CN117511415A - Chemical mechanical polishing composition and polishing method thereof - Google Patents

Abstract

The invention is applicable to the technical field of chemical industry, and particularly provides a chemical mechanical polishing composition for a silicon carbide substrate and a chemical mechanical polishing method. The composition comprises alumina abrasive particles having a negative zeta potential in the composition at a pH of 7.5 to 9.5, an oxidizing agent, and a clay, wherein the clay has a z-average particle size of 1nm to 20 μm as measured by dynamic light scattering. The CMP composition provided by the invention can improve the polishing effect of a silicon carbide substrate, and achieve good recycling performance and low surface defect count while achieving high material removal rate and low surface roughness.

Description

Chemical mechanical polishing composition and polishing method thereof

Technical Field

The invention belongs to the technical field of chemical industry, and relates to a chemical mechanical polishing composition for a silicon carbide substrate and a polishing method.

Background

Chemical mechanical polishing (Chemical Mechanical Polishing, CMP) is a common process in integrated circuit fabrication or other fields to achieve global planarization, which is primarily used to obtain a smooth surface that is both planar and free of scratches and impurities. The process polishes various target substrates by a combination of chemical and mechanical forces, and Chemical Mechanical Polishing (CMP) compositions play a decisive role in the process. These compositions are typically aqueous solutions containing a wide variety of chemical additives and abrasive particles dispersed uniformly. CMP compositions are also referred to as polishing slurries, polishing solutions, polishing compositions, and the like.

Semiconductor materials have evolved over decades, and the first generation of silicon material semiconductors has been nearly perfect crystals, and the research on silicon materials is very thorough, with the potential for improved device performance based on silicon materials becoming smaller and smaller. In this context, the third generation semiconductors represented by gallium nitride and silicon carbide provide a larger space for further improving the performance of electronic devices due to their excellent physical properties.

Silicon carbide (SiC) is taken as a typical representative of third-generation semiconductor materials, is one of wide-bandgap semiconductor materials which are most mature in the current crystal production technology and device manufacturing level and are most widely applied, and a device manufactured by the silicon carbide (SiC) has the characteristics of high temperature resistance, high voltage resistance, high frequency, high power, radiation resistance and the like, has the advantages of high switching speed and high efficiency, can greatly reduce the product power consumption, improve the energy conversion efficiency and reduce the product volume, is mainly applied to the radio frequency field represented by 5G communication, national defense and military industry and aerospace and the power electronics field represented by new energy automobiles and has clear and considerable market prospect in the civil and military fields.

Polishing of silicon carbide wafers is mainly divided into two steps, rough polishing and finish polishing. Rough polishing focuses on rapid removal and finish polishing focuses on achieving good flatness and smoothness. In rough polishing, on the one hand, since silicon carbide is a very hard substrate, it is very difficult to polish it and achieve high removal rates: if silicon carbide is polished using a CMP composition comprising colloidal silica abrasive particles for polishing a silicon substrate, a sufficiently high removal rate cannot be achieved; the substrate is generally polished with a CMP composition containing alumina abrasive grains, and a high removal rate can be achieved, but the silicon carbide wafer is easily scratched if large-sized alumina is used as abrasive grains. On the other hand, since silicon carbide is very hard, its polishing time is also very long, and generally its rough polishing slurry needs to be recycled for use in order to reduce manufacturing costs, reduce waste materials and reduce environmental burden, while good recycling performance (i.e., long recycling time + stable removal rate during recycling) is important for recycling of slurry. Thus, there remains a need for CMP compositions comprising small particle size alumina abrasive particles suitable for coarse polishing of silicon carbide that can achieve higher removal rates, good recycling performance, low surface roughness, low surface defect count.

Disclosure of Invention

It is an object of the present invention to overcome the above-mentioned problems of the prior art. In particular, embodiments of the present invention provide a chemical mechanical polishing composition suitable for rough polishing of silicon carbide, which exhibits high material removal rates and low surface roughness on the one hand, and good recycling properties, while achieving low surface defect counts on the other hand.

Specifically, embodiments of the present invention provide a chemical mechanical polishing composition comprising alumina abrasive particles, an oxidizing agent, and a clay, the abrasive particles having 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 1nm to 20 μm as measured by dynamic light scattering. .

It is another object of embodiments of the present invention to provide a polishing method for a silicon carbide substrate, preferably a rough polishing method for a silicon carbide substrate, which is achieved using the above composition.

The CMP composition provided by the invention not only can realize higher removal rate of the silicon carbide substrate, but also can ensure low surface defect number of the silicon carbide substrate, realize long recycling time, can keep stable removal rate during recycling, is environment-friendly and has higher economic benefit. Products polished with the CMP compositions of the invention have low surface roughness, low surface defect counts.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The chemical mechanical polishing composition typically comprises abrasive particles dispersed in an aqueous carrier. Abrasive particles can assist in removing material from the substrate surface during polishing. Preferably, the abrasive particles may be metal oxide abrasive particles selected from the group consisting of cerium oxide (ceria), aluminum oxide (alumina), silicon oxide (silica), zirconium oxide (zirconia), titanium oxide (titania), germanium oxide (germania), magnesium oxide (magnesia), nickel oxide, gallium oxide (gallium oxide), yttrium oxide (yttria), and combinations thereof. Preferably, the abrasive particles comprise at least 67wt% (weight percent), more preferably at least 74wt%, more preferably at least 81wt%, more preferably at least 88wt%, most preferably at least 93wt% alumina. In a particularly preferred embodiment, the abrasive particles are all alumina abrasive particles.

