Polishing composition

Abstract

Provided is a polishing composition that can reduce post-polishing haze at the surface of a polished object. A polishing composition according to the present invention includes a silica sol that includes silica particles that have an average aspect ratio of at least 1.50, the percentage of silica particles in the silica sol that have an aspect ratio of at least 1.50 being at least 40%.

Description

polishing composition

[0001] The present invention relates to a polishing composition.

[0002] In order to realize high integration and high speed of integrated circuits such as ULSI used in computers, design rules for semiconductor devices are becoming finer year by year. As a result, there are increasing cases where even minute surface defects adversely affect the performance of semiconductor devices, and the importance of managing nano-order defects, which were not previously considered a problem, is increasing.

[0003] Surface defect inspection equipment is used to manage surface defects on single crystal silicon substrates (silicon wafers). Defects detected by surface defect inspection equipment include foreign matter and residues on the single crystal silicon substrate that were not completely removed during the polishing, rinsing, and cleaning processes. A typical surface defect inspection equipment irradiates the surface of the single crystal silicon substrate with light such as a laser beam, and receives and analyzes the reflected light as a signal to detect the presence and size of defects.

[0004] When intense light is shone on the mirror-finished surface of a single-crystal silicon substrate after polishing or polishing and rinsing, cloudiness can be observed due to diffused reflection caused by very fine roughness on the surface of the single-crystal silicon substrate. This cloudiness is called haze, and haze can be used as a measure of the roughness of the single-crystal silicon substrate surface. If haze is present on the surface of a single-crystal silicon substrate, the diffused reflection caused by the haze can become noise and interfere with defect detection using a surface defect inspection system. Therefore, as the size of the defects to be detected, i.e., the size of the defects to be controlled, becomes smaller, the need to reduce haze is increasing.

[0005] As a technique for reducing the haze of single crystal silicon substrates (silicon wafers), for example, Japanese Patent Application Laid-Open No. 2016-127268 discloses a polishing liquid composition for silicon wafers obtained by mixing a silica particle dispersion containing silica particles, a basic compound, and an aqueous medium with an aqueous additive solution containing a water-soluble polymer compound and an aqueous medium, wherein the transmittance of the silica particle dispersion at a wavelength of 600 nm is 5.0% or more and 30% or less when the silica particle content is 5% by mass or more and 20% by mass or less.

[0006] However, the technique described in JP 2016-127268 A has a problem in that the reduction of haze is still insufficient.

[0007] Therefore, an object of the present invention is to provide a polishing composition that can reduce haze on the surface of an object to be polished after polishing.

[0008] In order to solve the above problems, the present inventors have conducted extensive research and have found that the above problems can be solved by a polishing composition containing a silica sol, the silica sol containing silica particles having an average aspect ratio of 1.50 or more, and in which the proportion of the number of silica particles having an aspect ratio of 1.50 or more to the total number of silica particles in the silica sol is 40% or more, thereby completing the present invention.

[0009] The following describes in detail the embodiments of the present invention. The embodiments described herein are merely illustrative examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other possible embodiments, methods of use, and operational techniques conceivable by those skilled in the art without departing from the spirit of the present invention are within the scope and spirit of the present invention, as well as within the scope of the claims and their equivalents. The embodiments described herein can be arbitrarily combined to produce other embodiments. Furthermore, in this specification, the range "X to Y" means "X or more and Y or less," and "weight," "weight %," "mass %," and "parts by weight" and "parts by mass" are treated as synonyms. Unless otherwise specified, in this specification, operations and measurements of physical properties are performed at room temperature (20°C to 25°C) and a relative humidity of 40% RH to 50% RH.

[0010] <Polishing Composition> One aspect of the present invention relates to a polishing composition comprising a silica sol, the silica sol containing silica particles having an average aspect ratio of 1.50 or more, and wherein the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the silica sol is 40% or more. With this configuration, it is possible to reduce haze on the surface of an object to be polished after polishing. According to one aspect of the present invention, there is provided a polishing composition that can reduce haze on the surface of an object to be polished after polishing.

[0011] The polishing composition of the present invention contains silica particles having a high average aspect ratio and a silica sol containing a high proportion (abundance rate) of silica particles having a high aspect ratio. By using such silica particles as abrasive grains, it is believed that scraping of the wafer surface is optimized and haze (surface roughness) is reduced.

[0012] (Silica sol) The silica sol according to the present invention contains silica particles having an average aspect ratio of 1.50 or more, and in the silica sol, the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles is 40% or more.

[0013] In this specification, the aspect ratio refers to the value obtained by measuring the long side and short side of the smallest rectangle circumscribing a silica particle and calculating the ratio of the long side to the short side (long side value / short side value). The average aspect ratio is the value obtained by calculating the average aspect ratio of a predetermined number of silica particles (e.g., 100 or more). The aspect ratio and average aspect ratio can be determined, for example, by observation with a scanning electron microscope (SEM). More specifically, the aspect ratio and average aspect ratio are values ​​measured by the method described in the examples.

[0014] The ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles can be determined by observing with a scanning electron microscope (SEM), checking the aspect ratio of all silica particles (for example, 100 or more) in the SEM image, and calculating the ratio (%) of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the SEM image (= the number of silica particles having an aspect ratio of 1.50 or more in the SEM image / the number of all silica particles in the SEM image x 100).Details of the measurement method will be described in Examples.

[0015] In the silica sol according to the present invention, the lower limit of the average aspect ratio of the silica particles is 1.50 or more, preferably 1.55 or more, and more preferably 1.60 or more. The upper limit of the average aspect ratio of the silica particles is, for example, 5.00 or less, preferably 4.00 or less, and more preferably 3.00 or less. The average aspect ratio of the silica particles is preferably 1.50 or more and 5.00 or less, more preferably 1.55 or more and 4.00 or less, and even more preferably 1.60 or more and 3.00 or less.

[0016] In the silica sol according to the present invention, the lower limit of the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the total number of silica particles is 40% or more, preferably 50% or more.The upper limit of the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the total number of silica particles is not particularly limited, and may be, for example, 80% or less or 70% or less.The ratio of the number of silica particles having an aspect ratio of 1.50 or more to the total number of silica particles is preferably 40% or more and 80% or less, more preferably 50% or more and 70% or less.

[0017] In the silica sol according to the present invention, the average circularity of the silica particles is preferably 0.80 or less, from the viewpoint of being able to more effectively exhibit the effects of the present invention. In a preferred embodiment, the silica sol according to the present invention contains silica particles having an average aspect ratio of 1.50 or more and an average circularity of 0.80 or less, and the proportion of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the silica sol is 40% or more.

[0018] In this specification, the average circularity refers to the calculated average circularity of all silica particles contained in the silica sol. The average circularity is measured by the method described in the Examples.

[0019] The upper limit of the average circularity of the silica particles is more preferably 0.75 or less, and even more preferably 0.70 or less. The lower limit of the average circularity of the silica particles is not particularly limited, and may be, for example, 0.30 or more, 0.40 or more, or 0.50 or more. The average circularity of the silica particles is preferably 0.30 or more and 0.80 or less, more preferably 0.40 or more and 0.75 or less, and even more preferably 0.50 or more and 0.70 or less.

[0020] In the silica sol according to the present invention, the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles is preferably 40% or less. In a preferred embodiment, the silica sol according to the present invention comprises silica particles having an average aspect ratio of 1.50 or more, and the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the silica sol is 40% or more, and the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles is 40% or less. In a more preferred embodiment, the silica sol according to the present invention comprises silica particles having an average aspect ratio of 1.50 or more and an average circularity of 0.80 or less, and the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the silica sol is 40% or more, and the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles is 40% or less.

[0021] The ratio of the number of silica particles with a circularity of 0.90 or more to the number of all silica particles can be obtained by carrying out scanning electron microscope (SEM) observation, measuring the circularity of each silica particle in SEM image, and calculating the ratio (%) of the number of silica particles with a circularity of 0.90 or more to the number of all silica particles (for example, 100 or more) in SEM image (= the number of silica particles with a circularity of 0.90 or more in SEM image / the number of all silica particles in SEM image x 100).The details of measurement method will be described in Examples.

[0022] In the silica sol according to the present invention, the upper limit of the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles is more preferably 30% or less.The lower limit of the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles is not particularly limited, and may be, for example, 5% or more or 10% or more.The ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles is preferably 5% or more and 40% or less, more preferably 10% or more and 30% or less.

[0023] In the silica sol according to the present invention, the average primary particle diameter of the silica particles is, for example, 5 nm to 40 nm, preferably 10 nm to 30 nm. The average primary particle diameter of the silica particles can be calculated, for example, based on the specific surface area (SA) of the silica particles calculated by the BET method and the density of the silica particles. More specifically, the average primary particle diameter of the silica particles is a value measured by the method described in the examples.

[0024] In the silica sol according to the present invention, the average secondary particle diameter of the silica particles is, for example, 30 nm or more and 90 nm or less, preferably 30 nm or more and 80 nm or less, more preferably 30 nm or more and 70 nm or less, and even more preferably 40 nm or more and 60 nm or less. The average secondary particle diameter of the silica particles can be measured, for example, by a dynamic light scattering method, such as a laser diffraction scattering method. More specifically, the average secondary particle diameter of the silica particles is a value measured by the method described in the examples.

[0025] In the silica sol according to the present invention, the average degree of association of silica particles (ratio of average secondary particle size to average primary particle size) is, for example, 1.8 or more and 5.5 or less, preferably 2.0 or more and 5.0 or less, and more preferably 2.2 or more and 4.5 or less.

[0026] When the polishing composition of the present invention is in the form of a concentrated solution that is used for polishing after being diluted with a dispersion medium or the like, the content of silica particles (abrasive grains) in this concentrated solution is not particularly limited.The lower limit of the content of silica particles in the concentrated solution is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.025% by mass or more, even more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, even more particularly preferably 1% by mass or more, and most preferably 3% by mass or more.From the viewpoint of storage stability, filterability, etc., the upper limit of the content of silica particles (abrasive grains) in the concentrated solution is preferably 50% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, particularly preferably 9% by mass or less.

[0027] When the polishing composition of the present invention is in the form of a diluted solution, the content of silica particles (abrasive grains) in the diluted solution is not particularly limited.The lower limit of the content of silica particles in the diluted solution is not particularly limited, and is, for example, 0.001 mass% or more, preferably 0.010 mass% or more, more preferably 0.025 mass% or more, and even more preferably 0.050 mass% or more.The upper limit of the content of silica particles in the diluted solution is not particularly limited, and is, for example, 3.000 mass% or less, preferably 1.000 mass% or less, more preferably 0.500 mass% or less, and even more preferably 0.100 mass% or less.The content of silica particles in the diluted solution is, for example, 0.001 mass% or more to 3.000 mass% or less, preferably 0.010 mass% or more to 1.000 mass% or less, more preferably 0.025 mass% or more to 0.500 mass% or less, and even more preferably 0.050 mass% or more to 0.100 mass% or less.

[0028] When the polishing composition of the present invention is in the form of a diluted solution, it is preferable to adjust the content of silica particles (abrasive grains) in the diluted solution by diluting a concentrated solution of the polishing composition with a dispersant such as water, or a solution or dispersion containing an optional polishing aid.

[0029] In the silica sol according to the present invention, the content of silica particles can be appropriately adjusted so as to be the same as the content of silica particles in the polishing composition described above.

[0030] The silica sol according to the present invention may contain water as a component other than silica particles. The content of water in the silica sol can be appropriately adjusted based on the desired content of silica particles.

[0031] An example of a method for producing a silica sol according to the present invention will be described below, but the method for producing a silica sol according to the present invention is not limited to the following method.

[0032] In one embodiment, the method for producing a silica sol according to the present invention includes a silica core particle preparation step of preparing a first liquid containing silica core particles having an average longest diameter of primary particles of 20 nm or less, and a bonding step of holding the first liquid for 72 hours or more to prepare a second liquid containing linked silica core particles.

