles, aggregates, agglomerates, or mixtures thereof. Individual particles may adhere to one another through van der Waals forces and electrostatic interactions, thereby forming aggregates of more than one individual particle. Aggregates themselves may further adhere to one another through physical interactions, forming agglomerates of more than one aggregate. The formation of aggregates and agglomerates is reversible. As used herein, the term abrasive particles refers to individual particles, aggregates, and agglomerates.

[0017] The abrasive particles can have any suitable morphology, such as irregular shapes, spheres, cubes, octahedrons, truncated octahedrons, hexagons, rods, grapes, peanuts, worms, flakes, cocoons, or other shapes. The surface of the abrasive particles can have any suitable morphological characteristics, such as being smooth or having a plurality of protrusions. The morphology can be determined by one skilled in the art, for example, using transmission electron microscopy (TEM) or scanning electron microscopy (SEM) images.

[0018] The average particle size (diameter) of the abrasive particles can affect the material removal rate. As known to those skilled in the art, the average particle size can be obtained by laser diffraction measurement (for example, using an LA-960 from Horiba). The graph obtained by this measurement provides the cumulative volume percentage of particles of a certain size. The particle size of the abrasive particles used in this application refers to the particle size of the abrasive particles in the composition. The average particle size (D50) is the particle size at which 50% by volume of the particles have a particle size less than this value. A smaller D50 will reduce the material removal rate. Preferably, the abrasive particles have a D50 of at least 5 nm, more preferably at least 10 nm, more preferably at least 25 nm, more preferably at least 35 nm, and most preferably at least 50 nm, as measured by laser diffraction. However, if the D50 is too large, a large number of undesirable surface defects, such as scratches and pits, will appear during the CMP process. Therefore, the abrasive particles preferably have a D50 of at most 400 nm, more preferably at most 300, more preferably at most 250 nm, more preferably at most 200 nm, and most preferably at most 170 nm, as measured by laser diffraction. In a preferred embodiment, the abrasive particles have a D50 measured by laser diffraction of 10 nm to 300 nm, more preferably 25 nm to 250 nm, more preferably 35 nm to 200 nm, more preferably 50 nm to 170 nm.

[0019] D10 is the particle size at which 10% by volume of the particles have a particle size less than this value. It has been found that a smaller D10 can achieve a smaller surface roughness during the CMP process. Preferably, the abrasive particles have a D10 of at most 200 nm, more preferably at most 175 nm, more preferably at most 150 nm, more preferably at most 125 nm, and most preferably at most 100 nm, as measured by laser diffraction. However, a smaller D10 can reduce the material removal rate. Preferably, the abrasive particles have a D10 of at least 2 nm, more preferably at least 8 nm, more preferably at least 15 nm, more preferably at least 25 nm, and most preferably at least 35 nm, as measured by laser diffraction. In a preferred embodiment, the abrasive particles have a D10 of 2 nm to 200 nm, more preferably 8 nm to 175 nm, more preferably 15 nm to 150 nm, more preferably 25 nm to 125 nm, and most preferably 35 nm to 100 nm, as measured by laser diffraction.

[0020] D90 is the particle size at which 90% of the particles by volume have a particle size less than this value. A higher D90 of an abrasive particle results in a higher material removal rate. Preferably, the abrasive particle has a D90 of at least 20 nm, more preferably at least 50 nm, more preferably at least 80 nm, more preferably at least 100 nm, and most preferably at least 150 nm, as measured by laser diffraction. However, if the D90 is too large, a large number of undesirable surface defects, such as scratches and pits, will appear during the CMP process. The abrasive particle preferably has a D90 of at most 600 nm, more preferably at most 500, more preferably at most 400 nm, more preferably at most 350 nm, and most preferably at most 300 nm, as measured by laser diffraction. In a preferred embodiment, the abrasive particle has a D90 of 20 nm to 600 nm, more preferably 50 nm to 500 nm, more preferably 80 nm to 400 nm, more preferably 100 nm to 350 nm, and most preferably 150 nm to 300 nm, as measured by laser diffraction.

[0021] D30 is the particle size at which 30% by volume of the particles have a particle size less than this value. Studies have found that the lower the D30, the lower the surface roughness and the fewer scratches on the substrate surface during the CMP process. Preferably, the abrasive particles have a D30 of at most 300 nm, more preferably at most 200 nm, and most preferably at most 150 nm, as measured by laser diffraction. A smaller D30 can reduce material removal rates. Preferably, the abrasive particles have a D30 of at least 4 nm, more preferably at least 20 nm, and most preferably at least 40 nm, as measured by laser diffraction. In a preferred embodiment, the abrasive particles have a D30 of 4 nm to 300 nm, more preferably 20 nm to 200 nm, and most preferably 40 nm to 150 nm, as measured by laser diffraction.

[0022] D70 is the particle size at which 70% by volume of the particles have a particle size less than this value. Studies have also found that a smaller D70 can reduce the surface roughness and the number of scratches on the substrate surface during CMP. Preferably, the abrasive particles have a D70 of at most 500 nm, more preferably at most 400 nm, and most preferably at most 280 nm as measured by laser diffraction. A smaller D70 can reduce the material removal rate. Preferably, the abrasive particles have a D70 of at least 16 nm, more preferably at least 43 nm, and most preferably at least 62 nm as measured by laser diffraction. In a preferred embodiment, the abrasive particles have a D70 of 16 nm to 500 nm, more preferably 43 nm to 400 nm, and most preferably 62 nm to 280 nm as measured by laser diffraction.

