Composition for polishing

Abstract

To provide a polishing composition capable of achieving both excellent stability and a high polishing speed of an object to be polished.SOLUTION: The polishing composition contains: abrasive grains which have a positive zeta potential in an aqueous solution having a pH of less than 7 and in which the number of silanol groups per unit surface area is 2.5 / nm2 or less; and a copolymer of a monomer represented by the following general formula (1) and a vinyl ester monomer, the copolymer having a degree of saponification of 95 mol% or more and having a 1,2-diol structure in a side chain. The polishing composition has a pH of less than 7.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, due to the high integration brought about by the miniaturization of the LSI manufacturing process, electronic devices such as computers have achieved high performance such as miniaturization, multifunctionality, and high speed. In such new microfabrication technologies accompanying the high integration of LSI, the Chemical Mechanical Polishing (CMP) method is used. The CMP method is a technique frequently used in the LSI manufacturing process, particularly in the planarization of the interlayer insulating film, the formation of metal plugs, and the formation of embedded wiring (damascene wiring) in the multilayer wiring formation process.

[0003] In recent years, CMP has been applied to each process in semiconductor manufacturing, and as one aspect thereof, for example, application to the gate formation process in transistor fabrication can be mentioned.

[0004] When fabricating transistors, it is sometimes necessary to polish Si-containing materials such as polycrystalline silicon (polysilicon) and silicon oxide, and it is required to reduce metal contamination after polishing. For example, Patent Document 1 proposes a polishing composition that can reduce contamination on the surface of the object to be polished after polishing while suppressing aggregation of abrasive grains, including a copolymer of a vinyl ester monomer and vinyl alcohol, an organic acid, and abrasive grains whose surface is chemically modified so that the zeta potential of the surface is negative and does not have an isoelectric point in a solution with a pH of 2.0 or higher.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the polishing composition of Patent Document 1 has a problem that the polishing rate with respect to an object to be polished (particularly an object to be polished containing silicon oxide or polycrystalline silicon) is low.

[0007] Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a polishing composition capable of achieving both excellent stability and a high polishing rate of an object to be polished (particularly an object to be polished containing silicon oxide or polycrystalline silicon).

Means for Solving the Problems

[0008] In order to solve the above problems, the present inventors have conducted intensive research. As a result, abrasive grains having a positive zeta potential in an aqueous solution having a pH of less than 7 and having 2.5 silanol groups per unit surface area of / nm 2 or less, a copolymer of a monomer represented by the following general formula (1) and a vinyl ester monomer, having a saponification degree of 95 mol% or more and having a 1,2-diol structure in the side chain, and a polishing composition having a pH of less than 7 It has been found that the above problems can be solved.

[0009]

Chemical formula

[0010] In the general formula (1), R 1 ~R 6 are each independently a hydrogen atom or an organic group, X is a single bond or a linking group, R 7 and R 8 are each independently a hydrogen atom or R 9 -CO-(R 9 is an alkyl group).

Effects of the Invention

[0011] The present invention can provide a novel polishing composition that can achieve both excellent stability and a high polishing rate for a polishing object (particularly a polishing object containing silicon oxide or polycrystalline silicon).

Embodiments for Carrying Out the Invention

[0012] The present invention has a positive zeta potential in an aqueous solution with a pH of less than 7, and the number of silanol groups per unit surface area is 2.5 per nm 2 The polishing composition contains abrasive grains as described below, and a copolymer of a monomer represented by the following general formula (1) and a vinyl ester monomer, having a saponification degree of 95 mol% or more and having a 1,2-diol structure in the side chain, and has a pH of less than 7.

[0013]

Chemical formula

[0014] In the general formula (1), R 1 ~R 6 are each independently a hydrogen atom or an organic group, X is a single bond or a linking group, R 7 and R 8 are each independently a hydrogen atom or R 9 -CO-(R 9 is an alkyl group).

[0015] With such a configuration, the polishing composition can be stably stored without generating precipitates in a wide temperature range from low temperature to high temperature (particularly low temperature) (excellent storage stability), and a high polishing rate can be achieved for a polishing object (particularly a polishing object containing silicon oxide or polycrystalline silicon). Here, the mechanism of exerting the above-mentioned effects by the configuration of the present invention is presumed as follows. Note that the present invention is not limited to the following presumption.

[0016] The abrasive grains contained in the polishing composition of the present invention have a small number of silanol groups (low silanol group density). Usually, on the surface of abrasive grains (for example, silica particles), a film of dispersion medium molecules (for example, water molecules) is formed through hydrogen bonds or the like by surface silanol groups. When abrasive grains with a small number of silanol groups and a small amount of dispersion medium (for example, water) covering the surface of the abrasive grains are used in the polishing composition, there is no or little presence of a dispersion medium molecular film between the surface of the abrasive grains and the object to be polished during polishing. For this reason, the abrasive grains can easily and efficiently (with high frequency) approach the object to be polished, and it becomes possible to efficiently scrape (polish) the surface of the object to be polished. In particular, in the polishing of an object to be polished containing silicon atoms such as silicon oxide and polycrystalline silicon, when there is little dispersion medium molecular film (for example, water molecule film), the abrasive grains are more likely to approach the surface of the object to be polished during polishing. Furthermore, not only hydrogen bonds but also charge interactions are involved between such abrasive grains and the surface of the object to be polished. For this reason, the silanol groups on the surface of the abrasive grains and the silanol groups on the surface of the object to be polished are more likely to bind strongly, and the surface of the object to be polished can be polished at high speed and efficiently. Also, the abrasive grains contained in the polishing composition of the present invention have a positive zeta potential in the polishing composition. Since polishing pad debris generally has a positive zeta potential under acidic conditions, aggregation of abrasive grains with each other and aggregation of abrasive grains with polishing pad debris are suppressed, and it is less likely to form coarse particles. For this reason, generation of precipitates during storage (preservation) of the polishing composition can be effectively suppressed and prevented (storage stability can be improved). Also, generation of scratches on the surface of the object to be polished can be effectively reduced. Note that due to the small number of anionic silanol groups, the isoelectric point of the abrasive grains shifts to the higher side. For this reason, especially under strongly acidic conditions (for example, pH = 3 or less), the zeta potential is charged more positively to further improve the dispersibility of the abrasive grains (further improve storage stability).