[0033] In the silica core particle preparation step, a first liquid containing silica core particles having an average longest diameter of primary particles of 20 nm or less is prepared.

[0034] In this specification, the silica core particles contained in the first liquid include silica particles in which two or more primary particles are bonded together.

[0035] In this specification, the average longest diameter of the primary particles of the silica core particles means a value obtained by measuring the longest diameter of the primary particle of each silica core particle in a photographed scanning electron microscope (SEM) image and calculating the average longest diameter of the primary particles of all silica core particles in the SEM image. The average longest diameter of the primary particles is a value calculated by the method described in the examples.

[0036] In this specification, the average value of the longest diameter of the primary particles of the silica core particles is also simply referred to as the "average longest diameter of the silica core particles."

[0037] The first liquid according to the present invention contains silica core particles having an average longest diameter of primary particles of 20 nm or less. If the average longest diameter of the primary particles of the silica core particles exceeds 20 nm, irregularly shaped silica particles cannot be obtained in the bonding step described below. The upper limit of the average longest diameter of the silica core particles is preferably 18 nm or less. The lower limit of the average longest diameter of the silica core particles is not particularly limited and is, for example, 2 nm or more, preferably 5 nm or more, and more preferably 10 nm or more. The average longest diameter of the silica core particles is preferably 2 nm or more and 20 nm or less, more preferably 5 nm or more and 20 nm or less, even more preferably 10 nm or more and 20 nm or less, and particularly preferably 10 nm or more and 18 nm or less.

[0038] In the silica core particle preparation step, the method for preparing the first liquid is not particularly limited, and a conventionally known method can be used. For example, the first liquid containing silica core particles can be obtained by reacting an alkoxysilane or a condensate thereof in an organic solvent containing water and an alkali catalyst.

[0039] Hereinafter, one embodiment of the silica core particle preparation step will be described.

[0040] In one embodiment, the silica core particle preparation step includes adding and mixing a liquid (B1) containing at least one of an alkoxysilane and a condensate thereof and a second organic solvent to a liquid (A) containing an alkali catalyst, water, and a first organic solvent, or a liquid (C1) containing the liquid (B1) and water but not containing an alkali catalyst, and terminating the addition when the average longest diameter of the primary particles of the silica core particles is 20 nm or less to prepare the first liquid.

[0041] The liquid (A) according to the present embodiment contains an alkali catalyst, water, and a first organic solvent. In addition to the alkali catalyst, water, and first organic solvent, the liquid (A) may contain other components as long as the effects of the present invention are not impaired.

[0042] In a preferred embodiment, the liquid (A) comprises an alkaline catalyst, water, and a first organic solvent. By using the liquid (A) comprising an alkaline catalyst, water, and a first organic solvent, the impurities contained in the first liquid can be reduced as much as possible. This reduces the impact of impurities on polishing when the silica sol obtained by the manufacturing method of this embodiment is used in a polishing composition. Furthermore, the polishing slurry can be used for polishing objects that require high concentrations of metal impurities, such as silicon wafers and device wafers, providing a polishing slurry that can be widely used.

[0043] As the alkali catalyst contained in liquid (A), conventionally known catalysts can be used. From the viewpoint of minimizing the inclusion of metal impurities and the like, examples of the alkali catalyst include ammonia, tetramethylammonium hydroxide and other ammonium salts, ethylenediamine, diethylenetriamine, triethylenetetraamine, urea, monoethanolamine, diethanolamine, triethanolamine, and tetramethylguanidine. Among these, from the viewpoint of excellent catalytic activity, ammonia, tetramethylammonium hydroxide and other ammonium salts are more preferred, and ammonia is even more preferred. Ammonia is highly volatile and can be easily removed during the silica sol production process. The alkali catalyst may be used alone or in combination of two or more. The alkali catalyst may also be in the form of an aqueous solution.

[0044] The water contained in the liquid (A) is preferably pure water or ultrapure water from the viewpoint of minimizing the inclusion of metal impurities and the like. When the alkali catalyst is in the form of an aqueous solution, the water contained therein is the water contained in the liquid (A). Therefore, the water contained in the aqueous solution of the alkali catalyst is also preferably pure water or ultrapure water.

[0045] The first organic solvent contained in the liquid (A) is preferably a hydrophilic organic solvent, and specific examples thereof include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; etc. The first organic solvent may be used alone or in combination of two or more.

[0046] The first organic solvent according to this embodiment is preferably an alcohol. The use of an alcohol has the effect of easily replacing the alcohol with water by thermal distillation during the water replacement step described below. Furthermore, from the viewpoint of recovery and reuse of the organic solvent, it is preferable to use the same type of alcohol as that produced by hydrolysis of the alkoxysilane.

[0047] Among alcohols, at least one of methanol, ethanol, isopropanol, etc. is particularly preferred. When tetramethoxysilane is used as the alkoxysilane, the first organic solvent is preferably methanol.

[0048] The contents of the alkali catalyst, water, and first organic catalyst in the liquid (A) are not particularly limited, and can be adjusted appropriately so that the average longest diameter of the silica core particles has a desired value.

[0049] The lower limit of the content of the alkali catalyst (e.g., ammonia) in the liquid (A) is, for example, 0.1 mass% or more, preferably 0.3 mass% or more, relative to the total amount (100 mass%) of the liquid (A), from the viewpoint of its function as a hydrolysis catalyst or the growth of silica particles. The lower limit of the content of the alkali catalyst (e.g., ammonia) may be 0.5 mass% or more, 1.0 mass% or more, or 2.0 mass% or more, relative to the total amount (100 mass%) of the liquid (A). The upper limit of the content of the alkali catalyst (e.g., ammonia) is not particularly limited. From the viewpoint of productivity and cost, the upper limit of the content of the alkali catalyst (e.g., ammonia) is preferably 50 mass% or less, relative to the total amount (100 mass%) of the liquid (A). The upper limit of the content of the alkali catalyst (e.g., ammonia) may be 40 mass% or less, 20 mass% or less, 15 mass% or less, or 10 mass% or less, relative to the total amount (100 mass%) of the liquid (A). The content of the alkali catalyst (e.g., ammonia) may be 0.1% by mass or more and 50% by mass or less, 0.3% by mass or more and 40% by mass or less, 0.5% by mass or more and 20% by mass or less, 1.0% by mass or more and 15% by mass or less, or 2.0% by mass or more and 10% by mass or less, relative to the total amount (100% by mass) of the liquid (A).

[0050] The water content in liquid (A) is adjusted according to the amount of alkoxysilane or its condensate used in the reaction. From the viewpoint of hydrolysis of alkoxysilane, the lower limit of the water content is preferably 5% by mass or more relative to the total amount (100% by mass) of liquid (A). From the viewpoint of compatibility with liquid (B1), the upper limit of the water content is preferably 50% by mass or less, more preferably 40% by mass or less, relative to the total amount (100% by mass) of liquid (A). The upper limit of the water content may be 20% by mass or less relative to the total amount (100% by mass) of liquid (A). The water content may be 5% by mass or more and 50% by mass or less, 5% by mass or more and 40% by mass or less, or 5% by mass or more and 20% by mass or less, relative to the total amount (100% by mass) of liquid (A).

[0051] The lower limit of the content of the first organic solvent (e.g., methanol) in the liquid (A) is preferably 10% by mass or more, more preferably 20% by mass or more, based on the total amount (100% by mass) of the liquid (A), from the viewpoint of compatibility with the liquid (B1). The lower limit of the content of the first organic solvent (e.g., methanol) may be 50% by mass or more or 75% by mass or more, based on the total amount (100% by mass) of the liquid (A). The upper limit of the content of the first organic solvent (e.g., methanol) is preferably 98% by mass or less, more preferably 95% by mass or less, based on the total amount (100% by mass) of the liquid (A), from the viewpoint of dispersibility. The upper limit of the content of the first organic solvent (e.g., methanol) may be 90% by mass or less or 85% by mass or less, based on the total amount (100% by mass) of the liquid (A). The content of the first organic solvent (e.g., methanol) may be 10% by mass or more and 98% by mass or less, 20% by mass or more and 95% by mass or less, 50% by mass or more and 90% by mass or less, or 75% by mass or more and 85% by mass or less, relative to the total amount (100% by mass) of the liquid (A).

[0052] The method for producing the liquid (A) is not particularly limited, and for example, a method in which an alkali catalyst, water, a first organic solvent, and, if necessary, other components are mixed by stirring can be used.

[0053] The liquid (B1) according to this embodiment contains at least one of an alkoxysilane and its condensate, and a second organic solvent. In addition to the at least one of an alkoxysilane and its condensate, and the second organic solvent, the liquid (B1) may contain other components within a range that does not impair the effects of the present invention.

[0054] In this specification, "at least one of an alkoxysilane and a condensate thereof" is also collectively referred to simply as "alkoxysilane, etc."

[0055] In a preferred embodiment, the liquid (B1) comprises at least one of an alkoxysilane and its condensate and a second organic solvent. By using the liquid (B1) comprising at least one of an alkoxysilane and its condensate and a second organic solvent, the impurities contained in the first liquid can be reduced as much as possible. This reduces the impact of impurities on polishing when the silica sol obtained by the manufacturing method of this embodiment is used in a polishing composition. Furthermore, the polishing slurry can be used for polishing objects that require high concentrations of metal impurities, such as silicon wafers and device wafers, providing a polishing slurry that can be widely applied.

[0056] Examples of the alkoxysilane or condensate thereof contained in the liquid (B1) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and condensates thereof. These may be used alone or in combination of two or more. Among them, tetramethoxysilane is preferred from the viewpoint of having suitable hydrolysis reactivity.

[0057] As the second organic solvent contained in the liquid (B1), it is preferable to use a hydrophilic organic solvent. Specific examples thereof include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, and 1,4-butanediol; and ketones such as acetone and methyl ethyl ketone.

[0058] The second organic solvent according to this embodiment is preferably an alcohol. The use of an alcohol has the effect of easily replacing the alcohol with water by thermal distillation during the water replacement step described below. Furthermore, from the viewpoint of recovery and reuse of the organic solvent, it is preferable to use the same type of alcohol as that produced by hydrolysis of the alkoxysilane.

[0059] Among alcohols, at least one of methanol, ethanol, isopropanol, etc. is particularly preferred. When tetramethoxysilane is used as the alkoxysilane, the second organic solvent is preferably methanol.

[0060] The contents of the alkoxysilane and the second organic solvent in the liquid (B1) are not particularly limited, and can be appropriately adjusted so as to make the average longest diameter of the silica core particles a desired value.

[0061] The lower limit of the content of alkoxysilanes etc. (e.g., tetramethoxysilane etc.) in the liquid (B1) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 75% by mass or more. The upper limit of the content of alkoxysilanes etc. (e.g., tetramethoxysilane etc.) is preferably 98% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and particularly preferably 85% by mass or less. The content of alkoxysilanes etc. (e.g., tetramethoxysilane etc.) is preferably 50% by mass or more and 98% by mass or less, more preferably 60% by mass or more and 95% by mass or less, even more preferably 70% by mass or more and 90% by mass or less, and particularly preferably 75% by mass or more and 85% by mass or less.

[0062] The lower limit of the content of the second organic solvent (e.g., methanol) in the liquid (B1) is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and particularly preferably 15% by mass or more. The upper limit of the content of the second organic solvent (e.g., methanol) is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. The content of the second organic solvent (e.g., methanol) is preferably 2% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, even more preferably 10% by mass or more and 30% by mass or less, and particularly preferably 15% by mass or more and 25% by mass or less.

[0063] When the contents of the alkoxysilane and the second organic solvent in the liquid (B1) are within the above ranges, the miscibility when mixed with the liquid (A) can be improved.

[0064] The alkoxysilane condensate in the liquid (B1) is, for example, a dimer to a dodecamer, and preferably a tetramer to an octamer.

