Polishing composition as well as preparation method and application thereof

Abstract

The invention relates to the technical field of chemical mechanical polishing, in particular to a polishing composition and a preparation method and application thereof.The preparation method comprises the following steps that silicon dioxide hydrosol, amino acid or amino acid salt and a silane coupling agent containing a first group are mixed, and dispersion liquid is obtained; the first group is selected from one or more of a sulfur-containing group, an epoxy group, an isocyanate group and an acyloxy group; mixing the dispersion liquid with an oxidizing agent, and heating at the temperature of 40-70 DEG C to obtain modified silicon dioxide hydrosol; and mixing the modified silicon dioxide hydrosol, an anionic water-soluble polymer, organic alkali and water to prepare the polishing composition. The polishing composition prepared by mixing the modified silicon dioxide hydrosol obtained by the specific method with the anionic water-soluble polymer, the organic alkali and the water can greatly reduce the DCN defect on the surface of a polished silicon wafer.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing, and particularly relates to a polishing composition, a preparation method thereof, and an application thereof. Background Art

[0002] Chemical-Mechanical Polishing (abbreviated as CMP), also known as chemical mechanical planarization, is a technology in the semiconductor device manufacturing process used to planarize a silicon wafer or other substrate material being processed. Generally, an alkaline silica polishing liquid is used in CMP. By using the chemical corrosion reaction between alkali and silicon to generate soluble silicate, and then through the adsorption of fine, soft, large specific surface area, negatively charged SiO2 colloidal particles and their mechanical friction with the polishing pad and the silicon wafer, the reaction products are polished and removed in a timely manner, so as to achieve the purpose of removing the damaged layer and contaminated impurities on the wafer surface. As the integrated circuit process nodes become smaller and smaller, the requirements for the substrate wafers are also getting higher and higher. In order to improve the surface quality of the silicon wafer and reduce the particle residues on the silicon wafer surface, silicon wafer CMP generally needs to be processed in three steps, namely rough polishing, medium polishing, and fine polishing. Medium polishing is the second step of CMP, and its CMP performance directly affects the surface condition after fine polishing.

[0003] The defect types after silicon wafer CMP are mainly divided into three categories, namely particle residues, scratches, and organic residues. And the scratch defects caused on the silicon wafer surface are an irreversible defect and cannot be removed by means of CMP cleaning or single-wafer cleaning after they occur. Therefore, the scratch defects on the silicon wafer surface are one of the most important parameters affecting the silicon wafer yield index. In defect detection equipment (such as the SP5 equipment produced by KLA Corporation), according to different incident angles of light, the defect types are further divided into three categories, namely DCO, DIC, and DCN defects. And DCN defects generally represent wide and shallow scratch defects, which directly affect the device performance and yield, and may cause circuit open or short circuit in severe cases. Under the condition that the fine polishing liquid is determined, the influence of the medium polishing liquid on DCN defects is very important. If the scratch depth caused to the silicon wafer during medium polishing is relatively large, it will cause great pressure on the repair of fine polishing. In the case of insufficient fine polishing repair, it is easy to cause the generation of DCN defects.

[0004] At present, there is little research on silicon wafer medium polishing liquid in China. Therefore, it is necessary to study new technologies to reduce the number of DCN defects occurring during silicon wafer CMP. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to reduce the number of DCN defects occurring during silicon wafer CMP, and thus provide a polishing composition, a preparation method thereof, and an application thereof.

[0006] To this end, in a first aspect, the present application provides a method for preparing a polishing composition, comprising the following steps: Step S1: Mix a silica sol, an amino acid or its salt with a silane coupling agent containing a first group to obtain a dispersion; the first group is selected from one or more of a sulfur-containing group, an epoxy group, an isocyanate group, and an acyloxy group; Step S2: Mix the dispersion with an oxidizing agent and perform a heat treatment at a temperature of 40-70 °C to obtain a modified silica sol; Step S3: Mix the modified silica sol, an anionic water-soluble polymer, an organic base, and water to prepare a polishing composition.

[0007] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the silica sol is 85%-99.8%.

[0008] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the amino acid or its salt is 0.009%-5%.

[0009] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the silane coupling agent containing the first group is 0.009%-5%.

[0010] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the oxidizing agent is 0.009%-5%.

[0011] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the silica sol is 86%-97.2%.