[0023] Alumina abrasive particle size distributions are categorized as either unimodal or multimodal. Unimodal distributions have a single peak on the particle size distribution curve, indicating a single mode particle size. Multimodal distributions, on the other hand, have two or more peaks on the particle size distribution curve, indicating two or more mode particle sizes. Preferably, the abrasive particles have a single peak.

[0024] The aluminum oxide abrasive grains should have a suitable steepness factor. The steepness factor used in this application refers to the value obtained by the formula (D30 / D70)*100. D30 and D70 can be obtained by laser diffraction as described above. D30 is the particle size at which 30% by volume of the particles have a particle size less than this value. D70 is the particle size at which 70% by volume of the particles have a particle size less than this value. Abrasive grains with a smaller steepness factor exhibit a high material removal rate, but at the same time will cause the polished substrate to have a higher surface roughness and more surface defects. Therefore, the abrasive grains preferably have a steepness factor of at most 98, more preferably at most 95, more preferably at most 92, more preferably at most 91, and most preferably at most 90. Preferably, the abrasive grains preferably have a steepness factor of at least 15, more preferably at least 30, more preferably at least 35, more preferably at least 40, and most preferably at least 45. In a preferred embodiment, the composition comprises abrasive grains having a steepness factor between 15 and 98, more preferably between 30 and 95, more preferably between 35 and 92, and more preferably between 40 and 91. Studies have shown that abrasive particles having the steepness factor of the present invention cause fewer scratches on the substrate surface during CMP processing while still having a high material removal rate.

[0025] The abrasive particles should have a suitable BET surface area. The BET surface area can be measured by one skilled in the art using the Brunauer-Emmett-Teller method by adsorbing nitrogen on the abrasive particle surface. A larger surface area of ​​the particles can increase the contact area between the particles and the substrate, thereby improving the material removal rate. Therefore, the abrasive particles preferably have a BET surface area of ​​at least 2 m2 / g, more preferably at least 4 m2 / g, more preferably at least 6 m2 / g, and most preferably at least 8 m2 / g. Preferably, the abrasive particles have a BET surface area of ​​at most 90 m2 / g, more preferably at most 60 m2 / g, more preferably at most 40 m2 / g, and most preferably at most 30 m2 / g.

[0026] The composition preferably comprises a coating agent. The coating agent can reversibly bind to the surface of the aluminum oxide abrasive particles through hydrogen bonding and / or ionic interactions. The coating agent used herein refers to a coating agent present in the composition in any form, for example, bound to the surface of the aluminum oxide abrasive particles and / or not bound to the surface of the aluminum oxide abrasive particles. Preferably, the coating agent is a polymer. The coating agent is preferably a copolymer composed of a sulfonic acid monomer unit and a carboxylic acid monomer unit. The copolymer can be used in any achievable form, such as an acid, a conjugate acid, a conjugate base, a salt or a combination thereof.

[0027] Preferably, the sulfonic acid monomer unit is selected from 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), 4-vinylbenzenesulfonic acid, vinylsulfonic acid, 2-sulfoethyl acrylate, 2-sulfoethyl methacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, sodium styrenesulfonate and 2-propylene-1-sulfonic acid, salts thereof, and combinations thereof. In a particularly preferred embodiment, the sulfonic acid monomer unit is 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS).

[0028] Preferably, the carboxylic acid monomer is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, succinic acid, terephthalic acid, aspartic acid, and combinations thereof. In a particularly preferred embodiment, the carboxylic acid monomer unit is acrylic acid.

[0029] Said coating agent should have low molecular weight (MW).Preferred said coating agent has and is at most 50,000g / mol, more preferably at the most 30,000g / mol, more preferably at the most 20,000g / mol, more preferably at the most 15,000g / mol, most preferably at the most molecular weight (MW) of 9,000g / mol.Preferred said coating agent has at least 100g / mol, more preferably at least 200g / mol, more preferably at least 300g / mol, more preferably at least 400g / mol, most preferably at least 500g / mol molecular weight.In preferred embodiments, said coating agent has 100g / mol to 50,000g / mol, more preferably 200g / mol to 30,000g / mol, more preferably 300g / mol to 20,000g / mol, more preferably 400g / mol to 15,000g / mol, more preferably 500g / mol to 9,000g / mol molecular weight.

[0030] Preferably, when used, the concentration of the coating agent included in the composition is at least 0.001 wt%, more preferably at least 0.005 wt%, more preferably at least 0.01 wt%, most preferably at least 0.02 wt%. Preferably, when used, the concentration of the coating agent is at most 14.0 wt%, more preferably at most 11.0 wt%, more preferably at most 8.0 wt%, most preferably at most 5.0 wt%. In a preferred embodiment, the concentration range of the coating agent is 0.001 wt% to 14.0 wt%, more preferably 0.005 wt% to 11.0 wt%, more preferably 0.01 wt% to 8.0 wt%, most preferably 0.02 wt% to 5.0 wt%.

[0031] Preferably, the aluminum oxide abrasive grains are coated with a coating agent. The surface of the aluminum oxide abrasive grains can be treated with the coating agent by any suitable method. For example, the coating agent can be dissolved in an aqueous carrier such as deionized water, and then the aluminum oxide abrasive grains can be added to form a mixture. The mixture is then stirred until the components are dissolved. The mixture of the coating agent and the aluminum oxide abrasive grains is then added to the composition.