[0017] In addition to the above, the polishing composition of the present invention contains a copolymer with a specific structure. The copolymer according to the present invention has a 1,2-diol structural unit in the side chain. Since the 1,2-diol structural unit is hydrophilic, it can further improve the dispersibility of abrasive grains in a wide temperature range (especially in a low-temperature environment) and suppress the aggregation of abrasive grains (coarse particles are less likely to be formed). Therefore, the generation of precipitates during the storage (storage) of the polishing composition can be effectively suppressed and prevented (the storage stability, especially the storage stability at low temperatures, can be improved). In addition, the generation of scratches on the surface of the object to be polished can also be effectively reduced. The copolymer also has a structural unit derived from a vinyl ester monomer (for example, vinyl alcohol). This structural unit shows an affinity for abrasive grains (especially colloidal silica) and the surface of the object to be polished (especially the surface of the object to be polished containing a silicon-containing material such as silicon oxide and polycrystalline silicon). Therefore, by adding the copolymer according to the present invention, the abrasive grains are more likely to come into contact with the surface of the object to be polished, and the action frequency increases. In particular, the copolymer containing a 1,2-diol structural unit in the side chain shows hydrophilicity, so it can further hydrophilize the surface of the object to be polished, which is a hydrophobic surface, and as a result, the polishing rate can be improved.

[0018] Hereinafter, embodiments of the present invention will be described. It should be noted that the present invention is not limited only to the following embodiments. Also, unless otherwise specified, measurements of operations and physical properties are performed under the conditions of room temperature (20 to 25 °C) / relative humidity 40 to 50%RH.

[0019] [Abrasive grains] The abrasive grains contained in the polishing composition according to the present invention have the function of mechanically polishing the object to be polished and improve the polishing rate of the object to be polished by the polishing composition.

[0020] The abrasive grains according to the present invention have a positive zeta potential in an aqueous solution with a pH of less than 7 and the number of silanol groups per unit surface area is 2.5 / nm 2The following is the case. Here, "having a positive zeta potential in an aqueous solution with a pH less than 7" means that the abrasive grains have a positive zeta potential in an aqueous solution containing at least water, which is synonymous with the abrasive grains showing a positive zeta potential in a polishing composition with a pH less than 7. Also, it is synonymous with the isoelectric point at which the zeta potential of the abrasive grains becomes 0 being in the range of pH 7 or higher. When the abrasive grains have a zeta potential of 0 or less in an aqueous solution with a pH less than 7 or the number of silanol groups per unit surface area of the abrasive grains exceeds 2.5 / nm 2 in the case, since a thick dispersion medium molecular film exists between the surface of the abrasive grains and the object to be polished during polishing, it is difficult for the abrasive grains to approach the object to be polished, and the polishing rate becomes low (see Comparative Examples 2, 5, and 6 below). The zeta potential of the abrasive grains in an aqueous solution (polishing composition) with a pH less than 7 is preferably more than 5 mV and 50 mV or less, more preferably 10 mV or more and 50 mV or less, still more preferably 10 mV or more and 30 mV or less, even more preferably 13 mV or more and 20 mV or less, and particularly preferably 13 mV or more and less than 20 mV. Also, the number of silanol groups per unit surface area of the abrasive grains is 2.4 / nm 2 or less, 2.4 / nm 2 less than, 2.3 / nm 2 or less, 2.2 / nm 2 or less, 2.1 / nm 2 or less, 2.0 / nm 2 or less, 1.9 / nm 2 or less, 1.8 / nm 2 in the following order is preferable. Since the lower limit of the number of silanol groups is preferably lower, it is 0 / nm 2 but usually 0.2 / nm 2 or more is sufficient, preferably 0.4 / nm 2 or more, more preferably 0.8 / nm 2 or more. Abrasive grains having such a zeta potential and / or number of silanol groups can further improve the storage stability and polishing rate. In this specification, the "zeta potential of the abrasive grains" and the "number of silanol groups per unit surface area of the abrasive grains" are respectively the values measured by the methods described in <Method for Measuring Zeta Potential> and <Method for Calculating Number of Silanol Groups> in the following examples.

[0021] The zeta potential of the abrasive grains according to the present invention can be achieved by reducing the number of silanol groups on the abrasive grains or by cation-modifying the surface of the abrasive grains.

[0022] In one embodiment of the present invention, specific examples of the abrasive grains include, for example, particles composed of metal oxides such as silica. These abrasive grains may be used alone or in a mixture of two or more. Also, commercially available products or synthetic products may be used as the abrasive grains. Among these abrasive grains, silica is preferable, fumed silica and colloidal silica are more preferable, and colloidal silica is particularly preferable. Examples of the production method of colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by any production method can be suitably used as the abrasive grains of the present invention. However, colloidal silica produced by the sol-gel method, which can be produced with high purity, is preferable.

[0023] In one embodiment of the present invention, in order to make the number of silanol groups per unit surface area of the abrasive grains 2.5 per nm 2 or less, it can be controlled by selecting the production method of the abrasive grains, etc. For example, it is preferable to perform heat treatment such as firing. In one embodiment of the present invention, the firing treatment means, for example, holding the abrasive grains (for example, silica) in an environment of 120 to 200°C for 30 minutes or more. By performing such heat treatment, the number of silanol groups on the surface of the abrasive grains can be made to be a desired value such as 2.5 per nm 2 or less. Unless such special treatment is performed, the number of silanol groups on the surface of the abrasive grains will not be 2.5 per nm 2 or less.

[0024] In one embodiment of the present invention, abrasive grains with a cation-modified surface can be used. Here, as the colloidal silica with a cation-modified surface, colloidal silica with an amino group or a quaternary ammonium group immobilized on the surface is preferably mentioned. As a method for producing such colloidal silica having a cationic group, as described in JP-A-2005-162533, silane coupling agents having an amino group such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, aminobutyltriethoxysilane, etc. or silane coupling agents having a quaternary ammonium group such as N-trimethoxysilylpropyl-N,N,N-trimethylammonium are immobilized on the surface of the abrasive grains. Thereby, colloidal silica with an amino group or a quaternary ammonium group immobilized on the surface can be obtained. In one embodiment of the present invention, the abrasive grains are obtained by immobilizing a silane coupling agent having an amino group or a silane coupling agent having a quaternary ammonium group on the surface of the abrasive grains.

[0025] In one embodiment of the present invention, it is preferable that the average primary particle size of the abrasive grains is 10 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, and particularly preferably 30 nm or more. In the polishing composition of one embodiment of the present invention, it is preferable that the average primary particle size of the abrasive grains is 60 nm or less, more preferably 55 nm or less, even more preferably 50 nm or less, and particularly preferably 40 nm or less. By adjusting the average primary particle size of the abrasive grains within the above range, the polishing rate of the object to be polished can be further improved. In this specification, the value measured by the method described in the examples is adopted as the average primary particle size.

