Polishing composition, polishing method, and method for manufacturing semiconductor substrate

Abstract

To provide a means for improving the polishing speed of a workpiece (particularly silicon oxide) and reducing scratches on the surface of the polished workpiece (particularly silicon oxide).SOLUTION: A polishing composition contains abrasive particles having an average primary particle size of 1 nm or more and 150 nm or less, and a dispersing medium, and the agglomeration rate of the abrasive particles is 40% or more and less than 75%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition, a polishing method, and a method for producing a semiconductor substrate. [Background technology]

[0002] In recent years, with the trend toward multilayer wiring on semiconductor substrate surfaces, so-called chemical mechanical polishing (CMP) technology, which physically polishes and flattens semiconductor substrates, has come to be used in device manufacturing. CMP is a method of flattening the surface of an object to be polished (workpiece) such as a semiconductor substrate using a polishing composition (slurry) containing abrasive grains such as silica, alumina, or ceria, an anticorrosive agent, a surfactant, etc. The object to be polished (workpiece) can be a wiring or plug made of silicon, polysilicon, silicon oxide (SiO2), silicon dioxide containing carbon (SiOC), silicon nitride (SiN), metal, etc.

[0003] For example, Patent Document 1 discloses a polishing composition containing abrasive grains and at least one of polyacrylic acid and a polyacrylic acid derivative, and having an electrical conductivity of 2.0 mS / cm or more. According to Patent Document 1, it is possible to polish silicon oxide at a high polishing rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-56292 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technique described in Patent Document 1 still leaves room for improvement in terms of reducing scratches on the surface of the polished object.

[0006] Therefore, an object of the present invention is to provide a means for improving the polishing rate of an object to be polished (especially silicon oxide) and reducing scratches on the surface of the polished object to be polished (especially silicon oxide). [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by a polishing composition containing abrasive grains having an average primary particle size of 1 nm or more and 150 nm or less, and a dispersion medium, wherein the agglomeration rate of the abrasive grains is 40% or more and less than 75%, and have thus completed the present invention. [Effects of the Invention]

[0008] According to the present invention, a means can be provided that can improve the polishing rate of an object to be polished (especially silicon oxide) and reduce scratches on the surface of the polished object to be polished (especially silicon oxide). DETAILED DESCRIPTION OF THE INVENTION

[0009] According to one embodiment of the present invention, there is provided a polishing composition comprising abrasive grains having an average primary particle size of 1 nm or more and 150 nm or less, and a dispersion medium, wherein the agglomeration rate of the abrasive grains is 40% or more and less than 75%. The polishing composition of the present invention can improve the removal rate of an object to be polished (especially silicon oxide) and reduce scratches on the surface of the polished object to be polished (especially silicon oxide).

[0010] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments and can be modified in various ways within the scope of the claims. The embodiments described in this specification can be combined in any way to form other embodiments. Unless otherwise specified, in this specification, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20°C or higher and 25°C or lower) and a relative humidity of 40% RH or higher and 50% RH or lower.

[0011] [Abrasive grain] The polishing composition of the present invention contains abrasive grains, which have the function of mechanically polishing an object to be polished, thereby increasing the polishing rate of the object to be polished by the polishing composition.

[0012] The type of abrasive grain is not particularly limited, and examples thereof include metal oxides such as silica, alumina, zirconia, and titania. The abrasive grains can be used alone or in combination of two or more types. The abrasive grains may be commercially available products or synthetic products.

[0013] The type of abrasive grains is preferably silica, more preferably colloidal silica.Methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by either method can be suitably used as the abrasive grains of the present invention.However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method, which can be produced with high purity, is preferred.

[0014] Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by using a hydrolyzable silicon compound (e.g., an alkoxysilane or a derivative thereof) as a raw material and carrying out a hydrolysis-condensation reaction.

[0015] The shape of the abrasive grains is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and quadrangular prisms, cylinders, bale-shaped cylinders in which the center is bulged out more than the ends, doughnut-shaped discs with a central hole, plate-shaped discs, cocoon-shaped discs with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped discs with multiple protrusions on the surface, and rugby ball-shaped discs, and are not particularly limited.

[0016] The average primary particle size of the abrasive grains according to the present invention is 1 nm or more and 150 nm or less. If the average primary particle size of the abrasive grains is less than 1 nm, the polishing rate of the object to be polished (particularly silicon oxide) decreases. On the other hand, if the average primary particle size of the abrasive grains exceeds 150 nm, scratches on the surface of the polished object to be polished (particularly silicon oxide) increase. The average primary particle size of the abrasive grains is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, and particularly preferably 12 nm or more. As the average primary particle size of the abrasive grains increases, the polishing rate of the object to be polished using the polishing composition improves. Furthermore, the average primary particle size of the abrasive grains is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less. As the average primary particle size of the abrasive grains decreases, it becomes easier to obtain a surface with fewer defects by polishing using the polishing composition. That is, the average primary particle size of the abrasive grains is preferably 5 nm or more and 100 nm or less, more preferably 8 nm or more and 80 nm or less, even more preferably 10 nm or more and 60 nm or less, and particularly preferably 12 nm or more and 50 nm or less. The average primary particle size of the abrasive grains can be calculated, for example, based on the specific surface area (SA) of the abrasive grains calculated by the BET method, assuming that the abrasive grains are spherical. In this specification, the average primary particle size of the abrasive grains is the value measured by the method described in the Examples.

[0017] The average secondary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 25 nm or more. As the average secondary particle diameter of the abrasive grains increases, the resistance during polishing decreases, enabling stable polishing. The average secondary particle diameter of the abrasive grains is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and particularly preferably 100 nm or less. As the average secondary particle diameter of the abrasive grains decreases, the surface area per unit mass of the abrasive grains increases, increasing the frequency of contact with the workpiece to be polished and further improving the polishing rate. That is, the average secondary particle diameter of the abrasive grains is preferably 10 nm or more and 400 nm or less, more preferably 15 nm or more and 300 nm or less, even more preferably 20 nm or more and 200 nm or less, and particularly preferably 25 nm or more and 100 nm or less. The average secondary particle diameter of the abrasive grains can be measured, for example, by dynamic light scattering, such as laser diffraction scattering.

