Polishing silica particle dispersion liquid and polishing composition

Abstract

The purpose of the present invention is to provide a polishing silica particle dispersion liquid, a polishing composition, and a polishing method that suppresses the occurrence of scratches while maintaining a high polishing rate when used for CMP polishing of a device wafer.　Provided is a polishing silica particle dispersion liquid containing silica particles and water, wherein: the weight loss rate on heating of the silica particles at 200°C-700°C is 2.5% or less; and there are 25 or fewer spherical foreign particles that have an equivalent circle diameter of 0.48 µm or more and a shape factor SF1LP of less than 1.50 as measured according to the measurement method A or the measurement method B described below.　In the measurement method A, pure water is added to the dispersion liquid to dilute the dispersion liquid to a silica concentration of 0.1 mass%, 30 g of the diluted liquid is filtered through a filter (with a filtering area of 1.8 cm2) that has an absolute pore diameter of 0.4 µm, and subsequently 20 fields of view (having an area of 448 µm2) of the filter are examined at a magnification of 5,000 times by a scanning electron microscope (SEM). The equivalent circle diameter of each spherical foreign particle is calculated by an image analysis method, and the ratio (LLP 2 × π / 4) / SLP of the area of a circle, the diameter of which is the maximum particle length LLP that is the length of the longest straight line connecting arbitrary two points on the contour line of the spherical foreign particle, to the projected area SLP of the spherical foreign particle is defined as a shape factor SF1LP. In the measurement method B, pure water is added to the dispersion liquid to dilute the dispersion liquid to a silica concentration of 0.03 mass%, 30 g of the diluted liquid is filtered through a filter (with a filtering area of 1.8 cm2) that has an absolute pore diameter of 0

Description

Abrasive silica particle dispersion and abrasive composition 【0001】 The present invention relates to a silica particle dispersion for polishing, a polishing composition, and a polishing method. 【0002】 Polishing compositions using silica-based abrasives are used for polishing the surfaces of silicon wafers and device wafers. 【0003】 Furthermore, with the increasing multilayer wiring on semiconductor substrate surfaces in recent years, integrated circuits are manufactured by embedding silicon oxide films or metal wiring on stepped substrates during device formation, planarizing them using chemical mechanical polishing (CMP), and then performing lithography on the surface to create multilayer wiring. As pattern integration progresses, pattern miniaturization continues, chemical beams used in lithography are becoming shorter in wavelength, and the demands for flatness and low defects (scratches, contamination, etc.) are becoming more sophisticated. Polishing speed is also a requirement from a productivity standpoint. 【0004】 Thus, semiconductor polishing requires flatness, low defect rate, and high polishing speed. Among defects, scratches cannot be removed by subsequent cleaning processes, so their reduction through polishing is essential. 【0005】 Patent Document 1 aims to provide an abrasive composition that contributes to improving step performance (especially erosion), comprising abrasive particles such as silica and a dispersion medium, wherein the average primary particle diameter of the abrasive particles is 40 nm or less, and of the abrasive particles, coarse particles with a particle diameter of 0.2 to 1,600 μm are present in the abrasive composition 1 cm ３ An abrasive composition is disclosed that has 20,000 or fewer particles per unit area. 【0006】 Patent Document 2 discloses colloidal silica that can be used as abrasive particles in a polishing slurry to reduce the surface roughness of a surface to be polished in a chemical mechanical polishing process. The colloidal silica contains water and silica particles, the average particle diameter of the silica particles is 60 to 130 nm, and the content of coarse silica particles with a particle size of 0.2 μm or more in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass. 【0007】Patent Document 3 discloses a method for producing a polishing composition that can reduce the surface roughness and particles of an object to be polished after polishing. The method comprises a step of filtering a silica dispersion to be treated, which contains colloidal silica with an average particle diameter of primary particles of 1 to 100 nm, through a filter containing a filter aid, wherein the filter aid has an average pore diameter of 0.1 to 3.5 μm, obtained by the mercury intrusion method. 【0008】 Patent Document 4 discloses a purified alkali silicate aqueous solution in which the amount of flat, plate-shaped fine particles of foreign matter has been reduced, and a method for producing silica sol using the same. 【0009】 Japanese Patent Publication No. 2023-107781, Japanese Patent No. 7129576, International Publication No. 2012 / 039428, Japanese Patent No. 6103285 【0010】 On the other hand, in this technical field, including the prior art mentioned above, silica particles and foreign matter are often defined only by particle size, but their shape is rarely discussed. Patent document 4 describes that the foreign matter consists of minute particles and has a flat shape, but there is no mention of other sizes or shapes, and the effect of the foreign matter on the surface of the object to be polished (after the polishing process) is not described with specific data such as the suppression of scratches. The present invention aims to provide a silica particle dispersion for polishing, a method for producing the same, a polishing composition, and a polishing method that suppress the generation of scratches while maintaining a high polishing speed when used for CMP polishing of device wafers. 【0011】As a result of intensive research, the present inventors have found that, by using a scanning electron microscope (SEM), coarse foreign matter in a silica particle dispersion for polishing can be classified by shape, and that, by restricting the average particle diameter of the silica particles (the particle diameter measured by the dynamic light scattering method) to a specific range and reducing or removing coarse foreign matter having a specific equivalent circle diameter and a specific shape factor that is spherical or approximately spherical, it is possible, surprisingly, to suppress scratches on the surface of the polishing object that deteriorate flatness and reduce the yield of the device, and to maintain a high polishing rate, thus finding that the above problems can be solved and completing the present invention. That is, the gist of the present invention is as follows. [1] A silica particle dispersion for polishing containing silica particles and water, wherein the heating loss rate of the silica particles at 200°C to 700°C is 2.5% or less, and the equivalent circle diameter is 0.48 µm or more and the shape factor SF1 ＬＰ is less than 1.50 and the number of spherical foreign matter is 25 or less, in the silica particle dispersion for polishing: The measuring method A is to add pure water to the dispersion and dilute it to a silica concentration of 0.1% by mass, and then filter 30 g of the diluted solution through a filter with an absolute pore diameter of 0.4 µm (filter area 1.8 cm ２ ). After filtration, the filter is magnified 5000 times with a scanning electron microscope (SEM) in a field of view (area 448 µm ２ ), and 20 fields of view are observed. The equivalent circle diameter of the spherical foreign matter is calculated by an image analysis method. Further, with respect to the projected area S ＬＰ of the spherical foreign matter, the ratio of the area of a circle having a diameter equal to the maximum length L ＬＰ of the particle, which is the length of the longest straight line connecting any two points on the contour line of the spherical foreign matter, to S ＬＰ ２ × π / 4) / S ＬＰ is defined as the shape factor SF1 ＬＰ The measuring method B is to add pure water to the dispersion and dilute it to a silica concentration of 0.03% by mass, and then filter 30 g of the diluted solution through a filter with an absolute pore diameter of 0.4 µm (filter area 1.8 cm ２ ). After filtration, the filter is magnified 5000 times with a scanning electron microscope (SEM) in a field of view (area 448 µm ２When the field of view is magnified to 67 and observed, the equivalent diameter of the spherical foreign object is calculated by image analysis, and further, the projected area S of the spherical foreign object is calculated. ＬＰ The maximum diameter L of the particle is the length of the longest straight line connecting any two points on the contour line of the spherical foreign object. ＬＰ The ratio of the area of ​​a circle with diameter (L) ＬＰ ２ ×π / 4) / S ＬＰ shape coefficient SF1 ＬＰ This is the method of