[0032] Preferably, the abrasive particles have a negative charge in the composition. Charge refers to the zeta potential, which can be measured, for example, by a Mastersizer S (Malvern Instruments). As known to those skilled in the art, zeta potential refers to the electrical potential at the interface between a moving fluid in a composition and a fluid stabilizing layer attached to the abrasive particles dispersed in the composition. A higher absolute value of the zeta potential results in stronger electrostatic repulsion between particles, thereby increasing the stability of the particle dispersion in the composition. The negative charge of the abrasive particles in the composition is obtained after coating with a coating agent. Preferably, the abrasive particles have a negative zeta potential in the composition at a pH of 7.5 to 9.5. Preferably, the abrasive particles have a zeta potential of at least -10 mV, more preferably at least -15 mV, more preferably at least -20 mV, more preferably at least -25 mV, and most preferably at least -28 mV in the composition at a pH of 7.5 to 9.5. Preferably, the abrasive particles have a zeta potential of at most -90 mV, more preferably at most -80 mV, more preferably at most -70 mV, more preferably at most -60 mV, and most preferably at most -50 mV in a composition at a pH of 7.5 to 9.5. Preferably, the abrasive particles have a zeta potential of from -10 mV to -90 mV, more preferably from -15 mV to -80 mV, more preferably from -20 mV to -70 mV, more preferably from -25 mV to -60 mV, and most preferably from -28 mV to -50 mV in a composition at a pH of 7.5 to 9.5. Surprisingly, according to the present invention, a negative zeta potential results in less scratching of the substrate surface during CMP while still exhibiting high material removal rates.

[0033] Preferably, the composition further comprises one or more chemical additives. The chemical additives can interact with the abrasive and / or with the substrate and / or with the polishing pad during the CMP process. The interactions can be based on hydrogen bonding, van der Waals forces, electrostatic forces, etc. The chemical additives can be any suitable component, for example, a polishing rate inhibitor, a surfactant, a thickener, a chelating agent, a preservative, a film former, an etching inhibitor, a terminating compound, a dissolution inhibitor, or a combination thereof.

[0034] Preferably, the composition further comprises an aqueous carrier in which the abrasive particles and chemical additives are suspended or dissolved. The aqueous carrier enables the abrasive particles and chemical additives to come into contact with the substrate and polishing pad during the CMP process. The aqueous carrier can be any suitable component for suspending the abrasive particles and chemical additives. The aqueous carrier can be water, ethers (such as dioxane or tetrahydrofuran), alcohols (such as methanol and ethanol), and combinations thereof. Preferably, the aqueous carrier comprises at least 50 wt % water, preferably at least 70 wt % water, more preferably at least 90 wt % water, more preferably at least 95 wt % water, more preferably at least 99 wt % water. Most preferably, the aqueous carrier is deionized water.

[0035] Preferably, the CMP composition further comprises an oxidizing agent. The oxidizing agent can react with the surface of the silicon carbide substrate and promote material removal during the polishing process. The oxidizing agent can be used in any feasible form, such as an acid, a conjugate acid, a conjugate base, a salt (such as a potassium salt, a sodium salt, an ammonium salt, etc.), or a combination thereof. Preferably, the oxidizing agent is selected from inorganic or organic per-compounds, oxones, chlorates, chlorous acid, bromates, iodic acid, iodates, nitrates, chromates, and mixtures thereof. Examples of inorganic or organic per-compounds include hydrogen peroxide, benzoyl peroxide, peracetic acid, di-tert-butyl peroxide, sodium peroxide, urea peroxide, percarbonates, monopersulfates, dipersulfates, persulfates, perboric acid, perborate, perchloric acid, perchlorate, perbromic acid, perbromate, periodic acid, periodate, permanganate, ferrate, perrhenate, perruthenate, and combinations thereof. Permanganate, periodate and persulfate can be any permanganate, periodate and persulfate or a combination thereof, such as potassium periodate, periodic acid, ammonium persulfate, potassium persulfate or potassium permanganate. Examples of nitrate compounds include ferric nitrate, barium nitrate, neodymium praseodymium nitrate, nickel nitrite, potassium nitrate, aluminum nitrate, sodium nitrate, uranyl nitrate, ammonium nitrate, cerium nitrate, cerium ammonium nitrate, and a combination thereof. More preferably, the oxidant is selected from permanganate, persulfate, iodate, periodate, hydrogen peroxide, chlorite and a combination thereof. Most preferably, the oxidant is selected from permanganate.

[0036] The oxidizing agent may be present in the CMP composition in any suitable amount. Preferably, when used, the composition comprises at least 0.02 wt%, more preferably at least 0.15 wt%, more preferably at least 0.30 wt%, more preferably at least 0.50 wt%, and most preferably at least 0.80 wt% of the oxidizing agent. Preferably, when used, the composition comprises at most 24.0 wt%, more preferably at most 20.0 wt%, more preferably at most 16.0 wt%, more preferably at most 12.0 wt%, and most preferably at most 8.0 wt% of the oxidizing agent. In a preferred embodiment, the composition comprises from 0.02 wt% to 24.0 wt%, more preferably from 0.15 wt% to 20.0 wt%, more preferably from 0.30 wt% to 16.0 wt%, more preferably from 0.50 wt% to 12.0 wt%, and more preferably from 0.80 wt% to 8.0 wt% of the oxidizing agent.

