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

Abstract

The invention relates to a polishing composition, a polishing method, and a method for manufacturing a semiconductor substrate. The present disclosure provides a means capable of increasing the polishing speed of an object to be polished (in particular, silicon oxide) and reducing scratches on the surface of the polished object (in particular, silicon oxide). The present disclosure is a polishing composition containing abrasive grains having an average primary particle diameter of 1-150 nm (inclusive) and a dispersion medium, the aggregation rate of the abrasive grains being 40% or more and less than 75%.

Description

Technical Field

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

[0002] In recent years, with the increasing number of multilayered wiring on semiconductor substrate surfaces, chemical mechanical polishing (CMP) technology has been used to planarize semiconductor substrates by physically polishing them during device manufacturing. CMP is a method that uses a polishing composition (slurry) containing abrasives such as silicon dioxide, aluminum oxide, and cerium oxide, an anticorrosive agent, a surfactant, and the like to planarize the surface of an object to be polished, such as a semiconductor substrate. The polishing object (object to be polished) includes silicon, polycrystalline silicon, silicon oxide (SiO2), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), wiring formed from metals, plugs, and the like.

[0003] For example, Japanese Patent Application Laid-Open No. 2016-56292 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 greater. Japanese Patent Application Laid-Open No. 2016-56292 discloses a polishing composition capable of polishing silicon oxide at a high polishing rate. Summary of the Invention

[0004] However, the technology described in Japanese Patent Application Laid-Open No. 2016-56292 still has room for improvement in reducing scratches on the surface of the polished object.

[0005] Therefore, an object of the present disclosure is to provide a means for increasing the polishing rate of an object to be polished (particularly silicon oxide) and reducing scratches on the surface of the polished object (particularly silicon oxide).

[0006] The inventors of the present disclosure conducted intensive research to address the aforementioned issues. As a result, they discovered that a polishing composition comprising abrasive particles having an average primary particle size of 1 nm to 150 nm, a dispersion medium, and an aggregation rate of the abrasive particles of 40% to less than 75% can address the aforementioned issues, thereby completing the present invention. DETAILED DESCRIPTION

[0007] According to one embodiment of the present disclosure, a polishing composition is provided, comprising abrasive particles having an average primary particle size of 1 nm to 150 nm, and a dispersion medium, wherein the abrasive particles have an aggregation rate of 40% to less than 75%. The polishing composition of the present disclosure can increase the polishing rate of an object to be polished (particularly silicon oxide) and reduce scratches on the surface of the polished object (particularly silicon oxide).

[0008] The following describes the embodiments of the present disclosure in detail, but the present disclosure 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 arbitrarily to form other embodiments. In this specification, unless otherwise specified, the operation and measurement of physical properties are carried out under the conditions of room temperature (above 20°C and below 25°C) / relative humidity of 40% RH and below 50% RH.

[0009] [Abrasive grains]

[0010] The polishing composition disclosed herein contains abrasive grains. The abrasive grains have the function of mechanically polishing an object to be polished and increase the polishing rate of the object to be polished by the polishing composition.

[0011] There are no particular restrictions on the type of abrasive grains, and examples thereof include metal oxides such as silicon dioxide, aluminum oxide, zirconium oxide, and titanium dioxide. These abrasive grains may be used alone or in combination of two or more. Each of these abrasive grains may be a commercially available product or a synthetic product.

[0012] The abrasive is preferably silicon dioxide, more preferably colloidal silicon dioxide. Examples of methods for producing colloidal silicon dioxide include the sodium silicate method and the sol-gel method. Colloidal silicon dioxide produced by any of these methods is suitable for use as the abrasive of the present disclosure. However, from the perspective of reducing metallic impurities, colloidal silicon dioxide produced by the sol-gel method, which allows for high-purity production, is preferred.

[0013] Colloidal silica can be produced by a sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by using a hydrolyzable silicon compound (for example, alkoxysilane or a derivative thereof) as a raw material and subjecting it to a hydrolysis-condensation reaction.

[0014] The shape of the abrasive particles is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include, but are not limited to, polygonal prisms such as triangular prisms and quadrangular prisms, cylindrical shapes, straw bag shapes with a cylinder bulging outward from the center, donut shapes with a disk having a through center, plate shapes, cocoon shapes with a constriction in the center, associated spherical shapes with multiple particles integrated, konpeito shapes with multiple protrusions on the surface, and rugby ball shapes.

[0015] The average primary particle size of the abrasive disclosed herein is 1 nm or more and 150 nm or less. When the average primary particle size of the abrasive is less than 1 nm, the polishing speed of the polishing object (particularly silicon oxide) decreases. On the other hand, when the average primary particle size of the abrasive exceeds 150 nm, the scratches on the surface of the polishing object (particularly silicon oxide) after polishing increase. The average primary particle size of the abrasive is preferably 5 nm or more, more preferably 8 nm or more, more preferably 10 nm or more, and particularly preferably 12 nm or more. As the average primary particle size of the abrasive increases, the polishing speed of the polishing object based on the polishing composition increases. In addition, the average primary particle size of the abrasive is preferably 100 nm or less, more preferably 80 nm or less, more preferably 60 nm or less, and particularly preferably 50 nm or less. As the average primary particle size of the abrasive becomes smaller, it becomes easier to obtain a surface with fewer defects by polishing using the polishing composition. That is, the average primary particle size of the abrasive is preferably 5 nm or more and 100 nm or less, more preferably 8 nm or more and 80 nm or less, 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 size 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 the value measured by the method described in the Examples.