[0012] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the amino acid or its salt is 0.1%-2%.

[0013] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the silane coupling agent containing the first group is 0.1%-2%.

[0014] Further, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the oxidizing agent is 0.1%-2%.

[0015] Further, the temperature of the heat treatment is 45-60 °C; and / or, the time of the heat treatment is 3-60 min.

[0016] Furthermore, the particle size of the silica sol is 30 - 120 nm.

[0017] Furthermore, the solid content of the silica sol is 10 wt% - 50 wt%.

[0018] Furthermore, the amino acid is selected from one or more of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine.

[0019] Furthermore, the sulfur-containing group is selected from one or more of a mercapto group, a disulfide group, a tetrasulfide group.

[0020] Furthermore, the silane coupling agent containing the first group is selected from at least one of 3-mercaptopropyltrimethoxysilane, bis-(3-triethoxysilylpropyl)tetrasulfide, bis-(3-triethoxysilylpropyl)disulfide, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, γ-(2,3-epoxypropoxy)propylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloyloxypropyltrichlorosilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, 3-isocyanatopropyltriethoxysilane, isocyanatopropyltrimethoxysilane.

[0021] Furthermore, the oxidant is selected from at least one of hypochlorous acid and its salts, perchloric acid and its salts, Na2O2, K2O2, MgO2, CaO2, BaO2, hydrogen peroxide, permanganic acid and its salts, FeCl3, dichromic acid and its salts, periodic acid and its salts, oxygen, ozone.

[0022] Furthermore, the mass ratio of the modified silica sol to the anionic water-soluble polymer is 5 - 80:0.01 - 1.

[0023] Furthermore, the mass ratio of the modified silica sol to the organic base is 5 - 80:0.5 - 10.

[0024] Furthermore, the mass ratio of the modified silica sol to water is 5 - 80:9 - 95.

[0025] Furthermore, the mass ratio of the modified silica sol to the anionic water-soluble polymer is 10 - 40:0.1 - 1.

[0026] Furthermore, the mass ratio of the modified silica sol to the organic base is 10 - 40:1 - 5.

[0027] Furthermore, the mass ratio of the modified silica sol to water is 10 - 40:54 - 89.

[0028] Furthermore, the organic base is selected from one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, propylenediamine, butanediamine, hydroxyethyl ethylenediamine, diethylenetriamine, monoethanolamine, N-(2-aminoethyl)ethanolamine, hexamethylenediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, 1-(2-aminoethyl)piperazine, N-methylpiperazine, piperazine, imidazole, methylimidazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, guanidine carbonate, guanidine hydrochloride, guanidine nitrate, tetramethylammonium hydroxide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium fluoride, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium fluoride.

[0029] Furthermore, the anionic water-soluble polymer is selected from one or more of polyacrylic acid and its salts, polymethacrylic acid and its salts, anionic polyacrylamide and its salts, polyvinylsulfonic acid and its salts, polystyrenesulfonic acid and its salts.

[0030] Furthermore, the weight-average molecular weight of the anionic water-soluble polymer is 2000 - 10000000.

[0031] In a second aspect, the present application provides a polishing composition prepared by the preparation method described in any one of the above.

[0032] In a third aspect, the present application provides the use of the polishing composition prepared by the preparation method described in any one of the above in the chemical mechanical polishing of silicon wafers.

[0033] Furthermore, the polishing composition can be used as an intermediate polishing liquid.

[0034] The technical solution of the present invention has the following advantages: 1. The preparation method of the polishing composition provided by the present invention comprises the following steps: mixing a silica sol, an amino acid or its salt with a silane coupling agent containing a first group to obtain a dispersion; the first group is selected from one or more of a sulfur-containing group, an epoxy group, an isocyanate group, and an acyloxy group; mixing the dispersion with an oxidizing agent and performing a heat treatment at a temperature of 40°C - 70°C to obtain a modified silica sol; mixing the modified silica sol, an anionic water-soluble polymer, an organic base, and water to prepare the polishing composition. The polishing composition prepared by mixing the modified silica sol obtained by using the above specific method with an anionic water-soluble polymer, an organic base, and water can greatly reduce the DCN defects on the surface of the silicon wafer after polishing.

