JP2014080461A - Process for producing polishing composition, and polishing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a polishing composition which easily reduces LPD-N.SOLUTION: The process for producing a polishing composition includes a step for mixing a water-soluble polymer powder with water to form a water-soluble polymer mixture, wherein the content of particles having diameters of 50 μm or smaller in the water-soluble polymer powder is 40 vol% or less. It is preferable that the content of particles having a diameter of 10 μm or smaller in the water-soluble polymer powder is less than 1 vol%.

Description

  The present invention relates to a method for producing a polishing composition containing a water-soluble polymer and a polishing composition.

  Known types of defects observed on a polished surface after polishing with a polishing composition include LPD (Light Point Defects) and LPD-N (Light Point Defect Non-cleanable). LPD means a foreign substance generally called a particle. On the other hand, LPD-N means a foreign substance that cannot be removed by polishing, cleaning, drying, or the like such as crystal defects. For example, a polishing composition with a specific ion concentration reduced is known as a polishing composition for reducing LPD (see Patent Document 1).

JP 2008-053414 A

  Reducing LPD-N (Light Point Defect Non-cleanable) is an important issue in recent years. However, there is no report yet about the manufacturing method of the polishing composition effective in reducing LPD-N. For example, even if Patent Document 1 that discloses a polishing composition capable of reducing LPD (Light Point Defects) is referred to, a technical basis for predicting reduction of LPD-N cannot be found.

This invention is made | formed by finding the manufacturing method which can reduce LPD-N in the manufacturing method of polishing composition containing water-soluble polymer.
The objective of this invention is providing the manufacturing method of polishing composition and polishing composition which are easy to reduce LPD-N.

  In order to achieve the above object, according to the first aspect of the present invention, a water-soluble polymer powder having a content of particles of 50 μm or less and 40% by volume or less is mixed with water to increase the water solubility. A method for producing a polishing composition comprising a step of obtaining a molecular mixture is provided.

  In the second aspect of the present invention, the process includes a step of mixing a water-soluble polymer powder having a content of particles of 50 μm or less of 40% by volume or less and water to obtain a water-soluble polymer mixture. A polishing composition produced through is provided.

In the method for producing a polishing composition and the polishing composition, it is preferable to use a powder having a content of particles of 10 μm or less of less than 1% by volume as the water-soluble polymer powder.
In the method for producing a polishing composition and the polishing composition, the water-soluble polymer mixture is preferably made basic.

  The method for producing a polishing composition preferably includes a step of mixing the water-soluble polymer mixture with a silica particle mixture in which silica particles, a basic compound, and water are mixed. Then, it is preferable to manufacture through the process.

In the manufacturing method and polishing composition of the said polishing composition, it is preferable that the said polishing composition is used for the use which grind | polishes a silicon substrate.
In the method for producing a polishing composition and the polishing composition, the polishing is preferably final polishing of a silicon substrate.

  According to the present invention, an effect of easily reducing LPD-N can be obtained.

Hereinafter, an embodiment of the present invention will be described.
The method for producing a polishing composition includes a step of mixing a water-soluble polymer powder having a content of particles of 50 μm or less of 40% by volume or less with water to obtain a water-soluble polymer mixture. The production method of this embodiment further includes a step of mixing a silica particle mixture in which silica particles, a basic compound, and water are mixed, and a water-soluble polymer mixture that has been made basic.

  The obtained polishing composition is a stock solution for dilution, and is suitably used for polishing a silicon substrate as an object to be polished after dilution with water at the time of use. The silicon substrate polishing step includes, for example, a rough polishing step (primary polishing / secondary polishing) for planarizing the surface of a silicon substrate sliced into a disk shape from a silicon single crystal ingot, and a rough polishing step. And a final polishing step of further removing the fine irregularities present on the surface of the silicon substrate to make a mirror surface. The polishing composition of the present embodiment is particularly suitably used for the final polishing of the silicon substrate.