definition. [2] The shape coefficient SF1 of the silica particles measured according to the measurement method C below. ｐ The abrasive silica particle dispersion liquid described in [1], wherein the ratio is 1.20 or higher: Measurement method C involves observing the silica particles with a transmission electron microscope (TEM) at a magnification of 12,000x or 30,000x, calculating the equivalent circular diameter of 2,000 randomly selected silica particles using an image analysis method, and further calculating the projected area S of the silica particles. Ｐ The maximum diameter L of the particle is the length of the longest straight line connecting any two points on the contour line of the silica particle. Ｐ The ratio of the area of ​​a circle with diameter (L) Ｐ ２ ×π / 4) / S Ｐ shape coefficient SF1 Ｐ This is a method of definition. [3] The silica particle dispersion for polishing according to [1], wherein the average primary particle diameter of the silica particles, as measured by the BET method, is 10 to 120 nm. [4] The silica particle dispersion for polishing according to [1], wherein the average particle diameter of the silica particles, as measured by the dynamic light scattering method, is 28 to 200 nm. [5] The silica particle dispersion for polishing according to [1], wherein the amount of Na per 10% by mass of silica is 400 ppm or less. [6] The silica particle dispersion for polishing according to [1], wherein the pH is 8.0 or higher and 11.5 or lower. [7] A polishing composition comprising the silica particle dispersion for polishing according to any one of [1] to [6]. [8] The polishing composition according to [7], used for chemical mechanical polishing (CMP) of the surface of a device wafer having at least one of a silicon wafer, a metal, or an insulating material. [9] A polishing method for performing chemical mechanical polishing (CMP) in the wiring process of a semiconductor using the polishing composition according to [7]. 【0012】 According to the present invention, it is possible to provide a silica particle dispersion for polishing, a method for producing the same, a polishing composition, and a polishing method that suppress the generation of scratches, which worsen flatness and reduce device yield, while maintaining a high polishing speed when used for CMP polishing of device wafers. 【0013】 This is a magnified SEM image of a type (i) foreign object. This is a magnified SEM image of a type (ii) foreign object. This is an example of a concave defect identified as a scratch. 【0014】 Preferred embodiments of the present invention will be described below. However, the embodiments described below are illustrative for explaining the present invention, and the present invention is not limited in any way to the embodiments described below. In this specification, a numerical range expressed using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit. 【0015】 [Silica Particle Dispersion for Polishing] In one embodiment of the present invention, the silica particle dispersion for polishing contains silica particles and water, the weight loss rate of the silica particles at 200°C to 700°C is 2.5% or less, and the equivalent circle diameter is 0.48 μm or more and the shape coefficient SF1 is measured according to the following measurement method A or measurement method B. ＬＰ This refers to a silica particle dispersion for polishing in which there are 25 or fewer spherical foreign matter particles with a value of less than 1.50. The number of such spherical foreign matter particles is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, and most preferably 5 or less. Measurement method A involves adding pure water to the dispersion and diluting the solution to a silica concentration of 0.1% by mass. 30 g of this diluted solution is then filtered through a filter with an absolute pore size of 0.4 μm (filtration area 1.8 cm²). ２ After filtering with ), the filter is examined with a scanning electron microscope (SEM) at 5000x magnification (area 448 μm). ２ When the field of view is magnified to 20 and observed, the equivalent diameter of the spherical foreign object is calculated by image analysis, and further, the projected area S of the spherical foreign object is calculated. ＬＰ The maximum diameter L of the particle is the length of the longest straight line connecting any two points on the contour line of the spherical foreign object. ＬＰ The ratio of the area of ​​a circle with diameter (L) ＬＰ ２×π / 4) / S ＬＰ shape coefficient SF1 ＬＰ This is the method of definition. Measurement method B involves adding pure water to the dispersion and diluting it to a silica concentration of 0.03% by mass. 30 g of this diluted solution is then filtered through a filter with an absolute pore size of 0.4 μm (filtration area 1.8 cm²). ２ After filtering with ), the filter is examined with a scanning electron microscope (SEM) at 5000x magnification (area 448 μm). ２ When the field of view is magnified to 67 and observed, the equivalent diameter of the spherical foreign object is calculated by image analysis, and further, the projected area S of the spherical foreign object is calculated. ＬＰ The maximum diameter L of the particle is the length of the longest straight line connecting any two points on the contour line of the spherical foreign object. ＬＰ The ratio of the area of ​​a circle with diameter (L) ＬＰ ２ ×π / 4) / S ＬＰ shape coefficient SF1 ＬＰ This is the method of definition. 【0016】 In one embodiment of the present invention, the heating weight loss rate of the silica particles at 200°C to 700°C is preferably 2.5% or less, more preferably 2.2% or less, even more preferably 2.0% or less, and most preferably 1.8% or less, considering the effects achieved by the present invention. To obtain a high polishing rate, the upper limit of the heating weight loss rate of the silica particles at 700°C can be in the range of 2.5%, 2.2%, 2.0%, or 1.8%, and the lower limit can be in the range of 0.1%, 0.3%, 0.5%, 0.7%, or 0.9%. One factor that lowers the heating weight loss rate is the temperature during particle synthesis, which can preferably be 80°C or higher, more preferably 90°C or higher, and most preferably 100°C or higher. When synthesized at the above temperatures, the heating weight loss rate is lower and the polishing rate can be increased, but on the other hand, spherical foreign matter tends to be generated more easily and scratches tend to increase. When the heat loss rate is high, scratches tend to be less likely to occur due to the softness of the particles and foreign matter, but the polishing speed also decreases. 【0017】 The heat loss rate of the above silica particles can be measured by differential thermal and thermogravimetric analysis (TGDTA). 【0018】An example of a measuring device used to measure the heat loss of silica particles by simultaneous differential thermal and thermogravimetric analysis is a thermogravimetric differential thermal analyzer (product name TG-DTA2000SA, manufactured by Bruker). 【0019】 For measuring the heat loss described above, silica particles (silica powder) extracted from a silica particle dispersion for polishing can be used as an example. 【0020】 The silica particles (silica powder) are obtained by drying colloidal silica. The drying method is not particularly limited. Specific drying methods include hot air drying, forced air drying, far-infrared heating drying, dehumidified air drying, natural drying (including sun drying), vacuum reduced pressure drying, indirect heating drying, microwave heating drying, and vacuum freeze-drying. One or more drying methods can be used in combination. 【0021】 In the present invention, silica particles contained in an aqueous silica sol can be used as silica particles. The aqueous silica sol can be obtained, for example, by growing particles under heating of activated silicic acid obtained by cation exchange of water glass, or by hydrolysis and dehydration condensation of an organosilicon compound. As these aqueous silica sols, for example, silica sol manufactured by Nissan Chemical Corporation (product name: Snowtex®) can be used. Typically, the silica concentration in the aqueous silica sol can be 10% to 40% by mass. 【0022】 In one embodiment of the present invention, the shape coefficient SF1 is measured according to the above measurement method A or measurement method B, with an equivalent circle diameter of 0.48 μm or more. ＬＰ Considering the effects of the present invention, the number of spherical foreign objects with a value of less than 1.50 is 25 or less, preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, and most preferably 5 or less. 【0023】 The causes of spherical foreign matter are not limited to those described herein, but for example, when supplying raw materials into the reaction vessel while heating during particle synthesis, tiny droplets are generated by splashing liquid, and these droplets dry instantly in the high-temperature reaction vessel, resulting in the formation of spherical foreign matter. 