[0018] The average degree of association of the abrasive grains is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less. As the average degree of association of the abrasive grains decreases, defects can be further reduced. The average degree of association of the abrasive grains is also preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. This average degree of association is obtained by dividing the average secondary particle diameter of the abrasive grains by the average primary particle diameter. As the average degree of association of the abrasive grains increases, there is an advantageous effect of improving the polishing rate of the object to be polished with the polishing composition.

[0019] The upper limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, but is preferably less than 2.0, more preferably 1.8 or less, and even more preferably 1.5 or less. Within this range, defects on the surface of the object to be polished can be further reduced. The aspect ratio is the average value obtained by taking the smallest rectangle circumscribing the image of the abrasive grains using a scanning electron microscope and dividing the length of the long side of the rectangle by the length of the short side of the same rectangle, and can be determined using general image analysis software. The lower limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, but is preferably 1.0 or more, more preferably 1.2 or more.

[0020] In the particle size distribution of abrasive grains measured by laser diffraction scattering, the ratio of the particle diameter (D90) when the cumulative particle mass from the fine particle side reaches 90% of the total particle mass to the particle diameter (D10) when the cumulative particle mass from the fine particle side reaches 10% of the total particle mass of all particles, D90 / D10, is not particularly limited, but is preferably 1.1 or more, more preferably 1.4 or more, even more preferably 1.7 or more, and most preferably 2.0 or more.In addition, in the particle size distribution of abrasive grains in a polishing composition measured by laser diffraction scattering, the ratio of the particle diameter (D90) when the cumulative particle mass from the fine particle side reaches 90% of the total particle mass to the particle diameter (D10) when the cumulative particle mass from the fine particle side reaches 10% of the total particle mass of all particles, D90 / D10, is not particularly limited, but is preferably 3.0 or less, more preferably 2.5 or less.Within this range, defects on the surface of the object to be polished can be further reduced.

[0021] The size of the abrasive grains (average primary particle diameter, average secondary particle diameter, aspect ratio, D90 / D10, etc.) can be appropriately controlled by selecting the manufacturing method of the abrasive grains, etc.

[0022] <Abrasive grain agglomeration rate> The present invention is characterized in that the agglomeration rate of the abrasive grains is 40% or more and less than 75%. By using abrasive grains having an agglomeration rate in this range, the polishing rate of the object to be polished (particularly silicon oxide) can be improved and scratches on the surface of the polished object to be polished (particularly silicon oxide) can be reduced. If the agglomeration rate is less than 40%, the polishing rate of the object to be polished (particularly silicon oxide) decreases. On the other hand, if the agglomeration rate is 75% or more, scratches on the surface of the polished object to be polished (particularly silicon oxide) increase. The agglomeration rate is preferably 40% or more and 55% or less.

[0023] In this specification, the agglomeration rate of abrasive grains is a value measured by the following method: <Method for measuring aggregation rate> 1) 30.0 g of the sample polishing composition is weighed into a polypropylene container and the top lid is tightly closed. 2) Using a centrifuge, operate at 25°C and 15,000 rpm for 15 minutes. 3) The water in the upper part of the container is separated from the abrasive grains in the lower part by centrifugation, and the abrasive grains are compressed and settled to the bottom of the container (this is called cake): 4) The precipitated cake is dried in a dryer at 200°C for 24 hours, and the weight of the resulting solid is measured. 5) Separately, using an aqueous dispersion containing only abrasive grains, the weight of the solid matter after drying measured according to the above steps 1) to 4) is designated as (B), and the weight of the solid matter after drying measured using the sample polishing composition is designated as (A), and the agglomeration rate is calculated using the following formula (1).

[0024]

number

[0025] Although (A) and (B) may contain trace amounts of additives, the value calculated by formula (1) without taking this into consideration is the agglomeration rate of the abrasive grains. More specifically, it is measured by the method described in the Examples.

[0026] The agglomeration rate of the abrasive grains can be controlled by selecting the type and amount of inorganic salt and organic onium salt to be described later, filtering the polishing composition, adjusting the abrasive grain concentration, and the like.

[0027] In the polishing composition of the present invention, the abrasive grains preferably have a negative zeta potential. Here, the "zeta (ζ) potential" refers to the potential difference that occurs at the interface between a solid and a liquid in contact with each other when they undergo relative motion.

[0028] The zeta potential of the abrasive grains in the polishing composition of the present invention is preferably -60 mV or more and -10 mV or less, more preferably -50 mV or more and -10 mV or less, even more preferably -40 mV or more and -15 mV or less, and particularly preferably more than -35 mV and -15 mV or less. When the abrasive grains have a zeta potential in this range, the polishing rate of the object to be polished can be further improved. Here, the zeta potential of the abrasive grains in the polishing composition is a value measured by the method described in the Examples. The zeta potential of the abrasive grains can be adjusted by the amount of anionic groups (particularly organic acid groups) contained in the abrasive grains, the pH of the polishing composition, etc., as described below.

[0029] In some embodiments of the present invention, the colloidal silica contained in the polishing composition is preferably anion-modified colloidal silica (anion-modified colloidal silica), more preferably colloidal silica having an organic acid immobilized on its surface. Colloidal silica having an organic acid immobilized on its surface tends to have a higher absolute value of zeta potential in the polishing composition than ordinary colloidal silica having no organic acid immobilized on its surface. Therefore, the zeta potential of the colloidal silica in the polishing composition can be easily adjusted to a negative value (for example, in the range of -40 mV to -15 mV).

[0030] Preferred examples of colloidal silica having an organic acid fixed to its surface include colloidal silica having an organic acid group such as a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, or an aluminic acid group fixed to its surface. Of these, from the viewpoint of ease of production, colloidal silica having a sulfonic acid or a carboxylic acid fixed to its surface is preferred, and colloidal silica having a sulfonic acid fixed to its surface is more preferred.

[0031] Immobilization of an organic acid on the surface of colloidal silica cannot be achieved by simply coexisting colloidal silica with an organic acid. For example, immobilization of sulfonic acid, a type of organic acid, on colloidal silica can be achieved by the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups," Chem. Commun. 246-247 (2003). Specifically, colloidal silica with sulfonic acid immobilized on its surface (sulfonic acid-modified colloidal silica, sulfonic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to colloidal silica and then oxidizing the thiol group with hydrogen peroxide.