[0065] The method for producing the liquid (B1) is not particularly limited. From the viewpoint of miscibility, the method for producing the liquid (B1) is preferably a method in which the alkoxysilane and, if necessary, other components are stirred and mixed in the second organic solvent.

[0066] The liquid (C1) according to this embodiment contains water but does not contain an alkali catalyst. The absence of an alkali catalyst in the liquid (C1) can prevent the concentration of the alkali catalyst from becoming locally high during mixing. The liquid (C1) can contain components other than the alkali catalyst within a range that does not impair the effects of the present invention.

[0067] In a preferred embodiment, the liquid (C1) is made of water. By using the liquid (C1) as water, the impurities contained in the first liquid can be reduced as much as possible. This makes it possible to suppress the influence of impurities on polishing when the silica sol obtained by the manufacturing method of this embodiment is used in a polishing composition. In addition, it can be used for polishing objects that do not tolerate metal impurities, such as silicon wafers and device wafers, and a polishing slurry that can be widely applied can be provided.

[0068] The water contained in the liquid (C1) is preferably pure water or ultrapure water, from the viewpoint of minimizing the inclusion of metal impurities and the like.

[0069] The water content in the liquid (C1) is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass.

[0070] In this embodiment, liquid (B1), or liquid (B1) and liquid (C1), are added to liquid (A) and mixed. When liquid (B1) is mixed with liquid (A), silica core particles are generated by hydrolysis and polycondensation of alkoxysilanes, etc. The addition of liquid (B1), or liquid (B1) and liquid (C1), is terminated when the average longest diameter of the silica core particles is 20 nm or less. This stops the growth of the silica core particles and allows the preparation of the first liquid. In the silica core particle preparation step, the addition of liquid (B1), or the addition of liquid (B1) and liquid (C1), may be temporarily stopped in order to measure the average longest diameter of the silica core particles.

[0071] When adding and mixing the liquid (B1) or the liquid (B1) and the liquid (C1) to the liquid (A), it is preferable to stir the liquid (A). The stirring speed is not particularly limited and is, for example, 30 to 500 rpm.

[0072] When adding the liquid (B1) to the liquid (A) and mixing them, the method of adding the liquid (B1) is not particularly limited, and methods such as continuous addition and divided addition (e.g., dropwise addition) can be used.

[0073] When adding and mixing the liquid (B1) to the liquid (A), the addition rate of the liquid (B1) is not particularly limited and can be appropriately adjusted within a range in which a gel-like substance does not form. For example, the addition rate of the liquid (B1) is 8.5 × 10 silicon atoms per 1 mol of water contained in the liquid (A). －４ ~5.6 x 10 －３ mol / min. Silicon atom conversion means that the number of moles of silicon atoms contained in the alkoxysilane and its condensate is defined as the number of moles of the alkoxysilane and its condensate. For example, when the alkoxysilane is tetramethoxysilane, 1 mole of tetramethoxysilane is equivalent to 1 mole of silicon atoms. Furthermore, when the condensate of tetramethoxysilane is a tetramer, 1 mole of the condensate is equivalent to 4 moles of silicon atoms.

[0074] When adding liquid (B1) and liquid (C1) to liquid (A) and mixing them, the method of adding liquid (B1) and liquid (C1) is not particularly limited. Approximately constant amounts of each may be added to liquid (A) simultaneously, or liquid (B1) and liquid (C1) may be added alternately to liquid (A). Liquid (B1) and liquid (C1) may also be added at random. Among these, from the viewpoint of suppressing changes in the amount of water used in the synthesis reaction, the method of adding liquid (B1) and liquid (C1) simultaneously is preferred, and the method of adding constant amounts of liquid (B1) and liquid (C1) simultaneously is more preferred.

[0075] As a method for adding the liquid (B1) and the liquid (C1) to the liquid (A), a method in which the liquid (B1) and the liquid (C1) are added in portions (for example, dropwise) or continuously to the liquid (A) is preferably used, from the viewpoint of being able to prevent the concentration of the alkali catalyst from becoming locally high.

[0076] When adding and mixing the liquids (B1) and (C1) to the liquid (A), the addition rates of the liquids (B1) and (C1) are not particularly limited and can be adjusted as appropriate within a range that does not generate a gel. The addition rate of the liquid (B1) can be the same as that described above. The addition rate of the liquid (C1) is, for example, 1 mol / min or more and 3 mol / min or less, preferably 2 mol / min, calculated as water, per 1 mol (in terms of silicon atoms) of the alkoxysilane and its condensate added as the liquid (B1).

[0077] The temperatures of the liquid (A), the liquid (B1), and the liquid (C1) when preparing the first liquid are not particularly limited and are, for example, from 5° C. to 100° C., and preferably from 5° C. to 70° C. It is preferable that the temperatures of the liquid (A), the liquid (B1), the liquid (C1), and the first liquid during preparation are the same.

[0078] The preparation of the first liquid can be carried out under any pressure condition, such as reduced pressure, normal pressure, or increased pressure, although from the viewpoint of production costs, it is preferably carried out under normal pressure.

[0079] In this manner, the first liquid can be prepared. After preparing the first liquid, the first liquid can be diluted to adjust the formation of linked silica core particles in the bonding step described below. The same organic solvent as that contained in liquid (A) can be used for dilution.

[0080] Bonding Step In the bonding step, the first liquid is held for 72 hours or more to prepare a second liquid containing linked silica core particles.

[0081] In this specification, the term "connected silica core particles" refers to silica particles in which two or more primary particles, preferably three or more primary particles, are bonded together.

[0082] In this specification, "keeping" means maintaining the first liquid in a stirred or stationary state. The keeping may be performed in the same device after the preparation of the first liquid, or may be performed after the first liquid is transferred to another device. The keeping is preferably performed in the same device after the preparation of the first liquid.

[0083] In this specification, "holding the first liquid for 72 hours or more" means holding the first liquid for 72 hours or more from the completion of the preparation of the first liquid, and more specifically means holding the first liquid for 72 hours or more from the time when the addition of the above-mentioned liquid (B1) or the liquid (B1) and the liquid (C1) is completed.

[0084] The lower limit of the time for retaining the first liquid is not particularly limited as long as it is 72 hours or more. The lower limit of the time for retaining the first liquid may be 100 hours or more or 120 hours or more. The upper limit of the time for retaining the first liquid is preferably 200 hours or less, from the viewpoint of being able to suppress particle aggregation. The upper limit of the time for retaining the first liquid may be 170 hours or less or 150 hours or less. The time for retaining the first liquid may be 72 hours or more and 200 hours or less, 100 hours or more and 170 hours or less, or 120 hours or more and 150 hours or less.

[0085] When the first liquid is held, the first liquid may be stirred, left to stand, or a combination of stirring and standing. The stirring speed is not particularly limited and is, for example, 30 to 500 rpm.

[0086] The temperature at which the first liquid is maintained is not particularly limited and is, for example, from 5° C. to 100° C., preferably from 5° C. to 70° C., and more preferably from 5° C. to 60° C. The temperature at which the first liquid is maintained may be constant or may vary.

[0087] The first liquid may be retained under any of reduced pressure, normal pressure, and increased pressure, although normal pressure is preferred from the viewpoint of production costs.

[0088] In this manner, the second liquid can be prepared.

[0089] The prepared second liquid can be used as a silica sol as it is. The prepared second liquid may be subjected to a growth process, a post-process, etc., which will be described later, and then the resulting liquid may be used as a silica sol. In a preferred embodiment, a water substitution process is performed in which the organic solvent present in the second liquid is substituted with water, from the viewpoint of being able to suppress aggregation of silica particles.

[0090] Growth Step In one embodiment, the method for producing a silica sol according to the present invention can include a growth step in which, after the above-mentioned bonding step, a liquid (B2) containing at least one of an alkoxysilane and a condensate thereof and a third organic solvent, or a liquid (C2) containing the liquid (B2) and water but not containing an alkali catalyst, is added to and mixed with the second liquid to prepare a third liquid containing grown linked silica core particles.

[0091] In this specification, the term "grown linked silica core particles" means that at least one of the average primary particle size and the average secondary particle size of the grown linked silica core particles contained in the third liquid is larger than that of the grown linked silica core particles contained in the second liquid.

[0092] The liquid (B2) contains at least one of an alkoxysilane and its condensate and a third organic solvent. In addition to the at least one of an alkoxysilane and its condensate and the third organic solvent, the liquid (B2) can contain other components within a range that does not impair the effects of the present invention.

[0093] In a preferred embodiment, liquid (B2) comprises at least one of an alkoxysilane and its condensate and a third organic solvent. By using liquid (B2) comprising at least one of an alkoxysilane and its condensate and a third organic solvent, the impurities contained in the third liquid can be reduced as much as possible. This allows the silica sol obtained by the manufacturing method of this embodiment to be used in a polishing composition, thereby suppressing the influence of impurities on polishing. Furthermore, the silica sol can be used for polishing objects that are sensitive to metal impurities, such as silicon wafers and device wafers, providing a polishing slurry that can be widely applied.

[0094] The explanation of the liquid (B2) is the same as that of the liquid (B1) described above, and therefore will be omitted. The explanation of the liquid (C2) is the same as that of the liquid (C1) described above, and therefore will be omitted.

[0095] In the growth step, liquid (B2), or liquid (B2) and liquid (C2), are added to and mixed with the second liquid. When liquid (B2) is mixed with the second liquid, the alkoxysilane and the like undergo hydrolysis and polycondensation, causing the linked silica core particles contained in the second liquid to grow. By terminating the addition of liquid (B2), or liquids (B2) and (C2), the growth of the linked silica core particles can be stopped, and a third liquid can be prepared.

[0096] The conditions for adding and mixing the liquid (B2) or the liquids (B2) and (C2) to the second liquid are the same as the conditions for adding and mixing the liquid (B1) or the liquids (B1) and (C1) to the above-mentioned liquid (A), and therefore the explanation will be omitted. The second liquid, the liquid (B2), and the liquid (C2) correspond to the liquid (A), the liquid (B1), and the liquid (C1), respectively.

[0097] In this manner, the third liquid can be prepared.

[0098] The prepared third liquid can be used as a silica sol as it is. The prepared third liquid may be subjected to a post-processing step described below, and the resulting liquid may be used as a silica sol. In a preferred embodiment, a water substitution step is performed in which the organic solvent present in the third liquid is substituted with water, from the viewpoint of suppressing aggregation of silica particles.

[0099] Post-Step In the method for producing a silica sol of the present invention, after the above-mentioned bonding step or growing step is performed, a post-step described below may be performed.

[0100] Specifically, at least one of the following steps may be performed: a water replacement step in which the organic solvent present in the second or third liquid is replaced with water; or a concentration step in which the second or third liquid is concentrated. More specifically, only the concentration step in which the second or third liquid is concentrated may be performed; or only the water replacement step in which the organic solvent in the second or third liquid is replaced with water may be performed; or the concentration step may be followed by a water replacement step in which the organic solvent in the concentrated liquid is replaced with water; or the water replacement step may be followed by a concentration step in which the water-replaced liquid is concentrated. Furthermore, the concentration step may be performed multiple times, and in such cases, a water replacement step may be performed between concentration steps. For example, after the concentration step, a water replacement step in which the organic solvent in the concentrated liquid is replaced with water may be performed, and a concentration step in which the water-replaced liquid is concentrated may be further performed.

[0101] As one embodiment of the present invention, the method for producing a silica sol of the present invention may include a step of substituting the organic solvent contained in the second liquid or the third liquid with water (also referred to simply as a "water substitution step" in this specification). The second liquid or the third liquid in this form also includes a form in which the second liquid or the third liquid has been subjected to a concentration step.

[0102] When ammonia is selected as the alkaline catalyst by replacing the organic solvent in the second or third liquid with water, the pH of the produced silica sol can be adjusted to a neutral range, and by removing unreacted substances contained in the second or third liquid, a silica sol that is stable for a long period of time can be obtained.

