Polishing composition, polishing method, and method for manufacturing semiconductor substrate

Abstract

To provide a means for reducing scratches on the surface of a polished workpiece (particularly silicon oxide).SOLUTION: A polishing composition contains abrasive particles, inorganic salts, and organic onium salts, organic onium salts contains at least one of tetraalkylammonium salts represented by the following chemical formula 1 and tetraalkylphosphonium salts represented by the following chemical formula 2, and the zeta potential of the abrasive grains in the polishing composition is negative: in chemical formula 1 and chemical formula 2, R1 to R8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and A-and X-are each independently a monovalent anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition, a polishing method, and a method for producing a semiconductor substrate. [Background technology]

[0002] In recent years, with the trend toward multilayer wiring on semiconductor substrate surfaces, so-called chemical mechanical polishing (CMP) technology, which physically polishes and flattens semiconductor substrates, has come to be used in device manufacturing. CMP is a method of flattening the surface of an object to be polished (workpiece) such as a semiconductor substrate using a polishing composition (slurry) containing abrasive grains such as silica, alumina, or ceria, an anticorrosive agent, a surfactant, etc. The object to be polished (workpiece) can be a wiring or plug made of silicon, polysilicon, silicon oxide (SiO2), silicon dioxide containing carbon (SiOC), silicon nitride (SiN), metal, etc.

[0003] For example, Patent Document 1 discloses a polishing composition containing abrasive grains and at least one of polyacrylic acid and a polyacrylic acid derivative, and having an electrical conductivity of 2.0 mS / cm or more. According to Patent Document 1, it is possible to polish silicon oxide at a high polishing rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-56292 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technique described in Patent Document 1 still leaves room for improvement in terms of reducing scratches on the surface of the polished object.

[0006] Therefore, an object of the present invention is to provide a means capable of reducing scratches on the surface of a polished object (especially silicon oxide). [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by a polishing composition containing abrasive grains, an inorganic salt, and an organic onium salt, wherein the organic onium salt includes at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2, and the abrasive grains in the polishing composition have a negative zeta potential, thereby completing the present invention.

[0008] [ka]

[0009] In the above Chemical Formula 1 and Chemical Formula 2, R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A - and X - are each independently a monovalent anion. [Effects of the Invention]

[0010] According to the present invention, a means can be provided that can reduce scratches on the surface of a polished object (especially silicon oxide). DETAILED DESCRIPTION OF THE INVENTION

[0011] According to one embodiment of the present invention, there is provided a polishing composition comprising abrasive grains, an inorganic salt, and an organic onium salt, wherein the organic onium salt comprises at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2, and the abrasive grains in the polishing composition have a negative zeta potential.

[0012] [ka]

[0013] In the above Chemical Formula 1 and Chemical Formula 2, R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A - and X - are each independently a monovalent anion.

[0014] According to such a polishing composition of the present invention, scratches on the surface of a polished object (particularly silicon oxide) can be reduced.

[0015] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments and can be modified in various ways within the scope of the claims. The embodiments described in this specification can be combined in any way to form other embodiments. Unless otherwise specified, in this specification, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20°C or higher and 25°C or lower) and a relative humidity of 40% RH or higher and 50% RH or lower.

[0016] In this specification, "X or more and Y or less" is used to mean that the numerical values ​​(X and Y) written before and after it are included as the upper and lower limits. When "X or more and Y or less" is written multiple times, for example, when "X1 or more and Y1 or less, or X2 or more and Y2 or less" is written, disclosures with each numerical value as the upper limit, disclosures with each numerical value as the lower limit, and combinations of these upper and lower limits are all disclosed (i.e., they serve as legitimate grounds for amendment). Specifically, amendments to X1 or more, amendments to Y2 or less, amendments to X1 or less, amendments to Y2 or more, amendments to X1 or more and X2 or less, amendments to X1 or more and Y2 or less, etc. must all be deemed legitimate.

[0017] [Abrasive grain] The polishing composition of the present invention contains abrasive grains, which have the function of mechanically polishing an object to be polished, thereby increasing the polishing rate of the object to be polished by the polishing composition.

[0018] In the polishing composition of the present invention, the abrasive grains have a negative zeta potential. Here, "zeta (ζ) potential" refers to the potential difference that occurs at the interface between a solid and a liquid when they are in contact with each other and undergo relative motion. If the zeta potential of the abrasive grains is 0 mV or positive, scratches on the surface of the polished object will increase.

[0019] The zeta potential of the abrasive grains in the polishing composition of the present invention is preferably -60 mV or more and -10 mV or less, more preferably -50 mV or more and -10 mV or less, even more preferably -40 mV or more and -15 mV or less, and particularly preferably more than -35 mV and -15 mV or less. When the abrasive grains have a zeta potential in this range, the polishing rate of the object to be polished can be further improved. Here, the zeta potential of the abrasive grains in the polishing composition is a value measured by the method described in the Examples. The zeta potential of the abrasive grains can be adjusted by the amount of anionic groups (particularly organic acid groups) contained in the abrasive grains, the pH of the polishing composition, etc., as described below.

[0020] The type of abrasive grain is not particularly limited, and examples thereof include metal oxides such as silica, alumina, zirconia, and titania. The abrasive grains can be used alone or in combination of two or more types. The abrasive grains may be commercially available products or synthetic products.

[0021] The type of abrasive grains is preferably silica, more preferably colloidal silica.Methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by either method can be suitably used as the abrasive grains of the present invention.However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method, which can be produced with high purity, is preferred.

[0022] Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by using a hydrolyzable silicon compound (e.g., an alkoxysilane or a derivative thereof) as a raw material and carrying out a hydrolysis-condensation reaction.

[0023] In some embodiments of the present invention, the colloidal silica contained in the polishing composition is preferably anion-modified colloidal silica (anion-modified colloidal silica), more preferably colloidal silica having an organic acid immobilized on its surface. Colloidal silica having an organic acid immobilized on its surface tends to have a higher absolute value of zeta potential in the polishing composition than ordinary colloidal silica having no organic acid immobilized on its surface. Therefore, the zeta potential of the colloidal silica in the polishing composition can be easily adjusted to a negative value (for example, in the range of -40 mV to -15 mV).

[0024] Preferred examples of colloidal silica having an organic acid fixed to its surface include colloidal silica having an organic acid group such as a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, or an aluminic acid group fixed to its surface. Of these, from the viewpoint of ease of production, colloidal silica having a sulfonic acid or a carboxylic acid fixed to its surface is preferred, and colloidal silica having a sulfonic acid fixed to its surface is more preferred.

[0025] Immobilization of an organic acid on the surface of colloidal silica cannot be achieved by simply coexisting colloidal silica with an organic acid. For example, immobilization of sulfonic acid, a type of organic acid, on colloidal silica can be achieved by the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups," Chem. Commun. 246-247 (2003). Specifically, colloidal silica with sulfonic acid immobilized on its surface (sulfonic acid-modified colloidal silica, sulfonic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to colloidal silica and then oxidizing the thiol group with hydrogen peroxide.

[0026] Alternatively, if a carboxylic acid, which is a type of organic acid, is to be immobilized on colloidal silica, this can be achieved, for example, by the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel," Chemistry Letters, 3, 228-229 (2000). Specifically, a silane coupling agent containing a photoreactive 2-nitrobenzyl ester is coupled to colloidal silica, followed by light irradiation, to obtain colloidal silica with a carboxylic acid immobilized on its surface (carboxylic acid-modified colloidal silica, carboxylic acid-modified colloidal silica).