[0035] Specifically, in the preparation process of the modified silica sol, the silica sol, an amino acid or its salt are first mixed with a silane coupling agent containing a first group, and then mixed with an oxidizing agent and subjected to a heat treatment under specific temperature conditions, so that the silane coupling agent and the amino acid modify the surface of the silica particles in the silica sol, and then an oxidation treatment is carried out under the above temperature conditions.

[0036] Among them, during the modification process, the amino group in the amino acid carries a positive charge, which can help the silane coupling agent to hydrolyze and attach to the surface of the silica particles. The carboxyl group and amino group in the amino acid can also directly form a bond with Si-OH on the surface of the silica particles and bind to the surface of the silica particles. After modification, the oxidizing agent can oxidize the first group of the silane coupling agent (for example, a mercapto group can be further oxidized to a sulfonic acid group) through the heat treatment under the above temperature conditions, significantly increasing the negative charge on the surface of the silica particles, increasing the electrostatic repulsion between the particles, and the amino part in the amino acid molecules attached to the surface of the silica particles can be oxidized to other groups such as nitro groups, which also increases the electrostatic repulsion between the particles, significantly reducing the number of large particles in the silica sol. Therefore, the combined use of the modified silica sol with an anionic water-soluble polymer and an organic base can reduce the scratching defects caused to the surface of the silicon wafer, that is, the DCN defects will be significantly reduced.

[0037] 2. The preparation method of the polishing composition provided by the present invention can further reduce the DCN defects after CMP of silicon wafers by controlling that, based on the total mass of the raw materials used for the modified silica hydrosol, the mass percentage content of the silica hydrosol is 85% - 99.8%, the mass percentage content of the amino acid or its salt is 0.009% - 5%, the mass percentage content of the silane coupling agent containing the first group is 0.009% - 5%, or the mass percentage content of the oxidant is 0.009% - 5%. In particular, by controlling that, based on the total amount of the raw materials used for the modified silica hydrosol, the mass percentage content of the silica hydrosol is 86% - 97.2%, the mass percentage content of the amino acid or its salt is 0.1% - 2%, the mass percentage content of the silane coupling agent containing the first group is 0.1% - 2%, or the mass percentage content of the oxidant is 0.1% - 2%.

[0038] 3. The preparation method of the polishing composition provided by the present invention can further reduce the DCN defects after CMP of silicon wafers by controlling the heating temperature to be 45 - 60 °C, or by controlling the heating time to be 3 - 60 min, especially 10 - 30 min.

[0039] 4. The preparation method of the polishing composition provided by the present invention can further reduce the DCN defects after CMP of silicon wafers by controlling the mass ratio of the modified silica hydrosol to the anionic water-soluble polymer to be 5 - 80:0.01 - 1; in particular, by controlling the mass ratio of the modified silica hydrosol to the anionic water-soluble polymer to be 10 - 40:0.1 - 1. Specific Embodiments

[0040] The following embodiments are provided to better further understand the present invention. They are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other prior arts falls within the protection scope of the present invention.

[0041] For those not specifying specific experimental steps or conditions in the embodiments, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments not indicating the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0042] The influence of the middle polishing liquid on DCN defects is very important. If the scratch depth on the silicon wafer during the middle polishing process is large, it will cause great pressure on the repair of the final polishing. In the case of insufficient repair during the final polishing, it is easy to cause the generation of DCN defects. There is less research on the middle polishing liquid for silicon wafers in China. Therefore, new technologies need to be studied to reduce the number of DCN defects occurring during the CMP process of silicon wafers.

[0043] To this end, in a first aspect, the present application provides a method for preparing a polishing composition, comprising the following steps: Step S1: Mix a silica sol, an amino acid or its salt with a silane coupling agent containing a first group to obtain a dispersion; the first group is selected from one or more of a sulfur-containing group, an epoxy group, an isocyanate group, and an acyloxy group; Step S2: Mix the dispersion with an oxidizing agent and perform a heat treatment at a temperature of 40 - 70 °C to obtain a modified silica sol; Step S3: Mix the modified silica sol, an anionic water-soluble polymer, an organic base, and water to prepare a polishing composition.

[0044] The polishing composition prepared by mixing the modified silica sol obtained by using the above specific method with an anionic water-soluble polymer, an organic base, and water can greatly reduce the DCN defects on the surface of the silicon wafer after polishing.

[0045] In the special treatment process of the silica sol of the present invention, there is no specific requirement for the stirring and mixing method, and a commonly used liquid stirring method in the industry can be adopted, such as magnetic stirring, stirring paddle stirring, etc.