【0024】In one embodiment of the present invention, the abrasive silica particle dispersion is measured according to the following measurement method C, and the shape coefficient SF1 of the silica particles is measured. ｐ This refers to a silica particle dispersion for polishing in which the ratio is 1.20 or higher. Measurement method C involves observing the silica particles under a transmission electron microscope (TEM) at a magnification of 12,000x or 30,000x, calculating the equivalent circular diameter of 2,000 randomly selected silica particles using an image analysis method, and further calculating the projected area S of the silica particles. Ｐ The maximum diameter L of the particle is the length of the longest straight line connecting any two points on the contour line of the silica particle. Ｐ The ratio of the area of ​​a circle with diameter (L) Ｐ ２ ×π / 4) / S Ｐ shape coefficient SF1 Ｐ This is the method of definition. 【0025】 In one embodiment of the present invention, the shape coefficient SF1 of silica particles, measured according to the above measurement method C, ｐ Considering the effects achieved by the present invention, the value is 1.20 or higher, preferably 1.40 or higher, more preferably 1.45 or higher, and most preferably 1.50 or higher. 【0026】 In one embodiment of the present invention, the silica particles are colloidal silica particles, and considering the effects of the present invention, the average particle diameter measured by dynamic light scattering is 28 to 200 nm, preferably 30 to 200 nm, more preferably 40 to 180 nm, even more preferably 50 to 160 nm, especially preferably 60 to 140 nm, and most preferably 70 to 120 nm. Furthermore, the average primary particle diameter measured by BET (nitrogen gas adsorption) of the silica particles in the dispersion is preferably 10 to 120 nm, or 15 to 100 nm, or 20 to 80 nm, or 25 to 60 nm. 【0027】In one embodiment of the present invention, the amount of Na per 10% by mass of silica in the silica particle dispersion for polishing is 400 ppm or less, preferably 300 ppm or less, more preferably 250 ppm or less, even more preferably 200 ppm or less, especially preferably 100 ppm or less, and most preferably 20 ppm or less, considering the effects achieved by the present invention. Since Na easily diffuses in insulating films, it is desirable to reduce Na contamination after polishing. By setting the amount of Na per 10% by mass of silica within the above range, Na contamination after polishing can be reduced. 【0028】 In one embodiment of the present invention, the pH of the silica particle dispersion for polishing is 8.0 or more and 11.5 or less, considering the effects achieved by the present invention, with a lower limit of preferably 8.5, more preferably 9.0, and an upper limit of preferably 11.0, more preferably 10.9. By limiting the pH to the above range, aggregation and dissolution of silica particles can be suppressed, allowing for stable storage and use. To adjust the pH of the dispersion, a pH adjusting agent (alkaline component and / or water-soluble compound) may be added. Examples of alkaline components include alkali metal hydroxides (sodium hydroxide, potassium hydroxide), ammonia, or amines. 【0029】 The dispersion of the present invention may contain at least one additive selected from the group consisting of alkaline components and acidic components. 【0030】 Examples of alkaline components include potassium hydroxide or potassium bicarbonate, or sodium hydroxide, ammonia, amines, primary ammonium hydroxide, secondary ammonium hydroxide, tertiary ammonium hydroxide, quaternary ammonium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium bicarbonate, sodium bicarbonate, or mixtures thereof. 【0031】 Examples of acidic components include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, phosphonic acid, and boric acid, or organic acids such as acetic acid, formic acid, lactic acid, tartaric acid, citric acid, malonic acid, gluconic acid, and glycine, or mixtures thereof. 【0032】The dispersion of the present invention may contain additives such as dispersants, surfactants, rust inhibitors, preservatives, disinfectants, wetting agents, thickeners, and chelating agents, to the extent that they do not impair the effects of the invention. 【0033】 [Polishing Composition] The polishing composition of the present invention means the above-described dispersion of silica particles for polishing or a composition containing said dispersion. In one embodiment of the present invention, the polishing composition can be used for chemical mechanical polishing (CMP) of the surface of a silicon wafer or a device wafer having at least one of a metal or insulating material. 【0034】 In another embodiment of the present invention, the object to be polished by the polishing composition is not limited, but for example, SiO ２ Examples include insulating films such as Low-k materials (SiOC, SiOF, etc.), BPSG (boron-phosphorus glass), and their porous films, carbon-containing films such as spin-on carbon and amorphous carbon films, metal wiring such as copper, aluminum, and tungsten, and composite films in which these materials coexist. 【0035】 Since the polishing composition of the present invention can be used to polish composite films in which insulating materials and metal wiring coexist, it may contain additives commonly used for polishing metal wiring. Examples include oxidizing agents, metal corrosion inhibitors, chelating agents, surfactants, and iron catalysts. 【0036】 Examples of oxidizing agents include hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozonated water. The oxidizing agent can be contained in a proportion of 0.01 to 100% by mass relative to the silica particles. 【0037】 Examples of metal corrosion inhibitors include triazole compounds, pyridine compounds, pyrazole compounds, pyrimidine compounds, imidazole compounds, guanidine compounds, thiazole compounds, tetrazole compounds, triazine compounds, and hexamethylenetetramine. 【0038】Triazole compounds include 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole, benzotriazole (BTA), 1-hydroxybenzotriazole, 1-hydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxy-1H-benzotriazole, 4-carboxy-1H-benzotriazole methyl ester (1H-benzotriazole-4-carboxylate methyl), 4-carboxy-1H-benzotriazole butyl ester (1H-benzotriazole-4-carboxylate butyl), 4-carboxy-1H-benzotriazole octyl ester (1H-benzotriazole-4-carboxylate octyl), 5-hexylbenzotriazole, (1,2,3-benzotriazolyl-1-methyl) (1,2,4-triazole Zolyl-1-methyl)(2-ethylhexyl)amine, tolyltriazol, naphthotriazol, bis[(1-benzotriazolyl)methyl]phosphonic acid, 3H-1,2,3-triazolo[4,5-b]pyridine-3-ol, 1H-1,2,3-triazolo[4,5-b]pyridine, 1-acetyl-1H-1,2,3-triazolo[4,5-b]pyridine, 3-hydroxypyridine, 1,2,4-triazolo[1,5-a]pyridine Examples include midin, 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, 2-methyl-5,7-diphenyl-[1,2,4]triazolo[1,5-a]pyrimidine, 2-methylsulfanyl-5,7-diphenyl-[1,2,4]triazolo[1,5-a]pyrimidine, and 2-methylsulfanyl-5,7-diphenyl-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine. 【0039】Examples of pyridine compounds include pyridine, 8-hydroxyquinoline, prothionamide, 2-nitropyridine-3-ol, pyridoxamine, nicotinamide, iproniazid, isonicotinic acid, benzo[f]quinoline, 2,5-pyridinedicarboxylic acid, 4-styrylpyridine, anabasine, 4-nitropyridine-1-oxide, pyridine-3-ethyl acetate, quinoline, 2-ethylpyridine, quinolinic acid, arecoline, citradilic acid, pyridine-3-methanol, 2-methyl-5-ethylpyridine, 2-fluoropyridine, pentafluoropyridine, 6-methylpyridine-3-ol, and pyridine-2-ethyl acetate. 【0040】 Examples of pyrazole compounds include pyrazole, 1-allyl-3,5-dimethylpyrazole, 3,5-di(2-pyridyl)pyrazole, 3,5-diisopropylpyrazole, 3,5-dimethyl-1-hydroxymethylpyrazole, 3,5-dimethyl-1-phenylpyrazole, 3,5-dimethylpyrazole, 3-amino-5-hydroxypyrazole, 4-methylpyrazole, N-methylpyrazole, and 3-aminopyrazole. 【0041】 Examples of pyrimidine compounds include pyrimidine, 1,3-diphenylpyrimidine-2,4,6-trione, 1,4,5,6-tetrahydropyrimidine, 2,4,5,6-tetraaminopyrimidine sulfate, 2,4,5-trihydroxypyrimidine, 2,4,6-triaminopyrimidine, 2,4,6-trichloropyrimidine, 2,4,6-trimethoxypyrimidine, 2,4,6-triphenylpyrimidine, 2,4-diamino-6-hydroxylpyrimidine, 2,4-diaminopyrimidine, 2-acetamidepyrimidine, 2-aminopyrimidine, and 4-aminopyrazolo[3,4-d]pyrimidine. 【0042】Examples of imidazole compounds include imidazole, 1,1'-carbonylbis-1H-imidazole, 1,1'-oxalyldiimidazole, 1,2,4,5-tetramethylimidazole, 1,2-dimethyl-5-nitroimidazole, 1,2-dimethylimidazole, 1-(3-aminopropyl)imidazole, 1-butylimidazole, 1-ethylimidazole, 1-methylimidazole, and benzimidazole. 【0043】 Examples of guanidine compounds include guanidine, 1,1,3,3-tetramethylguanidine, 1,2,3-triphenylguanidine, 1,3-di-o-tolylguanidine, and 1,3-diphenylguanidine. 【0044】 Examples of thiazole compounds include thiazole, 2-mercaptobenzothiazole, and 2,4-dimethylthiazole. 【0045】 Examples of tetrazole compounds include tetrazole, 5-methyltetrazole, 5-amino-1H-tetrazole, and 1-(2-dimethylaminoethyl)-5-mercaptotetrazole. 