[0016] In addition, the average secondary particle size of the abrasive is preferably 10 nm or more, more preferably 15 nm or more, more preferably 20 nm or more, and particularly preferably 25 nm or more. As the average secondary particle size of the abrasive becomes larger, the resistance during grinding becomes smaller, and it becomes possible to grind stably. In addition, the average secondary particle size of the abrasive is preferably 400 nm or less, more preferably 300 nm or less, more preferably 200 nm or less, and particularly preferably 100 nm or less. As the average secondary particle size of the abrasive becomes smaller, the surface area of ​​the abrasive per unit mass becomes larger, the contact frequency with the grinding object increases, and the grinding speed is further improved. That is, the average secondary particle size of the abrasive is preferably 10 nm or more and 400 nm or less, more preferably 15 nm or more and 300 nm or less, more preferably 20 nm or more and 200 nm or less, and particularly preferably 25 nm or more and 100 nm or less. It should be noted that the average secondary particle size of the abrasive can be measured, for example, by a dynamic light scattering method represented by a laser diffraction scattering method.

[0017] The average degree of association of the abrasive particles 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 particles decreases, defects can be further reduced. Furthermore, the average degree of association of the abrasive particles is preferably 1.0 or greater, more preferably 1.5 or greater, and even more preferably 2.0 or greater. This average degree of association is obtained by dividing the average secondary particle size of the abrasive particles by the average primary particle size. As the average degree of association of the abrasive particles increases, the polishing rate of the polishing composition increases.

[0018] The upper limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, and is preferably less than 2.0, more preferably less than 1.8, more preferably less than 1.5. When being such a scope, the defect of the polishing object surface can be further reduced. It should be noted that aspect ratio is the minimum rectangle obtained by utilizing a scanning electron microscope to circumscribe the image of the abrasive grains, and the average of the value obtained by dividing the length of the long side of the rectangle by the length of the short side of the same rectangle, can be obtained using common image analysis software. The lower limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, and is preferably more than 1.0, more preferably more than 1.2.

[0019] In the particle size distribution of the abrasive particles determined by the laser diffraction scattering method, the ratio of the particle diameter (D90) when the cumulative particle mass from the microparticle side reaches 90% of the total particle mass to the particle diameter (D10) when the total particle mass reaches 10% of the total particle mass, i.e., D90 / D10, has no particular lower limit, but is preferably 1.1 or greater, more preferably 1.4 or greater, more preferably 1.7 or greater, and most preferably 2.0 or greater. Furthermore, in the particle size distribution of the abrasive particles in the polishing composition determined by the laser diffraction scattering method, the ratio of the particle diameter (D90) when the cumulative particle mass from the microparticle side reaches 90% of the total particle mass to the particle diameter (D10) when the total particle mass reaches 10% of the total particle mass, i.e., D90 / D10, has no particular upper limit, 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.

[0020] The size of the abrasive grains (average primary particle size, average secondary particle size, aspect ratio, D90 / D10, etc.) can be appropriately controlled by, for example, selecting a method for producing the abrasive grains.

[0021] <Agglomeration Rate of Abrasive Particles>

[0022] The present disclosure is characterized in that the abrasive has an aggregation rate of 40% or more and less than 75%. By using abrasives having an aggregation rate within this range, the grinding speed of the grinding object (particularly silicon oxide) can be increased, and the scratches on the surface of the grinding object (particularly silicon oxide) after grinding can be reduced. When the aggregation rate is less than 40%, the grinding speed of the grinding object (particularly silicon oxide) is reduced. On the other hand, when the aggregation rate is more than 75%, the scratches on the surface of the grinding object (particularly silicon oxide) after grinding increase. The aggregation rate is preferably more than 40% and less than 55%.

[0023] In this specification, the aggregation rate of abrasive grains is a value measured by the following method:

[0024] Determination of aggregation rate

[0025] 1) Weigh 30.0 g of the polishing composition as a sample into a polypropylene container and tightly close the lid.

[0026] 2) Use a centrifuge and run it continuously at 25°C and 15,000 rpm for 15 minutes:

[0027] 3) Through centrifugal separation, the water in the upper part of the container is separated from the abrasive in the lower part, and the abrasive is compressed and settled to the lower part of the container (this is called filter cake):

[0028] 4) Use a dryer to dry the settled filter cake at 200°C for 24 hours, and then measure the weight of the obtained solid content:

[0029] 5) The aggregation rate is calculated using the following formula (1), with the weight of the solid content after drying measured using the aqueous dispersion containing only abrasive particles according to the steps 1) to 4) being (B) and the weight of the solid content after drying measured using the polishing composition as a sample being (A).

[0030] Aggregation rate (%) = [(A) / (B)] × 100 (1)

[0031] (A) and (B) may contain trace amounts of additives, but without taking this into account, the value calculated by formula (1) is defined as the abrasive aggregation rate. More specifically, the measurement is performed by the method described in Examples.

[0032] The aggregation rate of the abrasive can be controlled by selecting the types and amounts of the inorganic salt and organic onium salt described below, filtering the polishing composition, adjusting the abrasive concentration, and the like.

[0033] In the polishing composition disclosed herein, the abrasive preferably has a negative zeta potential. Here, "zeta (ζ) potential" refers to the potential difference generated at the interface between a solid and a liquid in contact with each other when the two are in relative motion.