[0026] It is preferable that the average secondary particle diameter of the abrasive grains is 40 nm or more, more preferably 45 nm or more, still more preferably 50 nm or more, even more preferably 55 nm or more, and particularly preferably 60 nm or more. In one embodiment of the present invention, it is preferable that the average secondary particle diameter of the abrasive grains is 110 nm or less, more preferably 100 nm or less, still more preferably 90 nm or less, even more preferably 80 nm or less, and particularly preferably 75 nm or less. By adjusting the average secondary particle diameter of the abrasive grains within the above range, the polishing rate of the object to be polished can be further improved. In this specification, the average secondary particle diameter is the value measured by the method described in the examples.

[0027] In one embodiment of the present invention, the lower limit of the average degree of aggregation (average secondary particle diameter / average primary particle diameter) of the abrasive grains in the polishing composition is preferably 1.5 or more, more preferably 1.8 or more, and particularly preferably 2.0 or more. In one embodiment of the present invention, the upper limit of the average degree of aggregation of the abrasive grains in the polishing composition is preferably 3.5 or less, more preferably 3.0 or less, and particularly preferably less than 2.5. By adjusting the average degree of aggregation of the abrasive grains within the above range, the object to be polished can be polished at a higher speed.

[0028] In one embodiment of the present invention, in the polishing composition, the content of the abrasive grains is preferably 0.03% by mass or more, more preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.3% by mass or more, still more preferably 0.9% by mass or more, and particularly preferably 2% by mass or more. In one embodiment of the present invention, in the polishing composition, the content of the abrasive grains is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less, still more preferably 5% by mass or less, still more preferably 3% by mass or less, and particularly preferably 1% by mass or less. With such a content, the object to be polished can be polished at a higher speed.

[0029] Particularly, when polishing an object to be polished containing silicon atoms, such as an object to be polished containing silicon oxide or polycrystalline silicon, in the polishing composition, it is preferable to adjust the content of the abrasive grains to 0.1 to 10% by mass, more preferably to 1 to 8% by mass, and particularly preferably to 2 to 7% by mass. Alternatively, particularly when polishing an object to be polished containing silicon atoms, such as an object to be polished containing silicon oxide or polycrystalline silicon, in the polishing composition, it is preferable to adjust the content of the abrasive grains to 0.1 to 5% by mass, more preferably to 0.2 to 3% by mass, and particularly preferably to 0.3 to 1% by mass. By adjusting to such a range, the object to be polished can be polished at a higher speed. It should be noted that all lower limit and upper limit values disclosed in this specification disclose all combinations.

[0030] [Copolymer] In one embodiment of the present invention, the polishing composition contains a copolymer of a monomer represented by the following general formula (1) and a vinyl ester monomer, and has a saponification degree of 95 mol% or more, and contains a copolymer having a 1,2-diol structure in the side chain. In this specification, "having a 1,2-diol structure in the side chain" means that the copolymer has a structural unit in which both R 7 and R 8 are hydrogen atoms in the following general formula (1).

[0031] [Chemical formula]

[0032] In one embodiment of the present invention, examples of the vinyl ester monomer constituting the copolymer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, and the like. These vinyl ester monomers may be used alone or in combination of two or more. In the latter case, the arrangement of each constitutional unit is not particularly limited and may be block-like (block copolymer), random-like (random copolymer), or alternating-like (alternating copolymer). Among these, vinyl acetate is preferable from the viewpoints of easy availability and affinity with the object to be polished. The above vinyl ester monomers may be used alone or in combination of two or more. In the latter case, the arrangement of each constitutional unit is not particularly limited and may be block-like (block copolymer), random-like (random copolymer), or alternating-like (alternating copolymer).

[0033] In one embodiment of the present invention, the monomer constituting the vinyl ester monomer and the copolymer is represented by the above general formula (1). Here, the monomer of the general formula (1) may be used alone or in combination of two or more. In the latter case, the arrangement of each constitutional unit is not particularly limited and may be block-like (block copolymer), random-like (random copolymer), or alternating-like (alternating copolymer).

[0034] In the general formula (1), R 1 ~R 6 is a hydrogen atom or an organic group. At this time, R 1 ~R 6 may be the same as or different from each other. Also, R 1 ~R 6When it is an organic group, examples of the organic group include linear or branched alkyl groups having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, an n-hexyl group, an isohexyl group, a 1,3-dimethylbutyl group, a 1-isopropylpropyl group, a 1,2-dimethylbutyl group, an n-heptyl group, a 1,4-dimethylpentyl group, a 3-ethylpentyl group, a 2-methyl-1-isopropylpropyl group, a 1-ethyl-3-methylbutyl group, an n-octyl group, a 2-ethylhexyl group, a 3-methyl-1-isopropylbutyl group, a 2-methyl-1-isopropyl group, a 1-tert-butyl-2-methylpropyl group, and the like.

[0035] In addition, at least one hydrogen atom of the organic group may be substituted with a substituent. Here, examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a hydroxyalkyl group, an alkoxyalkyl group, an alkoxy group, a cycloalkoxy group, an amino group, an alkoxycarbonyl group, an aryloxycarbonyl group, a hydroxyl group (-OH), a carboxyl group (-COOH), a thiol group (-SH), a cyano group (-CN), a sulfonic acid group, and the like.

[0036] Among these, R 1 ~R 6 is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a linear alkyl group having 1 to 3 carbon atoms, and particularly preferably all of R 1 ~R 6 are hydrogen atoms.

[0037] In the general formula (1), X is a single bond or a linking group. Here, examples of the linking group include an alkylene group (e.g., methylene group, ethylene group, trimethylene group, propylene group), an alkenylene group (e.g., vinylene group, 1-propenylene group, arylene group), a phenylene group, a naphthylene group, an oxygen atom (-O-), an oxyalkylene group [-(CH2O) m -; m = 1 to 3], -(OCH2) m -(m = 1 to 3), -(CH2O) m CH2-(m = 1 to 3), -CO-, -COCO-, -CO(CH2) m CO-(m = 1 to 3), -CO(C6H4)CO-, -S-, -CS-, -SO-, -SO2-, -NR-, -CONR-, -NRCO-, -CSNR-, -NRCS-, -NRNR-, -HPO4-, -Si(OR)2-, -OSi(OR)2-, -OSi(OR)2O-, -Ti(OR)2-, -OTi(OR)2-, -OTi(OR)2O-, -Al(OR)-, -OAl(OR)-, -OAl(OR)O- (where R is each independently an arbitrary substituent (preferably a hydrogen atom or an alkyl group)) and the like. Note that at least one hydrogen atom of the above linking group may be substituted with the same substituent as the organic group.