【0046】 Examples of triazine compounds include triazine and 3,4-dihydro-3-hydroxy-4-oxo-1,2,4-triazine. 【0047】 The metal corrosion inhibitor can be contained in a proportion of 0.0001 to 10% by mass relative to the silica particles. 【0048】 Examples of chelating agents include amino acids such as glycine and alanine, organic acids such as citric acid, oxalic acid, lactic acid, tartaric acid, malic acid, maleic acid, and malonic acid, and inorganic acids such as phosphoric acid. 【0049】 The chelating agent can be included in a proportion of 0.001 to 100% by mass relative to the silica particles. 【0050】 Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. 【0051】Examples of anionic surfactants include carboxylates, sulfonates, sulfates, and phosphates. 【0052】 Examples of cationic surfactants include aliphatic amine salts, aliphatic ammonium salts, and quaternary ammonium salts. 【0053】 Examples of amphoteric surfactants include amino acids, aminoacetic acid betaine, sulfobetaine, amine oxide, and amidoamine oxide. 【0054】 Examples of nonionic surfactants include polyoxyethylene, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, hydroxyethylcellulose, and cyclodextrin. 【0055】 The surfactant can be contained in a proportion of 0.001 to 100% by mass relative to the silica particles. 【0056】 Examples of iron catalysts include iron compounds such as iron nitrate, with compounds containing trivalent iron ions, such as ferric nitrate, being particularly preferred. The iron catalyst can be contained in a proportion of 0.001 to 10% by mass relative to the silica particles. 【0057】 In one embodiment of the present invention, the polishing composition can be used for chemical mechanical polishing (CMP) of the surface of a silicon wafer or a device wafer having at least one of a metal or insulating material, and may also be used in general for polishing semiconductor wafers or semiconductor devices. 【0058】 Examples of materials to be polished include conductive material layers (wiring layers), barrier layers (layers composed of barrier metals, such as titanium nitride and tantalum nitride to prevent copper from diffusing into the insulating layer), and insulating layers (layers composed of interlayer insulating materials, such as SiO ２ Examples include SiOC and porous silica. It may also be applied to polishing. 【0059】Among these, examples of materials that constitute the conductive material layer include copper-based metals such as copper, copper alloys, copper oxides, and copper alloy oxides; tungsten-based metals such as tungsten, tungsten nitride, and tungsten alloys; cobalt-based metals such as cobalt, cobalt alloys, cobalt oxides, and cobalt alloy oxides; silver; and gold. Of these, at least one copper-based metal selected from the group consisting of copper, copper alloys, copper oxides, and copper alloy oxides is preferred, and copper is more preferred. The conductive material can be formed by known sputtering methods, plating methods, etc. 【0060】 The barrier metal constituting the barrier layer is formed to prevent the diffusion of conductive material into the insulating material and to improve the adhesion between the insulating material and the conductive material. The barrier metal material constituting the barrier metal is preferably at least one selected from the group consisting of tantalum-based metals, titanium-based metals, tungsten-based metals, ruthenium-based metals, cobalt-based metals, and manganese-based metals. Specifically, examples include tantalum-based metals such as tantalum, tantalum nitride, and tantalum alloys; titanium-based metals such as titanium, titanium nitride, and titanium alloys; tungsten-based metals such as tungsten and tungsten alloys; ruthenium-based metals such as ruthenium and ruthenium alloys; cobalt-based metals such as cobalt and cobalt alloys; and manganese-based metals such as manganese and manganese alloys. 【0061】 Examples of constituent materials for insulating materials include silicon-based materials and organic polymers. The insulating material may also be in the form of a film (insulating film, for example, an interlayer insulating film). Examples of insulating films include silicon-based coatings and organic polymer films. Insulating films can be formed by methods such as CVD, spin coating, dip coating, and spray coating. 【0062】Examples of silicon-based materials include silica-based materials and low-k materials (low dielectric constant materials). Examples of silica-based materials include silicon dioxide and BPSG (boron phosphorus glass). Examples of low-k materials include fluorosilicate glass; organosilicate glass obtained from trimethylsilane or dimethoxydimethylsilane as starting materials; porous organosilicate glass; silicon oxynitride; and hydrogenated silsesquioxane. 【0063】 Examples of the aforementioned organic polymers include polyimide, epoxy, acrylic, and polybenzoxazole. 【0064】 [Method for producing a silica particle dispersion for polishing] In one embodiment of the present invention, the above-mentioned silica particle dispersion for polishing may be produced by the following steps (A) and (B), or by a method comprising steps (A), (C), (D), and (E): (A) an ion exchange step of an alkaline silicate aqueous solution, and a heat treatment of the resulting activated silicate aqueous solution to obtain an aqueous silica sol; (B) a step of filtering the aqueous silica sol obtained in step (A) with a filter; (C) a step of contacting the aqueous silica sol obtained in step (A) with a strongly acidic ion exchange resin to obtain an acidic silica sol; (D) a step of adding a basic compound to the acidic silica sol obtained in step (C) to adjust the pH; (E) a step of filtering the pH-adjusted aqueous silica sol obtained in step (D) with a filter. 【0065】 In a preferred embodiment, for the purpose of further achieving the effects of the present invention, the aqueous sodium silicate solution and / or the aqueous activated silicic acid solution used in step (A) may be filtered in advance. 【0066】 As one embodiment of the present invention, filtration may be performed using a diatomaceous earth-containing filter in whole or in part of the above-described filter. Alternatively, filtration may be performed using a filter that does not contain diatomaceous earth after the diatomaceous earth-containing filter. The filtration method may be a pass-through method (a method in which the liquid after passing through the filter is placed in a different tank from the one before passing through) or a circulation method (a method in which the liquid after passing through the filter is returned to the same tank as before passing through). 【0067】[Polishing Method] Using the above polishing composition, chemical mechanical polishing (CMP) in the semiconductor wiring process can be effectively performed. 【0068】 Furthermore, in another embodiment, the polishing method according to the present invention involves, for example, forming a conductive thin film made of a conductive material on a silicon substrate, forming a resist film on top of it, and exposing and developing the resist layer using a circuit pattern as a mask by lithography to transfer the pattern to the resist layer. Using the transferred pattern as a mask, the conductive film is dry-etched with a highly anisotropic ionic gas. Examples of gas species used include tetrafluoromethane (CF4). ４ ), perfluorocyclobutane (C ４ F ８ ), perfluoropropane (C ３ F ８ Gases such as trifluoromethane, carbon monoxide, argon, oxygen, nitrogen, sulfur hexafluoride, difluoromethane, nitrogen trifluoride, and chlorine trifluoride, chlorine, trichloroborane, and dichloroborane can be used. 【0069】 Furthermore, the resist film is ashing with oxygen gas to remove the resist layer. This removal of the resist layer can also be done using chemical solutions (for example, a mixture of sulfuric acid and hydrogen peroxide, or a mixture of ammonia and hydrogen peroxide) to protect the substrate. 【0070】 Subsequently, an insulating film is deposited to prevent short circuits with the upper layer wiring. The wafer surface on which this interlayer insulating film is deposited reflects the pattern of the lower layer wiring, resulting in various sizes of irregularities in the insulating film. In this state of irregularity, when a resist film is applied to the upper layer and wiring is processed by lithography, diffuse reflection occurs at the interface between the resist and the insulating film during exposure of the resist, preventing the formation of a rectangular resist pattern and making processing of the lower layer difficult. Therefore, the wafer surface is planarized. This planarization of the interlayer insulating film is performed by CMP. 