JP2014049633A - Polishing composition and manufacturing method for substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition which can easily exhibit both an effect for enhancing the polishing speed and an effect for enhancing the wettability of a polished surface, and to provide a manufacturing method for a substrate.SOLUTION: A polishing composition contains a water-soluble polymer having a weight-average molecular weight of 1000000 or less, and a molecular weight distribution of 5.0-8.0 represented by weight-average molecular weight (Mw)/number-average molecular weight (Mn). Preferably, the polishing composition further contains at least one kind of salt selected from organic salts and inorganic salts. A manufacturing method of a substrate includes a polishing step for polishing a substrate by using a polishing composition containing a water-soluble polymer having a weight-average molecular weight of 1000000 or less, and a molecular weight distribution of 5.0-8.0 represented by weight-average molecular weight (Mw)/number-average molecular weight (Mn).

Description

  The present invention relates to a polishing composition and a method for producing a substrate using the same.

  For example, for polishing a substrate such as a silicon substrate, a polishing composition containing a water-soluble polymer is used. The water-soluble polymer exhibits the effect of reducing the residue of foreign matters on the surface of the substrate by the function of increasing the wettability of the surface of the substrate. Patent Document 1 discloses a configuration in which a polishing rate is increased and a haze level is reduced in a polishing composition containing a water-soluble polymer or the like.

International Publication No. 2003/072669 Pamphlet

  The polishing composition containing the water-soluble polymer still has room for improvement from the viewpoint of the quality of the polished surface. In the present invention, the weight-average molecular weight of the water-soluble polymer and the molecular weight distribution represented by the weight-average molecular weight (Mw) / number-average molecular weight (Mn) are determined under conditions other than the water-soluble polymer in the polishing composition. It was made by finding out that it has an influence on the polishing rate and the wettability of the polished surface when it is constant. In addition, although patent document 1 describes the molecular weight and molecular weight distribution of water-soluble cellulose, it does not teach at all about the influence of the water-soluble polymer mentioned above.

  An object of the present invention is to provide a polishing composition and a method for producing a substrate that can easily exhibit both the effect of increasing the polishing rate and the effect of increasing the wettability of the polished surface.

  In order to achieve the above object, the polishing composition of the present invention has a weight average molecular weight of 1,000,000 or less and a molecular weight distribution represented by weight average molecular weight (Mw) / number average molecular weight (Mn) of 5. It contains 0 or more and 8.0 or less water-soluble polymer.

It is preferable that the polishing composition further contains at least one salt selected from organic acid salts and inorganic acid salts.
The polishing composition is preferably used for the purpose of polishing a substrate.

The polishing composition is preferably used for final polishing of the substrate.
The manufacturing method of the board | substrate of this invention includes the grinding | polishing process of grind | polishing a board | substrate using the said polishing composition.

  According to the present invention, it is easy to exhibit both the effect of increasing the polishing rate and the effect of increasing the wettability of the polished surface.

Hereinafter, embodiments embodying the present invention will be described.
The polishing composition has a weight average molecular weight of 1,000,000 or less and a water-soluble polymer having a molecular weight distribution of 5.0 or more and 8.0 or less represented by weight average molecular weight (Mw) / number average molecular weight (Mn). Containing. The polishing composition of the present embodiment is used for polishing a semiconductor substrate using, for example, a semiconductor substrate such as a silicon substrate or a compound semiconductor substrate as an object to be polished. Here, in the polishing process of the semiconductor substrate, for example, a rough polishing process (for example, primary polishing or secondary polishing) for planarizing the surface of the semiconductor substrate sliced into a disk shape from a single crystal ingot; And a final polishing step in which fine irregularities existing on the surface of the semiconductor substrate after the rough polishing step are further removed to make a mirror surface. The polishing composition can be suitably used for both the rough polishing of the semiconductor substrate and the final polishing. The polishing composition of the present embodiment is suitably used for the purpose of final polishing of a semiconductor substrate.

  The polishing composition of the present embodiment can contain at least one salt selected from organic acid salts and inorganic acid salts, abrasive grains, basic compounds, and water as components other than the water-soluble polymer. .