[0032] Alternatively, if a carboxylic acid, which is a type of organic acid, is to be immobilized on colloidal silica, this can be achieved, for example, by the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel," Chemistry Letters, 3, 228-229 (2000). Specifically, a silane coupling agent containing a photoreactive 2-nitrobenzyl ester is coupled to colloidal silica, followed by light irradiation, to obtain colloidal silica with a carboxylic acid immobilized on its surface (carboxylic acid-modified colloidal silica, carboxylic acid-modified colloidal silica).

[0033] The concentration (content) of the abrasive grains is not particularly limited, but is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, even more preferably 1% by mass or more, even more preferably more than 1% by mass, and particularly preferably 1.5% by mass or more, based on the total mass of the polishing composition. The upper limit of the concentration (content) of the abrasive grains is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the total mass of the polishing composition. That is, the concentration (content) of the abrasive grains is preferably 0.5% by mass or more and 20% by mass or less, more preferably 0.8% by mass or more and 20% by mass or less, even more preferably 1% by mass or more and 15% by mass or less, even more preferably more than 1% by mass but 10% by mass or less, and particularly preferably 1.5% by mass or more and 5% by mass or less, based on the total mass of the polishing composition. Within this range, the polishing rate can be improved while keeping costs down. When the polishing composition contains two or more types of abrasive grains, the concentration (content) of the abrasive grains means the total amount thereof.

[0034] [Inorganic salts] The polishing composition of the present invention preferably contains an inorganic salt. The inorganic salt has the function of reducing scratches on the surface of the polished object (particularly silicon oxide). The inorganic salt also has the function of increasing the electrical conductivity of the polishing composition, thereby further improving the polishing rate of the object (particularly silicon oxide). Furthermore, the inorganic salt has the function of controlling the agglomeration rate of abrasive grains.

[0035] Examples of inorganic salts include inorganic salts composed of the following cations and anions. Examples of cations include alkali metal ions such as lithium ion, sodium ion, and potassium ion; alkaline earth metal ions such as magnesium ion, calcium ion, and strontium ion; polyatomic ions such as ammonium ion; and complex ions. Examples of anions include halide ions (fluoride ion, chloride ion, bromide ion, iodide ion, etc.), oxoacid ions (borate ion, carbonate ion, nitrate ion, nitrite ion, metasilicate ion, phosphate ion, monohydrogen phosphate ion, dihydrogen phosphate ion, phosphonate ion, monohydrogen phosphonate ion, phosphinate ion, sulfate ion, sulfonate ion, sulfite ion, thiosulfate ion, chromate ion, dichromate ion, permanganate ion, etc.), thiocyanate ion, cyanate ion, and sulfamate ion.

[0036] calcium salts such as calcium chloride, calcium bromide, calcium carbonate, lithium nitrate, and calcium thiocyanate; iron salts such as iron nitrate and iron thiocyanate; potassium salts such as potassium chloride, potassium bromide, potassium nitrate, potassium sulfate, potassium thiocyanate, potassium sulfamate, potassium phosphate, potassium dihydrogen phosphate, potassium monohydrogen phosphate, and potassium monohydrogen phosphonate; sodium salts such as sodium chloride, sodium bromide, sodium nitrate, sodium sulfate, and sodium thiocyanate; zinc salts such as zinc chloride, zinc nitrate, and zinc thiocyanate; magnesium salts such as magnesium nitrate, magnesium sulfate, and magnesium thiocyanate; strontium salts such as strontium nitrate and strontium thiocyanate; and ammonium salts such as ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, ammonium phosphonate, ammonium monohydrogen phosphonate, ammonium sulfate, ammonium thiocyanate, and ammonium sulfamate. These inorganic salts can be used singly or in combination of two or more. Furthermore, the inorganic salts to be used may be commercially available products or synthetic products.

[0037] Among these, from the viewpoint of further exerting the effects of the present invention, at least one of an ammonium salt of an inorganic acid and a potassium salt of an inorganic acid is preferred. The inorganic acid is preferably sulfuric acid, nitric acid, or carbonic acid. Therefore, the inorganic salt is more preferably at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate, and even more preferably ammonium sulfate.

[0038] The concentration (content) of inorganic salt in the polishing composition is not particularly limited, but in the case of a polishing composition that is used as a polishing liquid for polishing an object to be polished as is, the lower limit of the concentration (content) of inorganic salt in the polishing composition is preferably 0.005 mass% (50 mass ppm) or more, more preferably 0.01 mass% (100 mass ppm) or more, even more preferably 0.1 mass% (1000 mass ppm) or more, and particularly preferably 0.5 mass% (5000 mass ppm) or more, based on the total mass of the polishing composition. In addition, the upper limit of the concentration (content) of inorganic salt in the polishing composition is preferably 2.0 mass% (20000 mass ppm) or less, more preferably 1.5 mass% (15000 mass ppm) or less, even more preferably 1.3 mass% (13000 mass ppm) or less, and particularly preferably 1.0 mass% (10000 mass ppm) or less, based on the total mass of the polishing composition.

[0039] That is, the concentration (content) of the inorganic salt is preferably 0.005 mass% (50 mass ppm) or more and 2.0 mass% (20,000 mass ppm) or less, more preferably 0.01 mass% (100 mass ppm) or more and 1.5 mass% (15,000 mass ppm) or less, even more preferably 0.1 mass% (1,000 mass ppm) or more and 1.3 mass% (13,000 mass ppm) or less, and particularly preferably 0.5 mass% (5,000 mass ppm) or more and 1.0 mass% (10,000 mass ppm) or less, relative to the total mass of the polishing composition.

[0040] When the polishing composition contains two or more inorganic salts, the concentration (content) of the inorganic salts means the total amount thereof.

[0041] [Organic onium salts] The polishing composition of the present invention preferably contains an organic onium salt. The organic onium salt has the function of reducing scratches on the surface of the polished object (particularly silicon oxide). In addition, the organic onium salt has the function of controlling the agglomeration rate of abrasive grains. The organic onium salt used in the present invention is preferably at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2.