When used, the composition preferably comprises at least 0.02wt%, more preferably at least 0.10wt%, more preferably at least 0.20wt%, more preferably at least 0.40wt%, most preferably at least 0.50wt% abrasive particles. The term "as used herein refers to the instant at which the composition is applied to the surface of a substrate during chemical mechanical polishing. If the concentration of abrasive particles is too high, the composition may cause undesirable surface defects, such as substrate scratches, during polishing. Thus, in use, the composition preferably comprises up to 24.0wt%, more preferably up to 20.0wt%, more preferably up to 16.0wt%, more preferably up to 12.0wt%, most preferably up to 8.0wt% abrasive particles. In preferred embodiments, the composition comprises from 0.02wt% to 24.0wt%, more preferably from 0.10wt% to 20.0wt%, more preferably from 0.20wt% to 16.0wt%, more preferably from 0.40wt% to 12.0wt%, most preferably from 0.50wt% to 8.0wt% abrasive particles.

As known to those skilled in the art, the alumina abrasive particles can be vapor phase alumina or alumina having different crystalline phases, such as alpha-alumina, beta-alumina, gamma-alumina, delta-alumina, theta-alumina, sigma-alumina, kappa-alumina, eta-alumina, chi-alumina, p-alumina, and combinations thereof. Preferably, the alumina abrasive particles are selected from the group consisting of alpha alumina, beta alumina, gamma alumina, delta alumina, sigma alumina, theta alumina, and combinations thereof.

Experiments have shown that alpha alumina can exhibit higher substrate material removal rates during chemical mechanical polishing than alumina abrasive particles having other crystalline phases. Accordingly, the alumina abrasive particles preferably comprise at least 60wt%, more preferably at least 70wt%, more preferably at least 80wt%, more preferably at least 90 wt%, and most preferably at least 99wt% alpha alumina. As known to those skilled in the art, the amount of α -alumina can be obtained by X-ray diffraction (XRD), for example, by D8X-ray diffractometry (Bruker Corp) from the integrated intensity ratio of the (113) planes. In a particularly preferred embodiment, all of the alumina abrasive particles in the compositions of the present invention are alpha alumina.

The abrasive particles may be present in the composition as individual particles, aggregates, agglomerates, or mixtures thereof. The individual particles may adhere to each other by van der waals forces and electrostatic interactions, thereby forming an aggregate of more than one individual particle. The aggregates themselves may further adhere to each other by physical interactions, forming agglomerates of more than one aggregate. The formation of aggregates and agglomerates is reversible. The term abrasive particles as used herein refers to individual particles, aggregates, and agglomerates.

The abrasive particles can have any suitable morphology, such as irregular shapes, spheres, cubes, octahedra, truncated octahedra, hexagons, rods, grapes, peanuts, worms, flakes, cocoons, or the like. The surface of the abrasive particles may have any suitable morphological characteristics, such as being smooth or having a plurality of protrusions. The morphology may be determined by one skilled in the art, for example, using Transmission Electron Microscope (TEM) or Scanning Electron Microscope (SEM) images.

The average particle size (diameter) of the abrasive particles affects the material removal rate. As known to those skilled in the art, the average particle size may be obtained by laser diffraction measurements (e.g., using LA-960 from Horiba). The graph obtained by this measurement provides the cumulative volume percent of particles having a certain size. The particle size of the abrasive particles as used herein refers to the particle size of the abrasive particles in the composition. The average particle diameter (D50) is a particle diameter in which 50% by volume of the particles have a particle diameter smaller than this value. Smaller D50 results in reduced material removal. Preferably the abrasive particles have a D50 measured by laser diffraction of at least 5nm, more preferably at least 10nm, more preferably at least 25nm, more preferably at least 35nm, most preferably at least 50 nm. However, if D50 is too large, a number of undesirable surface defects, such as scratches and pits, may occur during the CMP process. Thus, the abrasive particles preferably have a D50 of at most 400nm, more preferably at most 300, more preferably at most 250nm, more preferably at most 200nm, most preferably at most 170nm, as measured by laser diffraction. In a preferred embodiment, the abrasive particles have a D50 measured by laser diffraction of 10nm to 300nm, more preferably 25nm to 250nm, more preferably 35nm to 200nm, more preferably 50nm to 170 nm.