[0034] The zeta potential of the abrasive in the polishing composition disclosed herein is preferably -60 mV or more and -10 mV or less, more preferably -50 mV or more and -10 mV or less, more preferably -40 mV or more and -15 mV or less, and particularly preferably greater than -35 mV and -15 mV or less. By making the abrasive have a zeta potential in such a range, the polishing speed of the polishing object can be further improved. Here, the zeta potential of the abrasive in the polishing composition is a value measured by the method described in the examples. In addition, the zeta potential of the abrasive can be adjusted by the amount of anionic groups (particularly organic acid groups) possessed by the abrasive as described below, the pH of the polishing composition, etc.

[0035] In some embodiments of the present disclosure, the colloidal silica contained in the polishing composition is preferably anion-modified colloidal silica (anion-modified colloidal silica), more preferably colloidal silica with an organic acid immobilized on its surface. Colloidal silica with an organic acid immobilized on its surface tends to have a larger absolute value of the zeta potential in the polishing composition than conventional colloidal silica without an immobilized organic acid. Therefore, it is easy to adjust the zeta potential of the colloidal silica in the polishing composition to a negative value (e.g., in the range of -40 mV to -15 mV).

[0036] As colloidal silica having an organic acid immobilized on its surface, preferably, colloidal silica having organic acid groups such as carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups immobilized on its surface is used. Among these, colloidal silica having sulfonic acid or carboxylic acid immobilized on its surface is preferred from the viewpoint of ease of production, and colloidal silica having sulfonic acid immobilized on its surface is more preferred.

[0037] The immobilization of an organic acid on the surface of colloidal silica cannot be achieved simply by allowing colloidal silica and an organic acid to coexist. For example, if sulfonic acid, a type of organic acid, is to be immobilized on colloidal silica, it can be done by, for example, the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups," Chem. Commun. 246-247 (2003). Specifically, a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, can be coupled to colloidal silica, and then the thiol group can be oxidized using hydrogen peroxide to obtain colloidal silica with sulfonic acid immobilized on the surface (sulfonic acid-modified colloidal silica, sulfonic acid-modified colloidal silica).

[0038] Alternatively, carboxylic acid, a type of organic acid, can be immobilized on colloidal silica, 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, colloidal silica with carboxylic acid immobilized on its surface (carboxylic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating the resulting mixture with light.

[0039] The concentration (content) of abrasive particles is not particularly limited. It is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, more preferably 1% by mass or more, further more preferably exceeding 1% by mass, and particularly preferably 1.5% by mass or more relative to the gross mass of the polishing composition. In addition, the upper limit of the concentration (content) of abrasive particles is preferably 20% by mass or less, more preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less relative to the gross mass of the polishing composition. That is, the concentration (content) of abrasive particles 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, more preferably 1% by mass or more and 15% by mass or less, further more preferably exceeding 1% by mass and being 10% by mass or less, and particularly preferably 1.5% by mass or more and 5% by mass or less relative to the gross mass of the polishing composition. When it is such a range, it is possible to suppress cost and improve polishing speed. It should be noted that when the polishing composition includes more than two kinds of abrasive particles, the concentration (content) of abrasive particles refers to their total amount.

[0040] [Inorganic salts]

[0041] The polishing composition disclosed herein preferably contains an inorganic salt. The inorganic salt has the function of reducing scratches on the surface of the polished object (particularly silicon oxide). In addition, the inorganic salt has the function of increasing the electrical conductivity of the polishing composition, thereby further increasing the polishing speed of the polished object (particularly silicon oxide). Furthermore, the inorganic salt has the function of controlling the aggregation rate of the abrasive particles.

[0042] As inorganic salt, for example, the inorganic salt formed by the cation shown below and anion can be enumerated.As cation, for example, polyatomic ions, complex ions etc. such as alkali metal ions such as lithium ion, sodium ion, potassium ion, alkaline earth metal ions such as magnesium ion, calcium ion, strontium ion, ammonium ion can be enumerated.As anion, for example, halide ion (fluoride ion, chloride ion, bromide ion, iodide ion etc.), oxoacid ion (boric acid ion, carbonate ion, nitrate ion, nitrite ion, metasilicate ion, phosphate ion, monohydrogen phosphate ion, dihydrogen phosphate ion, phosphonic acid ion, monohydrogen phosphonic acid ion, phosphonic acid ion, sulfate ion, sulfonic acid ion, sulfite ion, thiosulfate ion, chromic acid ion, dichromic acid ion, permanganate ion etc.), thiocyanate ion, cyanate ion, sulfamic acid ion etc. can be enumerated.

[0043] More specific examples of inorganic salts include lithium salts such as lithium chloride, lithium bromide, lithium carbonate, lithium nitrate, and lithium thiocyanate; calcium salts such as calcium chloride, calcium bromide, calcium carbonate, calcium nitrate, and calcium thiocyanate; iron salts such as ferric nitrate and ferric 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; 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 may be used alone or in combination of two or more. In addition, the inorganic salts may be commercially available or synthesized.

[0044] Among these, from the viewpoint of further exerting the effects of the present disclosure, at least one of an ammonium salt of an inorganic acid and a potassium salt of an inorganic acid is preferred. 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 ammonium sulfate is more preferred.

[0045] The concentration (content) of the inorganic salt in the polishing composition is not particularly limited. However, in the case of a polishing composition used directly as a polishing liquid 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, more preferably 0.01 mass% (100 mass ppm) or more, further preferably 0.1 mass% (1000 mass ppm) or more, and particularly preferably 0.5 mass% (5000 mass ppm) or more, relative to the total mass of the polishing composition. 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, more preferably 1.5 mass% (15,000 mass ppm) or less, further preferably 1.3 mass% (13,000 mass ppm) or less, and particularly preferably 1.0 mass% (10,000 mass ppm) or less, relative to the total mass of the polishing composition.