[0037] Preferably, the CMP composition further comprises a catalyst. Catalysts often work together with oxidants to improve polishing removal rates. Preferably, the catalyst is selected from iron-containing compounds (such as iron (III) sulfate, iron (III) chloride), copper-containing compounds (such as copper (II) nitrate, copper (II) sulfate), cobalt-containing compounds (such as cobalt (II) nitrate), nickel-containing compounds (such as nickel (II) chloride), and combinations thereof. More preferably, the promoter or catalyst is selected from iron-containing compounds, which may include triferric (III) compounds, ferrous (II) compounds, and combinations thereof. The iron-containing compound may be present in the composition in any suitable form, such as an acid, a conjugate acid, a salt, or a combination thereof. The iron-containing compound may be an inorganic iron-containing compound, an organic iron-containing compound, or a combination thereof. Examples of inorganic iron-containing compounds are ferric nitrate, ferric cyanide, ferric sulfate, ferric fluoride, ferric chloride, ferric bromide, ferric iodide, ferric perchlorate, ferric perbromide, ferric periodate, ammonium ferric sulfate, and combinations thereof. Examples of organic iron-containing compounds are ferric acetate, ferric acetylacetonate, ferric citrate, ferric gluconate, ferric malonate, ferric oxalate, ferric phthalate, ferric succinate, and combinations thereof. Preferably, the iron-containing compound is an inorganic iron-containing compound. In a particularly preferred embodiment, the iron-containing compound is ferric nitrate.

[0038] The catalyst may be present in the CMP composition in any suitable amount. Preferably, when used, the composition comprises at least 0.01 wt%, more preferably at least 0.05 wt%, more preferably at least 0.10 wt%, more preferably at least 0.15 wt%, and most preferably at least 0.20 wt% of catalyst. Preferably, when used, the composition comprises at most 12.0 wt%, more preferably at most 10.0 wt%, more preferably at most 8.0 wt%, more preferably at most 6.0 wt%, and most preferably at most 5.0 wt% of catalyst. In a preferred embodiment, the composition comprises from 0.01 wt% to 12.0 wt%, more preferably from 0.05 wt% to 10.0 wt%, more preferably from 0.10 wt% to 8.0 wt%, more preferably from 0.15 wt% to 6.0 wt%, and most preferably from 0.20 wt% to 5.0 wt% of catalyst.

[0039] Preferably, the composition comprises a pH adjusting agent when in use. The pH adjusting agent helps the composition achieve a suitable pH. The pH adjusting agent can be a base or a salt thereof. The base or salt thereof can be an organic base, an inorganic base, or a combination thereof.

[0040] Examples of inorganic bases include alkali metal hydroxides (e.g., potassium hydroxide, sodium hydroxide, lithium hydroxide), alkaline earth metal hydroxides (e.g., magnesium hydroxide, calcium hydroxide, beryllium hydroxide), alkali metal carbonates (e.g., potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, lithium bicarbonate), alkaline earth metal carbonates (e.g., magnesium carbonate, calcium carbonate, beryllium carbonate), alkali metal phosphates (e.g., tripotassium phosphate, trisodium phosphate, dipotassium phosphate, disodium phosphate), alkaline earth metal phosphates (e.g., magnesium phosphate, calcium phosphate, beryllium phosphate), ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, aqueous ammonia, and combinations thereof.

[0041] Examples of organic bases are aliphatic amines, aromatic amines, quaternary ammonium hydroxides (eg, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH)), and combinations thereof.

[0042] Preferably, the pH adjuster is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof. In a particularly preferred embodiment, the pH adjuster is selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, potassium hydroxide, sodium hydroxide, potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, and combinations thereof. The pH adjuster of the present invention has been found to increase the material removal rate of the substrate during CMP treatment. The composition may include the pH adjuster at a concentration suitable to achieve the pH of the present invention.

[0043] The composition preferably has an alkaline pH. Typically, an acidic pH (for SiC polishing compositions containing aluminum oxide, an oxidant, and a catalyst) can increase the removal rate, but acidic pH values ​​can cause corrosion to the polishing tool. The alkaline nature of the composition of the present invention can avoid this risk of corrosion while still providing a good removal rate. Therefore, when used, the composition preferably has a pH of at least 6.0, more preferably at least 6.5, more preferably at least 7.0, and most preferably at least 7.5. When used, the composition preferably has a pH of at most 12, more preferably at most 11.0, more preferably at most 10.0, and more preferably at most 9.5. In a preferred embodiment, the composition has a pH of 6.0 to 12.0, more preferably 6.5 to 11.0, more preferably 7.0 to 10.0, and most preferably 7.5 to 9.5.

[0044] Preferably, the CMP composition further comprises clay. For example, clay can be purchased from Shengxinxin Chemical Technology Co., Ltd. (Guangzhou, China). It has been found that the composition of the present invention comprising clay can achieve lower surface roughness and fewer defects on the substrate surface. It has also been found that the clay of the present invention can reduce particle shrinkage during recycling and increase the recycling time of the composition. The term clay as used herein refers to layered silicates. The clay can be natural clay, synthetic clay, modified clay, or a combination thereof. Synthetic clay can be purchased or synthesized, for example, by solid phase reaction, melt synthesis, or hydrothermal synthesis. Examples of clays include kaolin (e.g., kaolin, dickite, halloysite, and nacrite), montmorillonite (e.g., saponite, hectorite, laponite, nontronite, beidellite, magnesite, bentonite, andalusite, kyanite, sillimanite, kaolinite, metakaolin, mullite, aluminum silicate, dihydrate aluminum silicate, potassium aluminum silicate, sodium aluminum silicate, calcium aluminum silicate, aluminum oxide silicate, magnesium aluminum silicate, and boroaluminum silicate), illite (e.g., micas such as phlogopite, biotite, lepidolite, muscovite, and glauconite), chlorite, palygorskite, sepiolite, vermiculite, talc, pyrophyllite, modifications of such clays, and combinations thereof. In a preferred embodiment, the clay is montmorillonite. In a particularly preferred embodiment, the clay is selected from bentonite, laponite, magnesium aluminum silicate, kaolinite, or combinations thereof.