[0103] The organic solvent in the second or third liquid may be replaced with water by a conventional method, for example, by adding water dropwise to the second or third liquid while maintaining the liquid volume at a certain level or higher, followed by distillation under heating. In this case, the replacement operation is preferably carried out until the liquid temperature and the column top temperature reach the boiling point of the replaced water.

[0104] The water used in this step is preferably pure water or ultrapure water, from the viewpoint of minimizing the inclusion of metal impurities and the like.

[0105] As a method for replacing the organic solvent in the second liquid or the third liquid with water, a method in which the second liquid or the third liquid is centrifuged to separate the silica particles (including linked silica core particles or grown linked silica core particles) and then redispersed in water can also be mentioned.

[0106] Concentration Step As one embodiment of the present invention, the method for producing a silica sol of the present invention may further include a step of concentrating the second liquid or the third liquid (also referred to simply as a "concentration step" in this specification). Note that the second liquid or the third liquid in this embodiment also includes an embodiment in which the second liquid or the third liquid has been subjected to a water substitution step.

[0107] The method for concentrating the second or third liquid is not particularly limited, and any conventionally known method can be used, such as a heat concentration method or a membrane concentration method.

[0108] In the heat concentration method, the second liquid or the third liquid is heated and concentrated under normal pressure or reduced pressure, thereby obtaining a concentrated second liquid or third liquid.

[0109] In the membrane concentration method, for example, the second liquid or the third liquid can be concentrated by membrane separation using an ultrafiltration method that can filter silica particles (including linked silica core particles or grown linked silica core particles). The molecular weight cutoff of the ultrafiltration membrane is not particularly limited, but the molecular weight cutoff can be selected according to the particle size to be produced. The material constituting the ultrafiltration membrane is not particularly limited, but examples thereof include polysulfone, polyacrylonitrile, sintered metal, ceramic, and carbon. The form of the ultrafiltration membrane is not particularly limited, but examples thereof include spiral, tubular, and hollow fiber types. In the ultrafiltration method, the operating pressure is not particularly limited, but can be set to be equal to or lower than the operating pressure of the ultrafiltration membrane to be used.

[0110] (Dispersion Medium) In one embodiment of the present invention, the polishing composition preferably contains a dispersion medium (particularly water). The dispersion medium (particularly water) has the function of dissolving or dispersing the components contained in the polishing composition.

[0111] It is preferable that the water contains as few impurities as possible to prevent contamination of the polishing object or inhibition of the action of other components. For example, a water having a total transition metal ion content of 100 ppb or less is preferable. The purity of the water can be increased by, for example, removing impurity ions using an ion exchange resin, removing foreign matter using a filter, or by distillation. Specifically, it is preferable to use, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water, etc.

[0112] The dispersion medium may be a mixed solvent of water and an organic solvent for dispersing or dissolving each component. In this case, examples of the organic solvent used include acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, propylene glycol, and the like, which are organic solvents miscible with water. Alternatively, these organic solvents may be used without mixing with water, and the components may be dispersed or dissolved therein, and then mixed with water. These organic solvents may be used alone or in combination of two or more. Here, it is preferable that the dispersion medium is water alone.

[0113] (Basic Compound) In one embodiment of the present invention, the polishing composition may contain a basic compound. Here, the basic compound refers to a compound that has the function of increasing the pH of the polishing composition when added to the polishing composition. The basic compound has the function of chemically polishing the surface of the object to be polished by etching and the function of improving the dispersion stability of silica particles (abrasive grains). In addition, the basic compound can be used as a pH adjuster.

[0114] The basic compound can be selected from a variety of compounds depending on the desired function, and may be used singly or in combination of two or more.

[0115] Specific examples of basic compounds include hydroxides or salts of Group 2 elements or alkali metals, quaternary ammonium compounds, ammonia or its salts, amines, and the like.

[0116] In the hydroxides or salts of Group 2 elements or alkali metals, the Group 2 elements are not particularly limited, but alkaline earth metals are preferably used, such as calcium. Examples of alkali metals include potassium and sodium. Examples of salts include carbonates, bicarbonates, sulfates, and acetates. Examples of hydroxides or salts of Group 2 elements or alkali metals include calcium hydroxide, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium sulfate, potassium acetate, potassium chloride, sodium hydroxide, sodium bicarbonate, and sodium carbonate.

[0117] Quaternary ammonium compounds include salts such as hydroxides, chlorides, carbonates, hydrogen carbonates, sulfates, and phosphates of tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc. Specific examples include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; tetraalkylammonium carbonates such as tetramethylammonium carbonate, tetraethylammonium carbonate, and tetrabutylammonium carbonate; and tetraalkylammonium chlorides such as tetramethylammonium chloride, tetraethylammonium chloride, and tetrabutylammonium chloride. Other ammonium salts include ammonium carbonate and ammonium hydrogen carbonate.

[0118] Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, and guanidine.

[0119] In one embodiment of the present invention, the polishing composition contains ammonia as the basic compound.

[0120] In one embodiment of the present invention, when the polishing composition of the present invention is in the form of a concentrated liquid, the content of basic compounds in the polishing composition (when two or more are used, their total amount) is preferably 0.002 mass% or more, more preferably 0.02 mass% or more.By increasing the content of basic compounds, a high polishing rate can be easily obtained.In addition, in this case, from the viewpoint of storage stability, filterability, etc., the content of basic compounds in the polishing composition (when two or more are used, their total amount) is preferably 10 mass% or less, more preferably 5 mass% or less, even more preferably 3 mass% or less, and particularly preferably 1 mass% or less.

[0121] In one embodiment of the present invention, when the polishing composition of the present invention is in the state of diluted solution, the content of basic compound in the polishing composition (when two or more kinds are used, the total amount) is not particularly limited.The lower limit of the content of basic compound is preferably 0.0001 mass% or more, more preferably 0.001 mass% or more.From the viewpoint of storage stability, filterability, etc., the upper limit of the content of basic compound is preferably 5 mass% or less, more preferably 2 mass% or less, even more preferably 1 mass% or less, and particularly preferably 0.5 mass% or less.

[0122] (Water-soluble polymer) In one embodiment of the present invention, the polishing composition may contain a water-soluble polymer. The water-soluble polymer adheres to the surface of the object to be polished and protects the surface from uneven or excessive etching that may occur due to the action of the basic compound. This can improve the quality of the surface of the object to be polished after polishing.

[0123] In this specification, the term "polymer" refers to a (co)polymer having a weight-average molecular weight of 5,000 or more. The weight-average molecular weight can be measured by gel permeation chromatography (GPC), and specifically, the value measured by the method described in the Examples is used. Furthermore, only when measurement by GPC is not possible, the molecular weight calculated from the molecular formula is used as the weight-average molecular weight.

[0124] In one embodiment of the present invention, the water-soluble polymer may have at least one functional group selected from a cationic group, an anionic group, and a nonionic group in the molecule.

[0125] In one embodiment of the present invention, the water-soluble polymer may include those containing a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, an amide structure, an imide structure, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, or the like in the molecule.

[0126] In one embodiment of the present invention, examples of the water-soluble polymer include a polymer having a structural unit derived from vinyl alcohol (hereinafter also referred to as a "polyvinyl alcohol-based polymer"), a cellulose derivative, a starch derivative, a polymer having an oxyalkylene unit, and a water-soluble polymer having a nitrogen atom. Among these, it is preferable to include at least one of a polyvinyl alcohol-based polymer and a water-soluble polymer having a nitrogen atom. A polishing composition containing these polymers is likely to reduce the haze of the object to be polished.

[0127] Polyvinyl alcohol-based polymers may contain only vinyl alcohol units (hereinafter also referred to as "VA units") as repeating units, or may contain VA units and repeating units other than VA units (hereinafter also referred to as "non-VA units"). A vinyl alcohol unit is a unit represented by the following chemical formula: -CH ２ A structural moiety represented by -CH(OH)-. The polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, or may be a block copolymer or a graft copolymer. The polyvinyl alcohol-based polymer may contain only one type of non-VA unit, or may contain two or more types of non-VA units.

[0128] The polyvinyl alcohol-based polymer used in the polishing composition disclosed herein may be unmodified polyvinyl alcohol (unmodified PVA) or modified polyvinyl alcohol (modified PVA). Here, unmodified PVA is a polymer produced by hydrolysis (saponification) of polyvinyl acetate, and has a repeating unit (-CH) structure in which vinyl acetate is vinyl-polymerized. ２ -CH(OCOCH ３ )-) and a polyvinyl alcohol-based polymer that is substantially free of repeating units other than VA units. The degree of saponification of the unmodified PVA may be, for example, 60% or more, and from the viewpoint of water solubility, may be 70% or more, 80% or more, or 90% or more. In one embodiment, unmodified PVA having a degree of saponification of 95% or more or 98% or more can be preferably used as the water-soluble polymer compound.

[0129] The polyvinyl alcohol-based polymer may be a modified PVA containing a VA unit and a non-VA unit having at least one structure selected from an oxyalkylene group, a carbonyl group, an acetoacetyl group, a carboxy group, a (di)carboxylic acid group, a (di)carboxylic acid ester, a phenyl group, a naphthyl group, a sulfo group, an amino group, a hydroxy group, an amide group, an imide group, a nitrile group, an ether group, an ester group, and a salt thereof.

[0130] Non-VA units that may be contained in the modified PVA include, but are not limited to, repeating units derived from N-vinyl monomers or N-(meth)acryloyl monomers, as described below, repeating units derived from ethylene, repeating units derived from alkyl vinyl ethers, repeating units derived from vinyl esters of monocarboxylic acids having 3 or more carbon atoms, and repeating units derived from (di)acetone compounds. A preferred example of the N-vinyl monomer is N-vinylpyrrolidone. A preferred example of the N-(meth)acryloyl monomer is N-(meth)acryloylmorpholine. The alkyl vinyl ether may be, for example, a vinyl ether having an alkyl group having 1 to 10 carbon atoms, such as propyl vinyl ether, butyl vinyl ether, or 2-ethylhexyl vinyl ether. The vinyl ester of a monocarboxylic acid having 3 or more carbon atoms may be, for example, a vinyl ester of a monocarboxylic acid having 3 to 7 carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, or vinyl hexanoate. Preferred examples of the (di)acetone compound include diacetone (meth)acrylamide and acetylacetone.

[0131] The polyvinyl alcohol-based polymer may be a modified PVA in which a portion of the VA units contained in the polyvinyl alcohol-based polymer is acetalized with an aldehyde compound or a ketone compound. In a preferred embodiment of the technology disclosed herein, the acetalized modified PVA is a water-soluble polymer obtained by an acetalization reaction between the above-mentioned non-modified PVA and an aldehyde compound.

[0132] In one embodiment of the present invention, the aldehyde compound used to produce the acetalized modified PVA is not particularly limited. In a preferred embodiment, the aldehyde compound has 1 to 7 carbon atoms, more preferably 2 to 7 carbon atoms.

[0133] Examples of the aldehyde compound include formaldehyde; linear or branched alkyl aldehydes such as acetaldehyde, propionaldehyde, n-butylaldehyde, isobutyraldehyde, tert-butylaldehyde, hexylaldehyde, and n-pentylaldehyde; and alicyclic or aromatic aldehydes such as cyclohexanecarbaldehyde and benzaldehyde. These may be used alone or in combination of two or more. Furthermore, with the exception of formaldehyde, one or more hydrogen atoms may be substituted with a halogen or the like. Among these, linear or branched alkyl aldehydes are preferred because of their high solubility in water and ease of acetalization reaction, and among these, acetaldehyde, n-propylaldehyde, n-butylaldehyde, and n-pentylaldehyde are more preferred. In addition to the above, aldehyde compounds having 8 or more carbon atoms such as 2-ethylhexylaldehyde, nonylaldehyde, and decylaldehyde may also be used as the aldehyde compound.