[0046] That is, the concentration (content) of the inorganic salt relative to the total mass of the polishing composition is preferably from 0.005 mass% (50 mass ppm) to 2.0 mass% (20,000 mass ppm), more preferably from 0.01 mass% (100 mass ppm) to 1.5 mass% (15,000 mass ppm), further preferably from 0.1 mass% (1,000 mass ppm) to 1.3 mass% (13,000 mass ppm), and particularly preferably from 0.5 mass% (5,000 mass ppm) to 1.0 mass% (10,000 mass ppm).

[0047] In addition, when the polishing composition contains two or more inorganic salts, the concentration (content) of the inorganic salts refers to the total amount thereof.

[0048] [Organic onium salt]

[0049] The polishing composition disclosed herein preferably contains an organic onium salt. The organic onium salt has the function of reducing scratches on the surface of the polished object (particularly silicon oxide) after polishing. In addition, the organic onium salt has the function of controlling the aggregation rate of the abrasive particles.

[0050] The organic onium salt used in the present disclosure is preferably 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.

[0051] [NR 1 R 2 R 3 R 4 ] + A - Chemical formula 1

[0052] [PR 5 R 6 R 7 R 8 ] + X - Chemical formula 2

[0053] In the above Chemical Formula 1 and Chemical Formula 2,

[0054] R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms,

[0055] A - and X - Each is independently a monovalent anion.

[0056] When an organic onium salt having an alkyl group having 5 or more carbon atoms is used, scratches on the surface of the polished object may increase.

[0057] As 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 present invention include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl. From the viewpoint of further exerting the effects of the present disclosure, unsubstituted alkyl groups having 2 to 4 carbon atoms, such as ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl, are preferred.

[0058] As A in the above Chemical Formula 1 and Chemical Formula 2 - and X - Examples of monovalent anions used in the present invention are not particularly limited, and halide ions such as fluoride ions, chloride ions, bromide ions, and iodide ions; hydroxide ions; organic acid ions such as benzoate ions, etc. are suitable. Monovalent anions can be used alone or in combination of two or more. From the perspective of further exerting the effect of the present invention, A in the above chemical formula 1 and chemical formula 2 is preferably - and X - Preferably, hydroxide ions (OH - ).

[0059] More specific examples of the tetraalkylammonium salt represented by the above chemical formula 1 include 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, and tetra-tert-butylammonium fluoride; tetramethylammonium chloride, trimethylethylammonium chloride, dimethyldiethyl Ammonium 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, triethyl-n-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-propyl Ammonium iodide, tetra-n-propylammonium iodide, tetra-isopropylammonium 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, triethyl-n-propylammonium hydroxide, tetra-n-propylammonium hydroxide, tetraisopropylammonium hydroxide, tetra-n-butylammonium hydroxide, tetra-tert-butylammonium hydroxide;Tetramethylammonium benzoate, trimethylethylammonium benzoate, dimethyldiethylammonium benzoate, methyltriethylammonium benzoate, tetraethylammonium benzoate, trimethyln-propylammonium benzoate, trimethylisopropylammonium benzoate, dimethylethyln-propylammonium benzoate, dimethylethylisopropylammonium benzoate, methyldiethyln-propylammonium benzoate, methyldiethylisopropylammonium benzoate, triethylisopropylammonium benzoate, triethyln-propylammonium benzoate, tetra-n-propylammonium benzoate, tetraisopropylammonium benzoate, tetra-n-butylammonium benzoate, tetra-tert-butylammonium benzoate; etc.;

[0060] More specific examples of the tetraalkylphosphonium salts represented by the above chemical formula 2 include 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, triethyl-n-propylphosphonium fluoride, tetra-n-propylphosphonium fluoride, tetraisopropylphosphonium fluoride, tetra-n-butylphosphonium fluoride, and tetra-tert-butylphosphonium fluoride; tetramethylphosphonium chloride, trimethylethylphosphonium chloride, dimethyldiethylphosphonium fluoride, and tetra-tert-butylphosphonium fluoride; Phosphonium chloride, methyltriethylphosphonium chloride, tetraethylphosphonium chloride, trimethyl-n-propylphosphonium chloride, trimethyl-isopropylphosphonium chloride, dimethylethyl-n-propylphosphonium chloride, dimethylethyl-isopropylphosphonium chloride, methyldiethyl-n-propylphosphonium chloride, methyldiethyl-isopropylphosphonium chloride, triethyl-isopropylphosphonium chloride, triethyl-n-propylphosphonium chloride, tetra-n-propylphosphonium chloride, tetra-isopropylphosphonium chloride, tetra-n-butylphosphonium chloride, tetra-tert-butylphosphonium chloride; tetramethylphosphonium bromide, trimethylethylphosphonium bromide, dimethyldiethylphosphonium bromide, methyltriethylphosphonium bromide, tetraethylphosphonium bromide, trimethyl-n-propylphosphonium bromide, trimethyl-isopropylphosphonium bromide, dimethylethyl-n-propylphosphonium bromide, Dimethylethylisopropylphosphonium bromide, methyldiethyl-n-propylphosphonium bromide, methyldiethylisopropylphosphonium bromide, triethylisopropylphosphonium bromide, triethyl-n-propylphosphonium bromide, tetra-n-propylphosphonium bromide, tetraisopropylphosphonium bromide, tetra-n-butylphosphonium bromide, tetra-tert-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, triethyl-n-propylphosphonium iodide Phosphonium iodide, tetra-n-propylphosphonium iodide, tetra-isopropylphosphonium iodide, tetra-n-butylphosphonium iodide, tetra-tert-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, triethyl-n-propylphosphonium hydroxide, tetra-n-propylphosphonium hydroxide, tetra-isopropylphosphonium hydroxide, tetra-n-butylphosphonium hydroxide, tetra-tert-butylphosphonium hydroxide;Tetramethylphosphonium benzoate, trimethylethylphosphonium benzoate, dimethyldiethylphosphonium benzoate, methyltriethylphosphonium benzoate, tetraethylphosphonium benzoate, trimethyl-n-propylphosphonium benzoate, trimethylisopropylphosphonium benzoate, dimethylethyl-n-propylphosphonium benzoate, dimethylethylisopropylphosphonium benzoate, methyldiethyl-n-propylphosphonium benzoate, methyldiethylisopropylphosphonium benzoate, triethylisopropylphosphonium benzoate, triethyl-n-propylphosphonium benzoate, tetra-n-propylphosphonium benzoate, tetraisopropylphosphonium benzoate, tetra-n-butylphosphonium benzoate, tetra-tert-butylammonium benzoate; etc.;