【0071】Furthermore, while aluminum has traditionally been used as the wiring material, its low melting point has led to reliability issues such as disconnection when high currents flow, and there has been a shift from aluminum wiring to copper wiring. However, the diffusion of copper into the insulating layer is a problem. Therefore, in the damascene process, grooves called damascene are formed before embedding the copper, but a barrier layer is also formed between the copper and the insulating layer to prevent the diffusion of copper into the insulating layer. The unevenness of the copper resulting from the embedding of copper for the formation of the copper wiring layer requires flattening of the copper wiring layer surface for lithography of the upper layer, and flattening of copper is difficult with gas dry etching due to its hardness, so polishing by CMP is performed. 【0072】 [Image analysis of foreign objects] 【0073】 The analysis of foreign matter in the abrasive silica particle dispersion of the present invention consists of "(1) sampling of foreign matter" and "(2) image analysis of foreign matter." For sampling of foreign matter and image analysis, images taken with a scanning electron microscope (SEM), such as the JSM-7400F (manufactured by JEOL Ltd.), can be used. 【0074】 (1) Collection of foreign matter When collecting foreign matter, measurement method A or measurement method B may be used depending on the sample to be analyzed. Measurement method A involves adding pure water to the dispersion and diluting the solution to a silica concentration of 0.1% by mass. 30 g of this diluted solution is then filtered through a filter with an absolute pore size of 0.4 μm (ipCELLCULTURE Track Etched Membrane Filter, manufactured by it4ip, with a filtration area of ​​1.8 cm²). ２ After passing liquid through the filter at a suction pressure of -80 kPa, 30 g of pure water is passed through it, and the filter is dried. The dried filter is then examined using a scanning electron microscope (SEM) at 5000x magnification (area 448 μm). ２ The field of view was magnified and 20 fields were observed. Measurement method B involves adding pure water to the dispersion and diluting it to a silica concentration of 0.03% by mass. 30 g of this diluted solution is then filtered through a filter with an absolute pore size of 0.4 μm (ipCELLCULTURE Track Etched Membrane Filter, manufactured by it4ip, with a filtration area of ​​1.8 cm²). ２After passing liquid through the filter at a suction pressure of -80 kPa, 30 g of pure water is passed through it, and the filter is dried. The dried filter is then examined using a scanning electron microscope (SEM) at 5000x magnification (area 448 μm). ２ ) The field of view has been enlarged to observe 67 fields. 【0075】 (2) Image analysis of foreign objects The image analysis of foreign objects further consists of "(2)-1 Identification of foreign objects" and "(2)-2 Image analysis". 【0076】 (2)-1 Identification of foreign matter Figure 1 shows an example of an SEM image observed to analyze foreign matter in a silica particle dispersion for polishing. In Figure 1, multiple particles (single particles and aggregated particles) are observed, but they can be broadly classified into type (i) and type (ii) based on their shape. 【0077】 Type (i) refers to "spherical or nearly spherical particles with an equivalent circular diameter of 0.48 μm or more." In contrast, Type (ii) refers to "non-spherical aggregated particles formed by the aggregation of primary particles in a planar or three-dimensional manner." These can be distinguished visually. 【0078】 Figure 1 is a magnified SEM image of a type (i) foreign object, and Figure 2 is a magnified SEM image of a type (ii) foreign object. 【0079】 From the standpoint of reducing scratches, it is preferable to have few of both type (i) and type (ii). On the other hand, as a result of diligent research, the inventors have found that among type (i), particles with a particularly large particle size (equivalent circle diameter of 0.48 μm or more) and a spherical shape (shape coefficient SF1 described later) are preferable. ＬＰ We have found that when there are few foreign substances (including both single particles and aggregated particles) with a value of less than 1.5, the number of scratches on the target substrate after polishing can be reduced. 【0080】 (2)-2 Image Analysis Below, for foreign matter of type (i), the particle size (equivalent diameter) and particle shape coefficient (SF1) are determined from the SEM image. ＬＰThis section describes a detailed method for analyzing the image. First, an SEM image (1,024 pixels in height x 1,280 pixels in width) taken at a magnification of 5,000x is imported as electronic data into an image analysis device (manufactured by Nireco Corporation, product name LUZEX AP), and the area (S) of the region occupied by the foreign object is calculated from the number of pixels. ＬＰ Convert it to a circle equivalent diameter D, then calculate the diameter of a perfect circle with the same area, and the resulting value is called the equivalent circle diameter D ＬＰ Next, the length of the longest straight line connecting any two points on the outer perimeter of the area occupied by the foreign object is determined, and the obtained value is called the maximum length L. ＬＰ It is stated that, in a 5,000x magnification photograph, the length of one side of a pixel is 18.5 nm, and therefore the area per pixel is 342 nm. ２ It is converted to L. ＬＰ The area of ​​a perfect circle with diameter and S ＬＰ Using the following formula (Formula X-1), the calculated value is the shape coefficient SF1 of the foreign object. ＬＰ This is the case. Furthermore, in the case of a perfectly round foreign object, SF1 ＬＰ The value becomes 1.00, and the further the shape deviates from a perfect circle, the larger the value becomes. SF1 ＬＰ = (L ＬＰ ２ ×π / 4) / S ＬＰ (Formula X-1) 【0081】 [Image Analysis of Silica Particles] Images taken with a transmission electron microscope (TEM) can be used to analyze silica particles. Specific examples of such equipment include the multi-function electron microscope JEM-F200 (manufactured by JEOL Ltd.). 【0082】 Below are the size (equivalent diameter of a circle) and shape factor (SF1) of silica particles from the TEM image. Ｐ The detailed method for analyzing the silica particles is described below. First, TEM images (4,096 pixels in height x 4,096 pixels in width) taken at a magnification of 12,000x or 30,000x are imported as electronic data into an image analysis device (manufactured by Nireco Corporation, product name LUZEX AP), and the area (S) is calculated from the number of pixels in the region occupied by the target silica particles. Ｐ Convert to a circle equivalent diameter D, and then determine the diameter of a perfect circle having the same area. Ｐis defined as follows. Next, the length of the longest straight line among the straight lines connecting any two points on the outer peripheral part of the region occupied by the silica particles is defined as the maximum length L Ｐ is defined as follows. In the photograph at 12,000 times magnification, the length of one side of one pixel is 0.651 nm, and thus the area per pixel is 0.424 nm ２ is converted as such. In the photograph at 30,000 times magnification, the length of one side of one pixel is 0.240 nm, and thus the area per pixel is 0.0576 nm ２ is converted as such. Finally, the area S Ｐ of a perfect circle with L Ｐ as the diameter is used to calculate the calculated value using the following formula (Formula X-2) as SF1 Ｐ is defined as follows. This analysis is the average value of the 2,000 silica particles detected by the image analysis device. In the case of perfect circular silica particles, SF1 Ｐ becomes 1.00, and the numerical value increases as the shape deviates from a perfect circle. SF1 Ｐ = (L Ｐ ２ ×π / 4) / S Ｐ (Formula X-2) 【0083】 Hereinafter, based on the examples, the effects of the present invention will be described in more detail. Note that the present invention is not limited to these examples 【0084】 (pH measurement) It shows the value obtained from the pH measurement result, and was measured using a pH meter (Multi Water Quality Meter MM-60R manufactured by Toa DKK Corporation, pH electrode GST-5741C) 【0085】 (Electrical conductivity measurement) Measured using a conductivity meter (Model number: CM-30R manufactured by Toa DKK Corporation) and a conductivity cell (Model number: CT57101B manufactured by Toa DKK Corporation) 【0086】 (Average particle diameter by DLS method (dynamic light scattering method): also referred to as DLS particle diameter) Using a particle size measuring device Zetasizer Nano (manufactured by Malvern Panalytical), the average particle diameter (D ＤＬＳ ) of the silica sol was determined by the dynamic light scattering method 【0087】(LPC (Large Coarse Particle Count) Measurement) The number of particles with a size of 0.48 μm or larger contained in each of the abrasive silica particle dispersions in the examples and comparative examples was measured using an Accusizer FXnano (manufactured by Entegris). Unlike the measurement of spherical foreign matter, LPC indicates the number of foreign matter measured without limiting the shape. 