D10 is the particle diameter of 10% by volume of the particles, the particle diameter of which is smaller than this value. Smaller D10 was found to achieve less surface roughness during CMP processing. Preferably the abrasive particles have a D10 measured by laser diffraction of at most 200nm, more preferably at most 175nm, more preferably at most 150nm, more preferably at most 125nm, most preferably at most 100 nm. While smaller D10 reduces material removal. Preferably the abrasive particles have a D10 measured by laser diffraction of at least 2nm, more preferably at least 8nm, more preferably at least 15nm, more preferably at least 25nm, most preferably at least 35 nm. In a preferred embodiment, the abrasive particles have a D10 measured by laser diffraction of 2nm to 200nm, more preferably 8nm to 175nm, more preferably 15nm to 150nm, more preferably 25nm to 125nm, most preferably 35nm to 100 nm.

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

D30 is the particle size of 30% by volume of the particles smaller than this value. It was found that the smaller D30, the lower the surface roughness, and the fewer scratches the substrate surface was in the CMP process. Preferably the abrasive particles have a D30 measured by laser diffraction of at most 300nm, more preferably at most 200nm, most preferably at most 150 nm. While smaller D30 reduces the material removal rate. Preferably the abrasive particles have a D30 measured by laser diffraction of at least 4nm, more preferably at least 20nm, most preferably at least 40 nm. In a preferred embodiment, the abrasive particles have a D30 of 4nm to 300nm, more preferably 20nm to 200nm, most preferably 40nm to 150nm, as measured by laser diffraction.

D70 is the particle size of 70% by volume of the particles smaller than this value. It has also been 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 500nm, more preferably at most 400nm, most preferably at most 280nm as measured by laser diffraction. While smaller D70 reduces material removal. Preferably the abrasive particles have a D70 of at least 16nm, more preferably at least 43nm, most preferably at least 62nm as measured by laser diffraction. In a preferred embodiment, the abrasive particles have a D70 of 16nm to 500nm, more preferably 43nm to 400nm, most preferably 62nm to 280nm, as measured by laser diffraction.

The particle size distribution of alumina abrasive grains is classified into unimodal and multimodal. The unimodal distribution is that there is only one peak in the particle size distribution curve and only one mode particle size. Whereas a multimodal distribution is one in which there are two or more peaks, i.e. two or more mode particle sizes, on the particle size distribution curve. Preferably, the abrasive particles have only one peak.

The alumina abrasive grain should have a suitable steepness factor. The steepness factor as used herein refers to the value obtained by the formula (D30/D70) ×100. D30 and D70 may be obtained by laser diffraction as described above. D30 is the particle size of 30% by volume of the particles smaller than this value. D70 is the particle size of 70% by volume of the particles smaller than this value. Abrasive particles with a smaller steepness factor exhibit a high material removal rate, but at the same time result in a polished substrate with a higher surface roughness and more surface defects. Thus, the abrasive particles preferably have a steepness factor of at most 98, more preferably at most 95, more preferably at most 92, more preferably at most 91, most preferably at most 90. Preferably the abrasive particles preferably have a steepness factor of at least 15, more preferably at least 30, more preferably at least 35, more preferably at least 40, most preferably at least 45. In a preferred embodiment, the composition comprises abrasive particles having a steepness factor of between 15 and 98, more preferably between 30 and 95, more preferably between 35 and 92, more preferably between 40 and 91. It has been found that abrasive particles having the steepness factor of the present invention cause less scratching of the substrate surface during CMP processing, while still having a higher material removal rate.

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

The composition preferably comprises a coating agent. The coating agent can be reversibly bound to the surface of the alumina abrasive grain by hydrogen bonding and/or ionic interactions, etc. As used herein, a coating agent refers to a coating agent that is present in the composition in any form, such as in combination with the surface of alumina abrasive particles and/or not in combination with the surface of alumina abrasive particles. Preferably, the coating agent is a polymer. The coating agent is preferably a copolymer composed of a combination of sulfonic acid monomer units and carboxylic acid monomer units. The copolymer can be used in any practicable form, such as an acid, conjugate base, salt, or combination thereof.

Preferably, the sulfonic acid monomer units are selected from the group consisting of 2-acrylamido-2-methyl-l-propane sulfonic Acid (AMPS), 4-vinylbenzene sulfonic acid, vinyl sulfonic acid, 2-sulfonic acid ethyl acrylate, 2-sulfonic acid ethyl methacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, sodium styrene sulfonate, and 2-propylene-l-sulfonic acid, and salts thereof, and combinations thereof. In a particularly preferred embodiment, the sulfonic acid monomer unit is 2-acrylamido-2-methyl-l-propanesulfonic Acid (AMPS).

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.

The capping agent should have a low Molecular Weight (MW). Preferably the coating agent has a Molecular Weight (MW) of at most 50,000g/mol, more preferably at most 30,000g/mol, more preferably at most 20,000g/mol, more preferably at most 15,000g/mol, most preferably at most 9,000 g/mol. Preferably the coating agent has a molecular weight of 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 500 g/mol. In a preferred embodiment, the coating agent has a molecular weight of 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 9,000 g/mol.