[0042] [ka]

[0043] In the above chemical formula 1 and chemical formula 2, R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A - and X - are each independently a monovalent anion.

[0044] When an organic onium salt having an alkyl group with 5 or more carbon atoms is used, scratches on the surface of the polished object may increase.

[0045] R in the above Chemical Formula 1 and Chemical Formula 2 1 ~R 8 Specific examples of the unsubstituted alkyl group having 1 to 4 carbon atoms used in the above include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group. From the viewpoint of further exerting the effects of the present invention, an unsubstituted alkyl group having 2 to 4 carbon atoms, such as an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, or a tert-butyl group, is preferred.

[0046] A in the above chemical formula 1 and chemical formula 2 - and X -Examples of the monovalent anion used in are not particularly limited, but include halide ions such as fluoride ion, chloride ion, bromide ion, and iodide ion; hydroxide ion; and organic acid ions such as benzoate ion. The monovalent anion may be used alone or in combination of two or more. From the viewpoint of further exerting the effects of the present invention, A in the above chemical formula 1 and chemical formula 2 is preferably used. - and X - is a hydroxide ion (OH - ) is preferred.

[0047] More specific examples of the tetraalkylammonium salt represented by the above chemical formula 1 include, for example, tetramethylammonium fluoride, trimethylethylammonium fluoride, dimethyldiethylammonium fluoride, methyltriethylammonium fluoride, tetraethylammonium fluoride, trimethyl-n-propylammonium fluoride, trimethylisopropylammonium fluoride, dimethylethyl-n-propylammonium fluoride, dimethylethylisopropylammonium fluoride, methyldiethyl-n-propylammonium fluoride, methyldiethylisopropylammonium fluoride, triethylisopropylammonium fluoride, triethyl-n-propylammonium fluoride, tetra-n-propylammonium fluoride, tetraisopropylammonium fluoride, tetra-n-butylammonium fluoride, ammonium fluoride, tetra tert-butylammonium fluoride; tetramethylammonium chloride, trimethylethylammonium chloride, dimethyldiethylammonium chloride, methyltriethylammonium chloride, tetraethylammonium chloride, trimethyl n-propylammonium chloride, trimethylisopropylammonium chloride, dimethylethyl n-propylammonium chloride, dimethylethylisopropylammonium chloride, methyldiethyl n-propylammonium chloride, methyldiethylisopropylammonium chloride, triethylisopropylammonium chloride, triethyln-propylammonium chloride, tetra n-propylammonium chloride, tetraisopropylammonium chloride, tetra n-butylammonium chloride, tetra tert-butylammonium chloride;Tetramethylammonium bromide, trimethylethylammonium bromide, dimethyldiethylammonium bromide, methyltriethylammonium bromide, tetraethylammonium bromide, trimethyl n-propylammonium bromide, trimethylisopropylammonium bromide, dimethylethyl n-propylammonium bromide, dimethylethylisopropylammonium bromide, methyldiethyl n-propylammonium bromide, methyldiethylisopropylammonium bromide, triethylisopropylammonium bromide, triethyl n-propylammonium bromide, tetra n-propylammonium bromide, tetraisopropylammonium bromide, tetra n-butylammonium bromide, tetra tert-butylammonium bromide; Tetramethylammonium iodide, trimethylethylammonium iodide, dimethyldiethylammonium iodide, methyltriethylammonium iodide, tetraethylammonium iodide, trimethyl n-propylammonium iodide, trimethylisopropylammonium iodide, dimethylethyl n-propylammonium iodide, dimethylethylisopropylammonium iodide, methyldiethyl n-propylammonium iodide, methyldiethylisopropylammonium iodide, triethylisopropylammonium iodide, triethyl n-propylammonium iodide, tetra n-propylammonium iodide, tetraisopropylammonium iodide, tetra n-butylammonium iodide, tetra tert-butylammonium iodide;Tetramethylammonium hydroxide, trimethylethylammonium hydroxide, dimethyldiethylammonium hydroxide, methyltriethylammonium hydroxide, tetraethylammonium hydroxide, trimethyl n-propylammonium hydroxide, trimethylisopropylammonium hydroxide, dimethylethyl n-propylammonium hydroxide, dimethylethylisopropylammonium hydroxide, methyldiethyl n-propylammonium hydroxide, methyldiethylisopropylammonium hydroxide, triethylisopropylammonium hydroxide, triethyln-propylammonium hydroxide, tetran-propylammonium hydroxide, tetraisopropylammonium hydroxide, tetran-n-butylammonium hydroxide, tetratert-butylammonium hydroxide; tetramethylammonium hydroxide methylammonium benzoate, trimethylethylammonium benzoate, dimethyldiethylammonium benzoate, methyltriethylammonium benzoate, tetraethylammonium benzoate, trimethyl n-propylammonium benzoate, trimethylisopropylammonium benzoate, dimethylethyl n-propylammonium benzoate, dimethylethylisopropylammonium benzoate, methyldiethyl n-propylammonium benzoate, methyldiethylisopropylammonium benzoate, triethylisopropylammonium benzoate, triethyl n-propylammonium benzoate, tetra n-propylammonium benzoate, tetraisopropylammonium benzoate, tetra n-butylammonium benzoate, tetra tert-butylammonium benzoate; and the like.