[0045] The clay can interact with the abrasive and / or its substrate surface. The clay comprises particles. The particle size distribution and zeta potential of the clay are important for the interaction of the clay with the abrasive and / or its substrate surface. Therefore, the clay should have an appropriate particle size distribution relative to the particle size distribution of the abrasive. The zeta potential, z-average particle size and particle size distribution of the clay can be measured by ultrasonicating a 0.1 wt.% aqueous dispersion of the clay at 25°C for 30 minutes. The zeta potential, z-average particle size and particle size distribution of the clay are measured for the clay in the aqueous dispersion, not for the clay in the composition. The zeta potential of the clay can be measured using a Mastersizer S (Malvern Instruments Ltd., UK); the particle size distribution and z-average particle size of the clay can be measured by dynamic light scattering, for example, using a Zetasizer Nano ZSE (Malvern Instruments Ltd.); the z-average particle size refers to the intensity-weighted average hydrodynamic size of the particle ensemble measured by dynamic light scattering (for example, using a Zetasizer Nano ZSE (Malvern Instruments Ltd.). The D30 and D70 of the clay can be obtained from the particle size distribution measured as described above.

[0046] The clay should have a suitable z-average particle size. Preferably, the clay has a z-average particle size of at most 20 μm, preferably at most 10 μm, preferably at most 9 μm, preferably at most 6 μm, more preferably at most 5 μm, as measured by dynamic light scattering. Preferably, the clay has a z-average particle size of at least 1 nm, preferably at least 2 nm, preferably at least 5 nm, preferably at least 8 nm, more preferably at least 10 nm, as measured by dynamic light scattering. In a preferred embodiment, the clay preferably has a z-average particle size of from 1 nm to 20 μm, preferably from 2 nm to 10 μm, preferably from 5 nm to 9 μm, preferably from 8 nm to 6 μm, more preferably from 10 nm to 5 μm, as measured by dynamic light scattering.

[0047] The clay should have a suitable steepness factor. The steepness factor used in this application refers to the value obtained by the formula (D30 / D70)*100. The clay preferably has a steepness factor of at most 98, more preferably at most 95, more preferably at most 92, more preferably at most 91, and most preferably at most 90. Preferably, the clay preferably has a steepness factor of at least 15, more preferably at least 30, more preferably at least 35, more preferably at least 40, and most preferably at least 45. In a preferred embodiment, the clay has a steepness factor between 15 and 98, more preferably between 30 and 95, more preferably between 35 and 92, and more preferably between 40 and 91. Studies have found that the clay with a steepness factor according to the present invention can reduce surface roughness and reduce scratches on the substrate surface during the CMP process.

[0048] Preferably, the clay is negatively charged. The greater the absolute value of the negative zeta potential of the clay, the more stable the dispersion. Preferably, the zeta potential of the clay is at least -5 mV, preferably at least -10 mV, more preferably at least -15 mV, more preferably at least -18 mV, and most preferably at least -20 mV.

[0049] Preferably, when used, the composition comprises at least 0.002 wt%, more preferably at least 0.01 wt%, more preferably at least 0.03 wt%, more preferably at least 0.04 wt%, and most preferably at least 0.05 wt% of clay. However, the amount of clay should not be too high, as it can hinder the interaction of the abrasive particles with the substrate surface, thereby reducing the material removal rate during the CMP process. Thus, when used, the composition preferably comprises at most 7 wt%, more preferably at most 6 wt%, more preferably at most 5 wt%, more preferably at most 4 wt%, and most preferably at most 3 wt% of clay. In a preferred embodiment, when used, the composition comprises from 0.002 wt% to 7 wt%, more preferably from 0.01 to 6 wt%, more preferably from 0.03 wt% to 5 wt%, more preferably from 0.04 wt% to 4 wt%, and most preferably from 0.05 wt% to 3 wt% of clay.

[0050] Preferably, the composition comprises an amino acid. The amino acid can be a proteinogenic amino acid (e.g., alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, selenocysteine, pyrrolysine), a non-proteinogenic amino acid (e.g., ornithine, citrulline, carnitine, gamma-aminobutyric acid, levothyroxine, beta-alanine, aminoisobutyric acid), or a combination thereof. Preferably, the amino acid is a proteinogenic amino acid. In a preferred embodiment, the amino acid has a molecular weight of at most 150 g / mol, more preferably at most 140 g / mol, more preferably at most 130 g / mol, and most preferably at most 120 g / mol. The amino acids of the present invention have been found to reduce the number of defects in substrates during CMP treatment.