Preferably, when used, the composition comprises the coating agent at a concentration of at least 0.001wt%, more preferably at least 0.005wt%, more preferably at least 0.01wt%, most preferably at least 0.02wt%. Preferably, the concentration of the coating agent, when used, is at most 14.0wt%, more preferably at most 11.0wt%, more preferably at most 8.0wt%, most preferably at most 5.0wt%. In a preferred embodiment, the concentration of the coating agent ranges from 0.001wt% to 14.0wt%, more preferably from 0.005wt% to 11.0wt%, more preferably from 0.01wt% to 8.0wt%, most preferably from 0.02wt% to 5.0wt%.

Preferably, the alumina abrasive particles are coated with a coating agent. The surface of the alumina abrasive particles can be treated with a coating agent by any suitable method. For example, the coating agent may be dissolved in an aqueous carrier such as deionized water and then alumina abrasive particles added to form a mixture. The mixture is then stirred until the ingredients are dissolved. A mixture of a coating agent and alumina abrasive particles is then added to the composition.

Preferably, the abrasive particles are negatively charged in the composition. The charge is referred to as the zeta potential and can be measured, for example, by a Mastersizer S (Malvern Instruments). As known to those skilled in the art, zeta potential refers to the potential at the interface between a moving fluid within a composition and a fluid stabilizing layer attached to abrasive particles dispersed in the composition. Higher absolute values of zeta potential result in stronger electrostatic repulsion between particles, thereby increasing the stability of the dispersion of particles in the composition. The negative charge of the abrasive particles in the composition is obtained after being coated by 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, most preferably at least-28 mV at a pH of 7.5 to 9.5 in the composition. 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, most preferably at most-50 mV at a pH of 7.5 to 9.5 in the composition. 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, most preferably from-28 mV to-50 mV, in the composition at a pH of from 7.5 to 9.5. Unexpectedly, according to the present invention, a negative zeta potential causes less scratching of the substrate surface during CMP while still exhibiting a higher material removal rate.

Preferably, the composition further comprises one or more chemical additives. The chemical additives may interact with the abrasive and/or with the substrate and/or with the polishing pad during CMP. Interactions may be based on hydrogen bonding, van der Waals forces, electrostatic forces, and the like. The chemical additive may be any suitable ingredient, for example, that functions as a polishing rate inhibitor, surfactant, thickener, chelating agent, preservative, film former, etch inhibitor, termination compound, dissolution inhibitor, or a combination thereof.

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 contact the substrate and polishing pad during the CMP process. The aqueous carrier may be any suitable component for suspending the abrasive particles and chemical additives. The aqueous carrier may be water, ethers (e.g., dioxane or tetrahydrofuran), alcohols (e.g., methanol and ethanol), and combinations thereof. Preferably, the aqueous carrier comprises at least 50wt% water, preferably at least 70wt% water, more preferably at least 90wt% water, more preferably at least 95wt% water, more preferably at least 99wt% water. Most preferably the aqueous carrier is deionized water.

Preferably, the CMP composition further comprises an oxidizing agent. The oxidizing agent may react with the silicon carbide substrate surface and facilitate material removal during the polishing process. The oxidizing agent can be used in any practicable form, such as an acid, conjugate base, salt (e.g., potassium salt, sodium salt, ammonium salt, etc.), or a combination thereof. Preferably, the oxidizing agent is selected from the group consisting of inorganic or organic per-compounds (per-compounds), oxones, chlorates, chlorous acids, bromates, iodic acids, iodates, nitrates, chromates, and mixtures thereof. Examples of inorganic or organic per compounds are hydrogen peroxide, benzoyl peroxide, peracetic acid, di-t-butyl peroxide, sodium peroxide, carbamide peroxide, percarbonate, monopersulfate, dipersulfate, persulfate, perborate, perchloric acid, perchlorate, perbromic acid, perbromate, periodic acid, periodate, permanganate, ferrate, perrhenate, perruthenate, and combinations thereof. The permanganate, periodate and persulfate salt may be any permanganate, periodate and persulfate salt or combination thereof, such as potassium periodate, periodic acid, ammonium persulfate, potassium persulfate or potassium permanganate, or the like. Examples of nitrate compounds are ferric nitrate, barium nitrate, didymium nitrate, nickel nitrite, potassium nitrate, aluminum nitrate, sodium nitrate, uranyl nitrate, ammonium nitrate, cerium nitrate, ceric ammonium nitrate, and combinations thereof. More preferably, the oxidizing agent is selected from the group consisting of permanganate, persulfate, iodate, periodate, hydrogen peroxide, chlorite, and combinations thereof. Most preferably, the oxidizing agent is selected from permanganate.