<Water-soluble polymer>
The water-soluble polymer has a function of increasing the wettability of the polished surface. By using a water-soluble polymer having a smaller weight average molecular weight and a larger molecular weight distribution as the water-soluble polymer, both the effect of increasing the polishing rate and the effect of increasing the wettability of the polished surface should be exhibited. Becomes easy. In addition, it exists in the tendency for the dispersion stability of polishing composition to improve by using water-soluble polymer with smaller molecular weight distribution. From such a viewpoint, the weight average molecular weight and molecular weight distribution of the water-soluble polymer used in the polishing composition are set as described above.

  The molecular weight distribution of the water-soluble polymer is also called polydispersity. A weight average molecular weight (Mw) shows the weight average molecular weight of polyethylene oxide conversion. A weight average molecular weight, a number average molecular weight, and molecular weight distribution show the value measured by gel permeation chromatography (Gel Permeation Chromatography, GPC).

  For example, the dispersion stability of the polishing composition is evaluated as follows. In a cylindrical container having a length of about 1 m, the polishing composition is filled to a height of about 80 cm from the bottom of the container. Next, the container is allowed to stand at room temperature (for example, 25 ° C.) and stored for a period of 3 to 6 months. After storage, a polishing composition located 5 cm from the bottom of the container and a polishing composition located 75 cm from the bottom are collected, the specific gravity of these polishing compositions is measured, and the absolute value of the specific gravity difference is obtained. It can be said that the smaller the absolute value of the specific gravity difference, the higher the dispersion stability.

  As the water-soluble polymer, those having at least one functional group selected from a cationic group, an anionic group and a nonionic group in the molecule can be used. The water-soluble polymer has, for example, a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary nitrogen structure, a heterocyclic structure, a vinyl structure, a polyoxyalkylene structure and the like 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. Copolymers that are part of the structure, polyoxyethylene, polymers having a polyoxyalkylene structure, polymers having a plurality of types such as diblock type, triblock type, random type, and alternating type It is done.

A water-soluble polymer may be used individually by 1 type, and may be used in combination of 2 or more type.
The polishing rate tends to increase as the weight average molecular weight of the water-soluble polymer decreases. The stability of the polishing composition tends to be more maintained due to a decrease in the weight average molecular weight of the water-soluble polymer. The wettability of the polished surface tends to increase as the weight average molecular weight of the water-soluble polymer increases.

  When at least one water-soluble polymer (referred to as “water-soluble polymer A”) selected from a cellulose derivative and a polymer having a polyoxyalkylene structure is used as the water-soluble polymer, the weight average molecular weight of the water-soluble polymer A is , Preferably it is 900,000 or less, More preferably, it is 800,000 or less. The weight average molecular weight of the water-soluble polymer A is preferably 50000 or more, more preferably 100000 or more, still more preferably 400000 or more, and most preferably 600000 or more.

  When at least one water-soluble polymer (referred to as “water-soluble polymer B”) selected from an imine derivative and polyvinyl alcohol is used as the water-soluble polymer, the weight average molecular weight of the water-soluble polymer B is preferably 200,000 or less. Yes, more preferably 120,000 or less, still more preferably 80000 or less. The weight average molecular weight of the water-soluble polymer B is preferably 4000 or more, more preferably 8000 or more, and further preferably 10,000 or more.

  When polyvinyl alcohol is used as the water-soluble polymer B, the saponification degree of the polyvinyl alcohol is preferably 65 mol% or more, more preferably 70 mol% or more, and further preferably 80 mol% or more. The degree of saponification of polyvinyl alcohol is theoretically 100 mol% or less.

  As the water-soluble polymer, polyvinyl pyrrolidone, a copolymer containing polyvinyl pyrrolidone as part of its structure, polyvinyl caprolactam, and a copolymer containing polyvinyl caprolactam as part of its structure (“water-soluble polymer” In the case of using the water-soluble polymer C ″), the weight average molecular weight of the water-soluble polymer C is preferably 500,000 or less, and more preferably 100,000 or less. The weight average molecular weight of the water-soluble polymer C is preferably 3000 or more, more preferably 5000 or more, and further preferably 10,000 or more.