[0027] The shape of the abrasive grains is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and quadrangular prisms, cylinders, bale-shaped cylinders in which the center is bulged out more than the ends, doughnut-shaped discs with a central hole, plate-shaped discs, cocoon-shaped discs with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped discs with multiple protrusions on the surface, and rugby ball-shaped discs, and are not particularly limited.

[0028] The size of the abrasive grains is not particularly limited. For example, the average primary particle diameter of the abrasive grains is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, and particularly preferably 12 nm or more. As the average primary particle diameter of the abrasive grains increases, the polishing rate of the object to be polished using the polishing composition increases. Furthermore, the average primary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less. As the average primary particle diameter of the abrasive grains decreases, it becomes easier to obtain a surface with fewer defects by polishing using the polishing composition. That is, the average primary particle diameter of the abrasive grains is preferably 5 nm or more and 100 nm or less, more preferably 8 nm or more and 80 nm or less, even more preferably 10 nm or more and 60 nm or less, and particularly preferably 12 nm or more and 50 nm or less. The average primary particle diameter of the abrasive grains can be calculated, for example, based on the specific surface area (SA) of the abrasive grains calculated by the BET method, assuming that the abrasive grains are spherical. In this specification, the average primary particle size of the abrasive grains is a value measured by the method described in the Examples.

[0029] The average secondary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 25 nm or more. As the average secondary particle diameter of the abrasive grains increases, the resistance during polishing decreases, enabling stable polishing. The average secondary particle diameter of the abrasive grains is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and particularly preferably 100 nm or less. As the average secondary particle diameter of the abrasive grains decreases, the surface area per unit mass of the abrasive grains increases, increasing the frequency of contact with the workpiece to be polished and further improving the polishing rate. That is, the average secondary particle diameter of the abrasive grains is preferably 10 nm or more and 400 nm or less, more preferably 15 nm or more and 300 nm or less, even more preferably 20 nm or more and 200 nm or less, and particularly preferably 25 nm or more and 100 nm or less. The average secondary particle diameter of the abrasive grains can be measured, for example, by dynamic light scattering, such as laser diffraction scattering.

[0030] The average degree of association of the abrasive grains is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less. As the average degree of association of the abrasive grains decreases, defects can be further reduced. The average degree of association of the abrasive grains is also preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. This average degree of association is obtained by dividing the average secondary particle diameter of the abrasive grains by the average primary particle diameter. As the average degree of association of the abrasive grains increases, there is an advantageous effect of improving the polishing rate of the object to be polished with the polishing composition.

[0031] The upper limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, but is preferably less than 2.0, more preferably 1.8 or less, and even more preferably 1.5 or less. Within this range, defects on the surface of the object to be polished can be further reduced. The aspect ratio is the average value obtained by taking the smallest rectangle circumscribing the image of the abrasive grains using a scanning electron microscope and dividing the length of the long side of the rectangle by the length of the short side of the same rectangle, and can be determined using general image analysis software. The lower limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, but is preferably 1.0 or more, more preferably 1.2 or more.

[0032] In the particle size distribution of abrasive grains measured by laser diffraction scattering, the ratio of the particle diameter (D90) when the cumulative particle mass from the fine particle side reaches 90% of the total particle mass to the particle diameter (D10) when the cumulative particle mass from the fine particle side reaches 10% of the total particle mass of all particles, D90 / D10, is not particularly limited, but is preferably 1.1 or more, more preferably 1.4 or more, even more preferably 1.7 or more, and most preferably 2.0 or more.In addition, in the particle size distribution of abrasive grains in a polishing composition measured by laser diffraction scattering, the ratio of the particle diameter (D90) when the cumulative particle mass from the fine particle side reaches 90% of the total particle mass to the particle diameter (D10) when the cumulative particle mass from the fine particle side reaches 10% of the total particle mass of all particles, D90 / D10, is not particularly limited, but is preferably 3.0 or less, more preferably 2.5 or less.Within this range, defects on the surface of the object to be polished can be further reduced.

[0033] The size of the abrasive grains (average primary particle diameter, average secondary particle diameter, aspect ratio, D90 / D10, etc.) can be appropriately controlled by selecting the manufacturing method of the abrasive grains, etc.

[0034] The concentration (content) of the abrasive grains is not particularly limited, but is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, even more preferably 1% by mass or more, even more preferably more than 1% by mass, and particularly preferably 1.5% by mass or more, based on the total mass of the polishing composition. The upper limit of the concentration (content) of the abrasive grains is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the total mass of the polishing composition. That is, the concentration (content) of the abrasive grains is preferably 0.5% by mass or more and 20% by mass or less, more preferably 0.8% by mass or more and 20% by mass or less, even more preferably 1% by mass or more and 15% by mass or less, even more preferably more than 1% by mass but 10% by mass or less, and particularly preferably 1.5% by mass or more and 5% by mass or less, based on the total mass of the polishing composition. Within this range, the polishing rate can be improved while keeping costs down. When the polishing composition contains two or more types of abrasive grains, the concentration (content) of the abrasive grains means the total amount thereof.

[0035] [Inorganic salts] The polishing composition of the present invention contains an inorganic salt. The inorganic salt has the function of reducing scratches on the surface of a polished object (particularly silicon oxide). The inorganic salt also has the function of increasing the electrical conductivity of the polishing composition, thereby further improving the polishing rate of the object (particularly silicon oxide).

[0036] Examples of inorganic salts include inorganic salts composed of the following cations and anions. Examples of cations include alkali metal ions such as lithium ion, sodium ion, and potassium ion; alkaline earth metal ions such as magnesium ion, calcium ion, and strontium ion; polyatomic ions such as ammonium ion; and complex ions. Examples of anions include halide ions (fluoride ion, chloride ion, bromide ion, iodide ion, etc.), oxoacid ions (borate ion, carbonate ion, nitrate ion, nitrite ion, metasilicate ion, phosphate ion, monohydrogen phosphate ion, dihydrogen phosphate ion, phosphonate ion, monohydrogen phosphonate ion, phosphinate ion, sulfate ion, sulfonate ion, sulfite ion, thiosulfate ion, chromate ion, dichromate ion, permanganate ion, etc.), thiocyanate ion, cyanate ion, and sulfamate ion.

[0037] calcium salts such as calcium chloride, calcium bromide, calcium carbonate, lithium nitrate, and calcium thiocyanate; iron salts such as iron nitrate and iron thiocyanate; potassium salts such as potassium chloride, potassium bromide, potassium nitrate, potassium sulfate, potassium thiocyanate, potassium sulfamate, potassium phosphate, potassium dihydrogen phosphate, potassium monohydrogen phosphate, and potassium monohydrogen phosphonate; sodium salts such as sodium chloride, sodium bromide, sodium nitrate, sodium sulfate, and sodium thiocyanate; zinc salts such as zinc chloride, zinc nitrate, and zinc thiocyanate; magnesium salts such as magnesium nitrate, magnesium sulfate, and magnesium thiocyanate; strontium salts such as strontium nitrate and strontium thiocyanate; and ammonium salts such as ammonium chloride, ammonium bromide, ammonium iodide, ammonium nitrate, ammonium phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, ammonium phosphonate, ammonium monohydrogen phosphonate, ammonium sulfate, ammonium thiocyanate, and ammonium sulfamate. These inorganic salts can be used singly or in combination of two or more. Furthermore, the inorganic salts to be used may be commercially available products or synthetic products.

[0038] Among these, from the viewpoint of further exerting the effects of the present invention, it is preferable to contain at least one of an ammonium salt of an inorganic acid and a potassium salt of an inorganic acid. The inorganic acid is preferably sulfuric acid, nitric acid, or carbonic acid. Therefore, the inorganic salt is more preferably at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate, and even more preferably ammonium sulfate.