In the step of obtaining the water-soluble polymer mixture, the water-soluble polymer powder and water are mixed.
The water-soluble polymer has a function of increasing the wettability of the polished surface. The content of particles of 50 μm or less in the water-soluble polymer powder mixed with water is 40% by volume or less, preferably 30% by volume or less, more preferably 20% by volume or less, more preferably 10% by volume. Hereinafter, it is most preferably 5% by volume or less. The content of particles of 10 μm or less in the water-soluble polymer powder is preferably less than 1% by volume. By reducing the content of fine particles in the water-soluble polymer powder, LPD-N (Light Point Defect Non-cleanable) can be easily reduced.

  The content of particles of 50 μm or less and the content of particles of 10 μm or less are the particle size in the cumulative distribution (volume basis) accumulated from the smaller particle size to the larger particle size in the water-soluble polymer powder. Measured as 50 [mu] m accumulation [%] and 10 [mu] m particle diameter [%].

Thus, the water-soluble polymer powder in which the content of fine particles is reduced can be obtained, for example, by classification using a sieve or an air stream.
The average particle diameter of the water-soluble polymer powder is preferably 50 μm or more, more preferably 70 μm or more, and still more preferably 100 μm or more. Generally, as the weight average molecular weight of the water-soluble polymer increases, the average particle diameter of the water-soluble polymer powder tends to increase. That is, since the weight average molecular weight tends to increase as the average particle diameter increases, the wettability of the polished surface tends to increase.

  The average particle size of the water-soluble polymer powder is preferably 250 μm or less, more preferably 200 μm or less, and still more preferably 150 μm or less. By reducing the average particle size, the water-soluble polymer can be dissolved more uniformly.

  As the water-soluble polymer, those having at least one functional group (hydrophilic group) selected from a cationic group, an anionic group and a nonionic group in the molecule can be used. Examples of the water-soluble polymer include those containing a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary nitrogen structure, a heterocyclic structure, a vinyl structure, and a polyoxyalkylene structure in the molecule.

  Examples of the water-soluble polymer include cellulose derivatives, imine derivatives such as poly (N-acylalkyleneimine), polyvinyl alcohol, polyvinyl pyrrolidone, copolymers containing polyvinyl pyrrolidone as part of the structure, polyvinyl caprolactam, and polyvinyl caprolactam. A copolymer having a part of the structure, a polyoxyethylene, a polymer having a polyoxyalkylene structure, a copolymer having a plurality of types such as a diblock type, a triblock type, a random type, and an alternating type; and Examples include polyether-modified silicone.

A water-soluble polymer may be used individually by 1 type, and may be used in combination of 2 or more type.
Among water-soluble polymers, a cellulose derivative, polyvinyl pyrrolidone, and a polymer having a polyoxyalkylene structure are preferable from the viewpoint that the function of improving wettability of the polished surface is good. Examples of the cellulose derivative include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose. Among the cellulose derivatives, hydroxyethyl cellulose is preferable from the viewpoint that it has an excellent function of improving the wettability of the polished surface and has good detergency.

  Among water-soluble polymers, for example, from the viewpoint of suppressing poor dissolution (generation of mamaco), for example, it is preferable to use a powder in which a hydroxyl group in the molecule is hydrophobized with dialdehyde or the like. Examples of the dialdehyde include oxalic acid dialdehyde (ethane dial), malonic acid dialdehyde (propane dial), and succinic acid dialdehyde (butane dial).

  The weight average molecular weight of the water-soluble polymer is preferably 1000 or more in terms of polyethylene oxide, more preferably 10,000 or more, still more preferably 100,000 or more, and still more preferably 200,000 or more. As the weight average molecular weight of the water-soluble polymer increases, the wettability of the polished surface tends to increase.

  The weight average molecular weight of the water-soluble polymer is preferably 2000000 or less, more preferably 1500,000 or less, still more preferably 1000000 or less, and most preferably 500000 or less. By reducing the weight average molecular weight of the water-soluble polymer, the dispersion stability of the polishing composition is further maintained.

  The weight average molecular weight is a weight average molecular weight in terms of polyethylene oxide, and can be measured by gel permeation chromatography (GPC).

