Composition for polishing purposes, polishing process using the same and process for producing a substrate

Abstract

Polishing composition containing abrasive grains, a water-soluble polymer, an aggregation inhibitor and water, wherein the polishing composition is characterized in that, The water-soluble polymer of at least one is selected from the group consisting of cellulose and polysaccharides; The aggregation inhibitor of at least one is selected from a group consisting of vinyl-based water-soluble polymers, oxyalkylene polymers, oxyalkylene copolymers and silicone polymers; and If the mean particle size of the particles contained in the polishing composition is defined as R1, and the mean particle size of the abrasive grains in the case where the abrasive grains are dispersed in water to have the same concentration as the concentration of the abrasive grains in the polishing composition is defined as R2, then R1 / R2 is 1.3 or less.

Description

TECHNICAL AREA

[0001] The present invention relates to a polishing composition used for polishing a substrate, a method for polishing a substrate using the polishing composition, and a method for producing a substrate. STATE OF THE ART

[0002] In semiconductor devices used in computers, the miniaturization of the wiring width, known as design rules or guidelines, has progressed year after year to achieve higher integration and speed. Consequently, there is an increasing number of instances where nanometer-sized substrate surface defects, which were previously unproblematic, negatively impact the performance of semiconductor devices. Therefore, it is crucial to address these nanometer-sized substrate surface defects.

[0003] To polish a silicon substrate under semiconductor substrates, a polishing composition containing silicon dioxide particles and a water-soluble polymer is used (see, for example, Patent Document 1). The polishing composition disclosed in Patent Document 1 forms a protective film, derived from the water-soluble polymer, on the surface of a polished silicon substrate. This protective film imparts hydrophilicity to the surface of the polished substrate, thereby facilitating its handling. However, the water-soluble polymer used in the polishing composition has a molecular weight of several hundred thousand or more and therefore forms aggregates with the silicon dioxide particles. These aggregates, consisting of the silicon dioxide particles and the water-soluble polymer, can lead to substrate surface defects known as light point defects (LPDs).

[0004] To reduce LPDs caused by aggregates consisting of silicon dioxide particles and water-soluble polymer, it is important to eliminate these aggregates from the polishing compound. An effective example of this is to subject the polishing compound, which contains silicon dioxide particles and water-soluble polymer, to filtration to remove aggregates when it is manufactured and used. However, the polishing compound immediately clogs the filter, leading to the problem of frequent filter replacement.

[0005] To improve the flight characteristics or dispersion properties of abrasive grains in the polishing composition, a composition consisting of a dispersion agent or the like was proposed. Patent document 2 discloses that a surfactant is added to the polishing composition to improve the dispersion properties of the abrasive grains. The polishing composition disclosed in patent document 2 does not contain a water-soluble polymer with a molecular weight of several hundred thousand or more, which is assumed to form aggregates with abrasive grains. Patent document 2 only discloses that the polishing composition to which the surfactant is added is used to improve the polishing speed of a wafer.

[0006] Patent document 3 discloses a water-based polishing dispersion containing a water-soluble polymer and a surfactant as a dispersant. However, the water-based polishing dispersion does not contain a water-soluble polymer with a molecular weight of several hundred thousand or more, so it is predicted that the polymer would form aggregates with the abrasive grains. Patent document 3 only discloses that the water-based polishing dispersion, to which the dispersants are added, is used to reduce scratches on a copper film or foil.

[0007] Furthermore, patent document 4 discloses a polishing composition comprising at least one water-soluble polymer selected from polyvinylpyrrolidone and poly(N-vinylformamide) and an alkali. It is also disclosed that the polishing composition is effective in reducing LPDs. However, patent document 4 does not disclose a polishing composition comprising a water-soluble polymer with a molecular weight of several hundred thousand or more. It is assumed that the polymer forms aggregates with abrasive grains, and the document does not disclose the dispersibility of the abrasive grains.