[0039] The concentration (content) of the inorganic salt in the polishing composition is not particularly limited, but in the case of a polishing composition that is used as a polishing liquid as is for polishing an object to be polished, the lower limit of the concentration (content) of the inorganic salt in the polishing composition is preferably 0.005 mass% (50 mass ppm) or more, relative to the total mass of the polishing composition, and may be 0.01 mass% (100 mass ppm) or more, 0.1 mass% (1000 mass ppm) or more, 0.2 mass% (2000 mass ppm) or more, or 0.5 mass% (5000 mass ppm) or more. Furthermore, the upper limit of the concentration (content) of the inorganic salt in the polishing composition is preferably 2.0 mass% (20,000 mass ppm) or less, relative to the total mass of the polishing composition, and may be 1.5 mass% (15,000 mass ppm) or less, 1.3 mass% (13,000 mass ppm) or less, 1.0 mass% (10,000 mass ppm) or less, or 0.9 mass% (9,000 mass ppm) or less.

[0040] That is, the concentration (content) of the inorganic salt is preferably 0.005 mass% (50 mass ppm) or more and 2.0 mass% (20,000 mass ppm) or less, and may be 0.01 mass% (100 mass ppm) or more and 1.5 mass% (15,000 mass ppm) or less, 0.1 mass% (1,000 mass ppm) or more and 1.3 mass% (13,000 mass ppm) or less, 0.2 mass% (2,000 mass ppm) or more and 1.0 mass% (10,000 mass ppm) or less, 0.2 mass% (2,000 mass ppm) or more and 0.9 mass% (9,000 mass ppm) or less, 0.5 mass% (5,000 mass ppm) or more and 1.0 mass% (10,000 mass ppm) or less, or 0.5 mass% (5,000 mass ppm) or more and 0.9 mass% (9,000 mass ppm) or less, relative to the total mass of the polishing composition.

[0041] When the polishing composition contains two or more inorganic salts, the concentration (content) of the inorganic salts means the total amount thereof.

[0042] [Organic onium salts] The polishing composition of the present invention contains an organic onium salt, which has the function of reducing scratches on the surface of a polished object (particularly silicon oxide).

[0043] The organic onium salt used in the present invention includes at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2.

[0044] [ka]

[0045] In the above chemical formula 1 and chemical formula 2, R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A - and X - are each independently a monovalent anion.

[0046] When an organic onium salt having an alkyl group with 5 or more carbon atoms is used, scratches on the surface of the polished object increase.

[0047] R in the above Chemical Formula 1 and Chemical Formula 2 1 ~R 8 Specific examples of the unsubstituted alkyl group having 1 to 4 carbon atoms used in the above include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group. From the viewpoint of further exerting the effects of the present invention, an unsubstituted alkyl group having 2 to 4 carbon atoms, such as an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, or a tert-butyl group, is preferred.

[0048] A in the above chemical formula 1 and chemical formula 2 - and X -Examples of the monovalent anion used in are not particularly limited, but include halide ions such as fluoride ion, chloride ion, bromide ion, and iodide ion; hydroxide ion; and organic acid ions such as benzoate ion. The monovalent anion may be used alone or in combination of two or more. From the viewpoint of further exerting the effects of the present invention, A in the above chemical formula 1 and chemical formula 2 is preferably used. - and X - is a hydroxide ion (OH - ) is preferred.

[0049] More specific examples of the tetraalkylammonium salt represented by the above chemical formula 1 include, for example, tetramethylammonium fluoride, trimethylethylammonium fluoride, dimethyldiethylammonium fluoride, methyltriethylammonium fluoride, tetraethylammonium fluoride, trimethyl-n-propylammonium fluoride, trimethylisopropylammonium fluoride, dimethylethyl-n-propylammonium fluoride, dimethylethylisopropylammonium fluoride, methyldiethyl-n-propylammonium fluoride, methyldiethylisopropylammonium fluoride, triethylisopropylammonium fluoride, triethyl-n-propylammonium fluoride, tetra-n-propylammonium fluoride, tetraisopropylammonium fluoride, tetra-n-butylammonium fluoride, ammonium fluoride, tetra tert-butylammonium fluoride; tetramethylammonium chloride, trimethylethylammonium chloride, dimethyldiethylammonium chloride, methyltriethylammonium chloride, tetraethylammonium chloride, trimethyl n-propylammonium chloride, trimethylisopropylammonium chloride, dimethylethyl n-propylammonium chloride, dimethylethylisopropylammonium chloride, methyldiethyl n-propylammonium chloride, methyldiethylisopropylammonium chloride, triethylisopropylammonium chloride, triethyln-propylammonium chloride, tetra n-propylammonium chloride, tetraisopropylammonium chloride, tetra n-butylammonium chloride, tetra tert-butylammonium chloride;Tetramethylammonium bromide, trimethylethylammonium bromide, dimethyldiethylammonium bromide, methyltriethylammonium bromide, tetraethylammonium bromide, trimethyl n-propylammonium bromide, trimethylisopropylammonium bromide, dimethylethyl n-propylammonium bromide, dimethylethylisopropylammonium bromide, methyldiethyl n-propylammonium bromide, methyldiethylisopropylammonium bromide, triethylisopropylammonium bromide, triethyl n-propylammonium bromide, tetra n-propylammonium bromide, tetraisopropylammonium bromide, tetra n-butylammonium bromide, tetra tert-butylammonium bromide; Tetramethylammonium iodide, trimethylethylammonium iodide, dimethyldiethylammonium iodide, methyltriethylammonium iodide, tetraethylammonium iodide, trimethyl n-propylammonium iodide, trimethylisopropylammonium iodide, dimethylethyl n-propylammonium iodide, dimethylethylisopropylammonium iodide, methyldiethyl n-propylammonium iodide, methyldiethylisopropylammonium iodide, triethylisopropylammonium iodide, triethyl n-propylammonium iodide, tetra n-propylammonium iodide, tetraisopropylammonium iodide, tetra n-butylammonium iodide, tetra tert-butylammonium iodide;Tetramethylammonium hydroxide, trimethylethylammonium hydroxide, dimethyldiethylammonium hydroxide, methyltriethylammonium hydroxide, tetraethylammonium hydroxide, trimethyl n-propylammonium hydroxide, trimethylisopropylammonium hydroxide, dimethylethyl n-propylammonium hydroxide, dimethylethylisopropylammonium hydroxide, methyldiethyl n-propylammonium hydroxide, methyldiethylisopropylammonium hydroxide, triethylisopropylammonium hydroxide, triethyln-propylammonium hydroxide, tetran-propylammonium hydroxide, tetraisopropylammonium hydroxide, tetran-n-butylammonium hydroxide, tetratert-butylammonium hydroxide; tetramethylammonium hydroxide methylammonium benzoate, trimethylethylammonium benzoate, dimethyldiethylammonium benzoate, methyltriethylammonium benzoate, tetraethylammonium benzoate, trimethyl n-propylammonium benzoate, trimethylisopropylammonium benzoate, dimethylethyl n-propylammonium benzoate, dimethylethylisopropylammonium benzoate, methyldiethyl n-propylammonium benzoate, methyldiethylisopropylammonium benzoate, triethylisopropylammonium benzoate, triethyl n-propylammonium benzoate, tetra n-propylammonium benzoate, tetraisopropylammonium benzoate, tetra n-butylammonium benzoate, tetra tert-butylammonium benzoate; and the like.