  The molecular weight distribution of the water-soluble polymer is preferably 5.1 or more, more preferably 5.2 or more, still more preferably 5.3 or more, and most preferably 5.5 or more. The molecular weight distribution of the water-soluble polymer is preferably 7.5 or less, more preferably 7.0 or less, still more preferably 6.5 or less, and most preferably 6 or less.

  Among water-soluble polymers, a cellulose derivative, polyvinyl pyrrolidone, or a polymer having a polyoxyalkylene structure is preferable from the viewpoint of improving wettability of the polished surface. 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 particularly preferable from the viewpoint that it has a high ability to impart wettability to the polished surface and has good detergency.

  The content of the water-soluble polymer in the polishing composition is preferably 0.002% by mass or more, more preferably 0.004% by mass or more, and further preferably 0.006% by mass or more. Most preferably, it is 0.01 mass% or more. By increasing the content of the water-soluble polymer in the polishing composition, the wettability of the polished surface tends to be further improved. The content of the water-soluble polymer in the polishing composition is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and still more preferably 0.1% by mass or less. Most preferably, it is 0.05 mass% or less. By reducing the content of the water-soluble polymer in the polishing composition, the stability of the polishing composition tends to be more maintained.

<Organic acid salt and inorganic acid salt>
The polishing composition preferably contains at least one salt selected from an organic acid salt and an inorganic acid salt from the viewpoint of further facilitating the effect of enhancing the wettability of the polished surface. Moreover, since these salts have a function of agglomerating the abrasive grains appropriately, an effect of further increasing the polishing rate is easily obtained.

  The organic acid salt is composed of an organic acid and a cation (excluding hydrogen ion) as its counter ion. 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 cation include alkali metal ions such as sodium and potassium, and ammonium ions.

  The inorganic acid salt consists of an inorganic acid and a cation (excluding hydrogen ions) as its counter ion. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of the cation include alkali metal ions such as sodium and potassium, and ammonium ions.

An organic acid salt and an inorganic acid salt may be used individually by 1 type, and may be used in combination of 2 or more type.
Among organic acid salts and inorganic acid salts, ammonium salts are preferable from the viewpoint of suppressing metal contamination of the semiconductor substrate.

  The content of at least one salt selected from an organic acid salt and an inorganic acid salt in the polishing composition is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and Preferably it is 0.01 mass% or more. By increasing the content of the salt in the polishing composition, the effect can be more easily exhibited. The content of at least one salt selected from an organic acid salt and an inorganic acid salt in the polishing composition is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and further Preferably it is 0.1 mass% or less. By reducing the salt content in the polishing composition, it becomes easy to reduce the haze level.

<Abrasive>
Abrasive grains can be contained in the polishing composition. The abrasive grains physically polish the surface of the semiconductor substrate by applying a physical action.

  Examples of the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Examples of the inorganic particles include particles made of a metal oxide such as silica, alumina, ceria, titania, and silicon nitride particles, silicon carbide particles, and boron nitride particles. Examples of the organic particles include polymethyl methacrylate (PMMA) particles.

  The average primary particle diameter of the abrasive grains is preferably 5 nm or more, more preferably 15 nm or more, and further preferably 25 nm or more. By increasing the average primary particle diameter of the abrasive grains, a high polishing rate is easily obtained when the semiconductor substrate is polished. The average primary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and still more preferably 40 nm or less. By reducing the average primary particle diameter of the abrasive grains, the stability of the polishing composition is easily improved.

  The value of the average primary particle diameter of the abrasive grains is calculated from the specific surface area measured by the BET method, for example. The specific surface area of the abrasive grains can be measured using, for example, “Flow SorbII 2300” manufactured by Micromeritex Corporation.

  The average secondary particle diameter of the abrasive grains is preferably 50 nm or more, more preferably 70 nm or more, and further preferably 80 nm or more. By increasing the average secondary particle diameter of the abrasive grains, a high polishing rate is easily obtained when the semiconductor substrate is polished. The average secondary particle diameter of the abrasive grains is preferably 300 nm or less, more preferably 280 nm or less, and further preferably 250 nm or less. By reducing the average secondary particle diameter of the abrasive grains, the stability of the polishing composition is easily improved. The average secondary particle diameter of the abrasive grains can be measured by a dynamic light scattering method.