【0088】 (Preparation of heated and dried powder sample) Add pure water to silica sol and SiO ２ A silica sol sample was prepared with a concentration of 10% by mass. Next, the obtained silica sol sample was subjected to the removal of as many cations and anions as possible using the hydrogen-type strongly acidic cation exchange resin Amberlite® IR-120B and the hydroxyl-type strongly basic anion exchange resin Amberlite® IRA-410. The sample was then heated and dried in an electric furnace (DX302, manufactured by Yamato Scientific Co., Ltd.) at 290°C for 1 hour under an atmospheric atmosphere. The dried powder was thoroughly ground in an agate mortar to obtain a heat-dried powder sample. 【0089】 (Preparation of freeze-dried powder sample) Add pure water to silica sol and SiO ２ A silica sol sample was prepared with a concentration of 10% by mass. Next, the obtained silica sol sample was subjected to the removal of as many cations and anions as possible using the hydrogen-type strongly acidic cation exchange resin Amberlite® IR-120B and the hydroxyl-type strongly basic anion exchange resin Amberlite® IRA-410. The sample was then freeze-dried under vacuum pressure of 5 Pa or less using a freeze-drying apparatus (FDU-2100, manufactured by Tokyo Rikakikai Co., Ltd.). The dried powder was thoroughly ground in an agate mortar to obtain a freeze-dried powder sample. 【0090】 (Specific surface area diameter by BET method (nitrogen gas adsorption method): also called the average primary particle diameter by the BET method, or BET particle diameter) The above heated and dried powder of each silica sol was used as the measurement sample. Using a specific surface area measuring device Monosorb (manufactured by Quantachrome Instruments Japan LLC), the specific surface area value of the measurement sample was measured by the nitrogen adsorption method (BET method), and the average primary particle diameter (hereinafter referred to as D) was calculated from the obtained specific surface area value. ＢＥＴ ) was sought. 【0091】(Measurement of heating weight loss rate) Using a thermogravimetric differential thermal analyzer (TG-DTA2000SA, manufactured by Bruker), the heating weight loss (%) was measured when silica powder was heated from room temperature to 700°C as follows. 【0092】 A predetermined amount of the freeze-dried powder of each silica sol was placed in a platinum container and heated in a nitrogen atmosphere from room temperature to 700°C at a heating rate of 10°C / min. The nitrogen gas flow rate was 100 ml / min. The weight loss rate of the silica powder was calculated using the following formula from the mass M1 of the sample at 200°C and the mass M2 of the sample at 700°C. 【0093】 Heating loss rate (%) = (M1-M2) ÷ M1 x 100 【0094】 (Measurement of Na concentration) The concentration of Na contained in each silica sol was measured using an atomic absorption spectrophotometer (AA-7000, manufactured by Shimadzu Corporation). 【0095】 (SEM observation: Analysis of foreign matter) An electron emission scanning electron microscope JSM-7400F (manufactured by JEOL Ltd.) was used to observe the object at 5,000x magnification with an acceleration voltage of 1.0 kV, and images were captured while maintaining constant contrast and brightness. 【0096】 (TEM observation: Analysis of silica particles) Using a multi-functional electron microscope JEM-F200 (manufactured by JEOL Ltd.), observations were made at an acceleration voltage of 200 kV, at 12,000x or 30,000x magnification, and images were captured while maintaining constant contrast and brightness. 【0097】 (Preparation of activated silicate aqueous solution (a1)) As the raw material, a sodium silicate aqueous solution of JIS No. 3 was prepared. The main components of this sodium silicate aqueous solution other than water are SiO ２ is 28.8% by mass, Na ２O was 9.47% by mass. 478 g of the aqueous sodium silicate solution was dissolved in 2,992 g of pure water to prepare 3,470 g of an aqueous sodium silicate solution. Next, the aqueous sodium silicate solution was filtered through a pleated filter (PED-005 manufactured by ROKITEKNO Co., Ltd., nominal pore size 0.5 μm, made of polypropylene non-woven fabric with mixed glass fiber and diatomaceous earth, removal rate of particles with a primary particle size of 1.0 μm is 99.9%, filtration area 0.2 m2, total filter length 250 mm), and then passed through a column filled with hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B at a space velocity of 4.5 per hour. After that, 3,000 g of the obtained active silicic acid aqueous solution (a1) was recovered in a container. 【0098】 (Synthesis Example A) A pressure-resistant container made of SUS with an internal volume of 3 L was used as a reaction device equipped with a stirrer, a heating device, etc. Using the active silicic acid aqueous solution (a1) (SiO ２ as 3.5% by mass), 10% aqueous potassium hydroxide solution, and pure water, after adjusting to pH = 11.1 and electric conductivity 14.8 mS / cm, the liquid temperature inside the container was adjusted to 100 - 120 °C by heating. After the temperature inside the container reached 100 - 120 °C, while maintaining the temperature inside the container at 100 - 120 °C, the active silicic acid aqueous solution (a1) (SiO ２ as 3.5% by mass) was continuously supplied as a feed solution until the pH of the reaction solution reached 11.0 and the electric conductivity reached 3. mS / cm, to obtain reaction solution A. 【0099】 Subsequently, the obtained reaction solution A was continuously heated for 1 hour while maintaining the temperature at 100 - 120 °C to obtain dispersion liquid A. 【0100】 The obtained dispersion liquid A was concentrated at room temperature using a commercially available ultrafiltration device equipped with an ultrafiltration membrane (made of polysulfone with a pore size of about 5 nm) until the SiO ２ concentration reached 40% by mass, to obtain silica sol A (pH 10.8, D ＤＬＳ 87 nm, D ＢＥＴ 28 nm). 【0101】 (Production of active silicic acid aqueous solution (a2)) In the active silicic acid aqueous solution (a1) (SiO ２ as 3.2% by mass), the content of sulfuric acid as a stabilizer was 0.9% by mass / SiO ２An 8% by mass aqueous sulfuric acid solution was added to obtain a stabilized activated silica aqueous solution (a2). 【0102】 (Synthesis Example B) A reaction apparatus was used that consisted of a SUS pressure vessel with an internal volume of 3 L, equipped with a stirrer, heating device, etc. The stabilized activated silica aqueous solution (a2) (SiO ２ Using 3.2% by mass of potassium hydroxide aqueous solution, 10% by mass of potassium hydroxide aqueous solution, and pure water, the pH was adjusted to 11.0 and the electrical conductivity to 10.1 mS / cm. After that, the temperature of the liquid inside the container was adjusted to 110-130°C by heating. After the temperature inside the container reached 100-130°C, the stabilized activated silica aqueous solution (a2) (SiO2) was further stabilized while maintaining the temperature inside the container at 110-130°C. ２ 3.2% by mass per minute was continuously supplied as the feed solution until the pH of the reaction solution reached 10.9 and the electrical conductivity reached 3.5 mS / cm, thereby obtaining reaction solution B. 【0103】 Subsequently, the obtained reaction solution B was heated for 2 hours while maintaining a temperature of 110-130°C to obtain dispersion B. 【0104】 The resulting dispersion B is subjected to SiO2 filtration at room temperature using a commercially available ultrafiltration apparatus equipped with an ultrafiltration membrane (polysulfone, pore size approximately 5 nm). ２ Concentrate until the concentration reaches 40% by mass, then add silica sol B (pH 9.8, D ＤＬＳ 55 nm, D ＢＥＴ (23 nm) 【0105】 (Synthesis Example C) A reaction apparatus was used that consisted of a SUS pressure vessel with an internal volume of 3 L, equipped with a stirrer, heating device, etc. Activated silica aqueous solution (a1) (SiO ２ Using 3.5% by mass of potassium hydroxide aqueous solution, 10% by mass of potassium hydroxide aqueous solution, and pure water, the pH was adjusted to 11.1 and the electrical conductivity to 11.7 mS / cm. After that, the temperature of the liquid inside the container was adjusted to 100-120°C by heating. After the temperature inside the container reached 100-120°C, the activated silica aqueous solution (a1) (SiO2) was further heated while maintaining the temperature inside the container at 100-120°C. ２ 3.5% by mass per minute was supplied as the feed solution, and this was converted to reaction solution C until the pH of the reaction solution reached 11.0 and the electrical conductivity reached 3.3 mS / cm. 【0106】Subsequently, the obtained reaction solution C was heated for 1 hour while maintaining a temperature of 100-120°C to obtain dispersion C. 