[0061] These organic onium salts may be used alone or in combination of two or more. In addition, the organic onium salt may be a commercially available product or a synthesized product.

[0062] Among these organic onium salts, from the viewpoint of more easily exerting the effects of the present disclosure, the tetraalkylammonium salt represented by the above Chemical Formula 1 is preferred, and at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide is more preferred.

[0063] 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, more preferably 0.005 mass% (50 mass ppm) or more, further preferably 0.007 mass% (70 mass ppm) or more, and particularly preferably 0.01 mass% (100 mass ppm) or more. 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, more preferably 0.1 mass% (1000 mass ppm) or less, further preferably 0.07 mass% (700 mass ppm) or less, and particularly preferably 0.05 mass% (500 mass ppm) or less. That is, the concentration (content) of the organic onium salt in the polishing composition is preferably 0.001 mass% (10 mass ppm) to 0.3 mass% (3000 mass ppm), more preferably 0.005 mass% (50 mass ppm) to 0.1 mass% (1000 mass ppm), further preferably 0.007 mass% (70 mass ppm) to 0.07 mass% (700 mass ppm), and particularly preferably 0.01 mass% (100 mass ppm) to 0.05 mass% (500 mass ppm).

[0064] In addition, when the polishing composition contains two or more organic onium salts, the concentration (content) of the organic onium salts refers to the total amount thereof.

[0065] [pH and pH adjusters]

[0066] The pH of the polishing composition disclosed herein is not particularly limited, but is preferably 1.0 or higher, more preferably 1.5 or higher, and even more preferably 2.0 or higher. Furthermore, the pH is preferably 9.0 or lower, more preferably 7.0 or lower, even more preferably less than 7.0, even more preferably 5.0 or lower, and particularly preferably 3.5 or lower. Specifically, the pH of the polishing composition disclosed herein is preferably 1.0 or higher and 9.0 or lower, more preferably 1.5 or higher and 7.0 or lower, even more preferably 1.5 or higher and less than 7.0, even more preferably 1.5 or higher and 5.0 or lower, and particularly preferably 2.0 or higher and 3.5 or lower.

[0067] The inorganic salts and organic onium salts that may be included in the polishing composition of the present disclosure may function as pH adjusters to adjust the pH of the polishing composition. Depending on the target pH, additional pH adjusters may also be included. Such pH adjusters may be either acids or bases, and may be either inorganic or organic compounds. pH adjusters may be used alone or in combination of two or more.

[0068] 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.

[0069] 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.

[0070] The amount of the 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, using a pH meter, specifically by the method described in the Examples.

[0071] [Dispersion medium]

[0072] The polishing composition disclosed in the present invention includes a dispersion medium. Examples of dispersion media include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone, and mixtures thereof. Among them, water is preferred as the dispersion medium. That is, according to a more preferred embodiment of the present invention, the dispersion medium includes water. According to a more preferred embodiment of the present invention, the dispersion medium is substantially composed of water. It should be noted that the above-mentioned "substantially" means that as long as the purpose of the present invention can be achieved, a dispersion medium other than water may be included. More specifically, it is preferably composed of 90% by mass or more and 100% by mass or less of water and 0% by mass or more and 10% by mass or less of a dispersion medium other than water, and more preferably composed of 99% by mass or more and 100% by mass or less of water and 0% by mass or more and 1% by mass or less of a dispersion medium other than water. The most preferred dispersion medium is water.

[0073] From the viewpoint of not inhibiting the effects of the components contained in the polishing composition, the dispersion medium is preferably water containing as few impurities as possible. Specifically, pure water, ultrapure water, or distilled water obtained by removing impurity ions with an ion exchange resin and then removing foreign matter with a filter is more preferred.