  The water used in the step of obtaining the water-soluble polymer mixture is preferably made to have a total content of transition metal ions of 100 ppb or less, for example, in order to avoid the action of other components from being inhibited as much as possible. For example, the purity of water can be increased by operations such as removal of impurity ions using an ion exchange resin, removal of foreign matters by a filter, and distillation. Specifically, it is preferable to use, for example, ion exchange water, pure water, ultrapure water, or distilled water. In addition, in the manufacturing method of polishing composition, it is preferable that the water of the same quality is used also about the water contained in a composition in processes other than the process of obtaining a water-soluble polymer mixture.

  In the step of obtaining the water-soluble polymer mixture, the water-soluble polymer powder and water are mixed in the mixing container. As the mixing container, a container provided with a stirrer or a disperser is used. Examples of such a stirrer or disperser include a wing stirrer, an ultrasonic disperser, and a homomixer. For example, a mixing container having a capacity of, for example, 10 to 10,000 L is used in consideration of production efficiency and quality stability. The liquid contact part with which the composition contacts in the mixing container is composed of only the resin layer or the resin layer laminated on the inner surface of the metal layer in order to suppress the mixing of the metal component into the polishing composition. It is preferable.

  The content of the water-soluble polymer in the water-soluble polymer mixture is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, when the total mass of the water-soluble polymer and water is 100. More preferably, it is 0.1% by mass or more. By increasing the content of the water-soluble polymer, the content of the water-soluble polymer in the polishing composition can be set high.

  The content of the water-soluble polymer in the water-soluble polymer mixture is preferably 10% by mass or less, more preferably 5% by mass or less, where the total mass of the water-soluble polymer and water is 100. Yes, and more preferably 3% by mass or less. By reducing the content of the water-soluble polymer, the dispersibility of the water-soluble polymer tends to increase.

  The water-soluble polymer mixture is made basic. The pH of the water-soluble polymer mixture is preferably 8 or more, more preferably 9 or more. The pH is measured at 25 ° C. By increasing the pH of the water-soluble polymer mixture, the dispersibility of the silica particles is easily maintained when the water-soluble polymer and the silica particle mixture are mixed.

The pH of the water-soluble polymer mixture is preferably 12 or less, more preferably 10.5 or less. By lowering the pH of the water-soluble polymer mixture, dissolution of silica particles is suppressed.
The pH of the water-soluble polymer mixture is adjusted by adding a basic compound to the water-soluble polymer mixture. As the basic compound, a basic compound used as a raw material for the silica particle mixture is suitable.

  The water-soluble polymer mixture is preferably filtered from the viewpoint of reducing foreign matters or aggregates contained in the mixture. Filtration can be performed by a conventional method using a filter. The material and structure of the filter used for filtration are not particularly limited. Examples of the filter material include cellulose, polyamide, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass. Examples of the filter structure include depth, pleats, and membranes.

  The filter used for the filtration can be selected based on the opening. The aperture of the filter is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.2 μm or more. Filtration efficiency can be improved by increasing the opening of the filter.

  The aperture of the filter is preferably 100 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less, still more preferably 5 μm or less, even more preferably 2 μm or less, and most preferably 1 μm or less. By reducing the aperture of the filter, a polishing composition with higher quality can be obtained.

In addition, the opening of the filter is presented as a nominal opening by the filter manufacturer.
As filtration, suction filtration, pressure filtration, or centrifugal filtration may be applied in addition to natural filtration performed at normal pressure.

The obtained water-soluble polymer mixture is mixed with the silica particle mixture.
The silica particle mixture is obtained by mixing silica particles, a basic compound, and water. The silica particle mixture is obtained by a process different from the process of obtaining the water-soluble polymer mixture. In the step of obtaining a silica particle mixture, silica particles, a basic compound, and water are mixed in a mixing container. In the step of obtaining the silica particle mixture, the mixing order of the raw materials is not particularly limited. In the step of obtaining the silica particle mixture, an aqueous dispersion of silica particles may be used as a raw material, or an aqueous solution of a basic compound may be used. That is, in the step of obtaining the silica particle mixture, water may be supplied alone into the mixing container to mix the raw materials, or the water contained in at least one of the silica particle aqueous dispersion and the basic compound aqueous solution. As an alternative, each raw material may be mixed by supplying water into the mixing container.