【0107】 The resulting dispersion C is subjected to SiO2 filtration at room temperature using a commercially available ultrafiltration apparatus equipped with an ultrafiltration membrane (polysulfone, pore size approximately 5 nm). ２ Concentrate until the concentration reaches 40% by mass, then add silica sol C (pH 10.7, D ＤＬＳ 44nm, D ＢＥＴ (19 nm) 【0108】 (Synthesis Example D) A reaction apparatus equipped with a stirrer, heating device, etc., in a SUS pressure vessel with an internal volume of 3 L was used. Using colloidal silica manufactured by Nissan Chemical Corporation: trade name Snowtex (registered trademark) O, a 10% by mass potassium hydroxide aqueous solution, and pure water, the pH was adjusted to 11.0 and the electrical conductivity to 3.2 mS / cm, and then the temperature of the liquid inside the vessel was adjusted to 100-120°C by heating. After the temperature inside the vessel reached 100-120°C, while maintaining the temperature inside the vessel at 100-120°C, 10% by mass KOH and an activated silicic acid aqueous solution (a1) (SiO2 ２ 3.5% by mass per minute was supplied as the feed solution, and this was continuously supplied until the pH of the reaction solution reached 10.7 and the electrical conductivity reached 1.5 mS / cm, and this was designated as reaction solution D. 【0109】 Subsequently, the obtained reaction solution D was heated for 1 hour while maintaining a temperature of 100-120°C to obtain dispersion D. 【0110】 The resulting dispersion D is subjected to SiO2 filtration at room temperature using a commercially available ultrafiltration apparatus equipped with an ultrafiltration membrane (polysulfone, pore size approximately 5 nm). ２ Concentrate until the concentration reaches 40% by mass, then add silica sol D (pH 10.7, D ＤＬＳ 51 nm, D ＢＥＴ (33 nm) 【0111】 Silica sol E is a commercially available colloidal silica dispersion, Quattron (registered trademark) PL-3 (pH 7.3, D ＤＬＳ 66 nm, D ＢＥＴ It is 35 nm in size (manufactured by Fuso Chemical Industries, Ltd.). 【0112】(Synthesis Example F) A reaction apparatus was used, which consisted of a SUS pressure-resistant vessel with an internal volume of 3 L, equipped with a stirrer, heating device, etc. After adjusting the pH to 13.1 and the electrical conductivity to 29.1 mS / cm using a 10% by mass sodium hydroxide aqueous solution and pure water, the temperature of the liquid inside the vessel was adjusted to 100-120°C by heating. After the temperature inside the vessel reached 100-120°C, the activated silicic acid aqueous solution (a1) (SiO2) was added while maintaining the temperature inside the vessel at 100-120°C. ２ 3.5% by mass per minute was supplied as the feed solution, and this was continuously supplied until the pH of the reaction solution reached 10.3 and the electrical conductivity reached 0.6 mS / cm, and this was designated as reaction solution F. 【0113】 Subsequently, the obtained reaction solution F was heated for 6 hours while maintaining a temperature of 100-120°C to obtain dispersion F-1. 【0114】 The resulting dispersion F-1 was subjected to SiO2 filtration at room temperature using a commercially available ultrafiltration apparatus equipped with an ultrafiltration membrane (polysulfone, pore size approximately 5 nm). ２ The solution was concentrated to a concentration of 32% by mass to obtain dispersion F-2. 【0115】 Furthermore, dispersion F-2 was passed through a column packed with hydrogen-type strong acid cation exchange resin Amberlite IR-120B at a space velocity of 3.5 per hour, and then SiO was added using pure water and a 10% potassium hydroxide aqueous solution. ２ The concentration (25.5% by mass), pH, and electrical conductivity were adjusted to obtain silica particle dispersion F (pH 10.3, electrical conductivity 2.2 mS / cm, D ＤＬＳ 31 nm, D ＢＥＴ (21 nm) 【0116】 Silica Sol G is a commercially available colloidal silica dispersion, Quattron (registered trademark) PL-2L (pH 7.2, D ＤＬＳ 26 nm, D ＢＥＴ It is 16 nm in size (manufactured by Fuso Chemical Industries, Ltd.). 【0117】(Example 1) 2.75 kg of silica sol A obtained in Synthesis Example A was mixed with 8.20 kg of pure water and 55 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring. Then, the mixture was filtered using filters PED-005 (manufactured by Rokitechno, filter material: polypropylene + diatomaceous earth + glass fiber, nominal pore size: 0.5 μm, total length: 250 mm), MGB-003 (manufactured by Rokitechno, filter material: resin-impregnated glass fiber, nominal pore size: 0.3 μm, total length: 250 mm), and CLN-001 (manufactured by Rokitechno, filter material: nylon, nominal pore size: 0.1 μm, total length: 250 mm) in that order. The mixture was then filtered to obtain a silica particle dispersion for polishing (silica 9.5% by mass, Na 10 ppm, pH 10.2, D ＤＬＳ 87 nm, D ＢＥＴ 28nm, SF1 Ｐ 1.50, heating loss rate of 1.6% at 200°C to 700°C, number of coarse particles 5.0 × 10⁶ ４ A sample size of 0 spherical foreign bodies was obtained (1 unit / ml). 【0118】 (Example 2) 2.75 kg of silica sol A obtained in Synthesis Example A was mixed with 8.20 kg of pure water and 55 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring. The mixture was then filtered using filters PED-005 and CLN-002 (manufactured by Rokitechno, filter material: nylon, nominal pore size: 0.2 μm, total length: 250 mm) in that order, and polishing silica particle dispersion (silica 9.5% by mass, Na 10 ppm, pH 10.2, D ＤＬＳ 87 nm, D ＢＥＴ 28nm, SF1 Ｐ 1.50, heating loss rate of 1.6% at 200°C to 700°C, number of coarse particles 4.9 × 10⁶ ４ We obtained (2 spherical foreign bodies per ml). 【0119】 (Example 3) 2.75 kg of silica sol A obtained in Synthesis Example A was mixed with 8.20 kg of pure water and 55 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring. The mixture was then filtered using filters PED-005 and CLP-003 (manufactured by Rokitechno, filter material: polypropylene, nominal pore size: 0.3 μm, total length: 250 mm) in that order, and polishing silica particle dispersion (silica 9.5% by mass, Na 10 ppm, pH 10.2, D ＤＬＳ 87 nm, D ＢＥＴ 28nm, SF1Ｐ 1.50, heating loss rate of 1.6% at 200°C to 700°C, number of coarse particles 5.0 × 10⁶ ４ We obtained (6 spherical foreign bodies per ml). 【0120】 (Example 4) 2.75 kg of silica sol A obtained in Synthesis Example A was mixed with 8.20 kg of pure water and 55 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring. The mixture was then filtered using filters PED-005 and CLP-005 (manufactured by Rokitechno, filter material: polypropylene, nominal pore size: 0.5 μm, total length: 250 mm) in that order, and polishing silica particle dispersion (silica 9.5% by mass, Na 10 ppm, pH 10.2, D ＤＬＳ 87 nm, D ＢＥＴ 28nm, SF1 Ｐ 1.50, heating loss rate of 1.6% at 200°C to 700°C, number of coarse particles 5.8 × 10⁶ ４ We obtained (13 spherical foreign bodies per ml). 【0121】 (Example 5) 2.75 kg of silica sol A obtained in Synthesis Example A was mixed with 8.20 kg of pure water and 55 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring, and then filtered using filter PED-005 to obtain a silica particle dispersion for polishing (silica 9.5% by mass, Na 10 ppm, pH 10.3, D ＤＬＳ 87 nm, D ＢＥＴ 28nm, SF1 Ｐ 1.50, heating loss rate of 1.6% at 200°C to 700°C, number of coarse particles 5.1 × 10⁶ ４ We obtained 19 spherical foreign bodies per ml. 【0122】 (Example 6) 2.75 kg of silica sol B obtained in Synthesis Example B was mixed with 8.24 kg of pure water and 15 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring. The mixture was then filtered using filters PED-005, MGB-003, and CLN-001 in that order to obtain a silica particle dispersion for polishing (silica 9.1% by mass, Na 3 ppm, pH 10.3, D ＤＬＳ 55 nm, D ＢＥＴ 23 nm, SF1 Ｐ 1.56, heating loss rate at 200°C to 700°C: 1.2%, number of coarse particles: 3.3 × 10⁶ ４ A sample size of 0 spherical foreign bodies was obtained (1 unit / ml). 【0123】 (Example 7) 2.75 kg of silica sol C obtained in Synthesis Example C was mixed with 8.16 kg of pure water and 86 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring, and then filtered using filter PED-005 to obtain a silica particle dispersion for polishing (silica 9.1% by mass, Na 10 ppm, pH 10.3, D ＤＬＳ 44nm, D ＢＥＴ 19nm, SF1 Ｐ 1.51, heating loss rate at 200°C to 700°C: 1.1%, number of coarse particles: 1.4 × 10⁶ ４ We obtained (3 spherical foreign bodies per ml). 【0124】 (Example 8) 2.75 kg of silica sol D obtained in Synthesis Example D was mixed with 8.25 kg of pure water and 5 g of 10% by mass potassium hydroxide aqueous solution under dispersive stirring, and then filtered using filter PED-005 to obtain a silica particle dispersion for polishing (silica 9.4% by mass, Na 12 ppm, pH 10.3, D ＤＬＳ 51 nm, D ＢＥＴ 33 nm, SF1 Ｐ 1.20, heating loss rate at 200°C to 700°C: 1.0%, number of coarse particles: 1.6 × 10⁶ ５ We obtained (3 spherical foreign bodies per ml). 【0125】 (Example 9) 4.40 kg of silica sol F obtained in Synthesis Example F was mixed with 6.58 kg of pure water and 24 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring. The mixture was then filtered using filters PED-005 and SL-010 in sequence to obtain a silica particle dispersion for polishing (silica 9.9% by mass, Na 210 ppm, pH 10.1, D ＤＬＳ 31 nm, D ＢＥＴ 21 nm, SF1 Ｐ 1.31, heating loss rate at 200°C to 700°C: 1.0%, number of coarse particles: 1.5 × 10⁶ ５ We obtained (four spherical foreign bodies per ml). 