[0074] [Electrical Conductivity of Polishing Composition]

[0075] The electrical conductivity (EC) of the polishing composition disclosed herein is not particularly limited, but is preferably 1 mS / cm or more, more preferably 2 mS / cm or more. In addition, the electrical conductivity (EC) of the polishing composition disclosed herein is preferably 25 mS / cm or less, more preferably 20 mS / cm or less. That is, the electrical conductivity (EC) of the polishing composition disclosed herein 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 such a range, the repulsion of the abrasive particles from each other can be appropriately adjusted to ensure stability. The electrical conductivity of the polishing composition can be adjusted by the type and amount of a pH adjusting agent, etc. In addition, the determination of electrical conductivity can be carried out according to the method described in the examples.

[0076] [Other ingredients]

[0077] The polishing composition disclosed herein may further include other ingredients, such as a water-soluble polymer, a complexing agent, a metal corrosion inhibitor, a preservative, a mildew inhibitor, a reducing agent, and a surfactant, as needed. Preferred ingredients, such as the preservative and mildew inhibitor, are described below. Oxidants are also described below.

[0078] (Preservatives and antifungal agents)

[0079] Examples of preservatives and antifungals that may be added to the polishing composition of the present disclosure include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, parabens, and phenoxyethanol. These preservatives and antifungals may be used alone or in combination of two or more.

[0080] (Oxidant)

[0081] The polishing composition disclosed herein is preferably substantially free of oxidizing agents. If the polishing composition contains an oxidizing agent, there is a concern that the surface of the polishing object will be oxidized to produce an oxide film, and the polishing time will be prolonged. As specific examples of the oxidizing agent mentioned here, hydrogen peroxide (H2O2), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. can be cited. It should be noted that the polishing composition being substantially free of oxidizing agents means that it is at least not intentionally contained. Therefore, the polishing composition that inevitably contains a trace amount of oxidizing agents derived from raw materials, preparation methods, etc. is included in the concept of the polishing composition being substantially free of oxidizing agents mentioned here. For example, the concentration (content) of the oxidizing agent in the polishing composition is preferably 0.01% by mass (100% by mass ppm) or less, more preferably less than 0.01% by mass (100% by mass ppm), and further preferably 0.005% by mass (50% by mass ppm) or less. The lower limit of the concentration (content) of the oxidizing agent is preferably 0% by mass or more, more preferably 0.0005% by mass (5% by mass ppm) or more.

[0082] [Form of Polishing Composition]

[0083] The grinding composition disclosed herein is typically supplied to the object to be ground in the form of a grinding liquid comprising the grinding composition, and is used for the grinding of the object to be ground. The grinding composition disclosed herein can, for example, be diluted (typically diluted with water) and used as a grinding liquid, or can be used directly as a grinding liquid. That is, the concept of the grinding composition disclosed herein includes a grinding composition (working slurry) supplied to the object to be ground and used for the grinding of the object to be ground, and a concentrated solution (stock solution of the working slurry) diluted for grinding. The concentration ratio of the above-mentioned concentrated solution can be, for example, set to more than 2 times and less than 100 times based on volume, and is usually more than 3 times and less than 50 times or so.

[0084] [Object to be polished]

[0085] The polishing object disclosed in 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), amorphous silicon doped with n-type or p-type impurities, silicon oxide, silicon nitride, silicon carbonitride (SiCN), metal, SiGe, carbon-containing materials, etc.

[0086] Examples of polishing objects containing silicon oxide include TEOS-type silicon oxide films (hereinafter also referred to as "TEOS" or "TEOS film") generated 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, RTO (Rapid Thermal Oxidation) films, etc.

[0087] Examples of the metal include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0088] Examples of the carbon-containing material include amorphous carbon, spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, and graphene.

[0089] As the object to be polished, a commercially available item may be used, or the object may be produced by a known method.

[0090] Among these, objects to be polished that contain silicon oxide are preferred. Therefore, according to a preferred embodiment of the present disclosure, the polishing composition is used for polishing an object to be polished that contains silicon oxide.

[0091] [Method for producing polishing composition]

[0092] The polishing composition of this embodiment can be prepared by, for example, stirring and mixing abrasive grains, an inorganic salt, an organic onium salt, and other additives as needed.

[0093] The temperature when mixing the components is not particularly limited, but is preferably 10° C. to 40° C., and heating may be performed to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is possible.

[0094] [Polishing Method and Semiconductor Substrate Manufacturing Method]

[0095] As described above, the polishing composition of this embodiment is particularly suitable for polishing an object containing silicon oxide. Therefore, the present disclosure provides a polishing method, which uses the polishing composition of this embodiment to polish an object containing silicon oxide. Furthermore, the present disclosure also provides a method for manufacturing a semiconductor substrate, which includes a step of polishing a semiconductor substrate containing silicon oxide using the polishing method described above.

[0096] As the polishing apparatus, a conventional polishing apparatus equipped with a holder for holding a substrate having an object to be polished, a motor with a variable rotation speed, and a polishing platen to which a polishing pad (polishing cloth) can be attached can be used.

[0097] As the polishing pad, any of ordinary nonwoven fabrics, polyurethane, and porous fluororesins can be used without particular limitation. The polishing pad is preferably provided with grooves for retaining the polishing liquid.

[0098] Regarding the grinding conditions, for example, the rotation speed of the grinding platform (platen) and the carrier (head) is preferably 10 rpm (0.17s -1 ) and above 500rpm(8.33s -1 The pressure applied to the substrate having the polishing object (polishing pressure) is preferably 0.5 psi (3.45 kPa) or more and 10 psi (68.9 kPa) or less.

[0099] The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the composition using a pump etc. is possible. The supply amount is also not limited, and it is preferred that the surface of the polishing pad is always covered with the polishing composition of the present disclosure.