[0050] More specific examples of the tetraalkylphosphonium salt represented by the above chemical formula 2 include, for example, tetramethylphosphonium fluoride, trimethylethylphosphonium fluoride, dimethyldiethylphosphonium fluoride, methyltriethylphosphonium fluoride, tetraethylphosphonium fluoride, trimethyl n-propylphosphonium fluoride, trimethylisopropylphosphonium fluoride, dimethylethyl n-propylphosphonium fluoride, dimethylethylisopropylphosphonium fluoride, methyldiethyl n-propylphosphonium fluoride, methyldiethylisopropylphosphonium fluoride, triethylisopropylphosphonium fluoride, triethyln-propylphosphonium fluoride, tetran-propylphosphonium fluoride, tetraisopropylphosphonium fluoride, tetran-butylphosphonium fluoride, fluoride, tetra tert-butylphosphonium fluoride; tetramethylphosphonium chloride, trimethylethylphosphonium chloride, dimethyldiethylphosphonium chloride, methyltriethylphosphonium chloride, tetraethylphosphonium chloride, trimethyl n-propylphosphonium chloride, trimethylisopropylphosphonium chloride, dimethylethyl n-propylphosphonium chloride, dimethylethylisopropylphosphonium chloride, methyldiethyl n-propylphosphonium chloride, methyldiethylisopropylphosphonium chloride, triethylisopropylphosphonium chloride, triethyln-propylphosphonium chloride, tetran-propylphosphonium chloride, tetraisopropylphosphonium chloride, tetran-butylphosphonium chloride, tetratert-butylphosphonium chloride;Tetramethylphosphonium bromide, trimethylethylphosphonium bromide, dimethyldiethylphosphonium bromide, methyltriethylphosphonium bromide, tetraethylphosphonium bromide, trimethyl n-propylphosphonium bromide, trimethylisopropylphosphonium bromide, dimethylethyl n-propylphosphonium bromide, dimethylethylisopropylphosphonium bromide, methyldiethyl n-propylphosphonium bromide, methyldiethylisopropylphosphonium bromide, triethylisopropylphosphonium bromide, triethyln-propylphosphonium bromide, tetran-propylphosphonium bromide, tetraisopropylphosphonium bromide, tetran-butylphosphonium bromide, tetratert-butylphosphonium bromide; Tetramethylphosphonium iodide, trimethylethylphosphonium iodide, dimethyldiethylphosphonium iodide, methyltriethylphosphonium iodide, tetraethylphosphonium iodide, trimethyl n-propylphosphonium iodide, trimethylisopropylphosphonium iodide, dimethylethyl n-propylphosphonium iodide, dimethylethylisopropylphosphonium iodide, methyldiethyl n-propylphosphonium iodide, methyldiethylisopropylphosphonium iodide, triethylisopropylphosphonium iodide, triethyln-propylphosphonium iodide, tetran-propylphosphonium iodide, tetraisopropylphosphonium iodide, tetran-butylphosphonium iodide, tetratert-butylphosphonium iodide;Tetramethylphosphonium hydroxide, trimethylethylphosphonium hydroxide, dimethyldiethylphosphonium hydroxide, methyltriethylphosphonium hydroxide, tetraethylphosphonium hydroxide, trimethyl n-propylphosphonium hydroxide, trimethylisopropylphosphonium hydroxide, dimethylethyl n-propylphosphonium hydroxide, dimethylethylisopropylphosphonium hydroxide, methyldiethyl n-propylphosphonium hydroxide, methyldiethylisopropylphosphonium hydroxide, triethylisopropylphosphonium hydroxide, triethyln-propylphosphonium hydroxide, tetran-propylphosphonium hydroxide, tetraisopropylphosphonium hydroxide, tetran-butylphosphonium hydroxide, tetratert-butylphosphonium hydroxide; tetramethyl trimethyl phosphonium benzoate, trimethylethyl phosphonium benzoate, dimethyldiethyl phosphonium benzoate, methyltriethyl phosphonium benzoate, tetraethyl phosphonium benzoate, trimethyl n-propyl phosphonium benzoate, trimethylisopropyl phosphonium benzoate, dimethylethyl n-propyl phosphonium benzoate, dimethylethyl isopropyl phosphonium benzoate, methyldiethyl n-propyl phosphonium benzoate, methyldiethylisopropyl phosphonium benzoate, triethylisopropyl phosphonium benzoate, triethyl n-propyl phosphonium benzoate, tetra n-propyl phosphonium benzoate, tetraisopropyl phosphonium benzoate, tetra n-butyl phosphonium benzoate, tetra tert-butyl ammonium benzoate; and the like.

[0051] These organic onium salts can be used singly or in combination of two or more. The organic onium salts to be used may be commercially available products or synthetic products.

[0052] Among these organic onium salts, the tetraalkylammonium salts represented by the above chemical formula 1 are preferred, from the viewpoint of more easily exerting the effects of the present invention, and at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide is more preferred.

[0053] The lower limit of the concentration (content) of the organic onium salt in the polishing composition is preferably 0.001 mass% (10 mass ppm) or more, and may be 0.0013 mass% (13 mass ppm) or more, 0.0015 mass% (15 mass ppm) or more, 0.002 mass% (20 mass ppm) or more, 0.0025 mass% (25 mass ppm) or more, 0.005 mass% (50 mass ppm) or more, 0.007 mass% (70 mass ppm) or more, or 0.01 mass% (100 mass ppm) or more, relative to the total mass of the polishing composition. Furthermore, the upper limit of the concentration (content) of the organic onium salt in the polishing composition is preferably 0.3 mass% (3000 mass ppm) or less, relative to the total mass of the polishing composition, and may be 0.1 mass% (1000 mass ppm) or less, 0.07 mass% (700 mass ppm) or less, 0.05 mass% (500 mass ppm) or less, 0.04 mass% (400 mass ppm) or less, 0.03 mass% (300 mass ppm) or less, 0.02 mass% (200 mass ppm) or less, 0.01 mass% (100 mass ppm) or less, 0.008 mass% (80 mass ppm) or less, or 0.005 mass% (50 mass ppm) or less.

[0054] That is, the concentration (content) of the organic onium salt in the polishing composition is preferably 0.001 mass% (10 mass ppm) or more and 0.3 mass% (3000 mass ppm) or less, and may be 0.005 mass% (50 mass ppm) or more and 0.1 mass% (1000 mass ppm) or less, 0.007 mass% (70 mass ppm) or more and 0.07 mass% (700 mass ppm) or less, or 0.01 mass% (100 mass ppm) or more and 0.05 mass% (500 mass ppm) or less, relative to the total mass of the polishing composition. Alternatively, from the viewpoint of further reducing scratches on the surface of the polished object, the concentration (content) of the organic onium salt in the polishing composition may be, relative to the total mass of the polishing composition, 0.001 mass% (10 ppm by mass) or more and 0.01 mass% (100 ppm by mass) or less, 0.0013 mass% (13 ppm by mass) or more and 0.01 mass% (100 ppm by mass) or less, 0.0015 mass% (15 ppm by mass) or more and 0.008 mass% (80 ppm by mass) or less, 0.002 mass% (20 ppm by mass) or more and 0.008 mass% (80 ppm by mass) or less, or 0.0025 mass% (25 ppm by mass) or more and 0.005 mass% (50 ppm by mass) or less.

[0055] When the polishing composition contains two or more kinds of organic onium salts, the concentration (content) of the organic onium salts means the total amount thereof.

[0056] [pH and pH adjusters] The pH of the polishing composition of the present invention is not particularly limited, but is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more.Furthermore, the pH is preferably 9.0 or less, more preferably 7.0 or less, even more preferably less than 7.0, even more preferably 5.0 or less, and particularly preferably 3.5 or less.That is, the pH of the polishing composition of the present invention is preferably 1.0 or more and 9.0 or less, more preferably 1.5 or more and 7.0 or less, even more preferably 1.5 or more and 7.0 or less, even more preferably 1.5 or more and 5.0 or less, and particularly preferably 2.0 or more and 3.5 or less.