[0038] Among these, from the viewpoint of further improving the storage stability effect, X is preferably a single bond or a methylene group, and more preferably a single bond.

[0039] R 7 and R 8 are each independently a hydrogen atom or R 9 -CO-(where R 9 is an alkyl group). At this time, R 7 and R 8 may be the same or different from each other. Also, when the alkyl group in R 9 is an alkyl group, it is a linear or branched alkyl group having 1 to 8 carbon atoms, and specific examples are the same as those exemplified for the above R 1 ~R 6 . Among these, R 7 and R8 is preferably, independently of each other, a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and particularly preferably a hydrogen atom or a methyl group.

[0040] That is, in a preferred embodiment of the present invention, the monomer of the general formula (1) is R 1 ~R 6 is a hydrogen atom, X is a single bond, and R 7 ~R 8 is R 9 -CO-, and at this time, it is preferable that R 9 is a linear or branched alkyl group having 1 to 3 carbon atoms, and the monomer of the general formula (1) in which R 1 ~R 6 is a hydrogen atom, X is a single bond, and R 7 and R 8 are a hydrogen atom (3,4-dihydroxy-1-butene) or CH3-CO- (3,4-diacetoxy-1-butene) is more preferable.

[0041] The copolymer according to one embodiment of the present invention essentially includes a structural unit derived from a monomer represented by the following general formula (1) and a structural unit derived from a vinyl ester monomer, but may further have another structural unit (a structural unit derived from another monomer). Here, examples of the other monomer include α-olefins such as ethylene and propylene; olefins having a hydroxyl group such as 3-buten-1-ol and 4-penten-1-ol and their acylates; unsaturated acids such as itaconic acid, maleic acid, and acrylic acid or their salts or alkyl esterified products (mono, di-alkyl esterified products); nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide, methacrylamide, and diacetone acrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid or their salts; vinyl compounds such as alkyl vinyl ether, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate; vinylidene chloride; 1,4-diacetoxy-2-butene; vinylene carbonate, and the like. The copolymer is preferably substantially composed of a structural unit derived from a monomer represented by the following general formula (1) and a structural unit derived from a vinyl ester monomer (the content of the structural unit derived from another monomer is less than 5 mol% based on all the structural units), more preferably composed of a structural unit derived from a monomer represented by the following general formula (1) and a structural unit derived from a vinyl ester monomer (the content of the structural unit derived from another monomer is 0 mol% based on all the structural units).

[0042] The method for producing the copolymer according to an embodiment of the present invention can be applied in the same manner as or with appropriate modifications to known methods. For example, copolymerization can be carried out by a conventionally known method such as bulk polymerization method, solution polymerization method, precipitation polymerization method, emulsion polymerization method, suspension polymerization method, or bulk-suspension polymerization method in the presence of a radical polymerization initiator or a catalyst. For example, in the presence of a radical polymerization initiator, and if necessary in a solvent, a vinyl ester monomer, the monomer represented by the general formula (1), and if necessary the other monomer are copolymerized by a conventionally known method such as bulk polymerization method, solution polymerization method, precipitation polymerization method, emulsion polymerization method, suspension polymerization method, or bulk-suspension polymerization method. Here, as the radical polymerization initiator (catalyst), for example, azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauryl peroxide, azobisdimethylvaleronitrile, azobismethoxydimethylvaleronitrile, etc. can be used. Also, the copolymerization conditions depend on other conditions such as the solvent and pressure used, but for example, it is carried out in the range of 35 to 150 °C, preferably 40 to 100 °C.

[0043] The copolymer according to an embodiment of the present invention has a saponification degree of 95 mol% or more and has a 1,2-diol structure in the side chain. Therefore, in order to have the above structure, the copolymer may be subjected to saponification treatment. Here, when the saponification degree of the copolymer is less than 95 mol%, the hydrophilicity is insufficient and the abrasive grains aggregate (the storage stability is low) (see Comparative Example 7 below). In an embodiment of the present invention, it is preferably more than 95 (95.0) mol%, and more preferably 98 (98.0) mol% or more (upper limit: 100 mol%). In this specification, the "saponification degree" is the value measured in accordance with JIS K6726-1994.

[0044] That is, in a preferred form of the present invention, the copolymer according to an embodiment of the present invention contained in the polishing composition is vinyl acetate and R 1 ~R 6 is a hydrogen atom, X is a single bond, and R 7 ~R 8 is R 9 -CO-(R 9= It is a saponified product of a copolymer of the monomer of the general formula (1) (a linear or branched alkyl group having 1 to 3 carbon atoms). In a more preferred form of the present invention, the copolymer according to one embodiment of the present invention contained in the polishing composition is a saponified product of a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene (having a structural unit derived from vinyl alcohol and a structural unit derived from 3,4-dihydroxy-1-butene).

[0045] Here, the saponification treatment can be carried out, for example, by dissolving the copolymer obtained by copolymerization as described above in a solvent and using an alkali catalyst or an acid catalyst. Here, as the solvent, alcohols such as methanol, ethanol, propanol, and tert-butanol can be used. Further, as the alkali catalyst that can be used for the saponification treatment, hydroxides and alcoholates of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, and lithium methylate can be used. Further, as the acid catalyst that can be used for the saponification treatment, sulfuric acid, hydrochloric acid, nitric acid, methanesulfonic acid, zeolite, cation exchange resin, etc. can be used. The reaction temperature of the saponification treatment reaction is not particularly limited, but 10 to 60 °C is preferable, and more preferably 20 to 50 °C.

[0046] The copolymer according to one embodiment of the present invention has a degree of polymerization of 50 to 3000. The copolymer according to one embodiment of the present invention has a degree of polymerization of 300 to 1200. The copolymer according to one embodiment of the present invention has a degree of polymerization of 400 to 800. By being such an embodiment, the storage stability of the object to be polished can be further improved. Further, the balance between the storage stability and the polishing rate of the object to be polished can be further improved.