[0046] Exemplarily, in Step S2, the temperature of the heat treatment can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, preferably 45 - 60 °C.

[0047] In some specific embodiments, the heating time is 3 - 60 min, such as 3 min, 5 min, 8 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc., preferably 10 - 30 min.

[0048] In some specific embodiments, the particle size of the silica sol is 30 - 120 nm, such as 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, etc., the particle size is the secondary particle size, and the solid content is 10 - 50 wt%, such as 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, etc.

[0049] In some specific embodiments, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the silica sol is 85% - 99.8%, the mass percentage content of the amino acid or its salt is 0.009% - 5%, the mass percentage content of the silane coupling agent containing a first group is 0.009% - 5%, and the mass percentage content of the oxidant is 0.009% - 5%.

[0050] In some specific embodiments, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the silica sol is 85% - 99.8%. Such as, including but not limited to, 85%, 88%, 91%, 94%, 97%, 99%, 99.8%, etc., and preferably 86% - 97.2%.

[0051] In some specific embodiments, based on the total mass of the raw materials used for the modified silica sol, the mass percentage content of the amino acid or its salt is 0.009% - 5%. For example, including but not limited to, 0.009%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, and preferably 0.1 - 2%.

[0052] In some specific embodiments, the amino acid is selected from one or more of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine. Preferably, it is one or more of glycine, alanine, valine, leucine.

[0053] In some specific embodiments, the sulfur-containing group is selected from one or more of a mercapto group, a disulfide group, a tetrasulfide group.

[0054] In some specific embodiments, the silane coupling agent containing the first group is selected from at least one of 3-mercaptopropyltrimethoxysilane, bis-(3-triethoxysilylpropyl)tetrasulfide, bis-(3-triethoxysilylpropyl)disulfide, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, γ-(2,3-epoxypropoxy)propylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloxypropyltrichlorosilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, 3-isocyanatopropyltriethoxysilane, and isocyanatopropyltrimethoxysilane. Preferably, it is 3-mercaptopropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrichlorosilane, or isocyanatopropyltriethoxysilane.

[0055] In some specific embodiments, based on the total mass of the raw materials used for the modified silica hydrosol, the mass percentage content of the silane coupling agent containing the first group is 0.009% - 5%. For example, it includes but is not limited to 0.009%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, and preferably 0.1 - 2%.

[0056] In some specific embodiments, the oxidant is selected from at least one of hypochlorous acid and its salts, perchloric acid and its salts, Na2O2, K2O2, MgO2, CaO2, BaO2, hydrogen peroxide, permanganic acid and its salts, FeCl3, dichromic acid and its salts, periodic acid and its salts, oxygen, and ozone. Preferably, it is hydrogen peroxide, potassium periodate, and potassium permanganate.

[0057] In some specific embodiments, based on the total mass of the raw materials used for the modified silica hydrosol, the mass percentage content of the oxidant is 0.009% - 5%. For example, it includes but is not limited to 0.009%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, and preferably 0.1 - 2%.

[0058] In some specific embodiments, the mass ratio of the modified silica hydrosol to the anionic water-soluble polymer is 5 - 80:0.01 - 1. For example, it includes but is not limited to 5:1, 10:0.5, 20:0.1, 80:0.01, and preferably 10 - 40:0.1 - 1.

[0059] In some specific embodiments, the mass ratio of the modified silica sol to the organic base is 5 - 80:0.5 - 10. For example, including but not limited to 5:10, 10:5, 20:1, 80:0.5, and preferably 10 - 40:1 - 5.

[0060] In some specific embodiments, the mass ratio of the modified silica sol to water is 5 - 80:9 - 95. For example, including but not limited to 5:95, 10:80, 20:50, 80:5, and preferably 10 - 40:54 - 89.

[0061] In some specific embodiments, the organic base is selected from one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, propylenediamine, butylenediamine, hydroxyethyl ethylenediamine, diethylenetriamine, monoethanolamine, N-(2-aminoethyl)ethanolamine, hexamethylenediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, 1-(2-aminoethyl)piperazine, N-methylpiperazine, piperazine, imidazole, methylimidazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, guanidine carbonate, guanidine hydrochloride, guanidine nitrate, tetramethylammonium hydroxide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium fluoride, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium fluoride. More preferably, it is tetramethylammonium hydroxide.