【0126】 (Comparative Example 1) 2.75 kg of silica sol A obtained in Synthesis Example A was mixed with 8.20 kg of pure water and 55 g of 8% by mass sulfuric acid aqueous solution under dispersive stirring, and then filtered using filter SL-010 to obtain a silica particle dispersion for polishing (silica 9.5% by mass, Na 10 ppm, pH 10.2, DＤＬＳ 87 nm, D ＢＥＴ 28nm, SF1 Ｐ 1.50, heating loss rate at 200°C to 700°C: 1.6%, number of coarse particles: 1.3 × 10⁶ ６ We obtained 29 spherical foreign bodies per ml. 【0127】 (Comparative Example 2) 5.50 kg of silica sol E was mixed with 5.23 kg of pure water and 272 g of 10% potassium hydroxide aqueous solution under dispersive stirring, and then filtered using filter SL-010 to obtain a silica particle dispersion for polishing (9.9% silica by mass, 0 ppm Na, pH 10.1, D ＤＬＳ 66 nm, D ＢＥＴ 35nm, SF1 Ｐ 1.47, heating loss rate at 200°C to 700°C: 2.8%, number of coarse particles: 2.6 × 10⁶ ４ We obtained (1 spherical foreign body per ml). 【0128】 (Comparative Example 3) 5.50 kg of silica sol G was mixed with 5.22 kg of pure water and 280 g of 10% potassium hydroxide aqueous solution under dispersive stirring, and then filtered using filter SL-010 to obtain a silica particle dispersion for polishing (10.0% silica by mass, 0 ppm Na, pH 9.9, D ＤＬＳ 26 nm, D ＢＥＴ 16 nm, SF1 Ｐ 1.43, heating loss rate from 200°C to 700°C: 2.7%, number of coarse particles: 1.9 × 10⁻⁶ ５ We obtained 29 spherical foreign bodies per ml. 【0129】 [Polishing Test] Using the polishing dispersion obtained in the example, the Low-k (BD-1) film on the wafer and SiO ２ The (p-TEOS) film was processed in the following order (1, 2, 3, 4) using a CMP apparatus F-REX300X (manufactured by Ebara Corporation). 【0130】<Process 1: Polishing> Polishing pressure: 210 hPa Retainer ring pressure: 270 hPa Plate rotation speed: 80 rpm Retainer ring rotation speed: 81 rpm Substrate rotation speed: 80 rpm Polishing pad: Nitta DuPont IC1000 Supply rate of polishing composition: 200 mL / min Polishing time: 1 minute Object to be polished (dummy): Wafer with thermal oxide film n=5 Object to be polished (monitor 1): Wafer with Low-k film n=2 Object to be polished (monitor 2): SiO ２ wafer with film, n=2 【0131】 <Process 2: Roll Cleaning> Roll: SCL dry sponge set Flow: Step (1) Roll cleaning, using chemical solution (30x diluted solution of Kanto Chemical's CMP-M02) for 30 seconds, Step (2) Rinse cleaning, using deionized water for 30 seconds 【0132】 <Process 3: Pencil Cleaning> Pencil: Convex pencil sponge Flow: Step (1) Use chemical solution (30x diluted solution of Kanto Chemical's CMP-M02) 3 scans, Step (2) Use deionized water 3 scans 【0133】 <Process 4: Drying> IPA drying 【0134】 [Evaluation of polishing speed] SiO before and after polishing test ２ The film thickness was measured using an optical film thickness measuring device, and the polishing speed was calculated from the difference in film thickness. 【0135】 [Evaluation of scratches] The Low-k film polished using the above polishing speed evaluation was inspected under the following conditions, and the number of scratches was determined. 【0136】 <Defect Inspection> Equipment: Surfscan SP-5 (manufactured by KLA Tencor) 【0137】 <Analysis of Defect Types> Equipment: Review SEM Number of Observations: 100 random points Concave defects like those shown in Figure 3 were identified as scratches. 【0138】 <Calculation of the number of scratches> The number of scratches on the wafer was calculated by multiplying the number of defects of 0.07 μm or larger obtained from the above defect inspection by the percentage of scratches (number of) among 100 defects observed in the analysis of the types of defects. 【0139】Table 1 shows the evaluation results of the abrasive silica particle dispersions for Examples 1-4 and Comparative Examples 1-3. 【0140】 From the results in Table 1, when a Low-k film on a wafer is polished using the silica particle dispersion of the embodiment of the present invention, the number of scratches decreases when the number of spherical foreign objects is 25 or less, regardless of the amount of LPC, and SiO ２ It can be seen that the polishing speed increases when the heat loss rate is 2.5% or less when the film is polished. Furthermore, when the number of spherical foreign objects is 5 or less, the number of scratches is particularly low when the Low-k film is polished, the DLS particle size is 60 nm or larger, and SF1 ｐ When the ratio is 1.40 or higher and the weight loss rate during heating is 2.5% or lower, then SiO ２ A particularly high polishing speed can be achieved when polishing a film. 【0141】 The present invention provides a silica particle dispersion for polishing, a method for producing the same, a polishing composition, and a polishing method that suppress the generation of scratches, which worsen flatness and reduce device yield, while maintaining a high polishing speed when used for CMP polishing of device wafers.

Claims

1. A silica particle dispersion for polishing, comprising silica particles and water, wherein the heating loss rate of the silica particles at 200°C to 700°C is 2.5% or less, and the equivalent circle diameter is 0.48 μm or more and the shape factor SF1 ＬＰ , ＬＰ , ＬＰ , ＬＰ , ２ , ＬＰ , ＬＰ , ２ , ２ is less than 1.50 and the number of spherical foreign substances is 25 or less: The measurement method A is to add pure water to the dispersion and dilute it to a silica concentration of 0.1% by mass. 30 g of the diluted solution is filtered through a filter with an absolute pore diameter of 0.4 μm (filter area 1.8 cm ２ ). After that, the filter is enlarged 5000 times (area 448 μm ２ ) with a scanning electron microscope (SEM) and 20 fields of view are observed. The equivalent circle diameter of the spherical foreign substances is calculated by an image analysis method. Furthermore, the ratio of the area of the circle with the maximum diameter L ＬＰ of the particle, which is the length of the longest straight line connecting any two points on the contour line of the spherical foreign substance, as the diameter, to the projected area S ＬＰ of the spherical foreign substance (L ＬＰ ２ ×π / 4) / S ＬＰ is defined as the shape factor SF1 ＬＰ . The measurement method B is to add pure water to the dispersion and dilute it to a silica concentration of 0.03% by mass. 30 g of the diluted solution is filtered through a filter with an absolute pore diameter of 0.4 μm (filter area 1.8 cm ２ ). After that, the filter is enlarged 5000 times (area 448 μm ２ ) with a scanning electron microscope (SEM) and 67 fields of view are observed. The equivalent circle diameter of the spherical foreign substances is calculated by an image analysis method. Furthermore, the ratio of the area of the circle with the maximum diameter L ＬＰ of the particle, which is the length of the longest straight line connecting any two points on the contour line of the spherical foreign substance, as the diameter, to the projected area S ＬＰ ​​​​​​​​ 2. The shape coefficient SF1 of the silica particles, measured according to the measurement method C below. ｐ The abrasive silica particle dispersion according to claim 1, wherein the ratio is 1.20 or higher: Measurement method C involves observing the silica particles with a transmission electron microscope (TEM) at a magnification of 12,000x or 30,000x, calculating the equivalent circular diameter of 2,000 randomly selected silica particles using an image analysis method, and further calculating the projected area S of the silica particles. Ｐ The maximum diameter L of the particle is the length of the longest straight line connecting any two points on the contour line of the silica particle. Ｐ The ratio of the area of ​​a circle with diameter (L) Ｐ ２ ×π / 4) / S Ｐ shape coefficient SF1 Ｐ This is the method of definition.

3. The abrasive silica particle dispersion according to claim 1, wherein the average primary particle diameter of the silica particles, as measured by the BET method, is 10 to 120 nm.

4. The abrasive silica particle dispersion according to claim 1, wherein the average particle diameter of the silica particles, as measured by dynamic light scattering, is 28 to 200 nm.

5. The abrasive silica particle dispersion according to claim 1, wherein the amount of Na per 10% by mass of silica is 400 ppm or less.

6. The abrasive silica particle dispersion according to claim 1, wherein the pH is 8.0 or higher and 11.5 or lower.

7. An abrasive composition comprising a dispersion of abrasive silica particles according to any one of claims 1 to 6.

8. The polishing composition according to claim 7, for use in chemical mechanical polishing (CMP) of the surface of a silicon wafer or a device wafer having at least one of a metal or insulating material.

9. A polishing method for performing chemical mechanical polishing (CMP) in a semiconductor wiring process using the polishing composition described in claim 7.

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