[0100] The polishing composition disclosed herein may be a single-component type or a multi-component type, including a two-component type. Furthermore, the polishing composition disclosed herein can be prepared by diluting a stock solution of the polishing composition with a diluent such as water to, for example, a volume ratio of 2 to 100 times, typically 3 to 50 times, on a volume basis.

[0101] [Number of scratches]

[0102] As described above, the polishing composition of the present disclosure can reduce scratches on the surface of an object to be polished.

[0103] In the present disclosure, the fewer the number of scratches on the surface of the polished object, the more preferred. Specifically, a scratch number of 25 or less is practical, preferably 20 or less, more preferably 15 or less, more preferably 10 or less, and particularly preferably less than 10. It should be noted that in this specification, the scratch number is the value measured by the method described in the Examples.

[0104] Although the embodiments of the present disclosure have been described in detail, this is illustrative and exemplary rather than restrictive, and it should be understood that the scope of the present disclosure should be interpreted in accordance with the appended claims.

[0105] This disclosure includes the following aspects and configurations:

[0106] 1. A polishing composition comprising abrasive particles having an average primary particle size of 1 nm to 150 nm and a dispersion medium, wherein the abrasive particles have an aggregation rate of 40% to less than 75%.

[0107] 2. The polishing composition according to 1. above, wherein the abrasive grains have an aggregation rate of 40% to 55%.

[0108] 3. The polishing composition according to 1. or 2. above, further comprising an inorganic salt.

[0109] 4. The polishing composition according to 3. above, wherein the inorganic salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate.

[0110] 5. The polishing composition according to any one of 1. to 4. above, further comprising an organic onium salt.

[0111] 6. The polishing composition according to 5. above, wherein the organic onium salt is 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.

[0112] [NR 1 R 2 R 3 R 4 ] + A - Chemical formula 1

[0113] [PR 5 R 6 R 7 R 8 ] + X - Chemical formula 2

[0114] In the above Chemical Formula 1 and Chemical Formula 2,

[0115] R 1 ~R 8 are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms,

[0116] A - and X - Each is independently a monovalent anion.

[0117] 7. The polishing composition according to 6. above, wherein the organic onium salt is a tetraalkylammonium salt represented by Chemical Formula 1.

[0118] 8. The polishing composition according to 6. or 7. above, wherein A in the above Chemical Formula 1 and Chemical Formula 2 is - and X - It is a hydroxide ion.

[0119] 9. The polishing composition according to any one of 6. to 8. above, wherein the tetraalkylammonium salt represented by Chemical Formula 1 is at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide.

[0120] 10. The polishing composition according to any one of 1. to 9. above, wherein the abrasive in the polishing composition has a negative zeta potential.

[0121] 11. The polishing composition according to 10. above, wherein the abrasive grains are anion-modified colloidal silica.

[0122] 12. The polishing composition according to any one of 1. to 11. above, wherein the pH is less than 7.0.

[0123] 13. The polishing composition according to any one of 1. to 12. above, which is used for polishing an object to be polished containing silicon oxide.

[0124] 14. A polishing method comprising the step of polishing an object to be polished containing silicon oxide using the polishing composition according to any one of 1. to 13. above.

[0125] 15. A method for producing a semiconductor substrate, comprising the step of polishing a semiconductor substrate made of silicon oxide by the polishing method according to 14.

[0126] [Example]

[0127] The present disclosure is described in more detail using the following examples and comparative examples. However, the scope of protection of the present disclosure is not limited to the following examples. It should be noted that, unless otherwise specified, "%" and "parts" refer to "mass %" and "mass parts" respectively. In addition, in the following examples, unless otherwise specified, the operation is carried out under the conditions of room temperature (above 20°C and below 25°C) / relative humidity above 40%RH and below 50%RH. It should be noted that the various physical properties are measured as follows.

[0128] <Average Primary Particle Size and Average Secondary Particle Size of Abrasive>

[0129] The average primary particle size of the abrasive was calculated based on the specific surface area of ​​the abrasive and the density of the abrasive measured by the BET method using a "Flow Sorb II 2300" manufactured by Micromeritics. The average secondary particle size of the abrasive was measured as the volume average particle size (volume-based arithmetic mean particle size; Mv) using a dynamic light scattering particle size and particle size distribution device UPA-UT151 (manufactured by Nikkiso Co., Ltd.).

[0130] <Zeta Potential of Abrasive Particles>

[0131] The zeta potential of the abrasive in the polishing composition was measured using a zeta potential measuring apparatus manufactured by Otsuka Electronics Co., Ltd. (device name: "ELS-Z2").

[0132] <pH of Polishing Composition>

[0133] The pH of the polishing composition was measured using a pH meter (manufactured by HORIBA, Ltd., model: LAQUA).

[0134] <Electrical Conductivity of Polishing Composition>

[0135] The electrical conductivity (EC) of the polishing composition was measured using a tabletop conductivity meter (manufactured by HORIBA, Ltd., model: DS-71LAQUA (registered trademark)).

[0136] <Manufacturing of Sulfonic Acid-Immobilized Colloidal Silica>

[0137] Sulfonic acid-modified colloidal silica as abrasive grains was obtained according to the following procedures.

[0138] (Process for preparing raw material colloidal silica dispersion (unmodified silica particles))

[0139] In a flask, 4080 g of methanol, 610 g of water, and 168 g of a 29% by mass ammonia solution were mixed. A mixture of 135 g of methanol and 508 g of tetramethoxysilane (TMOS) was added dropwise over 25 minutes, maintaining the solution temperature at 20°C. The mixture was then heated and concentrated to a pH of 7 or higher, replacing the water, yielding 1000 g of a 19.5% by mass silica sol (average primary particle size: 34 nm).