[0047] The copolymer according to an embodiment of the present invention has a melting point of 100°C to 230°C. The copolymer according to an embodiment of the present invention has a melting point of 130°C to 230°C. The copolymer according to an embodiment of the present invention has a melting point of 160°C or higher and less than 190°C. By being such an embodiment, the storage stability of the object to be polished can be further improved. Also, the balance between storage stability and the polishing rate of the object to be polished can be further improved. In the present specification, the "melting point" is the value measured by differential scanning calorimetry (DSC).

[0048] The copolymer according to an embodiment of the present invention may be synthesized as described above or a commercially available product may be used. As a commercially available product, Nichigo G polymer manufactured by Mitsubishi Chemical Corporation TM Series (butanediol vinyl alcohol copolymer obtained by hydrolyzing the product obtained by the reaction of vinyl acetate and 3,4-diacetoxy-1-butene) etc. can be used.

[0049] In an embodiment of the present invention, in the polishing composition, the content of the copolymer is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, still more preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and particularly preferably more than 0.1% by mass. In an embodiment of the present invention, in the polishing composition, the content of the copolymer is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably less than 2% by mass, and particularly preferably less than 1% by mass. With such a content, the storage stability of the object to be polished can be further improved. Also, the balance between storage stability and the polishing rate of the object to be polished can be further improved.

[0050] Particularly when polishing an object to be polished containing silicon atoms, such as an object to be polished containing silicon oxide or polycrystalline silicon, it is preferable to adjust the content of the copolymer in the polishing composition to 0.001 to 10% by mass, more preferably to exceed 0.05% by mass and be less than 10% by mass, and particularly preferably to exceed 0.1% by mass and be 7% by mass or less. Or, particularly when polishing an object to be polished containing silicon atoms, such as an object to be polished containing silicon oxide or polycrystalline silicon, it is preferable to adjust the content of the copolymer in the polishing composition to 0.01 to 5% by mass, more preferably to be 0.03% by mass or more and less than 2% by mass, and particularly preferably to be 0.05% by mass or more and less than 1% by mass. By adjusting to such a range, the storage stability of the object to be polished can be further improved. Also, the balance between the storage stability and the polishing rate of the object to be polished can be further improved. It should be noted that all the lower limit and upper limit values disclosed in this specification have all combinations disclosed.

[0051] [pH of the polishing composition] According to one embodiment of the present invention, the pH of the polishing composition is less than 7.0. By being such an embodiment, the zeta potential of the abrasive grains can be more effectively positively charged. According to one embodiment of the present invention, the pH of the polishing composition is 6.0 or less. According to one embodiment of the present invention, the pH of the polishing composition is 3.0 or less. According to one embodiment of the present invention, the pH of the polishing composition is 2.5 or less. By being such an embodiment, the surface of the object to be polished can be polished at high speed and efficiently. According to one embodiment of the present invention, the pH of the polishing composition is 1.0 or more. According to one embodiment of the present invention, the pH of the polishing composition is 1.6 or more. According to one embodiment of the present invention, the pH of the polishing composition is 2.0 or more. By being such an embodiment, the surface of the object to be polished can be polished at high speed and efficiently.

[0052] According to one embodiment of the present invention, the pH of the polishing composition is 1.0 or more and 3.0 or less. According to one embodiment of the present invention, the pH of the polishing composition is 1.6 or more and 2.5 or less. By virtue of such an embodiment, the surface of an object to be polished (particularly an object to be polished containing silicon oxide or polycrystalline silicon) can be polished at high speed and efficiently. Therefore, the above embodiment is particularly effective when polishing an object to be polished containing a silicon atom such as an object to be polished containing silicon oxide or polycrystalline silicon. Note that if the pH of the polishing composition is less than 1.5, the intended effects of the present invention may not be efficiently achieved in some cases. According to one embodiment of the present invention, the pH of the polishing composition is more than 1.5 and less than 3.0, more than 2.0 and less than or equal to 2.5. By virtue of such an embodiment, the surface of an object to be polished (particularly an object to be polished containing silicon oxide or polycrystalline silicon) can be polished even faster and more efficiently.

[0053] According to one embodiment of the present invention, the polishing composition contains a pH adjuster. According to one embodiment of the present invention, the pH adjuster may be either an acid or an alkali, and may be either an inorganic compound or an organic compound, as long as the pH of the polishing composition falls within a desired range. Preferably, the pH adjuster is an acid.

[0054] Specific examples of the alkali include aliphatic amines such as ethanolamine and 2-amino-2-ethyl-1,3-propanediol, amines such as aromatic amines, organic bases such as quaternary ammonium hydroxide, hydroxides of alkali metals such as potassium hydroxide, hydroxides of alkaline earth metals, quaternary ammonium salts such as tetramethylammonium and tetraethylammonium, and ammonia.

[0055] Specific examples of acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid, as well as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, maloacetic acid, and the like. Examples of organic acids include carboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, and etidronic acid (1-hydroxyethane-1,1-diphosphonic acid, HEDP).

[0056] [Liquid Carrier] In one embodiment of the present invention, the polishing composition may further contain a liquid carrier. According to one embodiment of the present invention, the liquid carrier may be an organic solvent or water (particularly pure water). From the viewpoint of inhibiting contamination of the object to be polished and the action of other components, water containing as few impurities as possible is preferred. Specifically, pure water or ultrapure water, which has been treated with an ion exchange resin to remove impurity ions and then passed through a filter to remove foreign matter, or distilled water is preferred.

[0057] [Other ingredients] According to one embodiment of the present invention, the polishing composition may further contain other components such as an oxidizing agent, a metal corrosion inhibitor, a preservative, an antifungal agent, and an organic solvent for dissolving poorly soluble organic substances.

[0058] (oxidizing agent) According to one embodiment of the present invention, the oxidizing agent includes hydrogen peroxide, sodium peroxide, barium peroxide, ozone water, silver (II) salt, iron (III) salt, permanganic acid, chromic acid, dichromic acid, peroxydisulfuric acid, peroxymonophosphoric acid, peroxymonosulfuric acid, peroxymonoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromous acid, hypoiodous acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfuric acid, dichloroisocyanuric acid, and the like. The oxidizing agent may be used alone or in combination of two or more. Also, the oxidizing agent may be a commercially available product or a synthetic product.