[0057] The inorganic salt and organic onium salt contained in the polishing composition of the present invention can act as a pH adjuster for adjusting the pH of the polishing composition, but may further contain a separate pH adjuster according to the target pH. Such a pH adjuster may be either an acid or a base, and may also be either an inorganic compound or an organic compound. The pH adjuster may be used alone or in combination of two or more kinds.

[0058] Specific examples of acids that can be used as pH adjusters include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; and organic acids such 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, malonic 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, and phenoxyacetic acid.

[0059] Examples of bases that can be used as pH adjusters include amines such as aliphatic amines and aromatic amines, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, hydroxides of Group 2 elements, and ammonia.

[0060] The amount of pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH. The pH of the polishing composition can be measured, for example, with a pH meter, specifically by the method described in the Examples.

[0061] [Dispersion medium] The polishing composition of the present invention preferably further contains a dispersion medium. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a more preferred embodiment of the present invention, the dispersion medium contains water. According to an even more preferred embodiment of the present invention, the dispersion medium consists essentially of water. Note that the above term "substantially" means that a dispersion medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0062] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium be water that contains as few impurities as possible. Specifically, pure water or ultrapure water that has had impurity ions removed using an ion exchange resin and then passed through a filter to remove foreign matter, or distilled water, is more preferable.

[0063] [Electrical Conductivity of Polishing Composition] The electrical conductivity (EC) of the polishing composition of the present invention is not particularly limited, but is preferably 1 mS / cm or more, more preferably 2 mS / cm or more. The electrical conductivity (EC) of the polishing composition of the present invention is preferably 25 mS / cm or less, more preferably 20 mS / cm or less. That is, the electrical conductivity (EC) of the polishing composition of the present invention is preferably 1 mS / cm or more and 25 mS / cm or less, more preferably 2 mS / cm or more and 20 mS / cm or less. When the electrical conductivity (EC) of the polishing composition is within this range, the repulsion between abrasive grains can be appropriately adjusted, ensuring stability. The electrical conductivity of the polishing composition can be adjusted by the type and amount of a pH adjuster, etc. The electrical conductivity can be measured by the method described in the Examples.

[0064] [Other ingredients] The polishing composition of the present invention may further contain other components such as a water-soluble polymer, a complexing agent, a metal corrosion inhibitor, a preservative, an antifungal agent, a reducing agent, and a surfactant, as necessary. The preservative and the antifungal agent, which are preferred components, will be described below. The oxidizing agent will also be described.

[0065] The other preferred components, namely, the water-soluble polymer, the preservative, and the antifungal agent, as well as the oxidizing agent, will be described below.

[0066] (Water-soluble polymer) The polishing composition of the present invention preferably further contains a water-soluble polymer. The water-soluble polymer is easily adsorbed to the surface of the object to be polished and serves to protect the surface of the object to be polished. As a result, when polishing is performed using a polishing composition containing the water-soluble polymer, the number of scratches on the surface of the polished object can be further reduced.

[0067] The term "water-soluble polymer" as used herein refers to a water-soluble polymer (homopolymer) having the same repeating structural unit, or a water-soluble polymer (copolymer) having different repeating structural units, and may typically be a compound with a weight-average molecular weight (Mw) of 100 or more. There are no particular restrictions on the type of polymer used as the water-soluble polymer, and any of anionic, cationic, nonionic, and amphoteric polymers can be used. Furthermore, when the water-soluble polymer is a copolymer, the copolymer may be in the form of a block copolymer, random copolymer, graft copolymer, alternating copolymer, or periodic copolymer.

[0068] Examples of anionic water-soluble polymers include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polymethallyl sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, and polymethacrylic acid.

[0069] Examples of cationic water-soluble polymers include polyethyleneimine (PEI), polyvinylamine, polyallylamine, polyvinylpyridine, cationic acrylamide polymers, etc. Specific examples of polyallylamine include polydiallyldimethylammonium chloride.

[0070] Examples of nonionic water-soluble polymers include polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinylpyrrolidone, polyacrylamide, poly(N-vinylacetamide), polyamine compounds, polyvinyl ether compounds (such as polyvinyl methyl ether, polyvinyl ethyl ether, and polyvinyl isobutyl ether), polyoxyalkylene compounds (such as polyethylene glycol (polyethylene oxide), polypropylene glycol (polypropylene oxide), polytrimethylene glycol (polytrimethylene oxide), and polybutylene glycol (polybutylene oxide)), polyglycerin, polysaccharides such as water-soluble celluloses (hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, and ethyl hydroxyethyl cellulose), alginic acid polyhydric alcohol esters, water-soluble urea resins, dextrin derivatives, and casein. In addition to polymers having such main chain structures, graft copolymers having nonionic polymer structures in their side chains can also be suitably used.

[0071] Examples of amphoteric water-soluble polymers include copolymers of a vinyl monomer having an anionic group and a vinyl monomer having a cationic group, and vinyl-based amphoteric polymers having a carboxybetaine group or a sulfobetaine group. Specific examples include acrylic acid / dimethylaminoethyl methacrylic acid copolymers and acrylic acid / diethylaminoethyl methacrylic acid copolymers.

[0072] Furthermore, copolymers of the water-soluble polymers exemplified above can also be used.

[0073] The water-soluble polymer may be used singly or in combination of two or more kinds. In addition, the water-soluble polymer may be a commercially available product or a synthetic product.

[0074] Among these water-soluble polymers, it is preferable to use a nonionic water-soluble polymer, from the viewpoint of further reducing scratches on the surface of the polished object (especially silicon oxide). More preferably, the water-soluble polymer contains polyvinyl alcohol. Even more preferably, the water-soluble polymer contains polyvinyl alcohol and a polyoxyalkylene compound. Furthermore, it is preferable that the polyoxyalkylene compound contains at least one of polyethylene glycol and polypropylene glycol.

[0075] The weight-average molecular weight (Mw) of the water-soluble polymer can be appropriately set depending on the type of water-soluble polymer. Generally, the lower limit of the weight-average molecular weight (Mw) of the water-soluble polymer is preferably 100 or more, and may be 200 or more, 300 or more, 400 or more, 500 or more, 600 or more, 800 or more, 1,000 or more, 1,500 or more, 2,000 or more, 3,000 or more, 4,000 or more, or 5,000 or more. The upper limit of the weight-average molecular weight (Mw) of the water-soluble polymer is preferably 500,000 or less, and may be 100,000 or less, 50,000 or less, 30,000 or less, 20,000 or less, 10,000 or less, 8,000 or less, 5,000 or less, 3,000 or less, 2,000 or less, 1,000 or less, or 800 or less.

[0076] For example, the weight-average molecular weight (Mw) of the water-soluble polymer may be 1,000 to 100,000, 1,500 to 50,000, 2,000 to 20,000, 3,000 to 20,000, or 5,000 to 20,000. In another example, the weight-average molecular weight (Mw) of the water-soluble polymer may be 100 to 2,000, 200 to 2,000, 200 to 1,000, or 300 to 800.

[0077] For example, when the water-soluble polymer is polyvinyl alcohol, the lower limit of the weight-average molecular weight (Mw) of the polyvinyl alcohol may be 1,000 or more, 1,500 or more, 2,000 or more, 3,000 or more, or 5,000 or more. The upper limit of the weight-average molecular weight (Mw) of the polyvinyl alcohol may be 100,000 or less, 50,000 or less, or 20,000 or less. That is, the weight-average molecular weight (Mw) of the polyvinyl alcohol may be 1,000 or more and 100,000 or less, 1,500 or more and 50,000 or less, 2,000 or more and 20,000 or less, 3,000 or more and 20,000 or less, or 5,000 or more and 20,000 or less.