[0051] Preferably, when used, the composition comprises at least 0.002 wt%, more preferably at least 0.02 wt%, more preferably at least 0.12 wt%, more preferably at least 0.28 wt%, most preferably at least 0.46 wt% amino acid. Preferably, when used, the composition comprises at most 18.3 wt%, more preferably at most 9.8 wt%, more preferably at most 6.3 wt%, more preferably at most 4.3 wt%, most preferably at most 2.9 wt% amino acid. In a preferred embodiment, when used, the composition comprises from 0.002 wt% to 18.3 wt%, more preferably from 0.02 wt% to 9.8 wt%, more preferably from 0.12 wt% to 6.3 wt%, more preferably from 0.28 wt% to 4.3 wt%, more preferably from 4.3 wt% to 2.9 wt% amino acid.

[0052] The composition may also optionally include one or more biocides. The biocide can be any suitable compound that prevents, inhibits, reduces the growth of, inhibits the activity of, or eliminates unwanted microorganisms. Examples of suitable biocides include sodium hypochlorite, methylisothiazolinone, benzisothiazolinone, chloromethylisothiazolinone, and combinations thereof. Preferably, the composition comprises at least 0.6 ppm by weight, more preferably at least 1.6 ppm by weight, more preferably at least 2.7 ppm by weight, more preferably at least 3.8 ppm by weight, and most preferably at least 4.6 ppm by weight of the biocide. High concentrations of biocide may lead to undesirable interactions between the biocide and other components of the composition and the substrate. Therefore, the composition preferably comprises at most 98 ppm by weight, more preferably at most 83 ppm by weight, more preferably at most 74 ppm by weight, and most preferably at most 69 ppm by weight of the biocide. As used herein, ppm refers to ppm by weight.

[0053] The present invention also provides a method for chemical mechanical polishing of a silicon carbide substrate, comprising the following steps: (a) providing a chemical mechanical polishing composition; (b) contacting the substrate with the chemical mechanical polishing composition and a polishing pad; (c) moving the polishing pad relative to the substrate with the chemical mechanical polishing composition positioned therebetween; and (d) removing at least a portion of the substrate. The CMP composition provided in step (a) is a composition of the present invention. The method may optionally include other steps.

[0054] The composition can be prepared using suitable techniques known to those skilled in the art. The abrasive particles, clay, and other chemical additives described above can be added to the aqueous carrier in any order and in appropriate amounts to achieve the desired concentration. The abrasive particles, clay, and other chemical additives can be mixed and stirred in the aqueous carrier. The pH value can be adjusted using the pH adjusting agents described above to obtain and maintain the desired pH. The abrasive particles, clay, and other chemical additives can be added at any time before use (e.g., one month, one day, one hour, or one minute) or during the CMP process.

[0055] The composition can be provided as a one-part system, a two-part system, or a multi-part system. For example, as a two-part system, the first part can include abrasive particles, clay, and a pH adjuster, and the second part can include an oxidizing agent and a catalyst. The first and second parts can be mixed at any time before the CMP process (e.g., one month, one day, one hour, or one minute) or during the CMP process, such as when using a polishing apparatus having multiple supply paths for the CMP composition.

[0056] The composition can be provided as a concentrate and can be diluted with a suitable amount of water before use. The concentration of the components in the composition can be any suitable concentration, for example, 2 times, 3 times, 10 times, or 25 times the above-mentioned concentrations for use. For example, the concentrate can contain the abrasive and chemical additives at concentrations such that, upon dilution with a suitable amount of water, the abrasive and chemical additives are present in the composition at the above-mentioned concentrations. If the composition is provided, for example, as a two-part system, one or both parts can be provided as a concentrate. The two parts can be provided at different concentrations, for example, the first part at a concentration of three times and the second part at a concentration of five times. The two parts can be diluted in any order before mixing.

[0057] The present invention also relates to the use of the above-mentioned composition of the present invention. Preferably, the composition of the present invention is used for chemical mechanical polishing of a silicon carbide substrate. The composition can be used for surface polishing of silicon carbide wafers, such as rough polishing and fine polishing. In a preferred embodiment, the composition according to the present invention is used for rough polishing of silicon carbide wafers. Preferably, the silicon carbide can be undoped silicon carbide or doped silicon carbide. In a specific embodiment, the silicon carbide can also include oxides of aluminum, iron, and calcium. As known to those skilled in the art, chemical mechanical polishing refers to: a substrate is arranged in contact with a polishing pad and a CMP composition located therebetween in a CMP device, and the polishing pad and substrate are moved relative to each other to remove a portion of the substrate, preferably, the substrate is silicon carbide.

[0058] The present application is described in detail below through specific embodiments.

[0059] Example 1

[0060] Compositions A1-A4 and E1-E3 were evaluated for silicon carbide material removal rate, surface roughness (Ra), and surface defects. Compositions A1-A4 and E1-E3 contained 2 wt.% aluminum oxide abrasive with a steepness factor of 60, 2 wt.% potassium permanganate, 1 wt.% ferric nitrate, 0.5 wt.% hectorite with a zeta potential of -30 mV and a steepness factor of 68, and 0.05 wt.% glycine. In addition to composition A1, compositions A2-A4 contained polyacrylic acid (PAA) at varying weight percentages as shown in Table 1, and compositions E1-E3 contained acrylic acid-2-acrylamido-2-methylpropanesulfonic acid (AA-AMPS) copolymer at varying weight percentages as shown in Table 1. The pH of these compositions was adjusted to 8 with KOH. The compositions were prepared by adding the chemical additives and clay to deionized water in no particular order to disperse the components; this solution was then added to the coating agent (except A1) and stirred.