[0008] Patent document 5 discloses a feeding device for supplying a dilute slurry obtained by diluting a slurry with colloidal silica, while controlling the cohesion of the colloidal silica dispersed in the slurry. A polishing method for obtaining a semiconductor wafer is also provided, controlling the cohesion of the colloidal silicon dioxide in the dilute slurry and the polishing properties of the resulting dilute slurry.

[0009] Therefore, there is a need for a polishing composition that gives the surface of a polished substrate high hydrophilicity, reduces LPDs and achieves a high dispersion of abrasive grains. DOCUMENTS OF THE STATE OF THE TECHNOLOGY Patent document 1: JP 2005 - 518 668 A Patent document 2: JP 2001 - 15 461 A Patent document 3: JP 2005 - 158 867 A Patent document 4: JP 2008 - 53 415 A Patent document 5: JP 2009 - 290 139 A SUMMARY OF THE INVENTION Problems that the invention is intended to solve

[0010] An object of the present invention is to provide a polishing composition which imparts high hydrophilicity to the surface of a polished substrate, reduces LPDs on the surface of a polished substrate, contains a water-soluble polymer, and abrasive grains finely dispersed therein. A further object of the present invention is to provide a method for polishing a substrate using the polishing composition and a method for producing a substrate. Means to solve the problems

[0011] To achieve the aforementioned objectives, and according to one aspect of the present invention, a polishing composition is provided which contains abrasive grains, a water-soluble polymer, an aggregation inhibitor, and water, wherein the water-soluble polymer is selected from the group consisting of cellulose and polysaccharides; the aggregation inhibitor is selected from the group consisting of vinyl-based water-soluble polymers, oxyalkylene polymers, oxyalkylene copolymers, and silicone polymers. If the mean particle size of the particles present in the polishing composition is defined as R1, and the mean particle size of the abrasive grains, in the case where the abrasive grains are dispersed in water to have the same concentration as the concentration of the abrasive grains in the polishing composition, is defined as R2, then R1 / R2 is 1.3 or less.

[0012] Another object of the present invention is to provide a method for polishing a silicon substrate using the polishing composition according to the first object. Yet another object of the present invention provides a method for producing a silicon substrate, including a step of polishing a silicon substrate using the polishing composition according to the above object. IMPACT OF THE INVENTION

[0013] According to the present invention, a polishing composition is provided which imparts high hydrophilicity to the surface of a polished silicon substrate and contains abrasive grains with a high dispersion capacity; a method for polishing a substrate using the same; and a method for producing a substrate. WAYS TO IMPLEMENT THE INVENTION

[0014] The following describes an embodiment of the present invention.

[0015] A polishing composition of the present embodiment is produced by mixing abrasive grains, a water-soluble polymer, an aggregation inhibitor and water, and adding a basic compound if necessary.

[0016] The abrasive grains are used to physically polish the surface of a substrate. Specific examples of abrasive grains include those made of silicon carbide, silicon dioxide, aluminum oxide, cerium dioxide, zirconium dioxide, calcium carbonate, and diamond. When the polishing composition is used to polish a semiconductor substrate, particularly a silicon substrate, the abrasive grains preferably consist of silicon dioxide, more preferably colloidal silicon dioxide or highly dispersed silicon dioxide, and further preferably colloidal silicon dioxide. When colloidal silicon dioxide or highly dispersed silicon dioxide is used, particularly when colloidal silicon dioxide is used, scratches produced on the surface of a substrate during a polishing step are reduced. The abrasive grains can be used individually or in combination with other grains.

[0017] In general, in a polishing compound containing a water-soluble polymer and abrasive grains, aggregates of the abrasive grains are readily formed by the water-soluble polymer. Therefore, a polishing compound containing a water-soluble polymer and abrasive grains tends to have a larger average particle size than a polishing compound that does not contain a water-soluble polymer. The term "particles present in the polishing compound" is used here to encompass not only aggregates of abrasive grains formed by the water-soluble polymer, but also abrasive grains that do not form aggregates.