[0048] More specific examples of the tetraalkylphosphonium salt represented by the above chemical formula 2 include, for example, tetramethylphosphonium fluoride, trimethylethylphosphonium fluoride, dimethyldiethylphosphonium fluoride, methyltriethylphosphonium fluoride, tetraethylphosphonium fluoride, trimethyl n-propylphosphonium fluoride, trimethylisopropylphosphonium fluoride, dimethylethyl n-propylphosphonium fluoride, dimethylethylisopropylphosphonium fluoride, methyldiethyl n-propylphosphonium fluoride, methyldiethylisopropylphosphonium fluoride, triethylisopropylphosphonium fluoride, triethyln-propylphosphonium fluoride, tetran-propylphosphonium fluoride, tetraisopropylphosphonium fluoride, tetran-butylphosphonium fluoride, fluoride, tetra tert-butylphosphonium fluoride; tetramethylphosphonium chloride, trimethylethylphosphonium chloride, dimethyldiethylphosphonium chloride, methyltriethylphosphonium chloride, tetraethylphosphonium chloride, trimethyl n-propylphosphonium chloride, trimethylisopropylphosphonium chloride, dimethylethyl n-propylphosphonium chloride, dimethylethylisopropylphosphonium chloride, methyldiethyl n-propylphosphonium chloride, methyldiethylisopropylphosphonium chloride, triethylisopropylphosphonium chloride, triethyln-propylphosphonium chloride, tetran-propylphosphonium chloride, tetraisopropylphosphonium chloride, tetran-butylphosphonium chloride, tetratert-butylphosphonium chloride;Tetramethylphosphonium bromide, trimethylethylphosphonium bromide, dimethyldiethylphosphonium bromide, methyltriethylphosphonium bromide, tetraethylphosphonium bromide, trimethyl n-propylphosphonium bromide, trimethylisopropylphosphonium bromide, dimethylethyl n-propylphosphonium bromide, dimethylethylisopropylphosphonium bromide, methyldiethyl n-propylphosphonium bromide, methyldiethylisopropylphosphonium bromide, triethylisopropylphosphonium bromide, triethyln-propylphosphonium bromide, tetran-propylphosphonium bromide, tetraisopropylphosphonium bromide, tetran-butylphosphonium bromide, tetratert-butylphosphonium bromide; Tetramethylphosphonium iodide, trimethylethylphosphonium iodide, dimethyldiethylphosphonium iodide, methyltriethylphosphonium iodide, tetraethylphosphonium iodide, trimethyl n-propylphosphonium iodide, trimethylisopropylphosphonium iodide, dimethylethyl n-propylphosphonium iodide, dimethylethylisopropylphosphonium iodide, methyldiethyl n-propylphosphonium iodide, methyldiethylisopropylphosphonium iodide, triethylisopropylphosphonium iodide, triethyln-propylphosphonium iodide, tetran-propylphosphonium iodide, tetraisopropylphosphonium iodide, tetran-butylphosphonium iodide, tetratert-butylphosphonium iodide;Tetramethylphosphonium hydroxide, trimethylethylphosphonium hydroxide, dimethyldiethylphosphonium hydroxide, methyltriethylphosphonium hydroxide, tetraethylphosphonium hydroxide, trimethyl n-propylphosphonium hydroxide, trimethylisopropylphosphonium hydroxide, dimethylethyl n-propylphosphonium hydroxide, dimethylethylisopropylphosphonium hydroxide, methyldiethyl n-propylphosphonium hydroxide, methyldiethylisopropylphosphonium hydroxide, triethylisopropylphosphonium hydroxide, triethyln-propylphosphonium hydroxide, tetran-propylphosphonium hydroxide, tetraisopropylphosphonium hydroxide, tetran-butylphosphonium hydroxide, tetratert-butylphosphonium hydroxide; tetramethyl trimethyl phosphonium benzoate, trimethylethyl phosphonium benzoate, dimethyldiethyl phosphonium benzoate, methyltriethyl phosphonium benzoate, tetraethyl phosphonium benzoate, trimethyl n-propyl phosphonium benzoate, trimethylisopropyl phosphonium benzoate, dimethylethyl n-propyl phosphonium benzoate, dimethylethyl isopropyl phosphonium benzoate, methyldiethyl n-propyl phosphonium benzoate, methyldiethylisopropyl phosphonium benzoate, triethylisopropyl phosphonium benzoate, triethyl n-propyl phosphonium benzoate, tetra n-propyl phosphonium benzoate, tetraisopropyl phosphonium benzoate, tetra n-butyl phosphonium benzoate, tetra tert-butyl ammonium benzoate; and the like.

[0049] These organic onium salts can be used singly or in combination of two or more. The organic onium salts to be used may be commercially available products or synthetic products.

[0050] Among these organic onium salts, the tetraalkylammonium salts represented by the above chemical formula 1 are preferred, from the viewpoint of more easily exerting the effects of the present invention, and at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide is more preferred.

[0051] The lower limit of the concentration (content) of organic onium salt in polishing composition is preferably 0.001 mass% (10 mass ppm) or more, more preferably 0.005 mass% (50 mass ppm) or more, even more preferably 0.007 mass% (70 mass ppm) or more, particularly preferably 0.01 mass% (100 mass ppm) or more.In addition, the upper limit of the concentration (content) of organic onium salt in polishing composition is preferably 0.3 mass% (3000 mass ppm) or less, more preferably 0.1 mass% (1000 mass ppm) or less, even more preferably 0.07 mass% (700 mass ppm) or less, particularly preferably 0.05 mass% (500 mass ppm) or less. That is, the concentration (content) of the organic onium salt in the polishing composition is preferably 0.001 mass% (10 mass ppm) or more and 0.3 mass% (3000 mass ppm) or less, more preferably 0.005 mass% (50 mass ppm) or more and 0.1 mass% (1000 mass ppm) or less, even more preferably 0.007 mass% (70 mass ppm) or more and 0.07 mass% (700 mass ppm) or less, and particularly preferably 0.01 mass% (100 mass ppm) or more and 0.05 mass% (500 mass ppm) or less.

[0052] When the polishing composition contains two or more kinds of organic onium salts, the concentration (content) of the organic onium salts means the total amount thereof.

[0053] [pH and pH adjusters] The pH of the polishing composition of the present invention is not particularly limited, but is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more.Furthermore, the pH is preferably 9.0 or less, more preferably 7.0 or less, even more preferably less than 7.0, even more preferably 5.0 or less, and particularly preferably 3.5 or less.That is, the pH of the polishing composition of the present invention is preferably 1.0 or more and 9.0 or less, more preferably 1.5 or more and 7.0 or less, even more preferably 1.5 or more and 7.0 or less, even more preferably 1.5 or more and 5.0 or less, and particularly preferably 2.0 or more and 3.5 or less.

[0054] The inorganic salt and organic onium salt that can be contained in the polishing composition of the present invention can act as a pH adjuster for adjusting the pH of the polishing composition, but may further contain a separate pH adjuster according to the target pH. Such a pH adjuster may be either an acid or a base, and may also be either an inorganic compound or an organic compound. The pH adjuster may be used alone or in combination of two or more kinds.