[0134] Furthermore, as the polyvinyl alcohol-based polymer, a cation-modified polyvinyl alcohol into which a cationic group such as a quaternary ammonium structure has been introduced may be used. Examples of the cation-modified polyvinyl alcohol include those into which a cationic group derived from a monomer having a cationic group, such as a diallyldialkylammonium salt or an N-(meth)acryloylaminoalkyl-N,N,N-trialkylammonium salt, has been introduced. Furthermore, as the polyvinyl alcohol-based polymer, a non-VA unit having the chemical formula: -CH ２ -CH(CR ５ (OR ８ )-CR ６ (OR ９ )-R ７ )-, where R ５ ~R ７ each independently represents a hydrogen atom or an organic group, R ８ and R ９ are each independently a hydrogen atom or R １０ -CO- (wherein, R １０represents an alkyl group). Such modified PVA includes modified PVA having a 1,2-diol structure in the side chain.

[0135] The proportion of moles of VA units to the total number of moles of repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. While not particularly limited, in one embodiment, the proportion of moles of VA units may be 50% or more, 65% or more, 75% or more, 80% or more, or 90% or more (e.g., 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100%" means that the polyvinyl alcohol-based polymer does not, at least intentionally, contain non-VA units. Typically, the proportion of moles of non-VA units to the total number of moles of repeating units is less than 2% (e.g., less than 1%), including 0%. In other embodiments, the ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 95% or less, 90% or less, 80% or less, or 70% or less.

[0136] The content of VA units in the polyvinyl alcohol-based polymer (content by mass) may be, for example, 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more. Although not particularly limited, in one embodiment, the content of VA units may be 50% by mass or more (e.g., more than 50% by mass), 70% by mass or more, or 80% by mass or more (e.g., 90% by mass or more, 95% by mass or more, or 98% by mass or more). Substantially 100% by mass of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100% by mass" means that non-VA units are not, at least intentionally, contained as repeating units constituting the polyvinyl alcohol-based polymer, and typically means that the content of non-VA units in the polyvinyl alcohol-based polymer is less than 2% by mass (e.g., less than 1% by mass). In other embodiments, the content of VA units in the polyvinyl alcohol-based polymer may be, for example, 95% by mass or less, 90% by mass or less, 80% by mass or less, or 70% by mass or less.

[0137] A polyvinyl alcohol-based polymer may contain multiple polymer chains with different VA unit contents within the same molecule. Here, the term "polymer chain" refers to a segment that constitutes a part of a single polymer molecule. For example, a polyvinyl alcohol-based polymer may contain, within the same molecule, a polymer chain A with a VA unit content of more than 50% by mass and a polymer chain B with a VA unit content of less than 50% by mass (i.e., a non-VA unit content of more than 50% by mass).

[0138] The polymer chain A may contain only VA units as repeating units, or may contain non-VA units in addition to VA units. The content of VA units in the polymer chain A may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. In one embodiment, the content of VA units in the polymer chain A may be 95% by mass or more, or 98% by mass or more. Substantially 100% by mass of the repeating units constituting the polymer chain A may be VA units.

[0139] The polymer chain B may contain only non-VA units as repeating units, or may contain VA units in addition to non-VA units. The content of non-VA units in the polymer chain B may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. In one embodiment, the content of non-VA units in the polymer chain B may be 95% by mass or more, or 98% by mass or more. Substantially 100% by mass of the repeating units constituting the polymer chain B may be non-VA units.

[0140] Examples of polyvinyl alcohol-based polymers containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The graft copolymer may be a graft copolymer having a structure in which polymer chain B (side chain) is grafted to polymer chain A (main chain), or a graft copolymer having a structure in which polymer chain A (side chain) is grafted to polymer chain B (main chain). In one embodiment, a polyvinyl alcohol-based polymer having a structure in which polymer chain B is grafted to polymer chain A can be used.

[0141] Examples of the polymer chain B include a polymer chain having a repeating unit derived from an N-vinyl type monomer as a main repeating unit, a polymer chain having a repeating unit derived from an N-(meth)acryloyl type monomer as a main repeating unit, a polymer chain having an oxyalkylene unit as a main repeating unit, etc. In this specification, the term "main repeating unit" refers to a repeating unit contained in an amount of more than 50% by mass, unless otherwise specified.

[0142] A suitable example of the polymer chain B is a polymer chain having an N-vinyl monomer as the main repeating unit, i.e., an N-vinyl polymer chain. The content of repeating units derived from N-vinyl monomers in the N-vinyl polymer chain is typically more than 50% by mass, and may be 70% by mass or more, 85% by mass or more, or 95% by mass or more. Substantially all of the polymer chain B may be repeating units derived from N-vinyl monomers.

[0143] Examples of N-vinyl monomers include monomers having a nitrogen-containing heterocycle (e.g., a lactam ring) and N-vinyl linear amides. Specific examples of N-vinyl lactam monomers include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Specific examples of N-vinyl linear amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide. Polymer chain B may be, for example, an N-vinyl polymer chain in which more than 50% by mass (e.g., 70% by mass or more, 85% by mass or more, or 95% by mass or more) of its repeating units are N-vinylpyrrolidone units. Substantially all of the repeating units constituting polymer chain B may be N-vinylpyrrolidone units.

[0144] Other examples of polymer chain B include polymer chains whose main repeating units are repeating units derived from N-(meth)acryloyl-type monomers, i.e., N-(meth)acryloyl-based polymer chains. The content of repeating units derived from N-(meth)acryloyl-type monomers in the N-(meth)acryloyl-based polymer chain is typically more than 50% by mass, and may be 70% by mass or more, 85% by mass or more, or 95% by mass or more. Substantially all of polymer chain B may be repeating units derived from N-(meth)acryloyl-type monomers.

[0145] Examples of the N-(meth)acryloyl type monomer include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. Examples of linear amides having an N-(meth)acryloyl group include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di(n-butyl)(meth)acrylamide; and N-hydroxyalkyl(meth)acrylamides such as N-hydroxyethyl(meth)acrylamide. Examples of cyclic amides having an N-(meth)acryloyl group include N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine.

[0146] Another example of the polymer chain B is a polymer chain containing an oxyalkylene unit as the main repeating unit, i.e., an oxyalkylene-based polymer chain. The content of the oxyalkylene unit in the oxyalkylene-based polymer chain is typically more than 50% by mass, and may be 70% by mass or more, 85% by mass or more, or 95% by mass or more. Substantially all of the repeating units contained in the polymer chain B may be oxyalkylene units.

[0147] Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxybutylene units, etc. Such oxyalkylene units may be repeating units derived from the corresponding alkylene oxides. The oxyalkylene units contained in the oxyalkylene polymer chain may be of only one type, or may be of two or more types. For example, the oxyalkylene polymer chain may contain a combination of oxyethylene units and oxypropylene units. In an oxyalkylene polymer chain containing two or more types of oxyalkylene units, the oxyalkylene units may be a random copolymer of the corresponding alkylene oxides, or may be a block copolymer or a graft copolymer.

[0148] Further examples of polymer chain B include polymer chains containing repeating units derived from alkyl vinyl ethers (e.g., vinyl ethers having an alkyl group having from 1 to 10 carbon atoms), polymer chains containing repeating units derived from monocarboxylic acid vinyl esters (e.g., vinyl esters of monocarboxylic acids having from 3 or more carbon atoms), polymer chains in which some of the VA units have been acetalized with an aldehyde (e.g., alkylaldehydes having an alkyl group having from 1 to 7 carbon atoms), and polymer chains into which a cationic group (e.g., a cationic group having a quaternary ammonium structure) has been introduced.

[0149] In one embodiment of the present invention, the polyvinyl alcohol-based polymer in the polishing composition may be unmodified PVA, modified PVA, or a combination of unmodified PVA and modified PVA.In the embodiment in which unmodified PVA and modified PVA are used in combination, the amount of modified PVA used relative to the total amount of polyvinyl alcohol-based polymer contained in the polishing composition may be, for example, less than 95% by mass, may be 90% by mass or less, may be 75% by mass or less, may be 50% by mass or less, may be 30% by mass or less, may be 10% by mass or less, may be 5% by mass or less, or may be 1% by mass or less.The polishing composition according to the present invention may be preferably implemented, for example, in an embodiment in which modified PVA is used as the polyvinyl alcohol-based polymer.

[0150] Cellulose Derivatives In one embodiment of the present invention, the term "cellulose derivative" refers to a cellulose in which some of the hydroxy groups of the cellulose have been substituted with other different substituents. The cellulose derivatives may be used alone or in combination of two or more. Examples of cellulose derivatives include cellulose derivatives such as hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose, as well as pullulan.

[0151] Starch Derivatives In one embodiment of the present invention, the water-soluble polymer comprises a starch derivative. Starch derivatives are polymers containing α-glucose units as the main repeating unit, and examples thereof include pregelatinized starch, pullulan, carboxymethyl starch, and cyclodextrin. One type of starch derivative may be used alone, or two or more types may be used in combination.

[0152] Polymer Having Oxyalkylene Units In one embodiment of the present invention, the water-soluble polymer comprises a polymer having an oxyalkylene unit. Examples of polymers having an oxyalkylene unit include polyethylene oxide (PEO), block copolymers of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and random copolymers of EO and PO or BO. Block copolymers of ethylene oxide (EO) and propylene oxide (PO) include block copolymers of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymers, PEO (polyethylene oxide)-PPO (polypropylene oxide)-PEO type triblock copolymers, PPO-PEO-PPO type triblock copolymers, etc.). Typically, PEO-PPO-PEO type triblock copolymers are more preferred. One type of polymer having an oxyalkylene unit may be used alone, or two or more types may be used in combination.

[0153] In one embodiment of the present invention, the water-soluble polymer contains a nitrogen atom from the viewpoint of reducing haze. By including a water-soluble polymer containing a nitrogen atom, the haze of the object to be polished can be reduced.

[0154] In one embodiment of the present invention, the water-soluble polymer having a nitrogen atom may be used alone or in combination of two or more. Examples of water-soluble polymers having a nitrogen atom include poly-N-acryloylmorpholine (PACMO), poly-N-vinylpyrrolidone (PVP), polyhydroxyethylacrylamide (PHEAA), poly-N-vinylimidazole (PVI), poly-N-vinylcarbazole, poly-N-vinylcaprolactam, and poly-N-vinylpiperidine. Among these, poly-N-acryloylmorpholine (PACMO) is preferred from the viewpoint of reducing haze on the object to be polished.

[0155] In one embodiment of the present invention, the weight-average molecular weight of the water-soluble polymer is preferably 5,000 or more, more preferably 6,000 or more, and more preferably 1×10 ４ According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, from the viewpoint of haze reduction and washability, the weight average molecular weight of the water-soluble polymer is 200×10 or more. ４ Preferably, it is 100×10 or less. ４ More preferably, it is 50×10 or less. ４ It is more preferable that the weight average molecular weight of the water-soluble polymer is 5,000 or less. In the above, when the polishing composition contains two or more water-soluble polymers, the weight average molecular weight of the smallest water-soluble polymer among them is 5,000 or more. By adopting such an embodiment, the desired effects of the present invention can be efficiently achieved.

[0156] In one embodiment of the present invention, the water-soluble polymer is a polyvinyl alcohol-based polymer. The weight-average molecular weight of the polyvinyl alcohol-based polymer is preferably 5,000 or more, more preferably 6,000 or more, and more preferably 1.0×10４ According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, the weight average molecular weight of the polyvinyl alcohol-based polymer is 100×10 ４ Preferably, it is 30×10 or less. ４ More preferably, it is 10×10 or less. ４ It is more preferable that the following is true: According to this embodiment, dispersion stability is improved.

[0157] In one embodiment of the present invention, the water-soluble polymer is a cellulose derivative. The weight-average molecular weight of the cellulose derivative is preferably 5,000 or more, and more preferably 1×10 ４ More preferably, it is 10×10 or more. ４ According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, the weight average molecular weight of the cellulose derivative is 200×10 or more. ４ Preferably, it is 150×10 or less. ４ More preferably, it is 100×10 ４ It is more preferable that the following is true: According to this embodiment, dispersion stability is improved.