[0018] The mean particle size of the particles present in the polishing composition of the present embodiment is preferably 10 nm or more, and more preferably 20 nm or more. Here, the value of the mean particle size is a volume-averaged particle size, measured by a particle size distribution measuring device according to a dynamic light scattering method.

[0019] The mean particle size of the abrasive grains is preferably 5 nm or more, and more preferably 10 nm or more. The value of the mean primary particle size of the abrasive grains can be calculated based on the specific surface area of ​​the abrasive grains, measured by the BET method.

[0020] If the mean particle size of the particles present in the polishing composition and the mean particle size of the abrasive grains are within the above ranges, the surface finishing performance, such as the polishing rate of a silicon substrate, will be improved.

[0021] The mean particle size of the particles present in the polishing composition is preferably 200 nm or less and more preferably 100 nm or less.

[0022] The mean primary particle size of the abrasive grains is preferably 100 nm or less and more preferably 50 nm or less.

[0023] If the mean particle size of the particles contained in the polishing compound and the mean primary particle size of the abrasive grains are within the ranges mentioned above, the dispersion stability of the abrasive grains in the polishing compound is improved. As a result, good filtration properties are achieved, even when the polishing compound is subjected to filtration using a filter with a small mesh size.

[0024] In the volume-based particle size distribution of the abrasive grains, measured by a particle size distribution measuring device using a dynamic light scattering method, the D90 / D10 value lies between 1 and 4 inclusive. D90 / D10 is obtained by dividing the particle size D90, at which the cumulative particle size distribution of the smaller particle size reaches 90%, by the particle size D10, at which the cumulative particle size distribution of the smaller particle size reaches 10%. When D90 / D10 is within this range, the polishing rate is higher, resulting in a polished surface with excellent smoothness.

[0025] The abrasive grains preferably have a non-spherical shape. Examples of non-spherical shapes include an elliptical shape with a constricted portion in a central region, described as a peanut shell shape, a spherical shape with numerous protrusions on the surface, and a rugby ball shape. Additionally, the abrasive grains may have a structure in which two or more primary particles are bonded together. The non-spherical shape is expressed as an aspect ratio. The aspect ratio is calculated as follows: In a scanning electron micrograph of the abrasive grains, the minimum bounding rectangle is defined with respect to each grain. Then, the length of a long side is divided by the length of a short side with respect to each minimum bounding rectangle. Finally, the average of the resulting values ​​is determined.

[0026] The aspect ratio of the abrasive grains is preferably greater than 1, more preferably 1.1 or more, and particularly preferably 1.2 or more. When the aspect ratio of the abrasive grains is in the range above, the polishing rate of a silicon substrate is improved by the polishing composition.

[0027] The aspect ratio of the abrasive grains is preferably 4.0 or less, preferably 3.0 or less, and particularly preferably 2.5 or less. If the aspect ratio of the abrasive grains is within the above range, the occurrence of surface defects and the increase in surface roughness after polishing an object using the polishing compound can be suppressed.

[0028] The abrasive grain content in the polishing compound is preferably 0.01 wt.% or more. When the abrasive grain content is in the above range, surface finishing performance, such as the polishing rate of a silicon substrate, is improved.

[0029] The abrasive grain content in the polishing composition is preferably 5 wt.% or less, more preferably 1 wt.% or less, and particularly preferably 0.5 wt.%. When the abrasive grain content is in the above range, the dispersion stability of the polishing composition is improved and the residue of abrasive grains after polishing is reduced, thereby reducing LPDs.