[0062] In some specific embodiments, the anionic water-soluble polymer is selected from one or more of polyacrylic acid and its salts, polymethacrylic acid and its salts, anionic polyacrylamide and its salts, polyvinylsulfonic acid and its salts, polystyrenesulfonic acid and its salts.

[0063] In some specific embodiments, the weight-average molecular weight of the anionic water-soluble polymer is 2000 - 10000000. For example, including but not limited to 2000, 5000, 8000, 10000, 80000, 10000000, and preferably 2000 - 80000.

[0064] In some specific embodiments, after mixing, it further includes the step of adjusting the pH value with a pH regulator.

[0065] In the present invention, by adding a pH regulator to the modified silica sol, the pH value of the silicon wafer polishing composition is adjusted to be between 9.5 and 11.5, such as 9.5, 10.0, 10.5, 11.0, 11.5. Among them, the pH regulator in the silicon wafer polishing composition is selected from at least any one of hydrogen chloride, nitric acid, sulfuric acid, phosphoric acid, sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, imidazole, N-methylimidazole, 1,2,4-triazole, tetramethylguanidine, formic acid, acetic acid, propionic acid, itaconic acid, succinic acid, tartaric acid, citric acid, maleic acid, glycolic acid, malonic acid, oxalic acid, butanedioic acid, malic acid, gluconic acid, alanine, glycine, lactic acid, trifluoroacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, triethylenediamine, propylenediaminetetraacetic acid, hydroxyethyl ethylenediamine, hydroxyethyl ethylenediaminetriacetic acid, pyrophosphoric acid, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, methane hydroxyphosphonic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid or its salts, preferably any one of oxalic acid, hydrogen chloride, potassium hydroxide, tetramethylammonium hydroxide; more preferably potassium hydroxide or oxalic acid.

[0066] In a second aspect, the present application provides a polishing composition prepared by the preparation method described in any one of the above.

[0067] In a third aspect, the present application provides the application of the polishing composition prepared by the preparation method described in any one of the above in the chemical mechanical polishing of silicon wafers.

[0068] In the present application, an anionic water-soluble polymer is a type of high molecular compound that can dissolve and dissociate negatively charged groups (such as carboxylate ions, sulfonate ions, etc.) in an aqueous solution.

[0069] In the present application, "or its salt" and "its salts" mean that it can be an acid, or a salt of the corresponding acid, or a combination of both. The salt can be a chemically acceptable salt, such as but not limited to sodium salt, potassium salt or ammonium salt, etc.

[0070] Unless otherwise specified, the raw materials and reagents used in the examples and comparative examples of the present invention are all obtained through commercial channels. Without special explanation, the purity is analytical pure or above. Silica sol (also known as "silicon sol") is a dispersion of nanoscale silica particles in water.

[0071] Example 1 This example provides a preparation method of a polishing composition, including the following steps: Step S1: Add 0.1 kg of glycine and 0.1 kg of 3-mercaptopropyltrimethoxysilane to 10 kg of silica sol (average particle size is 60 nm, solid content is 40 wt%), stir and mix well to obtain dispersion A; Step S2: Add 0.1 kg of hydrogen peroxide (mass percentage concentration is 30%) to dispersion A, and then carry out heat treatment under stirring. The heating temperature is 50 °C and the heating time is 20 min to obtain modified silica hydrosol; Step S3: Take 2500 g of modified silica hydrosol, and successively add 300 g of 25% tetramethylammonium hydroxide aqueous solution, 50 g of polyacrylic acid with a weight average molecular weight of 2000, and 100 g of oxalic acid during stirring, and supplement deionized water to 10 kg to obtain a polishing composition.

[0072] Example 2 This example provides a preparation method of a polishing composition, including the following steps: Step S1: Add 0.001 kg of alanine and 0.2 kg of γ-(2,3-epoxypropoxy)propyltrimethoxysilane to 10 kg of silica sol (average particle size is 120 nm, solid content is 50 wt%), stir and mix well to obtain dispersion A; Step S2: Add 0.5 kg of potassium periodate to dispersion A, and then carry out heat treatment under stirring. The heating temperature is 40 °C and the heating time is 3 min to obtain modified silica hydrosol; Step S3: Take 8000 g of modified silica hydrosol, and successively add 50 g of propylenediamine, 1 g of polymethacrylic acid with a weight average molecular weight of 80000, and 5 g of potassium hydroxide during stirring, and supplement deionized water to 10 kg to obtain a polishing composition.