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

Preferably, the CMP composition further comprises a catalyst. The catalyst often works with an oxidizing agent to enhance the polishing removal rate. Preferably, the catalyst is selected from the group consisting of iron-containing compounds (e.g., iron (III) sulfate, iron (III) chloride), copper-containing compounds (e.g., copper (II) nitrate, copper (II) sulfate), cobalt-containing compounds (e.g., cobalt (II) nitrate), nickel-containing compounds (e.g., nickel (II) chloride), and combinations thereof. More preferably, the promoter or catalyst is selected from iron-containing compounds, which may include tri-iron (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, conjugate acid, salt, or 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 iron nitrate, iron cyanide, iron sulfate, iron fluoride, iron chloride, iron bromide, iron iodide, iron perchlorate, iron perbromide, iron periodate, iron ammonium sulfate, and combinations thereof. Examples of organic iron-containing compounds are iron acetate, iron acetylacetonate, iron citrate, iron gluconate, iron malonate, iron oxalate, iron phthalate, iron 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.

The catalyst can be present in the CMP composition in any suitable amount. Preferably, when used, the composition comprises at least 0.01wt%, more preferably at least 0.05wt%, more preferably at least 0.10wt%, more preferably at least 0.15wt%, most preferably at least 0.20wt% of catalyst. Preferably, when used, the composition comprises up to 12.0wt%, more preferably up to 10.0wt%, more preferably up to 8.0wt%, more preferably up to 6.0wt%, most preferably up to 5.0wt% of catalyst. In preferred embodiments, the composition comprises from 0.01wt% to 12.0wt%, more preferably from 0.05wt% to 10.0wt%, more preferably from 0.10wt% to 8.0wt%, more preferably from 0.15wt% to 6.0wt%, more preferably from 0.20wt% to 5.0wt% of catalyst.

Preferably, the composition comprises a pH adjuster at the time of use. The pH adjuster aids in achieving the proper pH of the composition. The pH adjuster may be a base or a salt thereof. The base or salt thereof may be an organic base, an inorganic base, or a combination thereof.

Examples of inorganic bases are 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, ammonia, and combinations thereof.

Examples of organic bases are aliphatic amines, aromatic amines, quaternary ammonium hydroxides such as tetramethyl ammonium hydroxide (TMAH), tetraethyl ammonium hydroxide (TEAH), tetrapropyl ammonium hydroxide (TPAH), tetrabutyl ammonium hydroxide (TBAH), and combinations thereof.

Preferably, the pH adjustor is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof. In particularly preferred embodiments, the pH adjustor is selected from the group consisting of 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 adjustor of the present invention has been found to increase the material removal rate of the substrate during the CMP process. The composition may comprise a pH adjuster in a concentration suitable for achieving the pH of the present invention.

Preferably the composition has an alkaline pH. Typically an acidic pH (for SiC polishing compositions containing alumina, an oxidizing agent + a catalyst) can increase the removal rate, but an acidic pH value would risk causing corrosion of the polishing tool, while the composition of the invention is alkaline to avoid the risk of corrosion and still has a better removal rate. Thus, in use, the composition preferably has a pH of at least 6.0, more preferably at least 6.5, more preferably at least 7.0, 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, more preferably at most 9.5. In a preferred embodiment, the composition has a pH of from 6.0 to 12.0, more preferably from 6.5 to 11.0, more preferably from 7.0 to 10.0, most preferably from 7.5 to 9.5.

Preferably, the CMP composition further comprises a clay. For example, clay is available from Cheng Xin Xin chemical technology Co., ltd (Guangzhou, china). It was found that the clay-containing compositions of the present invention 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 silicate. The clay may be a natural clay, a synthetic clay, a modified clay, or a combination thereof. Synthetic clays can be purchased or synthesized, for example, by solid phase reaction, melt synthesis or hydrothermal synthesis. Examples of clays are kaolin (e.g., kaolin, dickite, halloysite, nacrite), montmorillonite (e.g., saponite, hectorite, nontronite, beidellite, magnesite, bentonite, andalusite, kyanite, sillimanite, kaolinite, metakaolin, mullite, aluminum silicate dihydrate, aluminum potassium silicate, sodium aluminum silicate, calcium aluminum silicate, aluminum silicate oxide, magnesium aluminum silicate, boron aluminum silicate), illite (e.g., micas such as phlogopite, biotite, petalite, muscovite, 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, hectorite, magnesium aluminum silicate, kaolinite, or combinations thereof.

The clay may interact with the abrasive particles and/or the substrate surface thereof. 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 particles and/or the substrate surface thereof. Thus, the clay should have a suitable particle size distribution relative to the particle size distribution of the abrasive particles. The zeta potential, z average particle size and particle size distribution of the clay may be tested after subjecting a 0.1wt.% aqueous clay dispersion to ultrasonic treatment at 25 ℃ 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 and not for the clay in the composition. The zeta potential of the clay can be measured by Mastersizer S (uk Malvern Instruments ltd.); the particle size distribution and z-average particle size of the clay can then be measured by dynamic light scattering, for example using Zetasizer Nano ZSE (Malvern Instruments ltd.); the Z-average particle size refers to the intensity weighted average hydrodynamic size of the collection of particles as measured by dynamic light scattering (e.g., using 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.

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 1nm, preferably at least 2nm, preferably at least 5nm, preferably at least 8nm, more preferably at least 10nm, as measured by dynamic light scattering. In a preferred embodiment, it is preferred that the clay has a z-average particle size of 1nm to 20 μm, preferably 2nm to 10 μm, preferably 5nm to 9 μm, preferably 8nm to 6 μm, more preferably 10nm to 5 μm, as measured by dynamic light scattering.