  The average value of the major axis / minor axis ratio of the abrasive grains is theoretically 1.0 or more, preferably 1.05 or more, and more preferably 1.1 or more. By increasing the average value of the major axis / minor axis ratio, a high polishing rate is easily obtained. The average value of the major axis / minor axis ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less. By reducing the average value of the major axis / minor axis ratio, scratches generated on the polished surface tend to decrease.

  Of all the abrasive grains contained in the polishing composition, in the comparison of the number of particles, the ratio of the number of particles having a major axis / minor axis ratio of 1.5 or more is preferably 10% or more, more preferably. Is 20% or more. By increasing the number ratio of particles having a major axis / minor axis ratio of 1.5 or more, a high polishing rate is easily obtained. The ratio of particles having a major axis / minor axis ratio of 1.5 or more is preferably 90% or less, and more preferably 80% or less. By reducing the number ratio of the abrasive grains having a major axis / minor axis ratio of 1.5 or more, the haze level of the polished surface is easily reduced.

  The major axis / minor axis ratio is a value indicating the particle shape of the abrasive grains, and can be determined, for example, by photographic observation using an electron microscope. Specifically, a predetermined number (for example, 200) of abrasive grains is observed using a scanning electron microscope, and a minimum rectangle circumscribing each particle image is drawn. And about the rectangle drawn with respect to each particle image, the value which remove | divided the length of the long side (major axis value) by the length of the short side (minor axis value) is calculated as a major axis / minor axis ratio. . Moreover, by calculating the average value, the average value of the major axis / minor axis ratio can be obtained. The major axis / minor axis ratio can be calculated based on, for example, photographic observation using a scanning electron microscope “S-4700” manufactured by Hitachi, Ltd.

  The content of abrasive grains in the polishing composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.3% by mass or more. By increasing the abrasive content, a high polishing rate is easily obtained. The content of abrasive grains in the polishing composition is preferably 10% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less. By reducing the content of the abrasive grains, the stability of the polishing composition tends to be more maintained.

  Here, silica as an abrasive is suitably used for polishing a silicon substrate, for example. Specific examples of the silica include silica particles selected from colloidal silica, fumed silica, and sol-gel silica. Among these silica particles, it is preferable to use silica particles selected from colloidal silica and fumed silica, particularly colloidal silica, from the viewpoint of reducing scratches generated on the polished surface of the semiconductor substrate. Of these, one kind may be used alone, or two or more kinds may be used in combination.

  The true specific gravity of silica is preferably 1.5 or more, more preferably 1.6 or more, and still more preferably 1.7 or more. Increasing the true specific gravity of silica makes it easy to obtain a high polishing rate. The true specific gravity of silica is preferably 2.2 or less, more preferably 2.0 or less, and still more preferably 1.9 or less. A decrease in the true specific gravity of silica tends to reduce scratches generated on the polished surface. The true specific gravity of the silica is calculated from the weight when the silica particles are dried and the weight when the silica particles are filled with ethanol having a known capacity.

<Basic compound>
A basic compound can be contained in the polishing composition. The basic compound chemically polishes the polishing surface by applying a chemical action (chemical etching). This makes it easy to improve the polishing rate.

  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 polishing composition 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. Most preferably, it is 0.005 mass% or more. A high polishing rate tends to be obtained by increasing the content of the basic compound in the polishing composition. The content of the basic compound in the polishing composition is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, Most preferably, it is 0.05 mass% or less. Due to the decrease in the content of the basic compound in the polishing composition, the shape of the semiconductor substrate tends to be easily maintained.

<Water>
Water in the polishing composition has a function of dissolving or dispersing other components. In order to avoid as much as possible that the function of other components contained in the polishing composition is inhibited, for example, the total content of transition metal ions is preferably 100 ppb or less. 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, for example, ion exchange water, pure water, ultrapure water, distilled water or the like is preferably used.

<PH>
The pH of the polishing composition is preferably 8.0 or more, more preferably 8.5 or more, and still more preferably 9.0 or more. By increasing the pH of the polishing composition, a high polishing rate tends to be obtained when the semiconductor substrate is polished. It is preferable that pH of polishing composition is 12.5 or less, More preferably, it is 11.5 or less, Most preferably, it is 11 or less. By reducing the pH of the polishing composition, the shape of the semiconductor substrate tends to be easily maintained.