[0059] According to one embodiment of the present invention, the polishing composition substantially does not contain an oxidizing agent. According to one embodiment of the present invention, the polishing composition substantially does not contain hydrogen peroxide, sodium peroxide, barium peroxide, ozone water, silver (II) salt, iron (III) salt, permanganic acid, chromic acid, dichromic acid, peroxydisulfuric acid, peroxymonophosphoric acid, peroxymonosulfuric acid, peroxymonoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromous acid, hypoiodous acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfuric acid or dichloroisocyanuric acid as an oxidizing agent. Also, according to one embodiment of the present invention, the polishing composition substantially does not contain bis[(1-benzotriazolyl)methyl]phosphonic acid. In the present specification, "substantially not contained" includes not only the concept of not being contained at all in the polishing composition, but also the case of containing 0.0001 g / L or less in the polishing composition.

[0060] According to one embodiment of the present invention, the content of the oxidizing agent in the polishing composition is preferably 0.1 g / L or more, more preferably 1 g / L or more, and still more preferably 3 g / L or more. As the content of the oxidizing agent increases, the polishing rate of the object to be polished by the polishing composition further improves. The content of the oxidizing agent in the polishing composition is also preferably 200 g / L or less, more preferably 100 g / L or less, and still more preferably 40 g / L or less. As the content of the oxidizing agent decreases, in addition to being able to suppress the material cost of the polishing composition, it is possible to reduce the load of treating the polishing composition after polishing, that is, waste liquid treatment. In addition, it is also possible to reduce the risk of excessive oxidation of the surface of the object to be polished by the oxidizing agent.

[0061] (Metal corrosion inhibitor) By adding a metal corrosion inhibitor to the polishing composition, it is possible to further suppress the occurrence of dents beside the wiring during polishing using the polishing composition. In addition, it is possible to further suppress the occurrence of dishing on the surface of the object to be polished after polishing using the polishing composition.

[0062] According to one embodiment of the present invention, the metal corrosion inhibitor is a heterocyclic compound or a surfactant. The number of members of the heterocyclic ring in the heterocyclic compound is not particularly limited. Further, the heterocyclic compound may be a monocyclic compound or a polycyclic compound having a condensed ring. The metal corrosion inhibitor may be used alone or in combination of two or more. Further, a commercially available product or a synthetic product may be used as the metal corrosion inhibitor.

[0063] According to one embodiment of the present invention, specific examples of the heterocyclic compound include, for example, nitrogen-containing heterocyclic compounds such as pyrrole compounds, pyrazole compounds, imidazole compounds, triazole compounds, tetrazole compounds, pyridine compounds, pyrazine compounds, pyridazine compounds, pyrimidine compounds, indolizine compounds, indole compounds, isoindole compounds, indazole compounds, purine compounds, quinolidine compounds, quinoline compounds, isoquinoline compounds, naphthyridine compounds, phthalazine compounds, quinoxaline compounds, quinazoline compounds, cinnoline compounds, pteridine compounds, thiazole compounds, isothiazole compounds, oxazole compounds, isoxazole compounds, furazan compounds, etc.

[0064] (Preservative and fungicide) According to one embodiment of the present invention, examples of the preservative and fungicide include, for example, isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, paraoxybenzoic acid esters, and phenoxyethanol. These preservatives and fungicides may be used alone or in combination of two or more.

[0065] [Method for producing polishing composition] According to one embodiment of the present invention, the method for producing a polishing composition is not particularly limited. For example, it can be obtained by stirring and mixing the above-mentioned specific abrasive grains, the above-mentioned specific copolymer, and, if necessary, a pH adjuster with a liquid carrier. Further, according to one embodiment of the present invention, the method for producing a polishing composition has a positive zeta potential in an aqueous solution with a pH of less than 7 and the number of silanol groups per unit surface area is 2.5 / nm 2 Select the following abrasive grains, and the abrasive grains can be obtained by stirring and mixing with the above-mentioned specific copolymer, and, if necessary, a pH adjuster and a liquid carrier. The temperature at the time of mixing each component is not particularly limited, but 10 to 40 °C is preferable, and heating may be performed to increase the dissolution rate. Also, the mixing time is not particularly limited.

[0066] [Polishing method] The present invention also provides a polishing method including a step of polishing an object to be polished using the polishing composition of the present invention. The polishing composition is suitably used for polishing silicon oxide and polycrystalline silicon.

[0067] According to one embodiment of the present invention, the polishing rate of silicon oxide is 190 Å / min or more and 2000 Å / min or less. According to one embodiment of the present invention, the polishing rate of silicon oxide exceeds 200 Å / min and is 1500 Å / min or less. According to one embodiment of the present invention, the polishing rate of silicon oxide is 240 Å / min or more and 1000 Å / min or less. According to one embodiment of the present invention, the polishing rate of silicon oxide is 500 Å / min or more and 800 Å / min or less. By applying the polishing composition of the embodiment of the present invention, such a polishing rate can be achieved. Further, in the embodiment of the present invention, the composition of the polishing composition may be further adjusted so as to achieve such a polishing rate. In this specification, the "polishing rate of silicon oxide" is the "polishing rate for the TEOS (silicon oxide) film" in the <polishing test> in the following examples.

[0068] According to one embodiment of the present invention, the polishing rate of polycrystalline silicon is 210 Å / min or more and 2000 Å / min or less. According to one embodiment of the present invention, the polishing rate of polycrystalline silicon exceeds 260 Å / min and is 1500 Å / min or less. According to one embodiment of the present invention, the polishing rate of polycrystalline silicon is 280 Å / min or more and 1000 Å / min or less. According to one embodiment of the present invention, the polishing rate of polycrystalline silicon is 300 Å / min or more and 500 Å / min or less. By applying the polishing composition of the embodiment of the present invention, such a polishing rate can be achieved. Further, in the embodiment of the present invention, the composition of the polishing composition may be further adjusted so as to achieve such a polishing rate. In this specification, the "polishing rate of polycrystalline silicon" is the "polishing rate for the polysilicon substrate" in the <polishing test> in the following examples.