[0055] Specific examples of acids that can be used as pH adjusters include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, and phenoxyacetic acid.

[0056] Examples of bases that can be used as pH adjusters include amines such as aliphatic amines and aromatic amines, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, hydroxides of Group 2 elements, and ammonia.

[0057] The amount of pH adjuster to be added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH. The pH of the polishing composition can be measured, for example, with a pH meter, specifically by the method described in the Examples.

[0058] [Dispersion medium] The polishing composition of the present invention contains a dispersion medium. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a more preferred embodiment of the present invention, the dispersion medium contains water. According to an even more preferred embodiment of the present invention, the dispersion medium consists essentially of water. Note that the above term "substantially" means that a dispersion medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0059] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium be water that contains as few impurities as possible. Specifically, pure water or ultrapure water that has had impurity ions removed using an ion exchange resin and then passed through a filter to remove foreign matter, or distilled water, is more preferable.

[0060] [Electrical Conductivity of Polishing Composition] The electrical conductivity (EC) of the polishing composition of the present invention is not particularly limited, but is preferably 1 mS / cm or more, more preferably 2 mS / cm or more. The electrical conductivity (EC) of the polishing composition of the present invention is preferably 25 mS / cm or less, more preferably 20 mS / cm or less. That is, the electrical conductivity (EC) of the polishing composition of the present invention is preferably 1 mS / cm or more and 25 mS / cm or less, more preferably 2 mS / cm or more and 20 mS / cm or less. When the electrical conductivity (EC) of the polishing composition is within this range, the repulsion between abrasive grains can be appropriately adjusted, ensuring stability. The electrical conductivity of the polishing composition can be adjusted by the type and amount of a pH adjuster, etc. The electrical conductivity can be measured by the method described in the Examples.

[0061] [Other ingredients] The polishing composition of the present invention may further contain other components such as a water-soluble polymer, a complexing agent, a metal corrosion inhibitor, a preservative, an antifungal agent, a reducing agent, and a surfactant, as necessary. The preservative and the antifungal agent, which are preferred components, will be described below. The oxidizing agent will also be described.

[0062] Other preferred ingredients, such as preservatives and antifungal agents, as well as oxidizing agents, will be described below.

[0063] (preservatives and fungicides) Examples of preservatives and antifungal agents that can be added to the polishing composition of the present invention include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, paraoxybenzoic acid esters, and phenoxyethanol. These preservatives and antifungal agents may be used alone or in combination of two or more.

[0064] (oxidizing agent) The polishing composition of the present invention preferably contains substantially no oxidizing agent. If an oxidizing agent is contained in the polishing composition, the surface of the object to be polished may be oxidized to form an oxide film, which may result in a prolonged polishing time. Specific examples of oxidizing agents include hydrogen peroxide (H2O2), sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. The term "substantially free of oxidizing agent" means that the polishing composition does not contain an oxidizing agent, at least intentionally. Therefore, a polishing composition that inevitably contains a trace amount of oxidizing agent due to raw materials, manufacturing method, etc., is encompassed by the concept of a polishing composition that is substantially free of oxidizing agent. For example, the concentration (content) of the oxidizing agent in the polishing composition is preferably 0.01% by mass (100 ppm by mass) or less, more preferably less than 0.01% by mass (100 ppm by mass), and even more preferably 0.005% by mass (50 ppm by mass) or less. The lower limit of the concentration (content) of the oxidizing agent is preferably 0% by mass or more, and more preferably 0.0005% by mass (5 ppm by mass) or more.

[0065] [Form of polishing composition] The polishing composition of the present invention is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition and used to polish the object. The polishing composition of the present invention may be used as a polishing liquid after dilution (typically with water), or may be used as a polishing liquid as is. That is, the concept of the polishing composition of the present invention encompasses both a polishing composition (working slurry) that is supplied to a polishing object and used to polish the object, and a concentrated liquid (raw solution of working slurry) that is diluted and used for polishing. The concentration ratio of the concentrated liquid can be, for example, about 2 to 100 times on a volume basis, and is usually about 3 to 50 times.

[0066] [Polished object] The object to be polished according to the present invention is not particularly limited, and examples thereof include single crystal silicon, polycrystalline silicon (polysilicon), polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon, amorphous silicon doped with n-type or p-type impurities, silicon oxide, silicon nitride, silicon carbonitride (SiCN), metals, SiGe, and carbon-containing materials.

[0067] Examples of polishing objects containing silicon oxide include TEOS-type silicon oxide films (hereinafter simply referred to as "TEOS" or "TEOS films") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0068] Examples of metals include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0069] Examples of carbon-containing materials include amorphous carbon, spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, and graphene.

[0070] The object to be polished may be a commercially available product or may be produced by a known method.

[0071] Among these, an object to be polished containing silicon oxide is preferred. Therefore, according to a preferred embodiment of the present invention, the polishing composition is used for polishing an object to be polished containing silicon oxide.

[0072] [Method for producing polishing composition] The method for producing the polishing composition according to this embodiment is not particularly limited, and the composition can be obtained, for example, by stirring and mixing abrasive grains, inorganic salts, organic onium salts, and other additives as needed. The details of each component are as described above.

[0073] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C. Heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0074] [Polishing method and semiconductor substrate manufacturing method] As described above, the polishing composition of this embodiment is particularly suitable for use in polishing an object having silicon oxide. Thus, the present invention provides a polishing method for polishing an object containing silicon oxide with the polishing composition of this embodiment. The present invention also provides a method for producing a semiconductor substrate, comprising polishing a semiconductor substrate containing silicon oxide by the polishing method.

[0075] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0076] The polishing pad may be made of any material, including ordinary nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0077] Regarding the polishing conditions, for example, the rotation speed of the polishing table (platen) and carrier (head) is 10 rpm (0.17 s -1 ) or more 500rpm (8.33s -1 The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.45 kPa) or more and 10 psi (68.9 kPa) or less.