<Chelating agent>
A chelating agent can be contained in the polishing composition. The chelating agent suppresses metal contamination of the semiconductor substrate by capturing metal impurity components in the polishing system to form a complex.

  Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid. , Sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid-based chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphone). 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 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- And methylphosphonosuccinic acid.

<Surfactant>
A surfactant can be contained in the polishing composition. The surfactant suppresses roughening of the polished surface of the semiconductor substrate. Thereby, it becomes easy to reduce the haze level of the polished surface. In particular, when a basic compound is contained in the polishing composition, the polishing surface of the semiconductor substrate tends to be roughened by chemical polishing (chemical etching) with the basic compound. For this reason, the combined use of the basic compound and the surfactant is particularly effective.

  As the surfactant, those having a weight average molecular weight of less than 1000 are preferable, and examples thereof include anionic or nonionic surfactants. Among the surfactants, nonionic surfactants are preferably used. Since the nonionic surfactant has low foaming property, it is easy to handle at the time of preparation and use of the polishing composition. In addition, for example, pH adjustment is easier than when an ionic surfactant is used.

  Nonionic surfactants include, for example, oxyalkylene polymers such as polyethylene glycol and polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene Examples include polyoxyalkylene adducts such as ethylene glycerether fatty acid esters and polyoxyethylene sorbitan fatty acid esters, and copolymers of a plurality of types of oxyalkylenes (diblock type, triblock type, random type, and alternating type).

  Specifically, polyoxyethylene polyoxypropylene copolymer, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene Oxyethylene-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 Nyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxy Ethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, monolaurate Polyoxyethylene sorbitan, polyoxyethylene sorbitan monopaltimate, Nosutearin Polyoxyethylene sorbitan monooleate polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan, polyoxyethylene sorbit tetraoleate, polyoxyethylene castor oil, polyoxyethylene hardened castor oil, and the like. Among these surfactants, polyoxyethylene alkyl ether, particularly polyoxyethylene decyl ether is preferably used.

As the surfactant, one kind may be used alone, or two or more kinds may be used in combination.
<Ingredients other than the above ingredients>
The polishing composition may further contain a known additive generally contained in the polishing composition, for example, an organic acid and an inorganic acid, if necessary.

  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 inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid.

An organic acid and an inorganic acid may be used individually by 1 type, and may be used in combination of 2 or more type.
The polishing composition may further contain a preservative, a fungicide, and the like. Examples of the antiseptic and antifungal agent include isothiazoline-based compounds, paraoxybenzoates, and phenoxyethanol.

<Preparation of polishing composition>
For the preparation of the polishing composition, for example, a well-known mixing device such as a wing stirrer, an ultrasonic disperser, a homomixer or the like can be used. Each raw material of polishing composition may be mixed simultaneously, and a mixing order may be set suitably.

  The polishing composition is preferably obtained through a step including a dilution step of diluting the dilution stock solution with water from the viewpoint of facilitating transportation and storage, for example. That is, after preparing a dilution stock solution containing a water-soluble polymer, a polishing composition is preferably obtained from the dilution stock solution.

  When the average secondary particle diameter of the abrasive grains contained in the dilution stock solution is R1, and the average secondary particle diameter R2 of the abrasive grains contained in the polishing composition is average secondary relative to the average secondary particle diameter R1 The ratio of the particle diameter R2 (ratio = R2 / R1) is preferably more than 0.75 and 3.0 or less, more preferably 0.80 or more, and still more preferably 0.85 or more. Yes, most preferably 0.90 or more. The average secondary particle diameter R1 and the average secondary particle diameter R2 are both values measured using FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. By increasing the ratio, the effect of improving the wettability of the polished surface is more easily exhibited. The ratio is more preferably 2.0 or less, and still more preferably 1.5 or less. As the ratio is reduced, scratches and particles generated on the polished surface tend to be reduced.

  The ratio is further increased by preliminarily containing at least one salt selected from an organic acid salt and an inorganic acid salt in a dilution stock solution or by blending it into a polishing composition obtained through a dilution process. Can do.