[0158] In one embodiment of the present invention, the water-soluble polymer is a water-soluble polymer having a nitrogen atom. The weight-average molecular weight of the water-soluble polymer having a nitrogen atom is preferably 5,000 or more, more preferably 7,500 or more, and more preferably 1×10 ４ It is more preferable that the weight average molecular weight of the water-soluble polymer having nitrogen atoms is 100×10 or more. According to such an embodiment, there is a technical effect of improving the haze reduction effect. ４ Preferably, it is 75×10 or less. ４ More preferably, it is 50×10 or less. ４ It is more preferable that the following is true: According to this embodiment, dispersion stability is improved.

[0159] In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of the water-soluble polymer in the concentrate is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, even more preferably 0.001% by mass or more, and particularly preferably 0.01% by mass or more, from the viewpoint of improving stability. In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of the water-soluble polymer in the concentrate is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, from the viewpoint of storage stability, filterability, etc.

[0160] In one embodiment of the present invention, when the polishing composition is in the form of a diluted solution, the content of the water-soluble polymer is preferably 0.00005 mass% or more, more preferably 0.0001 mass% or more, and even more preferably 0.0005 mass% or more, from the viewpoint of improving the haze reduction effect.In addition, in one embodiment of the present invention, when the polishing composition is in the form of a diluted solution, the content of the water-soluble polymer is preferably 0.1 mass% or less, more preferably 0.05 mass% or less, and even more preferably 0.02 mass% or less, from the viewpoint of maintaining the polishing rate.In addition, when two or more water-soluble polymers are used, the content refers to their total amount.In a preferred embodiment of the present invention, the water-soluble polymer contains a hydroxyl group, from the viewpoint of reducing haze.

[0161] In one embodiment of the present invention, the polishing composition can contain two or more water-soluble polymers. For example, two or more water-soluble polymers selected from the group consisting of polyvinyl alcohol-based polymers, cellulose derivatives, starch derivatives, and water-soluble polymers having nitrogen atoms can be used in combination. Among these, it is preferable to contain two or more water-soluble polymers selected from the group consisting of polyvinyl alcohol-based polymers, cellulose derivatives, and water-soluble polymers having nitrogen atoms. Polishing compositions containing these water-soluble polymers tend to reduce the haze of the object to be polished.

[0162] When the polishing composition contains two or more water-soluble polymers, they can be used in combination, for example, one or more polyvinyl alcohol-based polymers and water-soluble polymers having nitrogen atoms, one or more cellulose derivatives and polyvinyl alcohol-based polymers, one or more cellulose derivatives and water-soluble polymers having nitrogen atoms, etc.

[0163] When the polishing composition contains one or more water-soluble polymers selected from the group consisting of polyvinyl alcohol-based polymers and water-soluble polymers having nitrogen atoms, the water-soluble polymers described above as one embodiment of the present invention can be used as the polyvinyl alcohol-based polymer and the water-soluble polymer having nitrogen atoms. Among these, it is preferable to use water-soluble polymers in combinations such as one or more acetalized modified PVAs and poly-N-acryloylmorpholines, one or more unmodified PVAs and poly-N-acryloylmorpholines, one or more unmodified PVAs and poly-N-vinylpyrrolidones, and one or more unmodified PVAs and polyhydroxyethylacrylamides.

[0164] In one embodiment of the present invention, when two or more water-soluble polymers are used, the content ratio of the two or more water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or dilution) containing a polyvinyl alcohol-based polymer and a water-soluble polymer having a nitrogen atom, the lower limit of the ratio of the content of the polyvinyl alcohol-based polymer to the content of the water-soluble polymer having a nitrogen atom (polyvinyl alcohol-based polymer / water-soluble polymer having a nitrogen atom) is preferably 0.01 or more by mass, may be 0.05 or more, or may be 0.15 or more (e.g., 0.5 or more). The upper limit of this content ratio is not particularly limited, but is preferably 99 or less, may be 19 or less, or may be 6 or less (e.g., 2 or less). The content ratio of the polyvinyl alcohol-based polymer to the water-soluble polymer having a nitrogen atom is preferably 1:99 to 99:1 by mass, may be 5:95 to 95:5, or may be 15:85 to 85:15 (e.g., 65:35 to 35:65).

[0165] (Surfactant) In one embodiment of the present invention, the polishing composition may contain a surfactant, if necessary. By adding a surfactant to the polishing composition, haze on the surface of the object to be polished after polishing can be better reduced. Any of anionic, cationic, nonionic, and amphoteric surfactants can be used as the surfactant. Usually, anionic or nonionic surfactants are preferably used. From the viewpoint of low foaming and ease of pH adjustment, nonionic surfactants are more preferred. Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters (e.g., polyoxyalkylene adducts); and copolymers of multiple types of oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). The surfactant preferably includes a surfactant containing a polyoxyalkylene structure. The surfactant may be used alone or in combination of two or more.

[0166] Specific examples of nonionic surfactants containing a polyoxyalkylene structure include block copolymers of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymers, PEO (polyethylene oxide)-PPO (polypropylene oxide)-PEO type triblock copolymers, PPO-PEO-PPO type triblock copolymers, etc.), random copolymers of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, Examples of the hydroxypropyl ether include polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil.Among these, preferred surfactants include block copolymers of EO and PO (particularly, PEO-PPO-PEO type triblock copolymers), random copolymers of EO and PO, and polyoxyethylene alkyl ethers (for example, polyoxyethylene decyl ether).

[0167] The weight-average molecular weight of the surfactant is typically less than 5,000, and is preferably 4,000 or less (e.g., 3,000 or less) from the viewpoint of filterability, cleanability, etc. Furthermore, the weight-average molecular weight of the surfactant is usually suitably 200 or more from the viewpoint of surface activity, etc., and is preferably 250 or more (e.g., 300 or more) from the viewpoint of haze reduction effect, etc. The more preferable range of the weight-average molecular weight of the surfactant may vary depending on the type of surfactant. For example, when a polyoxyethylene alkyl ether is used as the surfactant, its weight-average molecular weight is preferably 1,500 or less, and may be 1,000 or less (e.g., 500 or less). Furthermore, when a PEO-PPO-PEO triblock copolymer is used as the surfactant, its weight-average molecular weight may be, for example, 500 or more, 1,000 or more, or even 1,200 or more.

[0168] In one embodiment of the present invention, when the polishing composition is in the form of a concentrated liquid, the content of the surfactant in the polishing composition is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, and even more preferably 0.001% by mass or more, from the viewpoint of improving the haze reduction effect. In one embodiment of the present invention, when the polishing composition is in the form of a concentrated liquid, the content of the surfactant in the polishing composition is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.2% by mass or less, from the viewpoint of suppressing foaming of the polishing composition.

[0169] In one embodiment of the present invention, when the polishing composition is in the state of a diluted solution, the content of surfactant is preferably 0.00001 mass% or more, more preferably 0.00005 mass% or more, and even more preferably 0.0001 mass% or more, from the viewpoint of improving haze reduction effect.In addition, in one embodiment of the present invention, when the polishing composition is in the state of a diluted solution, the content of surfactant in the polishing composition is preferably 0.02 mass% or less, more preferably 0.01 mass% or less, and even more preferably 0.005 mass% or less, from the viewpoint of maintaining polishing rate.In addition, in the above, the content of surfactant refers to the total amount of two or more surfactants.

[0170] (Chelating Agent) In one embodiment of the present invention, the polishing composition may contain a chelating agent. The chelating agent captures metal impurity components in the polishing system to form complexes, thereby suppressing metal contamination on the surface of the object to be polished.

[0171] Specific examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Specific examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Specific examples of the organic phosphonic acid chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), N,N,N',N'-ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid. Among these chelating agents, it is preferable to use an organic phosphonic acid chelating agent, particularly N,N,N',N'-ethylenediaminetetrakis(methylenephosphonic acid). The chelating agents may be used alone or in combination of two or more.

[0172] In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of the chelating agent in the polishing composition is preferably 0.001% by mass or more, more preferably 0.010% by mass or more, and even more preferably 0.050% by mass or more, from the viewpoint of utilizing the advantages of being a concentrate. In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of the chelating agent in the polishing composition is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.5% by mass or less, from the viewpoint of storage stability, filterability, etc.

[0173] In one embodiment of the present invention, when the polishing composition is in the state of a diluted solution, the content of the chelating agent is preferably 0.0001 mass% or more, more preferably 0.0005 mass% or more, and even more preferably 0.0010 mass% or more.In one embodiment of the present invention, when the polishing composition is in the state of a diluted solution, the content of the chelating agent in the polishing composition is preferably 1.00 mass% or less, more preferably 0.50 mass% or less, and even more preferably 0.01 mass% or less.In the above, the content of the chelating agent refers to the total amount of two or more chelating agents.

[0174] (Other Components) In one embodiment of the present invention, the polishing composition may further contain, as necessary, known additives that can be used in polishing compositions (typically polishing compositions used in the finish polishing process of silicon wafers), such as organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, and antifungal agents, as long as the effects of the present invention are not significantly impaired. Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acids, and organic phosphonic acids. Examples of organic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of organic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of inorganic acids. Organic acids and their salts, and inorganic acids and their salts, can be used alone or in combination of two or more. Examples of the antiseptic and antifungal agent include isothiazolinone compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

[0175] In one embodiment of the present invention, it is preferable that the polishing composition does not substantially contain an oxidizing agent. If an oxidizing agent is contained in the polishing composition, the surface of the object to be polished (particularly a silicon wafer) is oxidized to form an oxide film, which increases the required polishing time. Specific examples of the oxidizing agent include hydrogen peroxide (H２ O ２ ), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. The phrase "the polishing composition is substantially free of oxidizing agents" 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. (for example, a polishing composition in which the molar concentration of the oxidizing agent in the polishing composition is 0.001 mol / L or less, preferably 0.0005 mol / L or less, more preferably 0.0001 mol / L or less, even more preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less) can be included in the concept of a polishing composition that is substantially free of oxidizing agents.

[0176] (Method for producing polishing composition) The method for producing the polishing composition of the present invention is not particularly limited. For example, the polishing composition can be produced by sequentially adding silica sol and, if necessary, a basic compound, a water-soluble polymer, a surfactant, a chelating agent, and other components, and stirring them in a dispersion medium.

[0177] <Form of polishing composition, etc.> The polishing composition of the present invention may be a one-component type or a multi-component type consisting of two or more components. The polishing composition described above may be used for polishing as is, or may be prepared by adding water to dilute a concentrated solution of the polishing composition, or in the case of a multi-component polishing composition, by diluting it with an aqueous solution containing water and some of the constituents, and then used for polishing. For example, the concentrated solution of the polishing composition can be stored or transported, and then diluted at the time of use to prepare the polishing composition.

[0178] A concentrated polishing composition is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc. The concentration ratio can be, for example, about 2 to 100 times in volume terms, and is usually about 5 to 50 times in volume terms. The concentration ratio of the polishing composition according to a preferred embodiment is 10 to 40 times, for example, 15 to 25 times.

[0179] In one embodiment of the present invention, the polishing composition is preferably alkaline. The pH of the polishing composition is preferably 8.0 or higher, more preferably 9.0 or higher, and even more preferably 9.5 or higher. When the pH of the polishing composition is higher, the polishing rate tends to improve. The pH of the polishing composition is preferably 12.0 or lower, more preferably 11.0 or lower, and even more preferably 10.8 or lower. When the pH of the polishing composition is lower, the surface precision tends to improve.

[0180] In one embodiment of the present invention, the pH of the polishing composition is preferably in the range of 8.0 to 12.0, more preferably in the range of 9.0 to 11.0, and even more preferably in the range of 9.5 to 10.8. In particular, when the object to be polished is a silicon wafer, the pH of the polishing composition is preferably in the above range.