[0078] For example, when the water-soluble polymer is a polyoxyalkylene compound, the lower limit of the weight-average molecular weight (Mw) of the polyoxyalkylene compound may be 100 or more, 200 or more, or 300 or more. The upper limit of the weight-average molecular weight (Mw) of the polyoxyalkylene compound may be 2,000 or less, 1,000 or less, or 800 or less. That is, the weight-average molecular weight (Mw) of the polyoxyalkylene compound may be 100 or more and 2,000 or less, 200 or more and 2,000 or less, 200 or more and 1,000 or less, or 300 or more and 800 or less.

[0079] The weight average molecular weight (Mw) of the water-soluble polymer can be measured as a polyethylene glycol equivalent value using gel permeation chromatography (GPC).

[0080] The concentration (content) of water-soluble polymer in polishing composition is suitably set according to the type of water-soluble polymer used.Generally, the lower limit of the concentration (content) of water-soluble polymer is preferably 0.01 mass% (100 mass ppm) or more, and can be 0.02 mass% (200 mass ppm) or more, 0.03 mass% (300 mass ppm) or more, 0.04 mass% (400 mass ppm) or more, 0.05 mass% (500 mass ppm) or more, 0.06 mass% (600 mass ppm) or more, 0.07 mass% (700 mass ppm) or more, 0.08 mass% (800 mass ppm) or more, 0.09 mass% (900 mass ppm) or more, or 0.1 mass% (1000 mass ppm) or more, based on the total mass of polishing composition. Furthermore, the upper limit of the concentration (content) of the water-soluble polymer in the polishing composition is preferably 1% by mass (10,000 ppm by mass) or less, relative to the total mass of the polishing composition, and may be 0.9% by mass (9,000 ppm by mass) or less, 0.8% by mass (8,000 ppm by mass) or less, 0.7% by mass (7,000 ppm by mass) or less, 0.6% by mass (6,000 ppm by mass) or less, 0.5% by mass (5,000 ppm by mass) or less, 0.4% by mass (4,000 ppm by mass) or less, 0.3% by mass (3,000 ppm by mass) or less, or 0.2% by mass (2,000 ppm by mass) or less.

[0081] That is, the concentration (content) of the water-soluble polymer in the polishing composition is preferably 0.01 mass% (100 ppm by mass) or more and 1 mass% (10,000 ppm by mass) or less, more preferably 0.02 mass% (200 ppm by mass) or more and 0.9 mass% (9,000 ppm by mass) or less, 0.03 mass% (300 ppm by mass) or more and 0.8 mass% (8,000 ppm by mass) or less, 0.04 mass% (400 ppm by mass) or more and 0.7 mass% (7,000 ppm by mass) or less, or 0.05 mass% (500 ppm by mass) or more and 0.6 mass% (10,000 ppm by mass) or less, more preferably 0.05 mass% (100 ppm by mass) or more and 0.7 mass% (10,000 ppm by mass) or less, more preferably 0.05 mass% (100 ppm by mass) or more and 0.8 ... .6 mass% (6000 mass ppm) or less, 0.06 mass% (600 mass ppm) or more and 0.5 mass% (5000 mass ppm) or less, 0.07 mass% (700 mass ppm) or more and 0.4 mass% (4000 mass ppm) or less, 0.08 mass% (800 mass ppm) m) or more and 0.3 mass% (3000 mass ppm) or less, 0.09 mass% (900 mass ppm) or more and 0.3 mass% (3000 mass ppm) or less, or 0.1 mass% (1000 mass ppm) or more and 0.2 mass% (2000 mass ppm) or less.

[0082] When the polishing composition contains two or more water-soluble polymers, the content of the water-soluble polymers refers to the total amount thereof.

[0083] (preservatives and fungicides) Examples of preservatives and antifungal agents that can be added to the polishing composition of the present invention include 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 antifungal agents may be used alone or in combination of two or more.

[0084] (oxidizing agent) The polishing composition of the present invention preferably contains substantially no oxidizing agent. If an oxidizing agent is contained in the polishing composition, the surface of the object to be polished may be oxidized to form an oxide film, which may result in a prolonged polishing time. Specific examples of oxidizing agents include hydrogen peroxide (H2O2), sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. The term "substantially free of oxidizing agent" means that the polishing composition does not contain an oxidizing agent, at least intentionally. Therefore, a polishing composition that inevitably contains a trace amount of oxidizing agent due to raw materials, manufacturing method, etc., is encompassed by the concept of a polishing composition that is substantially free of oxidizing agent. For example, the concentration (content) of the oxidizing agent in the polishing composition is preferably 0.01% by mass (100 ppm by mass) or less, more preferably less than 0.01% by mass (100 ppm by mass), and even more preferably 0.005% by mass (50 ppm by mass) or less. The lower limit of the concentration (content) of the oxidizing agent is preferably 0% by mass or more, and more preferably 0.0005% by mass (5 ppm by mass) or more.

[0085] [Form of polishing composition] The polishing composition of the present invention is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition and used to polish the object. The polishing composition of the present invention may be used as a polishing liquid after dilution (typically with water), or may be used as a polishing liquid as is. That is, the concept of the polishing composition of the present invention encompasses both a polishing composition (working slurry) that is supplied to a polishing object and used to polish the object, and a concentrated liquid (raw solution of working slurry) that is diluted and used for polishing. The concentration ratio of the concentrated liquid can be, for example, about 2 to 100 times on a volume basis, and is usually about 3 to 50 times.

[0086] [Polished object] The object to be polished according to the present invention is not particularly limited, and examples thereof include single crystal silicon, polycrystalline silicon (polysilicon), polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon, amorphous silicon doped with n-type or p-type impurities, silicon oxide, silicon nitride, silicon carbonitride (SiCN), metals, SiGe, and carbon-containing materials.

[0087] Examples of polishing objects containing silicon oxide include TEOS-type silicon oxide films (hereinafter simply referred to as "TEOS" or "TEOS films") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0088] Examples of metals include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0089] Examples of carbon-containing materials include amorphous carbon, spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, and graphene.

[0090] The object to be polished may be a commercially available product or may be produced by a known method.

[0091] Among these, an object to be polished containing silicon oxide is preferred. Therefore, according to a preferred embodiment of the present invention, the polishing composition is used for polishing an object to be polished containing silicon oxide.

[0092] [Method for producing polishing composition] The method for producing the polishing composition according to this embodiment is not particularly limited, and the composition can be obtained, for example, by stirring and mixing abrasive grains, inorganic salts, organic onium salts, and other additives as needed. The details of each component are as described above.

[0093] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C. Heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0094] [Polishing method and semiconductor substrate manufacturing method] As described above, the polishing composition of this embodiment is particularly suitable for use in polishing an object having silicon oxide. Thus, the present invention provides a polishing method for polishing an object containing silicon oxide with the polishing composition of this embodiment. The present invention also provides a method for producing a semiconductor substrate, comprising polishing a semiconductor substrate containing silicon oxide by the polishing method.

[0095] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0096] The polishing pad may be made of any material, including ordinary nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0097] Regarding the polishing conditions, for example, the rotation speed of the polishing table (platen) and carrier (head) is 10 rpm (0.17 s -1 ) or more 500rpm (8.33s -1 The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.45 kPa) or more and 10 psi (68.9 kPa) or less.

[0098] The method for supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the polishing composition using a pump, etc. There is no limit to the amount of the polishing composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0099] The polishing composition according to this embodiment may be a one-component type or a multi-component type such as a two-component type. The polishing composition according to the present invention may be prepared by diluting the stock solution of the polishing composition with a diluent such as water, for example, by a volume ratio of 2 to 100 times, usually 3 to 50 times.