The value of the average secondary particle diameter R1 of the abrasive grains contained in the dilution stock solution can be measured by the dynamic light scattering method in the same manner as the average secondary particle diameter R2 of the abrasive grains contained in the dilution stock solution.
The average secondary particle diameter R1 of the abrasive grains contained in the dilution stock solution is preferably 10 nm or more, more preferably 20 nm or more. By increasing the average secondary particle diameter R1 of the abrasive grains, it becomes easy to obtain a high polishing rate when polishing the semiconductor substrate. The average secondary particle diameter R1 of the abrasive grains contained in the dilution stock solution is preferably 200 nm or less, and more preferably 150 nm or less. By decreasing the average secondary particle diameter R1 of the abrasive grains, the stability of the dilution stock solution tends to be improved.

  The dilution rate D in the dilution step is preferably 2 times or more, more preferably 5 times or more, and further preferably 10 times or more in terms of volume. By increasing the dilution rate D in the dilution step, the transportation cost can be reduced, and it is easy to secure a storage place for storage as a stock solution for dilution.

  The dilution rate D in the dilution step is preferably 100 times or less, more preferably 50 times or less, and still more preferably 30 times or less in terms of volume. By reducing the dilution rate D in the dilution step, it becomes easy to ensure the stability of the diluted solution and the polishing composition.

  The dilution stock solution is obtained by mixing the raw materials of the dilution stock solution described above. For mixing, for example, a known mixing device such as a blade-type stirrer, an ultrasonic disperser, or a homomixer can be used. In mixing the raw materials for dilution, each raw material may be mixed at the same time, or the mixing order may be set as appropriate.

  For the dilution in the dilution step, it is preferable to employ a dilution method in which water is gradually added while stirring the dilution stock solution with the above-described mixing apparatus. In addition, the dilution in a dilution process may be stirred with the mixing apparatus mentioned above, after adding water to the dilution undiluted | stock solution.

Next, a method for manufacturing a semiconductor substrate will be described together with the action of the polishing composition.
The semiconductor substrate is manufactured by a manufacturing method including a polishing process using a polishing composition. In the polishing step, while supplying the polishing composition to the surface of the semiconductor substrate, the polishing pad is pressed against the surface of the semiconductor substrate to rotate the semiconductor substrate and the polishing pad. At this time, the wettability of the polishing surface is increased by the water-soluble polymer contained in the polishing composition. Since the water-soluble polymer has a weight average molecular weight of 1000000 or less, the polishing rate is likely to increase. Furthermore, since the molecular weight distribution of the water-soluble polymer is 5.0 or more, the polishing rate and the wettability of the polished surface are further easily increased. The semiconductor substrate that has been subjected to the polishing process is subjected to a cleaning process for cleaning the surface.

According to the embodiment described in detail above, the following effects are exhibited.
(1) Since the polishing composition contains a water-soluble polymer having a weight average molecular weight of 1,000,000 or less and a molecular weight distribution of 5.0 or more, the effect of increasing the polishing rate and the effect of increasing the wettability of the polished surface. It becomes easy to exhibit any of these. For this reason, it becomes easy to ensure the quality of the polished surface, for example. In addition, since the molecular weight distribution of water-soluble polymer is 8.0 or less, it becomes easy to improve the dispersion stability of polishing composition.

  (2) When the polishing composition contains at least one salt selected from organic acid salts and inorganic acid salts, it becomes easier to exhibit the effect of improving the wettability of the polished surface. In addition, an effect of further increasing the polishing rate is easily obtained.

(3) The polishing composition is used for polishing a semiconductor substrate, so that it is easy to increase the polishing efficiency while maintaining the quality, for example.
(4) In the final polishing of the semiconductor substrate, quality is particularly important. The polishing composition can contribute to quality improvement based on the effect of increasing the polishing rate and the effect of increasing the wettability of the polished surface by being used for final polishing of the semiconductor substrate.

  (5) A method for producing a semiconductor substrate comprises a polishing step of polishing a semiconductor substrate using a polishing composition containing a water-soluble polymer having a weight average molecular weight of 1,000,000 or less and a molecular weight distribution of 5.0 or more. Including. For this reason, for example, it becomes easy to manufacture a semiconductor substrate with improved polishing efficiency while maintaining quality.