[0030] The water-soluble polymer in the polishing compound serves to impart hydrophilicity to the surface of a polished substrate. When the hydrophilicity of a substrate's surface deteriorates, the components of the polishing compound and foreign substances generated by the substrate remain on the surface, compromising the cleanliness of the cleaned substrate. Therefore, the surface finish of the substrate can be reduced. Furthermore, the water-soluble polymer also exhibits the property of crosslinking the abrasive grains to form aggregates. The water-soluble polymer is at least one selected from the group consisting of cellulose and polysaccharides. Specific examples of celluloses include hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose. Specific examples of polysaccharides include starch, cyclodextrin, trehalose, and pullulan.From the point of view of giving the surface of a substrate high wettability and good cleanliness after cleaning, the water-soluble polymer is preferably a cellulose and more preferably a hydroxyethylcellulose.

[0031] The weight-average molecular weight of the water-soluble polymer in the polishing composition is preferably 10,000 or more. If the weight-average molecular weight of the water-soluble polymer is in the above range, the hydrophilicity to be imparted to the surface of a silicon substrate can be improved.

[0032] The weight-average molecular weight of the water-soluble polymer in the polishing composition is preferably 2,000,000 or less, more preferably 1,000,000 or less, particularly preferably 500,000 or less, and most preferably 300,000 or less. When the weight-average molecular weight of the water-soluble polymer is in the above range, the dispersion stability of the polishing composition is improved, and the cleanliness of a purified silicon substrate is enhanced.

[0033] The content of the water-soluble polymer in the polishing composition is preferably 0.0001 wt.% or more, more preferably 0.001 wt.% or more, and particularly preferably 0.005 wt.% or more. When the content of the water-soluble polymer is in the above range, the hydrophilicity to be imparted to the surface of a silicon substrate is improved.

[0034] The content of the water-soluble polymer in the polishing composition is preferably 0.5 wt.% or less, particularly preferably 0.1 wt.% or less, and further preferably 0.05 wt.% or less. If the content of the water-soluble polymer is in the above range, the dispersion stability of the polishing composition is improved.

[0035] When the abrasive grains and the water-soluble polymer are present in the same solvent, the aggregation inhibitor in the polishing compound generally suppresses the aggregation of the abrasive grains by the water-soluble polymer. When the abrasive grains and the water-soluble polymer coexist, it is assumed that the water-soluble polymer adsorbs onto the abrasive grains, and the abrasive grains aggregate via the water-soluble polymer. On the other hand, in the presence of the aggregation inhibitor, the water-soluble polymer and the aggregation inhibitor adsorb competitively onto the abrasive grains. Therefore, it is assumed that the aggregation force between the abrasive grains is weakened compared to the case where only the water-soluble polymer adsorbs onto the abrasive grains, leading to an improvement in dispersion.The improvement in the dispersion properties of the abrasive grains is specifically manifested as the effect of improving the filtration properties of the polishing composition.

[0036] A compound exhibiting the above-mentioned effect can be used as an aggregation inhibitor. The aggregation inhibitor is at least one selected from the group consisting of vinyl-based water-soluble polymers, oxyalkylene polymers, oxyalkylene copolymers, and silicone polymers. Specific examples of vinyl-based water-soluble polymers include polyvinylpyrrolidone, polyvinylcaprolactam, polyacrylamide, and polyacrylic acid. Specific examples of oxyalkylene polymers include polyethylene glycol and polypropylene glycol. Further examples of oxyalkylene copolymers include diblock, triblock, random, and alternating copolymers of polyoxyethylene and polyoxypropylene. Specific examples of oxyalkylene copolymers include polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymers. Specific examples of silicone polymers include polyether-modified silicone.From the perspective of imparting high dispersibility to the polishing composition, the aggregation inhibitor is preferably one or more selected from the vinyl-based water-soluble polymer, the oxyalkylene copolymer, and the silicone polymer, and further preferably one or more selected from the vinyl-based water-soluble polymers and the oxyalkylene polymers. From the perspective of improving hydrophilicity, the aggregation inhibitor is even more preferably one or more selected from polyvinylpyrrolidone and polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymers.