[0100] [Number of scratches] As described above, the polishing composition of the present invention can reduce scratches on the surface of an object to be polished after polishing.

[0101] In the present invention, the fewer the number of scratches on the surface of the polished object, the better. Specifically, a scratch number of 25 or less is practical, preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, and particularly preferably less than 10. In this specification, the scratch number is the value measured by the method described in the examples.

[0102] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0103] The present invention encompasses the following aspects and configurations: 1. Abrasive grains, an inorganic salt, and an organic onium salt are contained, The organic onium salt includes at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2: A polishing composition, wherein the abrasive grains in the polishing composition have a negative zeta potential:

[0104] [ka]

[0105] In the above Chemical Formula 1 and Chemical Formula 2, R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A - and X - are each independently a monovalent anion: 2. The polishing composition according to 1 above, wherein the inorganic salt includes at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate. 3. The polishing composition according to 1. or 2. above, wherein the organic onium salt is a tetraalkylammonium salt represented by Chemical Formula 1. 4. A in the above Chemical Formula 1 and Chemical Formula 2 - and X - is a hydroxide ion. 5. The polishing composition according to any one of 1. to 4. above, wherein the tetraalkylammonium salt represented by Chemical Formula 1 includes at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide. 6. The polishing composition according to any one of 1. to 5. above, wherein the concentration of the organic onium salt relative to the total mass of the polishing composition is 0.001 mass% or more and 0.01 mass% or less. 7. The polishing composition according to any one of 1. to 6. above, which has a pH of less than 7.0. 8. The polishing composition according to any one of 1. to 7. above, wherein the abrasive grains are anion-modified colloidal silica. 9. The polishing composition according to any one of 1. to 8. above, further comprising a water-soluble polymer: 10. The polishing composition according to 9 above, wherein the water-soluble polymer includes polyvinyl alcohol. 11. The polishing composition according to claim 10, wherein the water-soluble polymer further contains a polyoxyalkylene compound. 12. The polishing composition according to 11 above, wherein the polyoxyalkylene compound contains at least one of polyethylene glycol and polypropylene glycol. 13. The polishing composition according to any one of 1. to 12. above, further comprising a dispersion medium: 14. The polishing composition according to any one of 1. to 13. above, which is used for polishing an object containing silicon oxide: 15. A polishing method comprising the step of polishing an object containing silicon oxide with the polishing composition according to any one of 1. to 14. above: 16. A method for producing a semiconductor substrate, comprising a step of polishing a semiconductor substrate containing silicon oxide by the polishing method described in 15 above. [Example]

[0106] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively. In the following examples, unless otherwise specified, operations were carried out under the conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH. Each physical property was measured as follows.

[0107] <Average primary particle size and average secondary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​the abrasive grains measured by the BET method using a Micromeritics Flow Sorb II 2300 and the density of the abrasive grains. The average secondary particle size of the abrasive grains was measured as the volume-average particle size (arithmetic mean diameter based on volume; Mv) using a dynamic light scattering particle size distribution analyzer UPA-UT151 (Nikkiso Co., Ltd.).

[0108] <Zeta potential of abrasive grains> The zeta potential of the abrasive grains in the polishing composition was measured using a zeta potential measuring device manufactured by Otsuka Electronics Co., Ltd. (device name "ELS-Z2").

[0109] <pH of polishing composition> The pH of the polishing composition was measured with a pH meter (manufactured by Horiba, Ltd., model number: LAQUA).

[0110] <Electrical Conductivity of Polishing Composition> The electrical conductivity (EC) of the polishing composition was measured using a desktop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71 LAQUA (registered trademark)).

[0111] <Weight-average molecular weight (Mw) of water-soluble polymer> The weight average molecular weight (Mw) of the water-soluble polymer was measured using gel permeation chromatography (GPC) under the following measurement conditions: (GPC measurement conditions) Measuring device: HLC-8320GPC (Tosoh Corporation) Sample concentration: 0.01% by mass Column: TSKgel (registered trademark) GMPWXL Detector: differential refractometer Eluent: 10 mM lithium bromide in N,N-dimethylformamide Flow rate: 1mL / min Measurement temperature: 40℃ Molecular weight conversion: Polyethylene glycol conversion Sample injection volume: 200 μL.

[0112] <Production of sulfonic acid-modified colloidal silica> Sulfonic acid-modified colloidal silica was obtained as abrasive grains according to the following procedure.

[0113] (Preparation process of raw colloidal silica dispersion (unmodified silica particles)) 4080 g of methanol, 610 g of water, and 168 g of 29% by mass aqueous ammonia solution were mixed in a flask, and the liquid temperature was kept at 20°C. A mixture of 135 g of methanol and 508 g of tetramethoxysilane (TMOS) was added dropwise over 25 minutes. After that, the mixture was heated to a pH of 7 or higher and subjected to water substitution, yielding 1000 g of 19.5% by mass silica sol (average primary particle size: 34 nm).

[0114] (Surface modification process) Next, 1.2 g of 3-mercaptopropyltrimethoxysilane (MPS, silane coupling agent, product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) (silane coupling agent concentration relative to the total mass of silica solids: 0.6 mass%) mixed with 4.8 g of methanol was added dropwise to 1,000 g of the silica sol obtained above (195 g in terms of silica solids) at a flow rate of 1 mL / min. The mixture was then heated and boiled, followed by substitution with pure water for 3 hours.

[0115] Next, the reaction solution was left to cool overnight, and then 0.0343 g of 30 mass % hydrogen peroxide solution (3 moles per mole of silane coupling agent) was added, and the mixture was boiled again. After that, the mixture was replaced with pure water for 2 hours, and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silica.

[0116] Example 1 <Preparation of Polishing Composition> The sulfonic acid-modified colloidal silica (average primary particle size: 34 nm) abrasive grains prepared in the above <Preparation of sulfonic acid-modified colloidal silica> was added to water as a dispersion medium to a final concentration of 2 mass%. Furthermore, ammonium sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.), an inorganic salt, was added to a final concentration of 6000 mass ppm (0.6 mass%), and tetraethylammonium hydroxide (TEAH, manufactured by Tokyo Chemical Industry Co., Ltd.), an organic onium salt, was added to a final concentration of 150 mass ppm (0.015 mass%), and the mixture was stirred and mixed (stirring temperature: 25°C, stirring time: 20 minutes). The pH of the polishing composition was adjusted to 2.0 using nitric acid, completing polishing composition 1.

[0117] Example 2 Polishing composition 2 was prepared in the same manner as in Example 1, except that the amount of ammonium sulfate added was changed to an amount that would give a final concentration of 2000 ppm by mass (0.2% by mass).

[0118] Example 3 Polishing composition 3 was prepared in the same manner as in Example 1, except that the amount of ammonium sulfate added was changed to an amount that would give a final concentration of 100 ppm by mass (0.01% by mass).

[0119] Example 4 Polishing composition 4 was prepared in the same manner as in Example 1, except that the amount of ammonium sulfate added was changed to an amount that would give a final concentration of 9000 ppm by mass (0.9% by mass).

[0120] Example 5 Polishing Composition 5 was prepared in the same manner as in Example 1, except that tetra-n-butylammonium hydroxide (TBAH, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of tetraethylammonium hydroxide.

[0121] Example 6 Polishing Composition 6 was prepared in the same manner as in Example 1, except that the pH of the polishing composition was adjusted to 4.0 with nitric acid.

[0122] Example 7 Polishing Composition 7 was prepared in the same manner as in Example 1, except that the pH of the polishing composition was adjusted to 7.0 with nitric acid.

[0123] (Comparative Example 1) Comparative Polishing Composition 1 was prepared in the same manner as in Example 1, except that ammonium sulfate and tetraethylammonium hydroxide were not used.