[0069] [Object to be polished] The object to be polished according to the present invention is not particularly limited and is appropriately selected according to the application. Specifically, it includes polycrystalline silicon (polysilicon), single-crystalline silicon, a silicon oxide film formed using tetraethyl orthosilicate (TEOS) as a raw material, amorphous silicon, silicon nitride, silicon carbonitride (SiCN), a film or substrate containing a metal, SiGe, etc., an HDP (High Density Plasma) film, an USG (Undoped Silicate Glass) film, a PSG (Phosphorus Silicate Glass) film, a BPSG (Boron-Phospho Silicate Glass) film, a silicon oxide film such as an RTO (Rapid Thermal Oxidation) film, and the like. Among these, it is preferable to apply the polishing composition of the embodiment of the present invention to an object to be polished containing silicon oxide (especially a film made from TEOS) or polycrystalline silicon. According to this embodiment, the polishing composition can be stably stored (excellent in stability) without generating precipitates in a wide temperature range from low temperature to high temperature (especially low temperature), and these objects to be polished can be polished at a high speed. Therefore, according to one embodiment of the present invention, the polishing composition is used for polishing an object to be polished containing at least one of silicon oxide and polycrystalline silicon (polysilicon) (for example, a silicon oxide film, a polycrystalline silicon substrate, or a polycrystalline silicon film). Or, according to one embodiment of the present invention, the polishing method is to obtain a polishing composition using the above-mentioned polishing composition or by the above-mentioned manufacturing method, and use the polishing composition to polish an object to be polished containing at least one of silicon oxide and polycrystalline silicon (polysilicon) (for example, a silicon oxide film, a polycrystalline silicon substrate, or a polycrystalline silicon film).

[0070] As the polishing apparatus, a general polishing apparatus having a holder for holding a substrate or the like having an object to be polished and a motor or the like whose rotation speed can be changed, and having a polishing platen to which a polishing pad (polishing cloth) can be attached can be used.

[0071] As the polishing pad, general non-woven fabrics, polyurethanes, porous fluororesins, etc. can be used without particular limitation. It is preferable that the polishing pad is grooved so that the polishing composition accumulates.

[0072] There are also no particular restrictions on the polishing conditions. For example, the rotation speed of the polishing platen is preferably 10 to 500 rpm, the rotation speed of the polishing head (carrier rotation speed) is preferably 10 to 500 rpm, and the pressure applied to the substrate having the object to be polished (polishing pressure) is preferably 0.1 to 10 psi. The method of supplying the polishing composition to the polishing pad is also not particularly limited. For example, a method of continuously supplying with a pump or the like is adopted. Although there is no limitation on this supply amount, it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0073] [Method for manufacturing a semiconductor substrate] The use of the polishing composition according to the present invention is not limited, but it is preferably used for a semiconductor substrate. Therefore, the present invention also provides a method for manufacturing a semiconductor substrate, which includes a step of polishing the semiconductor substrate by the above polishing method. According to such an embodiment, the production efficiency of the semiconductor substrate is improved.

Examples

[0074] The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, “%” and “parts” mean “mass %” and “parts by mass”, respectively. In the following examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (25 ° C) / relative humidity 40 to 50% RH.

[0075] <Method for calculating the number of silanol groups>[ The number of silanol groups per unit surface area of the abrasive grains (unit: number / nm 2 ) was calculated by the following method after measuring or calculating each parameter by the following measuring method or calculation method.

[0076] More specifically, C in the following formula is the total mass of the abrasive grains, and S in the following formula is the BET specific surface area of the abrasive grains. Even more specifically, first, 1.50 g of abrasive grains as solids are collected in a 200 ml beaker, 100 ml of pure water is added to make a slurry, and then 30 g of sodium chloride is added and dissolved. Next, 1N hydrochloric acid is added to adjust the pH of the slurry to about 3.0 - 3.5, and then pure water is added until the slurry reaches 150 ml. For this slurry, using an automatic titrator (manufactured by Hiranuma Sangyo Co., Ltd., COM-1700), at 25°C, an aqueous sodium hydroxide solution of 0.1N is used to adjust the pH to 4.0, and further, the volume V [L] of the 0.1N aqueous sodium hydroxide solution required to raise the pH from 4.0 to 9.0 is measured by pH titration. The average silanol group number (average silanol group density) (pieces / nm 2 ) can be calculated by the following formula.

[0077] [Number]

[0078] In the above formula, ρ represents the average silanol group number (average silanol group density) (pieces / nm 2 ); c represents the concentration (mol / L) of the aqueous sodium hydroxide solution used in the titration; V represents the volume (L) of the aqueous sodium hydroxide solution required to raise the pH from 4.0 to 9.0; N A represents Avogadro's constant (pieces / mol); C represents the total mass (solids) (g) of the abrasive grains; S represents the weighted average value of the BET specific surface area of the abrasive grains (nm 2 / g).

[0079] [Calculation method of particle size] The average primary particle size of the abrasive grains was calculated from the specific surface area of the abrasive grains by the BET method measured using "Flow Sorb II 2300" manufactured by Micromeritics and the density of the abrasive grains. The average secondary particle size of the abrasive grains was measured using a dynamic light scattering particle size and particle size distribution apparatus UPA-UTI151 manufactured by Nikkiso Co., Ltd.

[0080] <pH Measurement Method> The pH of the polishing composition (liquid temperature: 25°C) was confirmed using a pH meter (model number: LAQUA, manufactured by Horiba, Ltd.).

[0081] <Zeta Potential Measurement Method> The zeta potential X [mV] of the abrasive grains in the polishing composition was measured by the laser Doppler method (electrophoretic light scattering measurement method) using a flow cell at a measurement temperature of 25°C by subjecting the polishing composition to ELS-Z2 manufactured by Otsuka Electronics Co., Ltd., and the obtained data was analyzed by Smoluchowski's equation to calculate it.

[0082] [Example 1] (Preparation of Polishing Composition) To pure water as a liquid carrier, colloidal silica A as an abrasive grain (number of silanol groups: 1.8 per nm 2 , average primary particle size: 30 nm, average secondary particle size: 60 nm, average degree of aggregation: 2.0) was added in an amount of 0.45% by mass based on 100% by mass of the final polishing composition, and butenediol vinyl alcohol copolymer (product name: Nichigo G Polymer TM AZF8035W; manufactured by Mitsubishi Chemical Corporation; degree of polymerization 300; saponification degree 98.0 mol% or more, melting point 172°C) was added in an amount such that it was 0.05% by mass based on 100% by mass of the final polishing composition, and 1-hydroxyethane-1,1-diphosphonic acid (HEDP) as a pH adjuster was added so that the pH became 2.5, thereby preparing the polishing composition of Example 1. The zeta potential of colloidal silica A in the composition was +11 mV.

[0083] [Examples 2 to 6 and Comparative Examples 1 to 7] (Preparation of Polishing Composition) Except for changing the types and contents of the respective components, the pH of each polishing composition, and the zeta potential of the abrasive grains in each composition as shown in Table 1, the respective polishing compositions were prepared in the same manner as in Example 1. In addition, the following were used as colloidal silica B, colloidal silica C, and colloidal silica D in Table 1 below.