[0181] When the polishing composition is reused, the pH may be adjusted to the above range as needed. For adjusting the pH, a known pH adjuster or the above basic compound may be used. The pH value of the polishing composition can be confirmed by a pH meter. The detailed method for measuring pH is described in the Examples.

[0182] (Polished object) The object to be polished by using the polishing composition of the present invention is not particularly limited, and can be applied to polishing objects of various materials and shapes.The material of the object to be polished can be, for example, silicon material, aluminum, nickel, tungsten, steel, tantalum, titanium, stainless steel, etc. metal or semimetal, or their alloy; quartz glass, aluminosilicate glass, glassy carbon, etc. glassy material; alumina, silica, sapphire, silicon nitride, tantalum nitride, titanium carbide, etc. ceramic material; silicon carbide, gallium nitride, gallium arsenide, etc. compound semiconductor substrate material; polyimide resin, etc. resin material; etc.The object to be polished can also be composed of a plurality of the above-mentioned materials.

[0183] Among these, silicon materials are preferred because the effects of the polishing composition of the present invention are more pronounced. The polishing composition of some embodiments of the present invention is preferably used for polishing a substrate having a surface made of a silicon material.

[0184] The silicon material preferably contains at least one material selected from the group consisting of silicon single crystal, amorphous silicon, and polysilicon. From the viewpoint of obtaining the effects of the present invention more significantly, the silicon material is more preferably silicon single crystal or polysilicon, and particularly preferably silicon single crystal. The polishing composition according to some embodiments of the present invention is particularly preferably used for polishing a substrate (e.g., a silicon wafer) having a surface made of silicon single crystal.

[0185] The shape of the object to be polished is not particularly limited. The polishing composition according to some embodiments of the present invention can be preferably used for polishing an object to be polished having a flat surface, such as a plate-like or polyhedral shape.

[0186] <Polishing Method> Another aspect of the present invention provides a polishing method comprising polishing an object to be polished using the polishing composition. The polishing composition of the present invention is particularly suitable for use in a final polishing step due to its excellent haze-reducing effect. In one embodiment of the present invention, the polishing method is suitable for use in a final polishing step. The present invention also provides a method for manufacturing an object to be polished (e.g., a method for manufacturing a silicon wafer) comprising a final polishing step using the polishing composition. The final polishing step refers to the final polishing step in the manufacturing process of the object (i.e., a step in which no further polishing is performed after that step). The polishing composition of the present invention may be used in a polishing step upstream of the final polishing step (referring to a step between the rough polishing step and the final polishing step), for example, a polishing step performed immediately before the final polishing step.

[0187] As described above, the polishing composition of the present invention is preferably used for polishing silicon wafers. The polishing composition of the present invention is particularly suitable as a polishing composition used in the finish polishing step of silicon wafers. More specifically, the polishing composition of the present invention is suitable for use in polishing silicon wafers that have been prepared to a surface state with a surface roughness of 0.01 nm or more and 100 nm or less by a step upstream of the finish polishing step.

[0188] As the polishing apparatus, a general polishing apparatus 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 to which a polishing pad (polishing cloth) can be attached.

[0189] The polishing pad can be made of any material, including general nonwoven fabric, polyurethane, suede, etc. The polishing pad is preferably provided with grooves for collecting the polishing composition.

[0190] The polishing conditions are appropriately set depending on the stage of the polishing process in which the polishing composition is used.

[0191] In the preliminary polishing step, either a double-sided polishing machine or a single-sided polishing machine may be used, but a double-sided polishing machine is preferably used. The rotation speed of the platen is usually about 10 rpm to 100 rpm, preferably about 20 rpm to 50 rpm. When using a double-sided polishing machine, the rotation speeds of the upper and lower rotating platens may be different, but are usually set to the same relative speed with respect to the wafer. In addition, in the finish polishing step, a single-sided polishing machine is preferably used, and the rotation speed of the platen is usually about 10 rpm to 100 rpm, preferably about 20 rpm to 60 rpm, more preferably about 25 rpm to 55 rpm. Such a rotation speed can significantly reduce the haze level on the surface of the object to be polished.

[0192] The object to be polished is usually pressed by a platen. The pressure at this time can be selected appropriately, but in the preliminary polishing step, it is usually preferably about 5 kPa or more and 30 kPa or less, more preferably about 10 kPa or more and 25 kPa or less. In the finish polishing step, it is usually preferably about 5 kPa or more and 30 kPa or less, more preferably about 10 kPa or more and 20 kPa or less. With such a pressure, the haze level on the surface of the object to be polished can be significantly reduced.

[0193] The supply rate of the polishing composition can also be appropriately selected depending on the size of the platen, but in terms of economy, in the case of the preliminary polishing step, it is usually preferably about 0.1 L / min to 5 L / min, and more preferably about 0.2 L / min to 2 L / min. In the case of the finish polishing step, it is usually preferably about 0.1 L / min to 5 L / min, and more preferably about 0.2 L / min to 2 L / min. Such a supply rate can efficiently polish the surface of the object to be polished and significantly reduce the haze level on the surface of the object to be polished.

[0194] There are no particular restrictions on the temperature at which the polishing composition is maintained in the polishing apparatus, but from the standpoint of stabilizing the polishing rate and reducing the haze level, it is generally preferably about 15°C or higher and 40°C or lower, and more preferably about 18°C ​​or higher and 25°C or lower.

[0195] The above polishing conditions (polishing apparatus settings) are merely examples, and may be outside the above ranges or may be changed as appropriate. Such conditions can be appropriately set by a person skilled in the art.

[0196] Furthermore, it is preferable to carry out cleaning and drying after polishing. The methods and conditions for these operations are not particularly limited, and known methods may be used as appropriate. For example, it is preferable to carry out SC-1 cleaning as a step for cleaning the object to be polished. "SC-1 cleaning" is a cleaning method carried out using, for example, a mixed solution of ammonia and hydrogen peroxide (for example, 40°C or higher and 80°C or lower). By carrying out SC-1 cleaning, the surface of the silicon wafer can be lightly etched, and particles on the surface of the silicon wafer can be removed.

[0197] Although the embodiments of the present invention have been described in detail, it is clear that this is for illustrative and exemplary purposes only and not for limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0198] The present invention encompasses the following aspects and configurations: 1. A polishing composition comprising a silica sol, the silica sol containing silica particles having an average aspect ratio of 1.50 or more, wherein the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the silica sol is 40% or more; 2. The polishing composition according to 1. above, wherein the average circularity of the silica particles in the silica sol is 0.80 or less; 3. The polishing composition according to 1. or 2. above, wherein the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles in the silica sol is 40% or less; 4. The polishing composition according to any one of 1. to 3. above, which is used for polishing a substrate having a surface made of a silicon material; 5. A polishing method comprising polishing an object to be polished with the polishing composition according to any one of 1. to 4. above.

[0199] 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, the operations were carried out under the conditions of room temperature (25°C) and a relative humidity of 40% RH or more and 50% RH or less.

[0200] <Average primary particle diameter> The average primary particle diameter of silica particles in silica sol was determined based on the specific surface area (SA) of silica particles measured by the BET method using a fully automatic specific surface area measuring device Macsorb (registered trademark) HM Model-1201 (manufactured by Mountec Co., Ltd.), and the true specific gravity of silica was set to 2.2 g / cm. ３ The primary particle diameter was calculated using the formula: primary particle diameter = 6000 / (SA x 2.2).

[0201] <Average Secondary Particle Diameter> The average secondary particle diameter of silica particles in a silica sol was measured as a volume average particle diameter by a dynamic light scattering method using a particle size distribution measuring device (UPA-UT151, manufactured by Nikkiso Co., Ltd.).

[0202] <Scanning Electron Microscope (SEM) Image> SEM images of silica particles in the silica sol were taken using a scanning electron microscope (SEM) SU8000 (manufactured by Hitachi High-Technologies Corporation) at a magnification such that 100 to 1000 particles were photographed.

[0203] <Average value of longest diameter of primary particles of silica core particles> For all silica core particles in the photographed SEM image, the longest diameter of the primary particle of each silica core particle was measured, and the average value of the longest diameter of the primary particles of all silica core particles was calculated.

[0204] <Average aspect ratio> For silica particles in a silica sol, the long side and short side values ​​of the smallest rectangle circumscribing each silica particle in the captured SEM image were measured, and the ratio of the calculated long side value to the short side value (long side value / short side value) was defined as the aspect ratio, and the average aspect ratio of all silica particles in the captured SEM image was calculated.

[0205] <Proportion of the number of silica particles having an aspect ratio of 1.50 or more to the total number of silica particles> For silica particles in a silica sol, the values ​​of the long side and short side of the outermost circumferential rectangle of each silica particle in a photographed SEM image were measured, and the ratio of the calculated long side to short side (long side value / short side value) was taken as the aspect ratio. The proportion (%) of the number of silica particles having an aspect ratio of 1.50 or more in the SEM image to the total number of silica particles in the SEM image (=number of silica particles having an aspect ratio of 1.50 or more in the SEM image / total number of silica particles in the SEM image × 100) was calculated.

[0206] <Average circularity> The circularity of each silica particle in the photographed SEM image of the silica particles in the silica sol was measured, and the average value of the circularity of all silica particles in the photographed SEM image was calculated. The circularity was calculated from the area (S) and perimeter (L) of the silica particle using the following formula: Circularity = 4πS / L２ (S = area of ​​circle, L = perimeter).

[0207] <Proportion of the number of silica particles having a circularity of 0.90 or more to the total number of silica particles> The circularity of each silica particle in the SEM image of the silica particles in the silica sol was measured. The proportion (%) of the number of silica particles having a circularity of 0.90 or more to the total number of silica particles in the SEM image (= number of silica particles having a circularity of 0.90 or more in the SEM image / total number of silica particles in the SEM image × 100) was calculated.

[0208] <pH of Polishing Composition> The pH was measured using a pH meter (glass electrode hydrogen ion concentration indicator (Model F-72) manufactured by Horiba, Ltd.). More specifically, after three-point calibration using standard buffer solutions (phthalate pH buffer solution, pH: 4.01 (25°C), neutral phosphate pH buffer solution, pH: 6.86 (25°C), carbonate pH buffer solution, pH: 10.01 (25°C)), the glass electrode was placed in the polishing composition to be measured, and the value was measured after 2 minutes or more had passed and the value had stabilized.

[0209] <Measurement of Weight-Average Molecular Weight> The weight-average molecular weight of the water-soluble polymer and surfactant was measured using a GPC method under the following conditions: <GPC Measurement Conditions> Measurement apparatus: HLC-8320GPC (manufactured by Tosoh Corporation) Sample concentration: 0.1 mass % Column: TSKgel GMPWXL Detector: differential refractometer Eluent: 100 mM aqueous sodium nitrate solution / acetonitrile=10-8 / 0-2 Flow rate: 1 mL / min Measurement temperature: 40°C Molecular weight conversion: polyethylene glycol conversion Sample injection amount: 200 μL.

[0210] <Preparation of Silica Sol> (Preparation of Silica Sol 1) A liquid (A) prepared by mixing 3266 g of methanol (manufactured by Kanto Chemical Co., Inc.), 335 g of pure water, and 359 g of 29 mass % aqueous ammonia was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while maintaining the liquid temperature (reaction liquid temperature) in the reaction vessel at 55°C and stirring at 300 pm, a liquid (B1) prepared by dissolving 88 g of tetramethoxysilane (TMOS, manufactured by Tama Chemicals Co., Ltd.) in 22 g of methanol and a liquid (C1) of 21 g of pure water were simultaneously added to prepare a reaction liquid, and a synthesis reaction was allowed to proceed.

[0211] The addition rate of the liquid (B1) is 1.2 × 10 silicon atoms per 1 mol of water contained in the liquid (A). －３ The liquid (C1) was added at a rate of 2 mol / min in terms of water per 1 mol (in terms of silicon atom) of tetramethoxysilane added as the liquid (B1).