The details of the mixing container are the same as the mixing container used in the step of obtaining the water-soluble polymer mixture, and the description thereof is omitted.
Silica particles have a function of mechanically polishing a surface to be polished. Examples of the silica particles include colloidal silica, fumed silica, and sol-gel silica. One kind of silica particles may be used alone, or two or more kinds may be used in combination.

  Among the silica particles, when colloidal silica or fumed silica is used, particularly when colloidal silica is used, scratches generated on the polished surface when the silicon substrate is polished are reduced.

  The average primary particle diameter of the silica particles is preferably 5 nm or more, more preferably 10 nm or more, and further preferably 20 nm or more. As the average primary particle diameter of the silica particles increases, the polishing rate tends to increase.

  The average primary particle diameter of the silica particles is preferably 100 nm or less, more preferably 70 nm or less, and still more preferably 50 nm or less. A decrease in the average primary particle diameter of the silica particles tends to increase the dispersion stability of the polishing composition.

  The primary particle diameter of the silica particles can be calculated based on a photograph taken with a scanning electron microscope such as S-4700 manufactured by Hitachi High-Technologies Corporation. For example, a predetermined number (for example, 100 or more) of particles are randomly selected from an electron micrograph of silica particles photographed at a magnification of 10,000 to 50,000 times. About the selected particle | grains, an area is measured from the image of an electron micrograph, and the diameter of the circle | round | yen which becomes the same area as the area is calculated | required as a primary particle diameter of a silica particle. And the average value of the primary particle diameter (50% particle diameter in the volume-based integrated fraction) is calculated as the average primary particle diameter. In addition, calculation of a primary particle diameter and an average primary particle diameter can be performed using a commercially available image analyzer.

  It is preferable that the average secondary particle diameter of a silica particle is 10 nm or more, More preferably, it is 20 nm or more, More preferably, it is 30 nm or more. Increasing the average secondary particle diameter of the silica particles makes it easy to obtain a high polishing rate. And it is preferable that the average secondary particle diameter of a silica particle is 200 nm or less, More preferably, it is 150 nm or less, More preferably, it is 100 nm or less. By reducing the average secondary particle diameter of the silica particles, the dispersion stability of the polishing composition is easily improved. The average secondary particle diameter of the silica particles can be measured, for example, by a dynamic light scattering method using FPAR-1000 manufactured by Otsuka Electronics Co., Ltd.

  The content of silica particles in the silica particle mixture is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass when the total amount of silica particles, basic compound, and water is 100. % Or more. By increasing the content of silica particles, the content of silica particles in the polishing composition can be set high.

  The content of silica particles in the silica particle mixture is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass when the total amount of silica particles, basic compound, and water is 100. % Or less. Due to the decrease in the content of the silica particles, the dispersibility of the silica particles is easily maintained upon mixing with the water-soluble polymer mixture.

The basic compound has a function of chemically polishing the surface to be polished. Further, the basic compound has a function of improving the dispersion stability of the polishing composition.
Examples of the basic compound include an alkali metal hydroxide, quaternary ammonium hydroxide or a salt thereof, ammonia, and an amine. Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Examples of the quaternary ammonium hydroxide or a salt thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, Examples include piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, and guanidine.

A basic compound may be used individually by 1 type, and may be used in combination of 2 or more type.
Among the basic compounds, at least one selected from ammonia, alkali metal hydroxides, and quaternary ammonium hydroxides is preferable.

  Among the basic compounds, at least one selected from ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide is more preferable, and more preferably at least one of ammonia and tetramethylammonium hydroxide. Yes, most preferably ammonia.

  The content of the basic compound in the silica particle mixture is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, when the total amount of silica particles, basic compound, and water is 100. More preferably, it is 0.1 mass% or more. By increasing the content of the basic compound, the dispersibility of the silica particles is easily maintained when mixing with the water-soluble polymer mixture.