[0078] The method for supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the polishing composition using a pump, etc. There is no limit to the amount of the polishing composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0079] The polishing composition according to this embodiment may be a one-component type or a multi-component type such as a two-component type. The polishing composition according to the present invention may be prepared by diluting the stock solution of the polishing composition with a diluent such as water, for example, by a volume ratio of 2 to 100 times, usually 3 to 50 times.

[0080] [Number of scratches] As described above, the polishing composition of the present invention can reduce scratches on the surface of an object to be polished.

[0081] In the present invention, the fewer the number of scratches on the surface of the polished object, the better. Specifically, a scratch number of 25 or less is practical, preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, and particularly preferably less than 10. In this specification, the scratch number is the value measured by the method described in the examples.

[0082] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0083] The present invention encompasses the following aspects and configurations: 1. A polishing composition comprising abrasive grains having an average primary particle size of 1 nm or more and 150 nm or less and a dispersion medium, wherein the agglomeration rate of the abrasive grains is 40% or more and less than 75%: 2. The polishing composition according to 1 above, wherein the agglomeration rate of the abrasive grains is 40% or more and 55% or less. 3. The polishing composition according to 1. or 2. above, further comprising an inorganic salt: 4. The polishing composition according to 3 above, wherein the inorganic salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate. 5. The polishing composition according to any one of 1. to 4. above, further containing an organic onium salt: 6. The polishing composition according to 5 above, wherein the organic onium salt is at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2:

[0084] [ka]

[0085] In the above Chemical Formula 1 and Chemical Formula 2, R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A - and X - are each independently a monovalent anion: 7. The polishing composition according to 6. above, wherein the organic onium salt is a tetraalkylammonium salt represented by Chemical Formula 1. 8. A in the above Chemical Formula 1 and Chemical Formula 2 - and X - 8. The polishing composition according to 6. or 7. above, wherein 9. The polishing composition according to any one of 6. to 8. above, wherein the tetraalkylammonium salt represented by Chemical Formula 1 is at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide. 10. The polishing composition according to any one of 1. to 9. above, wherein the abrasive grains in the polishing composition have a negative zeta potential. 11. The polishing composition according to 10 above, wherein the abrasive grains are anion-modified colloidal silica. 12. The polishing composition according to any one of 1. to 11. above, which has a pH of less than 7.0. 13. The polishing composition according to any one of 1. to 12. above, which is used for polishing an object containing silicon oxide: 14. A polishing method comprising the step of polishing an object containing silicon oxide with the polishing composition according to any one of 1. to 13. above: 15. A method for producing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing silicon oxide by the polishing method described in 14 above. [Example]

[0086] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively. In the following examples, unless otherwise specified, operations were carried out under the conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH. Each physical property was measured as follows.

[0087] <Average primary particle size and average secondary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​the abrasive grains measured by the BET method using a Micromeritics Flow Sorb II 2300 and the density of the abrasive grains. The average secondary particle size of the abrasive grains was measured as the volume-average particle size (arithmetic mean diameter based on volume; Mv) using a dynamic light scattering particle size distribution analyzer UPA-UT151 (Nikkiso Co., Ltd.).

[0088] <Zeta potential of abrasive grains> The zeta potential of the abrasive grains in the polishing composition was measured using a zeta potential measuring device manufactured by Otsuka Electronics Co., Ltd. (device name "ELS-Z2").

[0089] <pH of polishing composition> The pH of the polishing composition was measured with a pH meter (manufactured by Horiba, Ltd., model number: LAQUA).

[0090] <Electrical Conductivity of Polishing Composition> The electrical conductivity (EC) of the polishing composition was measured using a desktop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71 LAQUA (registered trademark)).

[0091] <Production of sulfonic acid-immobilized colloidal silica> Sulfonic acid-modified colloidal silica was obtained as abrasive grains according to the following procedure.

[0092] (Preparation process of raw colloidal silica dispersion (unmodified silica particles)) 4080 g of methanol, 610 g of water, and 168 g of 29% by mass aqueous ammonia solution were mixed in a flask, and the liquid temperature was kept at 20°C. A mixture of 135 g of methanol and 508 g of tetramethoxysilane (TMOS) was added dropwise over 25 minutes. After that, the mixture was heated to a pH of 7 or higher and subjected to water substitution, yielding 1000 g of 19.5% by mass silica sol (average primary particle size: 34 nm).

[0093] (Surface modification process) Next, 1.2 g of 3-mercaptopropyltrimethoxysilane (MPS, silane coupling agent, product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) (silane coupling agent concentration relative to the total mass of silica solids: 0.6 mass%) mixed with 4.8 g of methanol was added dropwise to 1,000 g of the silica sol obtained above (195 g in terms of silica solids) at a flow rate of 1 mL / min. The mixture was then heated and boiled, followed by substitution with pure water for 3 hours.

[0094] Next, the reaction solution was left to cool overnight, and then 0.0343 g of 30 mass % hydrogen peroxide solution (3 moles per mole of silane coupling agent) was added, and the mixture was boiled again. After that, the mixture was replaced with pure water for 2 hours, and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silica.

[0095] Example 1 <Preparation of Polishing Composition> Abrasive sulfonic acid-modified colloidal silica (surface-modified silica 1, average primary particle size: 34 nm) was added to water as a dispersion medium to a final concentration of 2 mass%. Furthermore, inorganic salt ammonium sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to a final concentration of 6000 mass ppm, and organic onium salt tetraethylammonium hydroxide (TEAH, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to a final concentration of 150 mass ppm, followed by stirring and mixing (stirring temperature: 25°C, stirring time: 20 minutes). The pH of the polishing composition was adjusted to 2.0 using nitric acid, completing polishing composition 1.

[0096] Example 2 Polishing composition 2 was prepared in the same manner as in Example 1, except that the amount of tetraethylammonium hydroxide added was changed to 100 ppm by mass.

[0097] Example 3 Polishing composition 3 was prepared in the same manner as in Example 1, except that the amount of tetraethylammonium hydroxide added was changed to 1000 ppm by mass.

[0098] (Comparative Example 1) Comparative Polishing Composition 1 was prepared in the same manner as in Example 1, except that ammonium sulfate and tetraethylammonium hydroxide were not used.