[0212] When the average longest diameter of the primary particles of the synthesized silica core particles reached 17.8 nm, the addition of liquid (B1) and liquid (C1) was stopped to complete the synthesis reaction, and a first liquid was prepared.

[0213] The prepared first liquid was held in the same reaction vessel while being stirred at a rotation speed of 300 rpm. The liquid temperature at the start of holding was 55° C., and was then kept at room temperature. At the end of holding, the temperature was 25° C. Stirring was stopped 136 hours after the completion of the addition of liquid (B1) and liquid (C1), and a second liquid was prepared.

[0214] 3,570 g of the prepared second liquid was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while maintaining the liquid temperature in the reaction vessel at 55°C and stirring at 300 rpm, a liquid (B2) prepared by dissolving 324 g of tetramethoxysilane (TMOS) in 83 g of methanol and a liquid (C2) of 77 g of pure water were simultaneously added to prepare a third liquid.

[0215] The addition rate of the liquid (B2) is 1.2 × 10 silicon atoms per 1 mol of water contained in the second liquid. －３The liquid (C2) was added at a rate of 2 mol / min in terms of water per 1 mol (in terms of silicon atom) of tetramethoxysilane added as the liquid (B2).

[0216] The obtained third liquid was heated at a temperature at which the liquid boiled under normal pressure. While maintaining the liquid level constant during heating, pure water was added and distilled by heating to replace the methanol in the reaction liquid with pure water, thereby obtaining silica sol 1.

[0217] (Preparation of Silica Sol 2) A second liquid was prepared in the same manner as in Example 1.

[0218] 4,016 g of the prepared second liquid was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while maintaining the liquid temperature in the reaction vessel at 55°C and stirring at 300 rpm, a liquid (B2) prepared by dissolving 127 g of tetramethoxysilane (TMOS) in 33 g of methanol and a liquid (C2) of 30 g of pure water were simultaneously added to prepare a third liquid.

[0219] The addition rate of the liquid (B2) is 1.2 × 10 silicon atoms per 1 mol of water contained in the second liquid. －３ The liquid (C2) was added at a rate of 2 mol / min in terms of water per 1 mol (in terms of silicon atom) of tetramethoxysilane added as the liquid (B2).

[0220] The obtained third liquid was heated at a temperature at which the liquid boiled under normal pressure. While maintaining the liquid level constant during heating, pure water was added and distilled by heating to replace the methanol in the reaction liquid with pure water, thereby obtaining silica sol 2.

[0221] (Preparation of Silica Sol 3) A liquid (A) prepared by mixing 1,074 g of methanol, 91 g of pure water, and 42 g of 29% by mass ammonia water was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while the liquid temperature in the reaction vessel was kept at 20°C and the mixture was stirred at 300 rpm, a liquid (B1) prepared by dissolving 128 g of tetramethoxysilane (TMOS) in 32 g of methanol and a liquid (C1) of 30 g of pure water were simultaneously added to prepare a reaction liquid.

[0222] The addition rate of the liquid (B1) is 5.0 × 10 silicon atoms per 1 mol of water contained in the liquid (A).－３ The liquid (C1) was added at a rate of 2 mol / min in terms of water per 1 mol (in terms of silicon atom) of tetramethoxysilane added as the liquid (B1).

[0223] The resulting reaction solution was heated at a boiling point under normal pressure. While maintaining the liquid level constant during heating, pure water was added and distilled by heating to replace the methanol in the reaction solution with pure water, thereby obtaining silica sol 3.

[0224] (Preparation of Silica Sol 4) A liquid (A) prepared by mixing 995 g of methanol, 102 g of pure water, and 110 g of 29 mass % aqueous ammonia was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while maintaining the liquid temperature in the reaction vessel at 55°C and stirring at 300 rpm, a liquid (B1) prepared by dissolving 104 g of tetramethoxysilane (TMOS) in 27 g of methanol was added to prepare a reaction liquid.

[0225] The addition rate of liquid (B) is 1.1 × 10 silicon atoms per 1 mol of water contained in liquid (A). －３ mol / min.

[0226] The resulting reaction solution was heated at a boiling temperature under normal pressure. While maintaining the liquid level constant during heating, pure water was added and distilled by heating to replace the methanol in the reaction solution with pure water, thereby obtaining silica sol 4.

[0227] (Preparation of Silica Sol 5) For silica sol 5, a commercially available dispersion of silica particles (trade name "PL-3", manufactured by Fuso Chemical Co., Ltd.) was used.

[0228] (Preparation of Silica Sol 6) A first liquid was prepared in the same manner as in Example 1.

[0229] A second liquid was prepared in the same manner as in Example 1, except that 764 g of methanol was added to 2805 g of the prepared first liquid.

[0230] 3,569 g of the prepared second liquid was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while maintaining the liquid temperature in the reaction vessel at 30°C and stirring at 300 rpm, a liquid (B2) prepared by dissolving 264 g of tetramethoxysilane (TMOS) in 66 g of methanol and a liquid (C2) of 62 g of pure water were simultaneously added to prepare a second liquid.

[0231] The addition rate of the liquid (B2) is 1.2 × 10 silicon atoms per 1 mol of water contained in the second liquid. －３ The liquid (C2) was added at a rate of 2 mol / min, calculated as water, relative to the alkoxysilane and its condensate added as the liquid (B2), to prepare a third liquid.

[0232] The obtained third liquid was heated at a temperature at which the liquid boiled under normal pressure. While maintaining the liquid level constant during heating, pure water was added and distilled by heating to replace the methanol in the reaction liquid with pure water, thereby obtaining silica sol 6.

[0233] (Preparation of Silica Sol 7) A first liquid was prepared in the same manner as in Example 1.

[0234] A second liquid was prepared in the same manner as in Example 1, except that 594 g of methanol was added to 2805 g of the prepared first liquid.

[0235] 3,399 g of the prepared second liquid was added to a 5 L reaction vessel equipped with a stirrer and having a cooling function, and while maintaining the liquid temperature in the reaction vessel at 40°C and stirring at 300 rpm, a liquid (B2) prepared by dissolving 264 g of tetramethoxysilane (TMOS) in 66 g of methanol and a liquid (C2) of 62 g of pure water were simultaneously added to prepare a second liquid.

[0236] The addition rate of the liquid (B2) is 1.2 × 10 silicon atoms per 1 mol of water contained in the second liquid. －３ The liquid (C2) was added at a rate of 2 mol / min, calculated as water, relative to the alkoxysilane and its condensate added as the liquid (B2), to prepare a third liquid.

[0237] The obtained third liquid was heated at a temperature at which the liquid boiled under normal pressure. While maintaining the liquid level constant during heating, pure water was added and distilled by heating to replace the methanol in the reaction liquid with pure water, thereby obtaining silica sol 7.

[0238] The measurement results of various physical properties of Silica Sols 1 to 7 are shown in Table 1. In Silica Sol 5, the average primary particle size and average secondary particle size of the silica particles are the values ​​shown in the manufacturer's catalog.

[0239] (Examples 1 to 4 and Comparative Examples 1 to 3) Concentrated polishing compositions of Examples 1 to 4 and Comparative Examples 1 to 3 were prepared by mixing the respective components (abrasive grains, dispersion medium, basic compound, water-soluble polymer, surfactant, and chelating agent). The polishing compositions of Examples 1 to 4 and Comparative Examples 1 to 3 were obtained by diluting the resulting concentrates with water. The polishing compositions had the following compositions: Abrasive grains: Silica sols 1 to 7 Dispersion medium: Water Basic compound: Ammonia 0.01% by mass First water-soluble polymer: Poly-N-acryloylmorpholine (PACMO) 0.003% by mass Second water-soluble polymer: Acetalized modified polyvinyl alcohol (PVA) 0.003% by mass Surfactant: Polyoxyethylene decyl ether 0.0006% by mass Chelating agent: N,N,N',N'-ethylenediaminetetrakis(methylenephosphonic acid) 0.003% by mass

[0240] The details of the content of abrasive grains (silica particles) are as shown in Table 1 below. The pH of the polishing compositions of Examples 1 to 4 and Comparative Examples 1 to 3 is as shown in Table 1 below.

[0241] <Haze Measurement> A p-type COP (Crystal Originated Particle)-free silicon wafer with a crystal orientation of <100> and a size of 300 mm was prepared as the wafer species. Here, COP refers to concave defects formed on the surface of the silicon wafer, and is caused by crystal defects in the single crystal silicon that forms the silicon wafer or scratches (scratches) exceeding a certain width and depth caused by abrasives (abrasive grains).

[0242] <<Preliminary Polishing>> The silicon wafer was polished under the following preliminary polishing conditions: (Preliminary Polishing Conditions) Polishing apparatus: Single-fed polishing machine, model "PNX-332B", manufactured by Okamoto Machine Tool Works, Ltd. Polishing load: 20 kPa Platen rotation speed: 20 rpm Carrier rotation speed: 20 rpm Polishing pad: Product name "SUBA400" manufactured by Nitta DuPont Co., Ltd. Polishing composition supply rate: 1.0 L / min Polishing composition temperature: 20°C Platen cooling water temperature: 20°C Polishing time: 2 minutes Polishing composition for preliminary polishing: 0.6 mass % silica sol (average primary particle size of silica particles: 35 nm), 0.08 mass % tetramethylammonium hydroxide (TMAH), dispersion medium: water.

[0243] <<Finish Polishing>> The silicon wafers polished by the above-described preliminary polishing were subjected to finish polishing under the following conditions: (Finish Polishing Conditions) Polishing apparatus: Single-fed polishing machine, model "PNX-332B", manufactured by Okamoto Machine Tool Works, Ltd. Polishing load: 20 kPa Platen rotation speed: 52 rpm Carrier rotation speed: 50 rpm Polishing pad: Product name "POLYPAS27NX", manufactured by Fujibo Ehime Co., Ltd. Polishing composition supply rate: 1.5 L / min Polishing composition temperature: 20°C Platen cooling water temperature: 20°C Polishing time: 4 minutes Polishing composition for finish polishing: Polishing compositions of Examples 1 to 4 and Comparative Examples 1 to 3.

[0244] The silicon wafer polished by the above-mentioned finish polishing was cleaned under the following cleaning conditions: (Cleaning Conditions) The polished silicon wafer was removed from the polishing apparatus and, using a single-wafer wafer cleaning apparatus, cleaned with an ozone water cleaning solution (60 seconds), then cleaned with an SC-1 cleaning solution and a brush (110 seconds), then cleaned with an ozone water cleaning solution (20 seconds) and a hydrofluoric acid cleaning solution (15 seconds), which was one set, for a total of three sets, and then cleaned with an ozone water cleaning solution (20 seconds). Thereafter, the silicon wafer was dried.

[0245] The haze of the dried silicon wafers was measured in DW2O mode using a wafer inspection device (manufactured by KLA Tencor Corporation, product name "SURFSCAN SP5") Table 1 below shows the relative haze values ​​of Examples 1 to 4 and Comparative Examples 2 and 3 to the haze of Comparative Example 1.

[0246]

[0247] As is clear from Table 1 above, when the polishing compositions of Examples 1 to 4 were used, the surface quality (haze) of the object to be polished after polishing could be maintained at a good level.

[0248] This application is based on Japanese Patent Application No. 2024-055425, filed on March 29, 2024, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A polishing composition comprising a silica sol, the silica sol containing silica particles having an average aspect ratio of 1.50 or more, and the ratio of the number of silica particles having an aspect ratio of 1.50 or more to the number of all silica particles in the silica sol is 40% or more.

2. The polishing composition according to claim 1, wherein the silica particles in the silica sol have an average circularity of 0.80 or less.

3. The polishing composition according to claim 1, wherein the ratio of the number of silica particles having a circularity of 0.90 or more to the number of all silica particles in the silica sol is 40% or less.

4. The polishing composition according to claim 1, which is used for polishing a substrate having a surface made of a silicon material.

5. A polishing method comprising polishing an object to be polished with the polishing composition according to any one of claims 1 to 4.

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