[0073] Example 3 This example provides a preparation method of a polishing composition, including the following steps: Step S1: Add 0.01 kg of valine and 0.01 kg of γ-methacryloxypropyltrichlorosilane to 10 kg of silica sol (average particle size is 30 nm, solid content is 10 wt%), stir and mix well to obtain dispersion A; Step S2: Add 0.01 kg of potassium periodate to dispersion A, and then carry out heat treatment under stirring. The heating temperature is 45 °C and the heating time is 10 min to obtain modified silica hydrosol; Step S3: Take 500 g of modified silica hydrosol, and successively add 100 g of piperazine, 100 g of anionic polyacrylamide with a weight average molecular weight of 5000000, and 50 g of sodium hydroxide during stirring, and supplement deionized water to 10 kg to obtain a polishing composition.

[0074] Example 4 This example provides a preparation method of a polishing composition, which includes the following steps: Step S1: Add 0.2 kg of leucine and 0.001 kg of isocyanatopropyltriethoxysilane to 10 kg of silica sol (average particle size is 60 nm, solid content is 40 wt%), stir and mix thoroughly to obtain dispersion liquid A; Step S2: Add 0.2 kg of hypochlorous acid to dispersion liquid A, and then perform heat treatment under stirring. The heating temperature is 60 °C, and the heating time is 30 min to obtain modified silica hydrosol; Step S3: Take 1000 g of modified silica hydrosol, and sequentially add 1000 g of guanidine hydrochloride, 10 g of polystyrenesulfonic acid with a weight average molecular weight of 10000, and 200 g of acrylic acid during stirring, and supplement ionized water to 10 kg to obtain the polishing composition.

[0075] Example 5 This example provides a preparation method of a polishing composition, which includes the following steps: Step S1: Add 0.5 kg of proline and 0.5 kg of γ-methacryloxypropyltrimethoxysilane to 10 kg of silica sol (average particle size is 60 nm, solid content is 40 wt%), stir and mix thoroughly to obtain dispersion liquid A; Step S2: Add 0.001 kg of potassium dichromate to dispersion liquid A, and then perform heat treatment under stirring. The heating temperature is 70 °C, and the heating time is 60 min to obtain modified silica hydrosol; Step S3: Take 4000 g of modified silica hydrosol, and sequentially add 500 g of 35% aqueous solution of tetraethylammonium hydroxide, 5 g of polystyrenesulfonic acid with a weight average molecular weight of 10000, and 500 g of tartaric acid during stirring, and supplement ionized water to 10 kg to obtain the polishing composition.

[0076] Comparative Example 1 This comparative example is basically the same as Example 1, except that in Step S1, 3-mercaptopropyltrimethoxysilane is not added to the silica sol.

[0077] Comparative Example 2 This comparative example is basically the same as Example 1, except that in Step S2, hydrogen peroxide is not added to dispersion liquid A.

[0078] Comparative Example 3 This comparative example is basically the same as Example 1, except that in Step S1, glycine is not added to the silica sol.

[0079] Comparative Example 4 This comparative example is basically the same as Example 1, except that in step S1, the same mass of malonic acid is used instead of glycine.

[0080] Comparative Example 5 This comparative example is substantially the same as Example 1, except that, in step S1, γ-aminopropyltrimethoxysilane of the same mass is used instead of 3-mercaptopropyltrimethoxysilane.

[0081] Comparative Example 6 This comparative example is basically the same as Example 1, except that the treatment temperature of step S2 is different. Specifically, in this comparative example, step S2 is adjusted as follows: 0.2 kg of hypochlorous acid is added to dispersion A, and then stirred at room temperature (25°C) for 30 minutes to obtain a modified silica hydrosol.

[0082] Comparative Example 7 This comparative example is basically the same as Example 1, except that in step S2, the heating temperature is adjusted to 80°C.

[0083] Comparative Example 8 This comparative example is basically the same as Example 1, except that no polyacrylic acid is added in step S3.

[0084] Comparative Example 9 This comparative example is basically the same as Example 1, except that, in step S3, cationic polyacrylamide with a weight average molecular weight of 5,000,000 is used instead of polyacrylic acid with a weight average molecular weight of 2,000.