[0037] The weight-average molecular weight of the aggregation inhibitor in the polishing composition is preferably 300 or more, more preferably 1,000 or more, and particularly preferably 3,000 or more. Additionally, the weight-average molecular weight is preferably 2,000,000 or less, more preferably 1,000,000 or less, particularly preferably 500,000 or less, and most preferably 100,000 or less. When the weight-average molecular weight of the aggregation inhibitor is in the above range, the dispersion stability of the polishing composition is improved.

[0038] The content of the aggregation inhibitor in the polishing composition is preferably 0.00001 wt.% or more, more preferably 0.0001 wt.% or more, particularly preferably 0.001 wt.% or more, further preferably 0.002 wt.% or more, and most preferably 0.005 wt.% or more. When the content of the aggregation inhibitor is in the above range, the dispersion stability of the polishing composition is improved.

[0039] The concentration of the aggregation inhibitor in the polishing composition is preferably 0.1 wt.% or less, more preferably 0.05 wt.% or less, and particularly preferably 0.01 wt.% or less. When the concentration of the aggregation inhibitor is in the above range, the hydrophilicity on the surface of a substrate is improved.

[0040] Here, the term "degree of abrasive grain aggregation" is defined as R1 / R2. R1 represents the mean particle size of the particles present in the polishing compound, which contains the abrasive grains, the water-soluble polymer, the aggregation inhibitor, and water. R2 represents the mean particle size of the abrasive grains when dispersed in water to achieve the same concentration as the abrasive grains in the polishing compound. The degree of abrasive grain aggregation must be 1.3 times or less, and preferably 1.2 times or less. It is assumed that a lower degree of abrasive grain aggregation means that the aggregates of abrasive grains in the polishing compound are small. Such a polishing compound exhibits good filtration properties when a small-mesh filter is used.

[0041] The polishing compound may also contain a basic compound. The basic compound in the polishing compound has a chemically corrosive effect on the surface of a substrate and serves to chemically polish the surface of the substrate. The basic compound also serves to improve the dispersion stability of the polishing compound. Examples of basic compounds include ammonia, an alkali metal hydroxide, a quaternary ammonium hydroxide, and an amine. Specific examples of basic compounds include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetraamine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, and N-methylpiperazine.Among these, ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide are preferred; further preferred are ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, or tetraethylammonium hydroxide; and ammonia is particularly preferred. The basic compounds listed above can be used individually or in combination with two or more.

[0042] The content of the basic compound in the polishing composition is preferably 0.0001 wt.% or more, more preferably 0.001 wt.% or more, and further preferably 0.005 wt.% or more. When the content of the basic compound is in the above range, chemical etching of the substrate surface is facilitated and the polishing speed of a silicon substrate is improved. Additionally, the dispersion stability of the polishing composition is also enhanced.

[0043] The content of the basic compound in the polishing composition is preferably 0.5 wt.% or less, more preferably 0.1 wt.% or less, particularly preferably 0.05 wt.% or less, and most preferably 0.01 wt.% or less. When the content of the basic compound is in the above range, the smoothness of the surface of a polished substrate is improved.

[0044] The water contained in the polishing compound serves to dissolve or disperse other components within the compound. For example, water with a total transition metal ion content of 100 ppb or less is preferably used to avoid inhibiting the action of the other components. In particular, ion-exchange water from which impurity ions have been removed using an ion exchange resin and subsequently foreign substances have been removed by a filter, or pure water, ultrapure water, or distilled water is preferred.

[0045] The pH value of the polishing composition is preferably 8 or higher, and more preferably 9 or higher. Additionally, the pH value of the polishing composition is preferably 12 or lower, and more preferably 11 or lower. A polishing level that is practically preferred is achieved when the pH value of the polishing composition is within the above range.

[0046] The polishing compound may also contain a surfactant. The surfactant is added, and therefore the roughening of the substrate surface due to the chemical etching effect of the basic compound can be suppressed, thus improving the surface smoothness.