[0061] Prior to polishing, the zeta potential of the aluminum oxide abrasive particles in the composition was measured using a Mastersizer S (Malvern Instruments Ltd., UK) and is reported in Table 1. The particle size distribution of the aluminum oxide abrasive particles in the composition was measured using a Horiba LA960, and the steepness factor was obtained as described above. The zeta potential of the clay was measured using a Mastersizer S (Malvern Instruments Ltd., UK) in a 0.1 wt% aqueous dispersion. Prior to measuring the z-average particle size and zeta potential, the clay aqueous dispersion was sonicated at 25°C for 30 minutes to obtain a homogenous aqueous dispersion.

[0062] The steepness factor of the clay was measured by dynamic light scattering using a Zetasizer Nano ZSE (Malvern Instruments Ltd.) after ultrasonic treatment of a 0.1 wt.% aqueous dispersion of the clay at 25°C for 30 minutes before adding the clay to the composition. The steepness factor was obtained as described above.

[0063] A 9 cm2 SiC wafer with a thickness of 3 mm was polished for 8 h using a Kizi polishing tool (Dongguan Jinyan Precision Grinding Machinery Manufacturing Co., Ltd.) at a platen speed of 50 rpm, a down force of 5.2 psi, and a slurry flow rate of 120 ml / min.

[0064] The carbon side of the polished 6-inch silicon carbide wafer was visually inspected for surface defects, and the scratches were counted and classified as A = no corresponding defects, B = less than 10 corresponding defects, and C = more than 10 corresponding defects. The results are shown in Table 1. The material removal rate of the silicon side of the 6-inch silicon carbide wafer was measured using an electronic balance, and the weight difference before and after polishing was calculated. The material removal rate is listed in Table 1 as a value of how many nanometers are removed per hour of polishing. The surface roughness (average roughness, Ra) was measured using an SJ-410 surface roughness tester (Mitutoyo Corp) at a measuring length of 25 mm and is listed in Table 1. As known to those skilled in the art, surface roughness is the arithmetic mean of the absolute value of the deviation of the profile height from the average height within the measuring length.

[0065] Table 1

[0066] Table 1 shows that the charge properties of the alumina in compositions A1-A4 and E1-E3 shift relative to composition A1 without a coating agent, demonstrating that coating can alter the charge properties of alumina, rendering it strongly negative. Furthermore, the data in Table 1 demonstrate that coating improves scratch resistance but has no effect on roughness Ra. Furthermore, regarding removal rate, the compositions with AA-AMPS-coated alumina barely reduce the removal rate (RR) during silicon carbide polishing, while the compositions with PAA-coated alumina significantly reduce the removal rate.

[0067] Example 2

[0068] Composition A5 and compositions E4-E16 were evaluated for silicon carbide material removal rate, surface roughness, and surface defects. Composition A5 and compositions E4-E16 contained 3 wt.% alumina abrasive with a steepness factor of 60, 2.5 wt.% potassium permanganate, 1.5 wt.% ferric nitrate, 0.3 wt.% AA-AMPS, and X wt.% glycine. In addition to composition A5, compositions E4-E16 contained various clays as shown in Table 2, with the Z-average particle size of the clays shown in Table 2. The Z-average particle size of the clays was measured by dynamic light scattering using a Zetasizer Nano ZSE (Malvern Instruments Ltd.) after ultrasonicating a 0.1 wt.% aqueous dispersion of the clay at 25°C for 30 minutes before adding the clays to the compositions. The pH of these compositions was adjusted to 8 with NaOH. The compositions were prepared in the same manner as in Example 1. The zeta potential of the aluminum oxide abrasive grains in the composition was -35 mV, and the zeta potential of the aluminum oxide abrasive grains in the composition was measured using a Mastersizer S (Malvern Instruments) before polishing. The steepness factor of the aluminum oxide abrasive grains in the composition was obtained according to the method described in Example 1.

[0069] Silicon carbide wafers were polished using composition A5 and compositions E4-E16 under the same conditions as described in Example 1 for 8 hours, and the silicon carbide material removal rate, surface roughness, and surface defects of composition A5 and compositions E4-E16 were evaluated under the same conditions as described in Example 1. The results are shown in Table 2.

[0070] The shelf life of composition A5 and compositions E4-E16 was evaluated by placing 500 mL of each composition into a 500 mL polyethylene bottle and allowing it to stand at room temperature without stirring. "Shelf life" was defined as the time from the moment the composition began to stand (without stirring) until it settled and formed a hard cake that was difficult to redisperse. The results of the shelf life evaluation are shown in Table 1.

[0071] Table 2

[0072] As shown in Table 2, while clay slightly reduces removal efficiency, it can extend the shelf life of the composition and reduce scratching. The composition without clay formed a hard cake that could not be redispersed after 2 days. The composition containing clay showed sedimentation after 12 months but could be easily redispersed. No further shelf life observations were conducted after 12 months.

[0073] Example 3

[0074] Compositions A6-A8 and E17 were evaluated for silicon carbide material removal rate, surface roughness, and surface defects. Compositions A6-A8 and E17 contained 2.5 wt.% aluminum oxide abrasive with a steepness factor of 60, 2.2 wt.% potassium permanganate, 1.2 wt.% ferric nitrate, 0.5 wt.% AA-AMPS, 1 wt.% MAS with a zeta potential of -24 mV and a steepness factor of 84, and 0.01 wt.% glycine. The compositions were adjusted to the pH listed in Table 3 using KOH and nitric acid. The compositions were prepared in the same manner as in Example 1. The zeta potential and steepness factor of the clay, as well as the steepness factor of the aluminum oxide abrasive in the compositions, were measured as described in Example 1.