The embodiment may be modified as follows.
The molecular weight distribution of the water-soluble polymer contained in the polishing composition may be adjusted, for example, by mixing a plurality of types of water-soluble polymers having different weight average molecular weights. That is, the water-soluble polymer in the polishing composition is a water-soluble polymer composed of one or more types, and the molecular weight distribution (Mw / Mn) in the weight average molecular weight Mw of the entire water-soluble polymer is What is necessary is just the structure used as 5.0 or more.

-The polishing composition may be a one-part type or a multi-part type composed of two or more parts.
-Each component contained in the polishing composition of the said embodiment may be what was filtered with the filter immediately before manufacture. Further, the polishing composition of the above embodiment may be used after being filtered by a filter immediately before use. By performing the filtration treatment, coarse foreign matters in the polishing composition are removed, and the quality is improved.

  The material and structure of the filter used for the filtration process are not particularly limited. Examples of the filter material include cellulose, nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass. Examples of the filter structure include depth, pleats, membranes, and the like.

  -The polishing pad used in the polishing process using the polishing composition of the embodiment is not particularly limited. For example, any of non-woven fabric type, suede type, those containing abrasive grains, and those not containing abrasive grains may be used.

  When polishing a semiconductor substrate using the polishing composition of the above embodiment, the polishing composition once used for polishing may be collected and used again for polishing the semiconductor substrate. As a method of reusing the polishing composition, for example, a method of collecting the polishing composition discharged from the polishing apparatus in a tank and circulating it again into the polishing apparatus can be used. Reusing the polishing composition means that the environmental load can be reduced by reducing the amount of the polishing composition discharged as waste liquid, and the polishing of the semiconductor substrate by reducing the amount of the polishing composition to be used. This is useful in that the manufacturing cost can be suppressed.

  When the polishing composition is reused, it is preferable to add a part or all of each component such as abrasive grains consumed or lost by polishing as a composition modifier. The composition adjusting agent may be added to each component individually, or may be added in a state where each component is mixed at an arbitrary ratio according to the size of the circulation tank, polishing conditions, and the like. By adding a composition adjusting agent to the polishing composition to be reused, the composition of the polishing composition is maintained, and the function of the polishing composition can be exhibited continuously.

  -Examples of the material of the compound semiconductor substrate to be polished by the polishing composition include silicon carbide, gallium nitride, and gallium arsenide. The polishing composition is not limited to a semiconductor substrate, but is used for polishing a substrate made of a metal such as stainless steel, plastic, glass, sapphire, or the like, and a method for manufacturing the substrate. It is also possible to obtain the effect described in. Further, the polishing composition is not limited to a substrate, and can be used to obtain a polishing product made of various materials.

The technical idea that can be grasped from the above embodiment will be described below.
(A) A dilution stock solution for obtaining a polishing composition by diluting, wherein the abrasive grains are water-soluble and have a weight average molecular weight of 1000000 or less and a molecular weight distribution of 5.0 or more and 8.0 or less. Dilution stock solution containing a functional polymer.

(B) A method for producing a polishing composition, wherein a polishing composition is produced through a dilution step in which the dilution stock solution is diluted with water.
(C) A polishing method for polishing a substrate using the polishing composition.

Next, the embodiment will be described more specifically with reference to examples and comparative examples.
(Examples 1 to 13 and Comparative Examples 1 and 2)
A stock solution for dilution was prepared by mixing colloidal silica as abrasive grains, a water-soluble polymer, and a basic compound in ion-exchanged water. Colloidal silica having an average primary particle diameter of 35 nm was used as the abrasive grains, and ammonia was used as the basic compound. The dilution stock solutions of Examples 8 to 13 further contained salt. Next, the polishing composition containing the water-soluble polymer shown in Table 1 was obtained by performing a dilution step of diluting the dilution stock solution 20 times with pure water. In the diluting step, the polishing composition was filtered in order to remove coarse foreign matters contained in the polishing composition after performing an operation of stirring and dispersing using a homogenizer.