[0124] (Comparative Example 2) Comparative Polishing Composition 2 was prepared in the same manner as in Example 1, except that tetraethylammonium hydroxide was not used.

[0125] (Comparative Example 3) Comparative Polishing Composition 3 was prepared in the same manner as in Example 1, except that ammonium sulfate was not used.

[0126] Comparative Example 4 Comparative Polishing Composition 4 was prepared in the same manner as in Example 1, except that stearyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of tetraethylammonium hydroxide.

[0127] The compositions of the polishing compositions of Examples 1 to 7 and Comparative Examples 1 to 4 are shown in the following Table 1. In addition, "-" in the following Table 1 indicates that the component was not used.

[0128] [Table 1]

[0129] Example 8 <Preparation of Polishing Composition> The abrasive sulfonic acid-modified colloidal silica (average primary particle size: 34 nm) prepared in the above <Preparation of sulfonic acid-modified colloidal silica> was added to water as a dispersion medium to a final concentration of 4 mass%. Furthermore, ammonium sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.), an inorganic salt, was added to a final concentration of 2000 mass ppm (0.2 mass%), and tetraethylammonium hydroxide (TEAH, manufactured by Tokyo Chemical Industry Co., Ltd.), an organic onium salt, was added to a final concentration of 26 mass ppm (0.0026 mass%), and the mixture was stirred and mixed (stirring temperature: 25°C, stirring time: 20 minutes). The pH of the polishing composition was adjusted to 2.1 using nitric acid, completing Polishing Composition 8.

[0130] Example 9 Polishing Composition 9 was prepared in the same manner as in Example 8, except that polyvinyl alcohol (PVA, weight average molecular weight: 10,000) was further added so that the final concentration was 1000 ppm by mass (0.1% by mass).

[0131] Example 10 Polishing composition 10 was prepared in the same manner as in Example 8, except that polyvinyl alcohol (PVA, weight average molecular weight: 10,000) was further added to a final concentration of 1000 mass ppm (0.1 mass%) and polyethylene glycol (PEG, weight average molecular weight: 200) was further added to a final concentration of 3000 mass ppm (0.3 mass%).

[0132] Example 11 Polishing composition 11 was prepared in the same manner as in Example 8, except that polyvinyl alcohol (PVA, weight average molecular weight: 10,000) was further added to a final concentration of 1000 mass ppm (0.1 mass%) and polypropylene glycol (PPG, weight average molecular weight: 400) was further added to a final concentration of 600 mass ppm (0.06 mass%).

[0133] (Comparative Example 5) Comparative Polishing Composition 5 was prepared in the same manner as in Example 8, except that tetraethylammonium hydroxide (TEAH) was not used.

[0134] The following Table 2 shows the compositions of the polishing compositions of Examples 8 to 11 and Comparative Example 5. In Table 2 below, "-" indicates that the component was not used.

[0135] [Table 2]

[0136] [evaluation] The following (1) and (2) were prepared as polishing objects, and polishing was carried out under the following conditions: (1) Silicon nitride film (Si3N4 film): A silicon wafer (200 mm, blanket wafer) with a 2000 Å thick silicon nitride film (Si3N4 film) formed on the surface. (2) Silicon oxide film (TEOS film): A silicon wafer (200 mm, blanket wafer) with a 10,000 Å thick TEOS type silicon oxide (SiO2) film formed on its surface.

[0137] (Polishing equipment and polishing conditions) Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra Polishing pad: Nitta Haas IC1010 hard polyurethane pad Polishing pressure: 2.5 psi (1 psi = 6894.76 Pa) Polishing platen rotation speed: 47 rpm Head (carrier) rotation speed: 43 rpm Supply of polishing composition: free-flowing Polishing composition supply amount: 200mL / min Polishing time: 60 seconds.

[0138] <Polishing speed> The thickness of each polished object before and after polishing was measured using an optical film thickness measuring device (ASET-f5x, manufactured by KLA-Tencor Corporation). The film thickness was measured using an optical film thickness measuring device (ASET-f5x, manufactured by KLA-Tencor Corporation).

[0139] For each object to be polished, the polishing rate for each object to be polished was calculated by dividing the difference in film thickness before and after polishing [(thickness before polishing) - (thickness after polishing)] by the polishing time.

[0140] <Number of scratches> The number of scratches on the silicon oxide film surface after polishing was measured using a wafer inspection system "Surfscan® SP2" manufactured by KLA-Tencor Corporation to measure the coordinates of the entire surface of both sides of the polished object (excluding the outer 2 mm area). The measured coordinates were then observed with a Review-SEM (RS-6000, manufactured by Hitachi High-Technologies Corporation). Scratches were counted as scratches on the substrate surface with a depth of 10 nm to less than 100 nm, a width of 100 nm to less than 500 nm, and a length of 80 nm or more. The fewer the number of scratches, the better. A scratch count of 25 or less is practical, with 20 or less being preferred, 15 or less being more preferred, 10 or less being even more preferred, and less than 10 being particularly preferred.

[0141] The evaluation results of the polishing rate and the number of scratches are shown in the following Table 3. In the following Table 3, the silicon nitride film is represented by "Si3N4" and the silicon oxide film is represented by "SiO2".

[0142] [Table 3]

[0143] As is clear from Table 3 above, it was found that when the polishing compositions of Examples were used, scratches on the surface of the silicon oxide film could be reduced, whereas when the polishing compositions of Comparative Examples were used, scratches on the surface of the silicon oxide film increased.

Claims

1. Abrasive grains and Inorganic salts, an organic onium salt; Contains The organic onium salt includes at least one of a tetraalkylammonium salt represented by the following chemical formula 1 and a tetraalkylphosphonium salt represented by the following chemical formula 2: The zeta potential of the abrasive grains in the polishing composition is negative. 【Chemical 1】 In the above Chemical Formula 1 and Chemical Formula 2, R １ ~R ８ are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, A － and X － are each independently a monovalent anion.

2. 2. The polishing composition according to claim 1, wherein the inorganic salt comprises at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate.

3. The polishing composition according to claim 1 , wherein the organic onium salt is a tetraalkylammonium salt represented by Chemical Formula 1.

4. A in the above Chemical Formula 1 and Chemical Formula 2 － and X － The polishing composition according to claim 1 , wherein is a hydroxide ion.

5. 2. The polishing composition according to claim 1, wherein the tetraalkylammonium salt represented by Chemical Formula 1 includes at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide.

6. 2. The polishing composition according to claim 1, wherein the concentration of the organic onium salt relative to the total mass of the polishing composition is 0.001 mass % or more and 0.01 mass % or less.

7. The polishing composition according to claim 1 , having a pH of less than 7.

0.

8. 2. The polishing composition according to claim 1, wherein the abrasive grains are anion-modified colloidal silica.

9. The polishing composition according to claim 1 , further comprising a water-soluble polymer.

10. The polishing composition according to claim 9 , wherein the water-soluble polymer comprises polyvinyl alcohol.

11. The polishing composition according to claim 10 , wherein the water-soluble polymer further contains a polyoxyalkylene compound.

12. The polishing composition according to claim 11, wherein the polyoxyalkylene compound comprises at least one of polyethylene glycol and polypropylene glycol.

13. The polishing composition according to claim 1 , further comprising a dispersion medium.

14. The polishing composition according to claim 1 , which is used for polishing an object containing silicon oxide.

15. A polishing method comprising a step of polishing an object containing silicon oxide with the polishing composition according to any one of claims 1 to 14.

16. A method for producing a semiconductor substrate, comprising a step of polishing a semiconductor substrate containing silicon oxide by the polishing method according to claim 15.

Images