  The content of the basic compound in the silica particle mixture is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3 when the total amount of silica particles, basic compound, and water is 100. It is below mass%. By reducing the content of the basic compound, the content of the basic compound in the polishing composition can be set low.

  Water is used as a dispersion medium for silica particles and a solvent for basic compounds. Since the water used in the step of obtaining the silica particle mixture is the same as the water used in the step of obtaining the water-soluble polymer mixture, the description thereof is omitted.

  The obtained silica particle mixture is mixed with a water-soluble polymer mixture. The step of mixing the silica particle mixture and the water-soluble polymer mixture in the present embodiment includes a step of supplying the silica particle mixture and a step of supplying the water-soluble polymer mixture in the mixing container. The details of the mixing container are the same as the mixing container used in the step of obtaining the water-soluble polymer mixture, and thus the description thereof is omitted.

  In the present embodiment, after the step of supplying the silica particle mixture is completed, the step of supplying the water-soluble polymer mixture is started. The completion of the supplying step means that when the supply pump provided in the pipe for supplying the raw material to the mixing container is stopped, when the valve provided in the pipe is closed, or in the supply container This refers to the point in time when the ingredients are gone.

  The stirring operation or dispersing operation in the mixing container by the stirrer or the dispersing machine may be continuously performed in the step of supplying the silica particle mixture and the step of supplying the water-soluble polymer mixture, or may be performed intermittently. Also good. The stirring operation or dispersing operation in the mixing vessel is preferably continued after the step of supplying the silica particle mixture is completed until the step of supplying the water-soluble polymer mixture is completed. Furthermore, the stirring operation or the dispersing operation in the mixing container is preferably continued even after the step of supplying the water-soluble polymer mixture is completed, from the viewpoint of obtaining a polishing composition with higher dispersibility. .

The supply speed of the step of supplying the silica particle mixture and the step of supplying the water-soluble polymer mixture is set in accordance with, for example, supply efficiency and supply equipment such as a pump.
The supply rate of the water-soluble polymer in the step of supplying the water-soluble polymer mixture is preferably 1 part by mass / min or more, more preferably 3 parts by mass / min or more with respect to 100 parts by mass of the silica particles. More preferably, it is 5 parts by mass / min or more. By increasing the supply rate of the water-soluble polymer, the time required for supplying the water-soluble polymer mixture can be shortened.

  The supply rate of the water-soluble polymer in the step of supplying the water-soluble polymer mixture is 50 parts by mass or less, more preferably 20 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the silica particles. Preferably it is 10 mass parts / min or less. It becomes easy to disperse the water-soluble polymer by lowering the supply rate of the water-soluble polymer.

  Components other than the above may be contained in at least one of the silica particle mixture and the water-soluble polymer mixture. Moreover, the manufacturing method of polishing composition may have the supply process which supplies components other than the above to a mixing container. Examples of the components other than the above include surfactants, organic acids, organic acid salts, inorganic acids, inorganic acid salts, and chelating agents.

The surfactant has a function of improving the dispersibility and polishing performance of the polishing composition.
Examples of the surfactant include those having a weight average molecular weight of less than 1000, and ionic or nonionic surfactants. Among the surfactants, nonionic surfactants are preferably used.

  Nonionic surfactants include oxyalkylene polymers such as polyethylene glycol and polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene glyceryl ether. Examples thereof include polyoxyalkylene adducts such as fatty acid esters and polyoxyethylene sorbitan fatty acid esters.

  Nonionic surfactants include, for example, polyoxyethylene polyoxypropylene copolymer, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene Ethylene 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, polyoxyethylene oleyl ether Polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, poly Oxyethylene oleylamine, polyoxyethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene geo Rain esters, polyoxyethylene sorbitan monolaurate, poly monopartic acid poly Xylethylene sorbitan, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, and An acetylene glycol is mentioned.