The clay should have a suitable steepness factor. The steepness factor as used herein 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, 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, most preferably at least 45. In a preferred embodiment, the clay has a steepness factor of between 15 and 98, more preferably between 30 and 95, more preferably between 35 and 92, more preferably between 40 and 91. It was found that clay having a steepness factor according to the present invention can reduce surface roughness and reduce scratches caused to the substrate surface during CMP.

Preferably, the clay is negatively charged. The larger the absolute value of the Zeta negative potential of the clay, the more stable the dispersion. Preferably the clay Zeta potential has a value of at least-5 mV, preferably at least-10 mV, more preferably at least-15 mV, more preferably at least-18 mV, most preferably at least-20 mV.

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

Preferably the composition comprises an amino acid. The amino acid may 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 protein amino acid. In a preferred embodiment, the molecular weight of the amino acid is at most 150g/mol, more preferably at most 140g/mol, more preferably at most 130g/mol, most preferably at most 120g/mol. The amino acids of the present invention have been found to reduce the number of defects in a substrate during a CMP process.

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

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

The invention also provides a method of chemically-mechanically polishing a silicon carbide substrate, the method comprising the steps of: (a) providing a chemical mechanical polishing composition; (b) Contacting a substrate with a chemical mechanical polishing composition and a polishing pad; (b) Moving the polishing pad relative to the substrate with the composition therebetween; (c) removing at least a portion of the substrate. The CMP composition provided in step (a) is a composition of the invention. The method may optionally include other steps.

The composition may be prepared using suitable techniques known to those skilled in the art. The abrasive particles, clay, and other chemical additives described above may be added to the aqueous carrier in any order and in suitable amounts to achieve the desired concentrations. The abrasive particles, clay, and other chemical additives may be mixed and stirred in an aqueous carrier. The pH may be adjusted with the above-described pH adjusting agents to achieve and maintain the desired pH. The abrasive particles, clay, and other chemical additives may be added any time prior to use (e.g., a month, a day, an hour, or a minute) or during the CMP process.

The composition may 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 may include abrasive particles, clay, and a pH adjuster, and the second part may include an oxidizing agent and a catalyst. The first and second portions can be mixed at any time prior to (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.

The composition may be provided as a concentrate and may be diluted with an appropriate amount of water prior to use. The concentration of the components of the composition may be any suitable concentration, for example 2-fold, 3-fold, 10-fold or 25-fold as described above for use. For example, the concentrate may contain abrasive particles and chemical additives in concentrations such that, upon dilution with an appropriate amount of water, the abrasive particles and chemical additives are present in the composition at the concentrations described above. If the composition is provided, for example, as a two-part system, one or both parts may be provided as a concentrate. The two portions may be provided at different levels of concentration, for example, the first portion having three times the concentration and the second portion having five times the concentration. The two portions may be diluted in any order prior to mixing.

The invention also relates to the use of the above-described composition of the invention. Preferably, the composition of the present invention is used for chemical mechanical polishing of silicon carbide substrates. The composition can be used for surface polishing of silicon carbide wafers, such as rough polishing and finish polishing. In a preferred embodiment, the composition according to the invention is used for rough polishing of silicon carbide wafers. Preferably, the silicon carbide may be undoped silicon carbide or doped silicon carbide in particular embodiments, the silicon carbide may also include oxides of aluminum, iron, calcium. As known to those skilled in the art, chemical mechanical polishing refers to: the substrate is placed in contact with a polishing pad and a CMP composition therebetween in a CMP apparatus, the polishing pad and the substrate being relatively moved to remove a portion of the substrate, preferably the substrate is silicon carbide.

The present application is described in detail below by way of specific examples.

Example 1

The silicon carbide material removal rates, surface roughness (Ra), and surface defects of compositions A1-A4 and compositions E1-E3 were evaluated. Compositions A1-A4 and compositions E1-E3 contained 2wt.% alumina abrasive particles with a steepness factor of 60, 2wt.% potassium permanganate, 1wt.% ferric nitrate, 0.5wt.% hectorite with a zeta potential of-30 mV and a steepness factor of 68, and 0.05wt.% glycine. In addition to composition A1, compositions A2-A4 also contained different weight percentages of polyacrylic acid (PAA) as shown in Table 1, and compositions E1-E3 also contained different weight percentages of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid (AA-AMPS) copolymer as shown in Table 1. The pH of these compositions was adjusted to 8 with KOH. The preparation method of the composition comprises the following steps: adding chemical additives and clay to deionized water in no particular order and dispersing the components; subsequently, the solution was added to the coating agent (except for A1), followed by stirring.