[0084] Colloidal silica B: Colloidal silica with a sulfo group immobilized on the surface (number of silanol groups: 1.8 per nm 2 , average primary particle diameter 30 nm, average secondary particle diameter 60 nm, average aggregation degree 2.0) Colloidal silica C: Colloidal silica with an amino group immobilized on the surface (number of silanol groups: 1.8 per nm 2 , average primary particle diameter: 30 nm, average secondary particle diameter: 60 nm, average aggregation degree: 2.0) Colloidal silica D: Colloidal silica (number of silanol groups 5.7 per nm 2 , average primary particle diameter 35 nm, average secondary particle diameter 70 nm, average aggregation degree 2.0).

[0085] In addition, the details of the copolymers in Table 1 are as follows.

[0086] OKS1011: Butanediol vinyl alcohol copolymer (product name: Nichigo G Polymer TM OKS-1011; manufactured by Mitsubishi Chemical Corporation; degree of polymerization 300; saponification degree 98.0 mol% or more; melting point 206°C) OKS8039: Butanediol vinyl alcohol copolymer (product name: Nichigo G Polymer TM OKS-8039; manufactured by Mitsubishi Chemical Corporation; degree of polymerization 600; saponification degree 98.0 mol% or more; melting point 168°C) OKS1028: Butanediol vinyl alcohol copolymer (product name: Nichigo G Polymer TM OKS-1028; manufactured by Mitsubishi Chemical Corporation; degree of polymerization 600; saponification degree 98.0 mol% or more; melting point 206°C) OKS1009: Butanediol vinyl alcohol copolymer (product name: Nichigo G Polymer TMOKS-1009; manufactured by Mitsubishi Chemical Corporation; degree of polymerization 1200; saponification degree 98.0 mol% or more; melting point 190 °C) OKS8096: butanediol vinyl alcohol copolymer (product name: Nichigo G Polymer TM OKS-8096; manufactured by Mitsubishi Chemical Corporation; degree of polymerization 450; saponification degree 93.0 mol%; melting point 168 °C) JPR-10HH: polyvinyl alcohol (product name: HH type JPR-10HH; manufactured by Nippon Vinyl Alcohol Co., Ltd.; degree of polymerization 230; saponification degree over 98 mol%; melting point 230 °C).

[0087] Next, for each polishing composition prepared above, the polishing rate (Removal Rate) (Å / min) was evaluated according to the following method. The results are shown together in Table 1 below.

[0088] <Polishing test> Using each polishing composition, the surface of the object to be polished was polished under the following conditions. As the objects to be polished, a TEOS (silicon oxide) film with a thickness of 10,000 Å formed on the surface of a silicon substrate with a diameter of 300 mm and a polysilicon substrate with a thickness of 4500 Å were used respectively. In Table 1 below, the polishing rate for the TEOS (silicon oxide) film formed on the surface of the silicon substrate and the polishing rate for the polysilicon substrate are shown as "TEOS" and "poly Si", respectively.

[0089] [Polishing apparatus and polishing conditions] Polishing apparatus: FREX 300E manufactured by Ebara Corporation Polishing pad: IC1000XY-k groove (manufactured by Nitta Haas Co., Ltd., polyurethane) Polishing pressure: 140 hPa (about 2.0 psi) Rotational speed of the polishing platen: 30 rpm Rotational speed of the polishing head: 30 rpm Supply amount of the polishing composition: 200 mL / min Polishing time: 60 sec In-situ dressing.

[0090] [Evaluation] For each polishing composition, measurements and evaluations were performed on the following items.

[0091] [Measurement of Polishing Rate (Removal Rate)] The polishing rate (Å / min) was calculated by the following formula (1).

[0092] [Number]

[0093] Note that each film thickness was determined by an optical interference film thickness measuring device, and the difference in film thickness before and after polishing was divided by the polishing time to evaluate the polishing rate. The evaluation results are also shown in Table 1.

[0094] [Storage Stability Test] Each polishing composition was placed in a polypropylene (PP) container and left standing in a constant temperature chamber at 5°C, 25°C, and 80°C for 14 days.

[0095] [Evaluation of Storage Stability] The samples stored in the PP containers were visually observed at the bottom while still in the containers to confirm the presence or absence of precipitates, and the storage stability was classified into the following three types of results according to the degree of precipitate generation. Note that ○ and Δ are acceptable in practical use. The evaluation results are also shown in Table 1.

[0096] ○: No precipitation was observed even after returning to the storage temperature and 25°C. Δ: Precipitation was observed at the storage temperature, but it redispersed and the precipitate disappeared when returned to 25°C. ×: Precipitation was observed and no disappearance of the precipitate was seen even after returning to 25°C.

[0097] [Table 1-1]

[0098] [Table 1-2]

[0099] <Investigation> From the results in Table 1 above, it is shown that no precipitation was observed with the polishing composition of the examples regardless of the storage temperature. Also, it is shown that a high polishing rate could be achieved for both the silicon oxide film and the polycrystalline silicon substrate with the polishing composition of the examples. On the other hand, with the polishing composition of the comparative example, the storage stability or the polishing rate is inferior, and both cannot be achieved simultaneously.

Claims

1. Having a positive zeta potential in an aqueous solution with a pH of less than 7 and having 2.5 silanol groups per unit surface area per nm ２ an abrasive grain as described below, and A saponified product of a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, which is a copolymer having a 1,2-diol structure in the side chain and a saponification degree of 95 mol% or more, and contains the abrasive grains are colloidal silica, the pH is less than 7, is used for polishing an object to be polished containing at least one of silicon oxide and polycrystalline silicon, a polishing composition.

2. The polishing composition according to Claim 1, wherein the melting point of the copolymer which is the saponified product is 100°C to 230°C.

3. The polishing composition according to Claim 1 or 2, wherein the degree of polymerization of the copolymer which is the saponified product is 50 to 3000.

4. The polishing composition according to any one of Claims 1 to 3, wherein the zeta potential of the abrasive grains is 10 mV or more and 50 mV or less.

5. The polishing composition according to any one of Claims 1 to 4, wherein the pH is 1.0 or more and 3.0 or less.

6. A polishing method comprising a step of polishing an object to be polished containing at least one of silicon oxide and polycrystalline silicon using the polishing composition according to any one of Claims 1 to 5.

7. A method for manufacturing a semiconductor substrate, comprising a step of polishing the semiconductor substrate by the polishing method according to Claim 6.

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