As the surfactant, one kind may be used alone, or two or more kinds may be used in combination.
Examples of the organic acid 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 Examples include sulfonic acid and organic phosphonic acid. Examples of the organic acid salt include alkali metal salts such as sodium salt and potassium salt of organic acid, or ammonium salt.

  Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts such as sodium salts and potassium salts of inorganic acids, and ammonium salts.

An organic acid and its salt, and an inorganic acid and its salt may be used individually by 1 type, and may be used in combination of 2 or more type.
It is preferable that the mixture obtained through the supply step is filtered in the filtration step after being discharged from the mixing container. The filtration step can be performed by a conventional method using a filter. The filtration step can be performed in the same manner as the filtration of the water-soluble polymer mixture. The opening of the filter used in the filtration step is preferably 0.05 μm or more, more preferably 0.1 μm or more. Filtration efficiency can be improved by increasing the opening of the filter. The aperture of the filter used in the filtration step is preferably 1 μm or less, more preferably 0.45 μm or less, and still more preferably 0.2 μm or less. By reducing the aperture of the filter, it becomes easier to obtain a polishing composition with higher quality.

  The polishing composition of this embodiment is accommodated in a container for conveyance or storage. When the polishing composition is used, it is diluted with water or a basic aqueous solution. As the basic aqueous solution, a solution obtained by dissolving the above basic compound in water is used. The dilution factor is preferably 2 times or more, more preferably 5 times or more, and further preferably 10 times or more. By increasing the dilution ratio, the transportation cost of the polishing composition before dilution can be reduced, and the storage location can be saved. The dilution factor is preferably 100 times or less, more preferably 50 times or less, and still more preferably 40 times or less. By reducing the dilution ratio, the stability of the polishing composition before dilution is easily maintained.

The pH of the polishing composition before dilution is preferably in the range of 10 to 12, and the pH of the polishing composition at the time of use after dilution is preferably in the range of 10 to 11.
The content of the water-soluble polymer in the polishing composition at the time of use (after dilution) is preferably 0.002% by mass or more, more preferably 0.004% by mass or more, and still more preferably 0.8. It is 006 mass% or more. By increasing the content of the water-soluble polymer, the wettability of the polished surface tends to increase.

  The content of the water-soluble polymer in the polishing composition at the time of use is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and further preferably 0.1% by mass or less. is there. By reducing the content of the water-soluble polymer, the dispersion stability of the polishing composition is easily ensured.

  The content of silica particles in the polishing composition at the time of use is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass or more. By increasing the content of silica particles, the polishing rate tends to increase.

  The content of silica particles in the polishing composition at the time of use is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less. Due to the decrease in the content of silica particles, the dispersion stability of the polishing composition tends to increase.

  The content of the basic compound in the polishing composition at the time of use is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, and further preferably 0.003% by mass or more. . By increasing the content of the basic compound, the function of chemically polishing the surface to be polished is enhanced, and the dispersion stability of the polishing composition is easily secured.

  The content of the basic compound in the polishing composition at the time of use is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.2% by mass or less. . By reducing the content of the basic compound, the smoothness of the polished surface tends to increase.

  For polishing using the polishing composition, for example, a single-side polishing apparatus or a double-side polishing apparatus can be used. The polishing pad used for polishing is not particularly limited in terms of its material, physical properties such as hardness and thickness. As the polishing pad, for example, any of polyurethane type, non-woven fabric type, and suede type may be used. The polishing pad may contain abrasive grains or may not contain abrasive grains.

  The silicon substrate after the final polishing step is, for example, washed with a chemical solution after being subjected to a rinsing step and dried to obtain a silicon substrate which is a semiconductor substrate as a polished product. In the rinsing step, for example, a rinsing composition containing the above-described water-soluble polymer, surfactant, or the like, or water is used.