[0075] Silicon carbide wafers were polished using compositions A6-A8 and composition E17 under the same conditions as described in Example 1 for 8 hours, and the silicon carbide material removal rates, surface roughness, and surface defects of compositions A6-A8 and composition E17 were evaluated under the same conditions as described in Example 1. The results are shown in Table 3.

[0076] Table 3

[0077] As can be seen in Table 3, surprisingly, under the conditions described above, pH has no substantial effect on scratch formation, surface roughness, or removal rate of the material polished using the composition of the present invention.

[0078] Example 4

[0079] Compositions A9-A11 and E18-E20 were evaluated for silicon carbide material removal rate, surface roughness, and surface defects. Compositions A9-A11 and E18-E20 contained 1 wt.% aluminum oxide abrasive, 1.5 wt.% potassium permanganate, 0.5 wt.% ferric nitrate, 0.6 wt.% AA-AMPS, 1.2 wt.% clay with a steepness factor as listed in Table 4, and 0.04 wt.% glycine. The pH was adjusted to 8 with aqueous ammonia. The compositions were prepared in the same manner as in Example 1. The steepness factors of the aluminum oxide abrasives of compositions A9-A11 and E18-E20 were measured using a Horiba LA960 as described above and are listed in Table 4. The zeta potential of each aluminum oxide abrasive in the composition in Table 4 was -36 mV, as measured using a Mastersizer S (Malvern Instruments) before polishing. The steepness factor of clay is measured as described in Example 1.

[0080] Silicon carbide wafers were polished using compositions A9-A11 and compositions E18-E20 under the same conditions as described in Example 1 for 8 hours, and the silicon carbide material removal rates, surface roughness, and surface defects of compositions A9-A11 and compositions E18-E20 were evaluated under the same conditions as described in Example 1. The results are shown in Table 4.

[0081] Table 4

[0082] As can be seen from Table 4, aluminum oxide abrasive grains with smaller steepness factors can slightly increase the material removal rate, but will result in more scratches and worse roughness. E18-E20 with a steepness factor of 60 has the least scratches.

[0083] Example 5

[0084] Compositions A12 and E21 were evaluated for silicon carbide material removal rate, surface roughness, and surface defects during recycling. Compositions A12 and E21 contained 3 wt.% aluminum oxide abrasive grains with a steepness factor of 60, 2 wt.% potassium permanganate, 1.5 wt.% ferric nitrate, 0.8 wt.% kaolinite with a zeta potential of -18 mV and a steepness factor of 57, and 0.008 wt.% glycine. Composition E19 also contained 0.25 wt.% AA-AMPS. The pH of compositions A12 and E21 was adjusted to 8 with NaOH. The compositions were prepared in the same manner as in Example 1. The zeta potential and steepness factor of the clay, as well as the steepness factor of the aluminum oxide abrasive grains in the compositions, were measured as described in Example 1.

[0085] Compositions A12 and E21 were both used to polish a 6-inch diameter circular silicon carbide wafer under the conditions described in Example 1 for 6 hours. The compositions were recycled and reused during the polishing process, meaning that the used composition was collected in a tank and reapplied to the substrate. At the start of the polishing process, 1 L of the composition was used in the polishing system for polishing. Every 2 hours, an additional 100 ml of the composition was added to the polishing system to compensate for the loss of the recycled composition during the recycling process. At the start of the polishing process and every hour, the material removal rate, surface roughness, and surface defects were measured as described in Example 1, the particle size D50 of the aluminum oxide was measured using a Horiba LA960, the zeta potential of the aluminum oxide abrasive in the composition was measured using a Mastersizer S (Malvern Instruments), and the pH of the composition was measured, and all measurement results are listed in Table 5.

[0086] Table 5

[0087] As shown in Table 5, compared to composition A12 without a capping agent, composition E21 containing a capping agent maintained stable zeta potential and pH during recycling and also reduced the increase in alumina particle size D50. The capping agent prevented scratches during recycling and slightly reduced surface roughness.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A chemical mechanical polishing composition for a silicon carbide substrate, comprising aluminum oxide abrasive grains, an oxidizing agent, and clay, wherein the aluminum oxide abrasive grains have a negative zeta potential in the composition at a pH of 7.5 to 9.5, wherein the clay has a z-average particle size of 1 nm to 20 μm as measured by dynamic light scattering.

2. The composition according to claim 1, characterized in that It further comprises a coating agent.

3. The composition according to claim 2, characterized in that The coating agent is a copolymer composed of a sulfonic acid monomer unit and a carboxylic acid monomer unit.

4. The composition according to any one of claims 1 to 3, characterized in that The abrasive particles have a zeta potential of -10 mv to -90 mV at a pH of 7.5 to 9.5 in the composition.

5. The composition according to any one of claims 1 to 3, characterized in that It further comprises a catalyst.

6. The composition according to any one of claims 1 to 3, characterized in that The aluminum oxide abrasive grains have a steepness factor of at least 15, calculated as (D30 / D70)*100.

7. The composition according to any one of claims 1 to 3, characterized in that The clay has a steepness factor of at least 15.

8. The composition according to any one of claims 1 to 3, characterized in that The clay has a Zeta potential of at least -5 mV.

9. The composition according to any one of claims 1 to 3, characterized in that The composition has a pH of at least 6.

0.

10. A polishing method for a silicon carbide substrate, the method being implemented using the composition according to any one of claims 1 to 9.

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