[0085] Comparative Example 10 This comparative example provides a method for preparing a polishing composition, comprising the following steps: Step S1: Add 0.1 kg of 3-mercaptopropyltrimethoxysilane to 10 kg of silica sol (60 nm, 40 wt%) and stir thoroughly to obtain dispersion A; Step S2: 0.1 kg of hydrogen peroxide (mass percentage concentration is 30%) was added to the dispersion A, and then heated under stirring at 50°C for 20 minutes to obtain a modified silica hydrosol; Step S3: Take 2500g of modified silica hydrosol, and add 0.1kg of glycine, 300g of 25% by mass tetramethylammonium hydroxide solution, 50g of polyacrylic acid with a weight average molecular weight of 2000, and 100g of oxalic acid in sequence while stirring, and add ionized water to 10kg to obtain a polishing composition.

[0086] Test Case To verify the polishing effect of the polishing composition of the present application, silicon wafer substrates of the same batch (crystal orientation is P100, resistivity is 1 - 100 Ω·CM) are divided into several groups, and then rough polishing, medium polishing, and fine polishing processes are carried out in sequence. The polishing compositions of each example and comparative example are used for medium polishing of each group of silicon wafer substrate materials, and can be diluted with deionized water in different ratios according to needs before use. In this experiment, the polishing compositions of the examples and comparative examples are diluted with deionized water at a mass ratio of 1:30 before use. The process parameters of rough polishing, medium polishing, and fine polishing are shown in Table 1 and Table 2. Among them, the rough polishing liquid in the rough polishing process is all Glanzox 1306 produced by Fujimi Corporation of Japan, with a dilution ratio of 30X, and the fine polishing liquid in the fine polishing process is all Glanzox 3108 produced by Fujimi Corporation of Japan, with a dilution ratio of 30X.

[0087] Table 1 Rough Polishing and Medium Polishing Test Processes and Parameters

[0088] Table 2 Fine Polishing Test Processes and Parameters

[0089] The particle residues on the surface of the silicon wafers after fine polishing and cleaning are tested using SP5 produced by KLA Corporation, and only the DCN defects of 40 nm and above on the surface of each wafer after cleaning are counted. The cleaning is carried out using a standard RCA solution. The formulation of the SC-1 solution is as follows: ammonia water: 30% hydrogen peroxide: water = 1:1:6 (volume ratio). The formulation of the SC-2 solution is as follows: hydrogen chloride: 30% hydrogen peroxide: water = 1:1:7 (volume ratio). The number of particle residues of 40 nm and above on the silicon wafer surface is recorded as the number of DCN defects, and the results are shown in Table 3.

[0090] Table 3 Polishing Performance Test Results of the Polishing Composition

[0091] From the above data comparison, it can be seen that by using the silicon wafer polishing composition of the present invention, the DCN defects on the surface of the silicon wafer after polishing can be significantly reduced. The number of DCN defects on the silicon wafers after polishing in Examples 1-5 is less than 50. Compared with Comparative Examples 1-10, it has significant advantages. By comparing Example 1 with Comparative Examples 1-3, it can be seen that in Example 1, the DCN defects on the surface of the silicon wafer can be effectively reduced only by the synergistic addition of a silane coupling agent, an amino acid, and an oxidant. From the comparison between Example 1 and Comparative Example 4, it can be seen that using malonic acid instead of an amino acid to treat the silica hydrosol in Comparative Example 4 cannot effectively reduce the DCN defects on the surface of the silicon wafer. From the comparison between Example 1 and Comparative Example 5, it can be seen that in Example 1, by treating the silica hydrosol with a silane coupling agent containing a first group such as a mercapto group and an epoxy group, the particle residue on the surface of the silicon wafer can be effectively reduced. From Example 1 and Comparative Examples 6 and 7, it can be seen that in Example 1, by controlling the heating temperature of the silica hydrosol treatment within an appropriate range, the particle residue on the surface of the silicon wafer can be significantly reduced.

[0092] Obviously, the above examples are only illustrations for clear explanation and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a polishing composition, characterized in that, It includes the following steps: Step S1: Mix silica sol, amino acid or its salt with a silane coupling agent containing a first group to obtain a dispersion; the first group is selected from one or more of a sulfur-containing group, an epoxy group, an isocyanate group, and an acyloxy group; Step S2: Mix the dispersion with an oxidizing agent and perform a heat treatment at a temperature of 40°C - 70°C to obtain a modified silica sol; Step S3: Mix the modified silica sol, an anionic water-soluble polymer, an organic base, and water to prepare a polishing composition.