Next, the effect | action of the manufacturing method of polishing composition is demonstrated.
In the polished surface of a silicon substrate, the increase in the number of defects called LPD-N may be caused by water-soluble polymer powder used as a raw material for the polishing composition. In this regard, the present inventors have found that it is related to particles having a smaller particle diameter contained in the water-soluble polymer powder and a defect called LPD-N. And in the manufacturing method of the polishing composition of this embodiment, the water-soluble polymer powder in which the content of particles of 50 μm or less is 40% by volume or less is mixed with water to obtain a water-soluble polymer mixture. A process of obtaining. That is, by using a water-soluble polymer powder in which the content of particles having a smaller particle diameter is reduced, the generation of substances that cause LPD-N and the substances that cause LPD-N are polished. It is presumed that the remaining surface is suppressed.

According to the embodiment described in detail above, the following effects are exhibited.
(1) The method for producing a polishing composition comprises a step of mixing a water-soluble polymer powder having a content of particles of 50 μm or less of 40% by volume or less and water to obtain a water-soluble polymer mixture. Have. According to this polishing method and the polishing composition obtained through the above steps, it becomes easy to reduce defects called LPD-N.

(2) By using a powder having a content of particles of 10 μm or less of less than 1% by volume as the water-soluble polymer powder, it is easy to further reduce defects called LPD-N.
(3) When the water-soluble polymer mixture is made basic, when a polishing composition is mixed with the water-soluble polymer mixture and, for example, a silica particle mixture, defects called LPD-N are reduced. It becomes easy.

  (4) The manufacturing method of polishing composition has the process of mixing a water-soluble polymer mixture and a silica particle mixture. According to this polishing method and the polishing composition obtained through the above steps, defects called LPD-N are reduced when chemical polishing with a basic compound and mechanical polishing with silica particles are performed. It becomes easy.

  (5) The polishing composition is easily used for polishing a silicon substrate, particularly for final polishing of a silicon substrate, whereby it is easy to obtain a silicon substrate with reduced defects called LPD-N.

(Example of change)
The embodiment may be modified as follows.
The step of supplying the water-soluble polymer mixture is started after the step of supplying the silica particle mixture is completed, but is started between the start of the step of supplying the silica particle mixture and the completion thereof. May be.

  The step of supplying the water-soluble polymer mixture may be started simultaneously with the step of supplying the silica particle mixture, or the step of supplying the silica particle mixture after the step of supplying the water-soluble polymer mixture is started. May be started.

The water-soluble polymer mixture is basic, but may be neutral.
-Although the manufacturing method of the said polishing composition is applied to manufacture of the polishing composition used as the undiluted | stock solution for dilution, it is used without being diluted while content of each component is made into content at the time of use The present invention may be applied to the production of a polishing composition.

-The polishing composition obtained by the manufacturing method of the said polishing composition can also be used as an additive composition added to the already used polishing composition.
The polishing object to which the polishing composition is applied is a silicon substrate, but may be applied to a polishing object other than the silicon substrate. Examples of the polishing object other than the silicon substrate include a metal such as stainless steel, a silicon oxide substrate, a plastic substrate, a glass substrate, and a quartz substrate.

  -Polishing composition can also contain abrasive grains other than a silica particle. Examples of the abrasive grains other than the silica particles include alumina particles, zirconia particles, ceria particles, and titania particles. Silica particles and other particles may be used in combination. The abrasive grains may be those whose surfaces are chemically modified. When the polishing composition contains abrasive grains, the abrasive grain supplying step for supplying the abrasive grains to the mixing container may be performed before or after the step of supplying the water-soluble polymer mixture, or the water-soluble polymer mixture. May be carried out simultaneously with the step of supplying.

The technical idea that can be grasped from the above embodiment will be described below.
(A) A method for producing a polishing composition, wherein the silica particle mixture is supplied into a mixing container, and the water-soluble polymer mixture is supplied into the mixing container.

  (B) A method for producing a polishing composition, wherein the step of supplying the water-soluble polymer mixture is started after the step of supplying the silica particle mixture into the mixing container.

Next, the embodiment will be specifically described with reference to examples and comparative examples.
(Examples 1 to 4 and Comparative Example 1)
In Examples 1-4 and Comparative Example 1, the second stage was started after completion of the first stage shown in Table 1 using a container equipped with a stirrer as a mixing container. Stirring was continued until the polishing composition became uniform after the completion of the second stage to produce a polishing composition.