The content of the abrasive grains in the polishing composition of each example is 0.5% by mass, and the content of the basic compound is 0.01% by mass.
In the "Water-soluble polymer" column in Table 1, "Mw" is the weight average molecular weight, "Mn" is the number average molecular weight, "Mw / Mn" is the molecular weight distribution, and the GPC conditions for measuring the molecular weight distribution are as follows: It is as follows.

<GPC measurement conditions>
Column: Product name: TSKgel GMPWxl × 2 + G2500PWxl (φ7.8 mm × 300 mm × 3) manufactured by Tosoh Corporation
Column temperature: 40 ° C
Eluent: 200 mM sodium nitrate aqueous solution Sample concentration: 0.05% by mass
Flow rate: 1.0 mL / min
Injection volume: 200 μL
Detector: RI (differential refractometer)
Standard substance: Polyethylene oxide “HEC” described in the “Type” column in the “Water-soluble polymer” column in Table 1 represents hydroxyethyl cellulose. In the “Salt” column in Table 1, “TAC” described in the “Type” column represents triammonium citrate, and “AAc” represents ammonium acetate.

  The average secondary particle diameter R1 of the abrasive grains contained in the dilution stock solution and the average secondary particle diameter R2 of the abrasive grains contained in the polishing composition were measured using FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. The measurement results are shown in the “R1” and “R2” columns in Table 1. The ratio of the average secondary particle diameter R2 to the average secondary particle diameter R1 is shown in the “R2 / R1” column in Table 1.

<Polishing process>
Using the polishing composition thus obtained, the silicon substrate was finally polished under the conditions shown in Table 2. The silicon substrate used for this final polishing is previously polished using a commercially available abrasive (trade name: GLANZOX-1103, manufactured by Fujimi Incorporated). The silicon substrate has a diameter of 300 mm, a conductivity type of P type, a crystal orientation of <100>, and a resistivity of 0.1 Ω · cm to less than 100 Ω · cm.

<Polishing speed>
The thickness of the silicon substrate when the silicon substrate was polished under the conditions shown in Table 2 was measured using Nano Metro 300TT manufactured by Kuroda Seiko Co., Ltd., and the polishing rate was calculated by dividing the difference in thickness before and after polishing by the polishing time. . “A” shown in the “Polishing rate” column of Table 1 is a polishing rate of 0.04 μm / min or more, “B” is 0.03 μm / min or more and less than 0.04 μm / min, and “C” is 0.025 μm / min. Min. To less than 0.03 μm / min, “D” is from 0.02 μm / min to less than 0.025 μm / min, “E” is from 0.015 μm / min to less than 0.02 μm / min, and “F” is 0.015 μm / Less than a minute.

<Wettability>
The length from the edge of the substrate was measured for the water-repellent part of the polished surface after the polishing process. At this time, “A” indicates that there is no water-repellent portion, “B” indicates that the water-repellent portion is less than 2 mm, “C” indicates that the water-repellent portion is less than 2 mm, and “D” indicates that the water-repellent portion is less than 5 mm and less than 5 mm. The case of 10 mm or more and less than 15 mm was determined as “E”, and the case of 15 mm or more was determined as “F”. The determination result is shown in the “Wettability” column of Table 1.

As shown in Table 1, in each example, the result of polishing rate and wettability was A, B, C, or D. In Comparative Example 1, since the molecular weight distribution of the water-soluble polymer is less than 5, the results of the polishing rate and the wettability are inferior to each example. In Comparative Example 2, although the molecular weight distribution of the water-soluble polymer is 5 or more, since the weight average molecular weight exceeds 1000000, the result of the polishing rate is inferior to each example.

Claims (5)

  A water-soluble polymer having a weight average molecular weight of 1,000,000 or less and a molecular weight distribution expressed by weight average molecular weight (Mw) / number average molecular weight (Mn) of 5.0 or more and 8.0 or less. A polishing composition.   The polishing composition according to claim 1, further comprising at least one salt selected from organic acid salts and inorganic acid salts.   The polishing composition according to claim 1 or 2, which is used for polishing a substrate.   The polishing composition according to claim 3, which is used for final polishing of a substrate.   A method for producing a substrate, comprising a polishing step of polishing the substrate using the polishing composition according to any one of claims 1 to 4.