[0047] The surfactant can be ionic or non-ionic, but is preferably non-ionic. Furthermore, when a non-ionic surfactant is used, foaming of the polishing composition is suppressed compared to when a cationic or anionic surfactant is used, and therefore the polishing composition is easier to prepare or use. Since the surfactant also does not change the pH of the polishing composition, the pH of the polishing composition is easily controlled during preparation or use.Furthermore, since the non-ionic surfactant is excellent in terms of biodegradability and less toxic to living organisms, it is possible to reduce the impact on the environment and the risk associated with handling.

[0048] Nonionic surfactants are not limited by their structure. Examples of nonionic surfactants include polyoxyalkylene adducts such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Specific examples of nonionic surfactants include polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene centetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, and polyoxyethylene nonyl phenyl ether.Polyoxyethylene endodecyl phenyl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolauric ester, polyoxyethylene monostearic ester, polyoxyethylene distearic ester, polyoxyethylene monooleic ester, polyoxyethylene dioleic ester, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol tetraoleate, a polyoxyethylene castor oil, and a polyoxyethylene hydrogenated castor oil. The surfactants can be used individually or in combination with two or more.

[0049] The weight-average molecular weight of the polishing composition is preferably 200 or more, and more preferably 300 or more. Additionally, the weight-average molecular weight of the surfactant in the polishing composition is preferably 15,000 or less, and more preferably 10,000 or less. When the weight-average molecular weight of the surfactant in the polishing composition is in the above range, the effect of suppressing surface roughening of a substrate is strongly exerted.

[0050] The surfactant content in the polishing composition is preferably 0.00001 wt.% or more, and even more preferably 0.00005 wt.% or more. Additionally, the surfactant content in the polishing composition is preferably 0.1 wt.% or less, and even more preferably 0.05 wt.% or less. When the surfactant content in the polishing composition is in the above range, the effect of suppressing surface roughening of a substrate is strongly exerted.

[0051] The polishing compound may further contain one or more components selected from an organic acid, an inorganic acid, and salts thereof. These components have the effect of improving the hydrophilicity on the surface of a silicon substrate after the substrate has been polished.

[0052] Examples of organic acids include carboxylic acids, aromatic carboxylic acids, organic sulfonic acids, and organic phosphonic acids. Specific examples of carboxylic acids include formic acid, acetic acid, propionic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, and succinic acid. Specific examples of aromatic carboxylic acids include benzoic acid and phthalic acid. Specific examples of inorganic acids include carbonic acid, hydrochloric acid, sulfuric acid, and nitric acid. Additionally, examples of a basic ion that reacts with the organic or inorganic acid to form an organic or inorganic salt include an ammonium ion and an alkali metal ion. Among these, an ammonium ion is preferred from the point of view of reducing metallic impurities on a substrate.Organic acids, inorganic acids, organic salts or inorganic salts can be used alone or in combination with two or more.

[0053] The polishing compound may also contain a chelating agent. If the polishing compound contains a chelating agent, metallic impurities on a silicon substrate can be suppressed. Examples of chelating agents include aminocarboxylic acid chelators and organic phosphonic acid chelators. Specific examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetic acid, ammonium nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate.Specific examples of the organic phosphonic acid chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphononic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid.

[0054] The polishing composition of the present embodiment has the advantages shown.

[0055] The polishing composition contains the water-soluble polymer and exhibits a degree of abrasive grain aggregation of 1.3 or less. Therefore, the polishing composition possesses good filtration properties and imparts suitable hydrophilicity to the surface of a polished substrate, thereby reducing LPDs (low particle density) on the substrate surface. Consequently, the polishing composition of the present embodiment can be suitable for use in applications for polishing the surface of a substrate, particularly for applications involving the final polishing of the surface of a silicon substrate, which requires high substrate surface accuracy.

[0056] The embodiment can be modified as follows.