  The silica particle mixture was produced by mixing a colloidal silica dispersion having a pH of 7.0 (concentration 20% by mass) and 29% aqueous ammonia. The pH of the silica particle mixture is 10.3. The average primary particle diameter of the silica particles was found to be 35 μm as a result of photo observation using a scanning electron microscope “S-4700” manufactured by Hitachi, Ltd.

  The water-soluble polymer mixture was prepared by mixing dialdehyde-treated hydroxyethyl cellulose powder, water, and 29% aqueous ammonia. The pH of the water-soluble polymer mixture is 10.0.

“A” described in the “Process Type” column of Table 1 indicates a step of supplying a silica particle mixture, and “B” indicates a step of supplying a water-soluble polymer mixture.

  Table 1 “Content of Particles of 50 μm or Less” and “Content of Particles of 10 μm or Less” show the content of hydroxyethyl cellulose in a powder measured by Microtrac MT3000 (trade name) manufactured by Nikkiso Co., Ltd.

  The polishing composition was manufactured by implementing the filtration process which filters the composition obtained by said each example on the conditions shown in Table 2. FIG.

The polishing composition at the time of use was prepared by diluting the polishing composition of each example 20 times with water. The content of silica particles in the polishing composition at the time of use is 0.5% by mass, the content of ammonia is 0.01% by mass, and the content of hydroxyethyl cellulose is 0.01% by mass.

  Next, the surface of the silicon substrate was polished under the conditions shown in Table 3 using the polishing composition of each example. The silicon substrate has a diameter of 300 mm, a conductivity type of P-type, a crystal orientation of <100>, a resistivity of 0.1 Ω · cm or more and less than 100 Ω · cm, and a polishing slurry manufactured by Fujimi Incorporated (trade name: GLANZOX 1103) is pre-polished.

The LPD-N on the polished surface of the obtained silicon substrate was measured in the DCO mode of the same apparatus using a wafer inspection apparatus “Surfscan SP2” manufactured by KLA-Tencor Corporation. The results are shown in the column “Number of defects (LPD-N)” in Table 1.

  From the results of Table 1, it can be seen that the number of defects (LPD-N) in each Example is reduced as compared with Comparative Example 1.

Claims (12)

  Producing a polishing composition comprising a step of mixing a water-soluble polymer powder having a content of particles of 50 μm or less of 40% by volume or less and water to obtain a water-soluble polymer mixture. Method.   The method for producing a polishing composition according to claim 1, wherein a powder having a content of particles of 10 μm or less of less than 1% by volume is used as the water-soluble polymer powder.   The method for producing a polishing composition according to claim 1 or 2, wherein the water-soluble polymer mixture is made basic.   The manufacturing method of the polishing composition of Claim 3 which has the process of mixing the said water-soluble polymer mixture, and the silica particle mixture with which the silica particle, the basic compound, and water were mixed.   The said polishing composition is a manufacturing method of the polishing composition as described in any one of Claims 1-4 used for the use which grind | polishes a silicon substrate.   The method for producing a polishing composition according to claim 5, wherein the polishing is final polishing of a silicon substrate.   It is manufactured through a process including a step of mixing a water-soluble polymer powder having a content of particles of 50 μm or less of 40% by volume or less and water to obtain a water-soluble polymer mixture. Polishing composition.   The polishing composition according to claim 7, wherein a powder having a content of particles of 10 μm or less of less than 1% by volume is used as the water-soluble polymer powder.   The polishing composition according to claim 7 or 8, wherein the water-soluble polymer mixture is made basic.   The polishing composition according to claim 9, wherein the polishing composition is manufactured through a step of mixing the water-soluble polymer mixture with a silica particle mixture in which silica particles, a basic compound, and water are mixed.   The said polishing composition is a polishing composition as described in any one of Claims 7-10 used for the use which grind | polishes a silicon substrate.   The polishing composition according to claim 11, wherein the polishing is final polishing of a silicon substrate.