The zeta potential of the alumina abrasive particles in the composition was measured using a Mastersizer S (uk Malvern Instruments ltd.) and recorded in table 1 prior to polishing. The particle size distribution of the alumina abrasive particles in the composition was measured with Horiba LA960, and its steepness factor was obtained by the method described above. The zeta potential of the clay was measured in a 0.1wt% aqueous dispersion using a Mastersizer S (uk Malvern Instruments ltd.). The clay aqueous dispersion was sonicated at 25 ℃ for 30 minutes to obtain a uniform aqueous dispersion before measuring the z-average particle and zeta potential.

The steepness factor of the clay was measured by dynamic light scattering using Zetasizer Nano ZSE (Malvern Instruments ltd.) after an aqueous dispersion of 0.1wt.% clay was sonicated at 25 ℃ for 30 minutes before the clay was added to the composition, and the steepness factor was obtained by the method described above.

A Kizi polishing tool (Dongguan Jin Yan precision grinding machinery Co., ltd.) was used to measure 9cm in area at a platen speed of 50rpm, a downforce of 5.2psi and a slurry flow rate of 120ml/min ² Silicon carbide wafers having a thickness of 3mm were subjected to polishing treatment for 8 hours.

Visual inspection of the surface defects was performed on the polished 6 inch silicon carbide wafer carbon face and scratches were counted and classified as a=no corresponding defects, b=less than 10 corresponding defects, and c=greater than 10 corresponding defects, with the results shown in table 1. The material removal rate of the silicon face of the 6-inch silicon carbide wafer was measured with an electronic balance and calculated from the weight difference before and after polishing. The material removal rates are listed in table 1 as values of how many nanometers are removed per hour of polishing. The surface roughness (average roughness, ra) was measured at a measured length of 25mm using a SJ-410 surface roughness tester (Mitutoyo Corp) 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 over the measured length.

TABLE 1

From Table 1, it is seen that the coating changes the properties of the alumina charge to a strong negative charge, as compared to the alumina charge properties of compositions A1 to A4 and compositions E1 to E3, which are not coated with the coating agent. As is clear from the data in table 1, coating improved scratch but had no effect on roughness Ra. In addition, the composition having AA-AMPS coated alumina hardly reduced the removal rate RR of silicon carbide polishing in terms of removal rate, whereas the composition having PAA coated alumina reduced the removal rate more.

Example 2

Silicon carbide material removal rates, surface roughness, and surface defects were evaluated for composition A5 and compositions E4-E16. Composition A5 and compositions E4-E16 contained 3wt.% alumina abrasive particles with a steepness factor of 60, 2.5wt.% potassium permanganate, 1.5wt.% ferric nitrate, 0.3wt.% AA-Amp ps, X wt.% glycine. In addition to composition A5, compositions E4-E16 contained different clays as shown in Table 2, with the Z-average particle sizes of the clays as shown in Table 2. The Z-average particle size of the clay was measured by dynamic light scattering using Zetasizer Nano ZSE (Malvern Instruments ltd.) after an aqueous dispersion of 0.1wt.% clay was sonicated at 25 ℃ for 30 minutes before the clay was added to the composition. The pH of these compositions was adjusted to 8 with NaOH. The composition was prepared in the same manner as in example 1. The Zeta potential of the alumina abrasive grain in the composition was-35 mV, and the Zeta potential of the alumina abrasive grain in the composition was measured with a Mastersizer S (Malvern Instruments) prior to polishing. The steepness factor of the alumina abrasive grain in the composition was obtained as described in example 1.

Silicon carbide wafers were polished using composition A5 and compositions E4 to E16 under the same conditions as described in example 1 for 8 hours, and silicon carbide material removal rates, surface roughness, and surface defects of compositions A5 and compositions E4 to E16 were evaluated under the same conditions as described in example 1, and the results are shown in table 2.

The shelf life of compositions A5 and E4-E16 was evaluated: 500mL of each composition was separately filled into 500mL polyethylene bottles and left to stand at room temperature without stirring. The term "shelf life" is defined as the time from when the composition begins to stand (no longer stir) until the composition precipitates and forms a hard cake that is not easily redispersed. The shelf life evaluation results are shown in table 1.

TABLE 2

As can be seen from table 2, although clay slightly reduces removal, it can extend the shelf life of the composition and reduce scratches. The clay-free composition formed a hard cake that was not redispersible after 2 days. The clay-containing composition showed sedimentation after 12 months, but could be easily redispersed. No further observations of shelf life were made after 12 months.

Example 3

The silicon carbide material removal rates, surface roughness, and surface defects of compositions A6-A8 and composition E17 were evaluated. Compositions A6-A8 and composition E17 contained 2.5wt.% alumina abrasive particles with a steepness factor of 60, 2.2wt.% potassium permanganate, 1.2wt.% ferric nitrate, 0.5wt.% AA-Amp ps, 1wt.% MAS with a zeta potential of-24 mV and a steepness factor of 84, 0.01wt.% glycine. The composition was adjusted to the pH listed in table 3 with KOH and nitric acid. The composition was prepared in the same manner as in example 1. The zeta potential and steepness factor of the clay and the steepness factor of the alumina abrasive grain in the composition were measured as described in example 1.