[0057] The polishing composition of the embodiment may further contain known additives, such as a preservative and a mold detection agent, if necessary. Specific examples of the preservative and the mold detection agent include an isothiazolinone compound, paraoxybenzoates, and phenoxyethanol.

[0058] The polishing composition of the present invention can be a compound with one component or a multi-component compound containing two or more components.

[0059] The polishing compound can be prepared by dissolving or dispersing the components described above, with the exception of water, in water using a conventional method. The order in which the components are dissolved or dispersed in the water is not particularly restricted. The dissolution or dispersion method is also not particularly restricted. For example, a common method such as stirring with a rod stirrer or dispersion using a homogenizer can be employed.

[0060] The polishing composition of the present embodiment can be in the form of a concentrated stock solution when it is manufactured or sold. When the polishing composition is in the form of a concentrated stock solution, its volume is smaller, and therefore transportation and storage costs can be reduced. The concentration of the polishing composition's stock solution is preferably 5 times or more, more preferably 10 times or more, and further preferably 20 times or more, but is not limited to these concentrations. Here, the concentration refers to the ratio of the volume of the polishing composition after dilution to the volume of the polishing composition's stock solution.

[0061] The polishing composition of the present embodiment and the stock solution of the polishing composition can be diluted 5 to 60 times in use. Since the polishing composition and the stock solution of the polishing composition retain good dispersibility of the abrasive grains, they exhibit good filtration properties in this case. Additionally, the diluted solution is subjected to filtration and then used for polishing, which allows the LPDs on the surface of a polished substrate to be further reduced.

[0062] The polishing composition of the present embodiment can also be used in applications where a substrate other than a silicon substrate is polished. Specific examples of such a substrate include a silicon dioxide substrate, a plastic substrate, and a quartz substrate.

[0063] The polishing composition of the present embodiment can also be subjected to a filtration treatment and then used for polishing. The mesh size of a filter used in the filtration treatment is preferably 10 µm or less, more preferably 1 µm or less, and further preferably 0.5 µm or less, from the point of view of removing fine foreign substances. Additionally, the material and structure of the filter used in the filtration step are not particularly restricted. Examples of filter materials include nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, cellulose esters, and glass. The filter material is preferably nylon, polyethersulfone, or polypropylene, and more preferably nylon, from the point of view of the filtration flow rate.

[0064] Examples and comparative examples of the present invention are described.

[0065] Each of the polishing compositions in Examples 1 to 19 and Comparative Examples 1 to 6 was prepared by mixing part or all of the colloidal silicon dioxide, a water-soluble polymer, an aggregation inhibitor, a basic compound, and a salt with ion exchange water. The composition of each of the polishing compositions in Examples 1 to 19 and Comparative Examples 1 to 6 is shown in Table 1.

[0066] The mean particle size of the colloidal silicon dioxide was measured using the dynamic light scattering method with UPA-UT151 manufactured by Nikkiso Co., Ltd. The mean particle size of the colloidal silicon dioxide abrasive grains used in each of Examples 1 to 19 and Comparative Examples 1 to 6 is shown in the "Particle Size" column of the "Colloidal Silicon Dioxide" column in Table 1. This corresponds to R2 in the definition of the degree of aggregation of the abrasive grains. Additionally, with respect to each of the polishing compositions in Examples 1 to 19 and Comparative Examples 1 to 6, the mean particle size R1 of the particles present in the polishing compositions was determined in the same manner and is shown in the "Mean Particle Size of Particles in Polishing Composition" column in Table 1. This corresponds to R1 in the definition of the degree of aggregation of the abrasive grains.R1 was divided by R2 to determine the degree of aggregation of the abrasive grains. The resulting value is shown in the column "Degree of Aggregation of Abrasive Grains" in Table 1.