2. The preparation method of the polishing composition according to claim 1, wherein Based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the silica sol is 85% - 99.8%; and / or, based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the amino acid or its salt is 0.009% - 5%; and / or, based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the silane coupling agent containing a first group is 0.009% - 5%; and / or, based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the oxidizing agent is 0.009% - 5%.

3. The preparation method of the polishing composition according to claim 2, wherein, Based on the total amount of the raw materials used for the modified silica sol, the mass percentage of the silica sol is 86% - 97.2%; and / or, based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the amino acid or its salt is 0.1% - 2%; and / or, based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the silane coupling agent containing a first group is 0.1% - 2%; and / or, based on the total mass of the raw materials used for the modified silica sol, the mass percentage of the oxidizing agent is 0.1% - 2%.

4. The preparation method of the polishing composition according to any one of claims 1-3, characterized in that, The temperature of the heat treatment is 45 - 60°C; and / or, the time of the heat treatment is 3 - 60 min; and / or, in Step S3, a step of adding a pH regulator is further included.

5. The preparation method of the polishing composition according to any one of claims 1-3, characterized in that, The particle size of the silica sol is 30 - 120 nm; and / or, the solid content of the silica sol is 10 wt% - 50 wt%; and / or, the amino acid is selected from one or more of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, and histidine; and / or, the sulfur-containing group is selected from one or more of a mercapto group, a disulfide group, and a tetrasulfide group; And / or, the silane coupling agent containing the first group is selected from at least one of 3-mercaptopropyltrimethoxysilane, bis-(3-triethoxysilylpropyl)tetrasulfide, bis-(3-triethoxysilylpropyl)disulfide, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, γ-(2,3-epoxypropoxy)propylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloxypropyltrichlorosilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, 3-isocyanatopropyltriethoxysilane, isocyanatopropyltrimethoxysilane; And / or, the oxidant is selected from at least one of hypochlorous acid and its salts, perchloric acid and its salts, Na2O2, K2O2, MgO2, CaO2, BaO2, hydrogen peroxide, permanganic acid and its salts, FeCl3, dichromic acid and its salts, periodic acid and its salts, oxygen, ozone; 6. The preparation method of the polishing composition according to claim 1, characterized in that, The mass ratio of the modified silica hydrosol to the anionic water-soluble polymer is 5 - 80:0.01 - 1; And / or, the mass ratio of the modified silica hydrosol to the organic base is 5 - 80:0.5 - 10; And / or, the mass ratio of the modified silica hydrosol to water is 5 - 80:9 - 95; 7. The preparation method of the polishing composition according to claim 6, wherein, The mass ratio of the modified silica hydrosol to the anionic water-soluble polymer is 10 - 40:0.1 - 1; And / or, the mass ratio of the modified silica hydrosol to the organic base is 10 - 40:1 - 5; And / or, the mass ratio of the modified silica hydrosol to water is 10 - 40:54 - 89; 8. The preparation method of the polishing composition according to any one of claims 1, 6 or 7, characterized in that, The organic base is selected from one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, propylenediamine, butylenediamine, hydroxyethyl ethylenediamine, diethylenetriamine, monoethanolamine, N-(2-aminoethyl)ethanolamine, hexamethylenediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, 1-(2-aminoethyl)piperazine, N-methylpiperazine, piperazine, imidazole, methylimidazole, 1,2,4-triazole, 4-amino-1,2,4-triazole, guanidine carbonate, guanidine hydrochloride, guanidine nitrate, tetramethylammonium hydroxide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium fluoride, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium fluoride; And / or, the anionic water-soluble polymer is selected from one or more of polyacrylic acid and its salts, polymethacrylic acid and its salts, anionic polyacrylamide and its salts, polyvinylsulfonic acid and its salts, polystyrenesulfonic acid and its salts; And / or, the weight-average molecular weight of the anionic water-soluble polymer is 2000 - 10000000; 9. A polishing composition prepared by the preparation method according to any one of claims 1 - 8.

10. Use of a polishing composition prepared by the preparation method according to any one of claims 1-8 in chemical mechanical polishing of silicon wafers.

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