Silicon carbide wafers were polished for 8 hours under the same conditions as described in example 1 using compositions A6 to A8 and composition E17, and silicon carbide material removal rates, surface roughness, and surface defects of compositions A6 to A8 and composition E17 were evaluated under the same conditions as described in example 1, and the results are shown in table 3.

TABLE 3 Table 3

As can be seen from table 3, it is unexpected that under the above conditions, pH has no substantial effect on scratch formation, surface roughness, or removal rate of the material after polishing using the composition of the present invention.

Example 4

The silicon carbide material removal rates, surface roughness, and surface defects of compositions A9-a11 and compositions E18-E20 were evaluated. Compositions A9-a11 and compositions E18-E20 contained 1wt.% alumina abrasive particles, 1.5wt.% potassium permanganate, 0.5wt.% ferric nitrate, 0.6wt.% AA-Amp ps, 1.2wt.% clay with a steepness factor as listed in table 4, 0.04wt.% glycine. The pH was adjusted to 8 with ammonia. The composition was prepared in the same manner as in example 1. The steepness factors of the alumina abrasive grains of compositions A9-A11 and compositions E18-E20 were obtained after measurement with Horiba LA960 as described above, as listed in Table 4. A kind of electronic device. The Zeta potential of each alumina abrasive grain in the composition in Table 4 was-36 mV, which was measured with a Mastersizer S (Malvern Instruments) prior to polishing. The steepness factor of the clay was measured as described in example 1.

Silicon carbide wafers were polished using compositions A9 to a11 and compositions E18 to E20 under the same conditions as described in example 1 for 8 hours, and silicon carbide material removal rates, surface roughness, and surface defects of compositions A9 to a11 and compositions E18 to E20 were evaluated under the same conditions as described in example 1, and the results are shown in table 4.

TABLE 4 Table 4

As can be seen from table 4, alumina abrasive particles with smaller steepness factors can slightly increase the material removal rate, but can result in more scratches and poorer roughness. E18-E20 scratches with a steepness factor of 60 were minimal.

Example 5

Compositions a12 and E21 were evaluated for silicon carbide material removal, surface roughness, and surface defects during recycling. Compositions A12 and E21 contained 3wt.% alumina abrasive particles having a steepness factor of 60, 2wt.% potassium permanganate, 1.5wt.% ferric nitrate, and 0.8wt.% kaolinite having a zeta potential of-18 mV and a steepness factor of 57, 0.008wt.% glycine, and composition E19 also contained 0.25wt.% AA-AMPS. The pH of compositions a12 and E21 was adjusted to 8 with NaOH. The composition was prepared in the same manner as in example 1. The zeta potential and steepness factor of the clay and the steepness factor of the alumina abrasive grain in the composition were measured as described in example 1.

Compositions a12 and E21 each polished a 6 inch diameter round silicon carbide wafer for 6 hours under the conditions described in example 1. The composition is recycled and reused during polishing, meaning that the used composition is collected in a tank and reapplied to the substrate. At the beginning of the polishing process, 1L of the composition was used in the polishing system for polishing. An additional 100ml of the composition was added to the polishing system every 2 hours to compensate for the loss of recycled composition during recycling. At the beginning of the polishing process and every other hour, the material removal rate, surface roughness, and surface defects were measured as described in example 1, the particle size D50 of the alumina was measured using Horiba LA960, the Zeta potential of the alumina abrasive particles in the composition was measured using Mastersizer S (Malvern Instruments), while the pH of the composition was measured, and all measurements are listed in table 5.

TABLE 5

As can be seen from Table 5, composition E21 containing the coating agent maintained the zeta potential and pH stable during recycling and reduced the increase in alumina particle size D50 as compared to composition A12 containing no coating agent. The coating agent can prevent scratch generation during recycling and slightly reduce surface roughness.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the invention, but any modifications, equivalents, improvements, etc. within the principles of the present invention should be included in the scope of the present invention.

Claims (10)

1. A chemical mechanical polishing composition for silicon carbide substrates comprising alumina abrasive particles, an oxidizing agent, and a clay, wherein the alumina abrasive particles 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 1nm to 20 μιη as measured by dynamic light scattering.

2. The composition of claim 1, further comprising a capping agent.

3. The composition of claim 2, wherein the coating agent is a copolymer of a combination of sulfonic acid monomer units and carboxylic acid monomer units.

4. The composition of any of claims 1-3, wherein the abrasive particles have a zeta potential of from-10 mV to-90 mV in the composition at a pH of from 7.5 to 9.5.

5. A composition according to any one of claims 1 to 3, further comprising a catalyst.

6. A composition according to any one of claims 1 to 3, wherein the alumina abrasive grain has a steepness factor calculated with (D30/D70) x 100 of at least 15.

7. A composition according to any one of claims 1 to 3, wherein the clay has a steepness factor of at least 15.

8. A composition according to any one of claims 1 to 3, wherein the clay Zeta potential is at least-5 mV.

9. A composition according to any one of claims 1 to 3, wherein the composition has a pH of at least 6.0.

10. A polishing method for a silicon carbide substrate, the method being effected with the composition of any one of claims 1-9.