[0067] In the "Water-soluble polymer" column of Table 1, HEC represents hydroxyethylcellulose and CMC represents carboxymethylcellulose. Additionally, in the "Anti-aggregation agent" column of Table 1, PVP represents polyvinylpyrrolidone, Si-Oil represents polyether-modified silicone, and A1 represents a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer. Furthermore, in the "Salt" column of Table 1, B1 represents triammonium citrate.

[0068] The filtration properties of the polishing compound were determined as follows. For each of the polishing compounds in Examples 1 to 19 and Comparative Examples 1 to 6, filtration was carried out for 5 minutes under the conditions specified in Table 2, and the volume of the polishing compound passing through the filter was measured. In the "Filtration Properties" column in Table 1, "A" means that the volume of the polishing compound passing through the filter was 200 ml or more, "B" means that the volume was 100 ml or more and less than 200 ml, and "C" means that the volume was less than 100 ml.

[0069] The hydrophilicity on the surface of a substrate, imparted by the polishing composition, was evaluated using the method described below. First, a silicon wafer with a diameter of 200 mm, a conductive type P, was used. <100> Silicon substrates with a crystal orientation and a resistivity of 0.1 Ω·cm or more and less than 100 Ω·cm were cut into square chips with sides of 60 mm to produce silicon substrates. Each silicon substrate was pre-polished using a polishing slurry (trade name: GLANZOX 2100) manufactured by Fujimi Incorporated. Subsequently, each of the polishing compositions of Examples 1 to 19 and Comparative Examples 1 to 6 was used to polish each silicon substrate under the conditions specified in Table 3.The surface of each silicon substrate was then rinsed with running water at a flow rate of 7 l / min for 10 seconds. Each silicon substrate was then placed vertically and left to stand for 30 seconds. The maximum distance from an edge region to a wet area on each silicon substrate was then measured; that is, the maximum water-repellent distance was measured. It is stated that the hydrophilicity on the surface of each silicon substrate is lower the greater the maximum water-repellent distance. In the "Hydrophilicity" column of Table 1, "A" means that the maximum water-repellent distance was 5 mm or less, and "B" means that the maximum water-repellent distance was greater than 5 mm. [Table 2] Filtration process: Kissing Differential pressure filtration: 50 kPa Filtration time: 5 minutes Filter type: OMNIPORE MEMBRANE (disc type) (manufactured by Nihon Millipore KK) Filter diameter: 47 mm Filter mesh size: 5,0 µm [Table 3] Polishing machine: Polishing table machine EJ-380IN (manufactured by Engis Japan Corporation) Polishing charge: 15 kPa Table rotation speed: 30 rpm Head rotation speed: 30 rpm Polishing time: 1 minute Temperature of the polishing compound: 20°C Feed rate of the polishing compound: 0.25 l / min (pour onto the wafer)

[0070] As shown in Table 1, it was found that each of the polishing compositions of Examples 1 to 19 exhibited a high filtration property and imparted hydrophilicity to the surface of a polished silicon substrate, in contrast to each of the polishing compositions of Comparison Examples 1 to 6.

Claims

[1] Polishing composition comprising abrasive grains, a water-soluble polymer, an aggregation inhibitor and water, wherein the polishing composition characterized by is that, The water-soluble polymer of at least one is selected from the group consisting of cellulose and polysaccharides; The aggregation inhibitor of at least one is selected from a group consisting of vinyl-based water-soluble polymers, oxyalkylene polymers, oxyalkylene copolymers and silicone polymers; and If the mean particle size of the particles contained in the polishing composition is defined as R1, and the mean particle size of the abrasive grains in the case where the abrasive grains are dispersed in water to have the same concentration as the concentration of the abrasive grains in the polishing composition is defined as R2, then R1 / R2 is 1.3 or less. [2] Polishing composition according to claim 1, characterized by that the water-soluble polymer is a cellulose. [3] Method for polishing a substrate, characterized by Polishing a silicon substrate using the polishing composition according to one of claims 1 or 2. [4] Method for producing a silicon substrate, characterized by Polishing a silicon substrate using the polishing method according to claim 3.