[0099] (Comparative Example 2) Comparative Polishing Composition 2 was prepared in the same manner as in Example 1, except that tetraethylammonium hydroxide was not used.

[0100] (Comparative Example 3) Comparative Polishing Composition 3 was prepared in the same manner as in Example 1, except that n-pentylamine was added to the polishing composition in place of tetraethylammonium hydroxide so as to give a final concentration of 2000 ppm by mass.

[0101] The composition of the polishing composition of each Example and Comparative Example is shown in the following Table 1. In the following Table 1, "-" indicates that the agent was not used.

[0102] [Table 1]

[0103] [evaluation] <Abrasive grain agglomeration rate> The agglomeration rate of abrasive grains was measured by the following method: 1) 30.0 g of the sample polishing composition was weighed into a polypropylene container (Centrifuge Tube) manufactured by Beckman Coulter, Inc., and the top lid was tightly closed. 2) A Beckman Coulter Avanti HP-30I centrifuge was used, and the mixture was continuously operated at 25°C and 15,000 rpm for 15 minutes. 3) The water in the upper part of the container is separated from the abrasive grains in the lower part by centrifugation, and the abrasive grains are compressed and settled to the bottom of the container (this is called cake): 4) The precipitated cake was dried at 200°C for 24 hours using "ELECTRIC MUFFLE FURNACES KM-420" manufactured by Advantec Co., Ltd., and the weight of the obtained solid was measured. 5) Separately, using an aqueous dispersion of abrasive grains, the weight of the solid matter after drying measured using the above steps 1) to 4) was designated as (B), and the weight of the solid matter after drying measured using the sample polishing composition was designated as (A), and the agglomeration rate was calculated using the following formula.

[0104]

number

[0105] Although (A) and (B) may contain trace amounts of additives, this was not taken into consideration and the value calculated by formula (1) was used as the agglomeration rate of the abrasive grains.

[0106] <Polishing speed> A silicon wafer (200 mm, blanket wafer) with a 10,000 Å thick TEOS type silicon oxide (SiO2) film formed on its surface was prepared as the object to be polished, and polishing was carried out under the following conditions.

[0107] (Polishing equipment and polishing conditions) Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra Polishing pad: Nitta Haas IC1010 hard polyurethane pad Polishing pressure: 2.5 psi (1 psi = 6894.76 Pa) Polishing platen rotation speed: 47 rpm Head (carrier) rotation speed: 43 rpm Supply of polishing composition: free-flowing Polishing composition supply amount: 200mL / min Polishing time: 60 seconds.

[0108] The thickness of the polished object before and after polishing was measured using an optical film thickness measuring device (ASET-f5x: manufactured by KLA-Tencor Corporation). The film thickness was measured using an optical film thickness measuring device (ASET-f5x: manufactured by KLA-Tencor Corporation).

[0109] The polishing rate for the object to be polished was calculated by dividing the difference in film thickness before and after polishing [(thickness before polishing) - (thickness after polishing)] by the polishing time.

[0110] <Number of scratches> The number of scratches on the silicon oxide film surface after polishing was measured using a wafer inspection system "Surfscan® SP2" manufactured by KLA-Tencor Corporation to measure the coordinates of the entire surface of both sides of the polished object (excluding the outer 2 mm area). The measured coordinates were then observed with a Review-SEM (RS-6000, manufactured by Hitachi High-Technologies Corporation). Scratches were counted as scratches on the substrate surface with a depth of 10 nm to less than 100 nm, a width of 100 nm to less than 500 nm, and a length of 80 nm or more. The fewer the number of scratches, the better. A scratch count of 25 or less is practical, with 20 or less being preferred, 15 or less being more preferred, 10 or less being even more preferred, and less than 10 being particularly preferred.

[0111] The evaluation results of the abrasive grain agglomeration rate, polishing rate, and number of scratches are shown in Table 2 below.

[0112] [Table 2]

[0113] As is clear from Table 2 above, when the polishing compositions of Examples were used, the removal rate of the silicon oxide film was high and scratches on the surface of the polished silicon oxide film could be reduced. When the polishing compositions of Comparative Examples 1 and 2, which had a high abrasive agglomeration rate, were used, scratches on the surface of the silicon oxide film increased. Furthermore, when the polishing composition of Comparative Example 3, which had a low abrasive agglomeration rate, was used, the removal rate of the silicon oxide film decreased.

Claims

1. abrasive grains having an average primary particle diameter of 1 nm or more and 150 nm or less; A dispersion medium; wherein the agglomeration rate of the abrasive grains is 40% or more and less than 75%.

2. 2. The polishing composition according to claim 1, wherein the agglomeration rate of the abrasive grains is 40% or more and 55% or less.

3. The polishing composition of claim 1 , further comprising an inorganic salt.

4. 4. The polishing composition according to claim 3, wherein the inorganic salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate.

5. The polishing composition of claim 1 , further comprising an organic onium salt.

6. 6. The polishing composition according to claim 5, wherein the organic onium salt is at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2: 【Chemical 1】 In the above Chemical Formula 1 and Chemical Formula 2, R １ ~R ８ are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A － and X － are each independently a monovalent anion.

7. The polishing composition according to claim 6 , wherein the organic onium salt is a tetraalkylammonium salt represented by Chemical Formula 1.

8. A in the above Chemical Formula 1 and Chemical Formula 2 － and X － The polishing composition according to claim 6 , wherein is a hydroxide ion.

9. 7. The polishing composition according to claim 6, wherein the tetraalkylammonium salt represented by Chemical Formula 1 is at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide.

10. 2. The polishing composition according to claim 1, wherein the abrasive grains in the polishing composition have a negative zeta potential.

11. The polishing composition according to claim 10, wherein the abrasive grains are anion-modified colloidal silica.

12. The polishing composition according to claim 1 , having a pH of less than 7.

0.

13. The polishing composition according to claim 1 , which is used for polishing an object containing silicon oxide.

14. A polishing method comprising a step of polishing an object containing silicon oxide with the polishing composition according to any one of claims 1 to 13.

15. A method for producing a semiconductor substrate, comprising a step of polishing a semiconductor substrate containing silicon oxide by the polishing method according to claim 14.

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