[0140] (Surface modification process)

[0141] Next, 1.2 g of 3-mercaptopropyltrimethoxysilane (MPS, silane coupling agent, product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.), separately mixed with 4.8 g of methanol, was added dropwise at a flow rate of 1 mL / min to 1000 g of the silica sol obtained above (195 g in terms of silica solid content). (Silane coupling agent concentration relative to the total mass of the silica solid content: 0.6 mass %). The mixture was then heated, brought to a boil, and then replaced with pure water over 3 hours.

[0142] The reaction mixture was then left to cool overnight, and 0.0343 g of 30% by mass hydrogen peroxide (3 mol per 1 mol of the silane coupling agent) was added to bring it to a boil again. The mixture was then replaced with pure water over 2 hours and cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silica.

[0143] (Example 1)

[0144] <Preparation of Polishing Composition>

[0145] Sulfonic acid-modified colloidal silica (surface-modified silica 1, average primary particle size: 34 nm) was added to water as a dispersion medium to a final concentration of 2% by mass as abrasive. Furthermore, ammonium sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as an inorganic salt to a final concentration of 6000 ppm by mass, and tetraethylammonium hydroxide (TEAH, manufactured by Tokyo Chemical Industry Co., Ltd.) was added as an organic onium salt to a final concentration of 150 ppm by mass. 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 with nitric acid to complete Polishing Composition 1.

[0146] (Example 2)

[0147] Polishing composition 2 was prepared in the same manner as in Example 1 except that the amount of tetraethylammonium hydroxide added was changed to 100 ppm by mass.

[0148] (Example 3)

[0149] Polishing composition 3 was prepared in the same manner as in Example 1 except that the amount of tetraethylammonium hydroxide added was changed to 1000 ppm by mass.

[0150] (Comparative Example 1)

[0151] A polishing composition for comparison 1 was prepared in the same manner as in Example 1 except that ammonium sulfate and tetraethylammonium hydroxide were not used.

[0152] (Comparative Example 2)

[0153] A comparative polishing composition 2 was prepared in the same manner as in Example 1 except that tetraethylammonium hydroxide was not used.

[0154] (Comparative Example 3)

[0155] A comparative polishing composition 3 was prepared in the same manner as in Example 1, except that n-pentylamine was added to the polishing composition to a final concentration of 2000 ppm by mass instead of tetraethylammonium hydroxide.

[0156] The compositions of the polishing compositions of the Examples and Comparative Examples are shown in Table 1. In Table 1, "-" indicates that the component was not used.

[0157] [Table 1]

[0158]

[0159] [evaluate]

[0160] <Agglomeration Rate of Abrasive Particles>

[0161] The abrasive particle aggregation rate is measured by the following method:

[0162] 1) Weigh 30.0 g of the polishing composition as a sample into a polypropylene container (Centrifuge Tubes) manufactured by Beckman Coulter, Inc., and tightly close the upper lid.

[0163] 2) Using a "Centrifuge Avanti HP-30I" manufactured by Beckman Coulter, Inc., the centrifuge was continuously operated at 25°C and 15,000 rpm for 15 minutes:

[0164] 3) Through centrifugal separation, the water in the upper part of the container is separated from the abrasive in the lower part, and the abrasive is compressed and settled to the lower part of the container (this is called filter cake):

[0165] 4) The settled cake was dried at 200° C. for 24 hours using “ELECTRIC MUFFLE FURNACES KM-420” manufactured by Advantec Co., Ltd., and the weight of the obtained solid content was measured:

[0166] 5) The aggregation rate is calculated using the following formula: (B) is the weight of the solid content after drying, measured using the aqueous dispersion of the abrasive in the steps 1) to 4) above, and (A) is the weight of the solid content after drying, measured using the polishing composition as a sample.

[0167] Aggregation rate (%) = [(A) / (B)] × 100

[0168] It should be noted that (A) and (B) may contain a trace amount of additives, but this is not taken into consideration and the value calculated by formula (1) is used as the abrasive aggregation rate.

[0169] <Polishing Speed>

[0170] As the object to be polished, a surface having a thickness of A silicon wafer (200 mm, blank wafer) having a TEOS-type silicon oxide (SiO 2 ) film was polished under the following conditions.

[0171] (Grinding equipment and grinding conditions)

[0172] Polishing equipment: Applied Materials Inc. 200mm CMP single-side polishing equipment Mirra

[0173] Polishing pad: NITTA DuPont, Inc. hard polyurethane pad IC1010

[0174] Grinding pressure: 2.5 psi (1 psi = 6894.76 Pa)

[0175] Grinding platform speed: 47rpm

[0176] Grinding head (carrier) speed: 43 rpm

[0177] Supply of polishing composition: overflow

[0178] Polishing composition supply rate: 200 mL / min

[0179] Grinding time: 60 seconds.

[0180] The thickness of the polished object before and after polishing was measured using an optical film thickness meter (ASET-f5x: manufactured by KLA-Tencor Corporation). The film thickness was measured using an optical film thickness meter (ASET-f5x: manufactured by KLA-Tencor Corporation).

[0181] The polishing speed of the object to be polished is calculated by dividing the difference in film thickness before and after polishing [(thickness before polishing) - (thickness after polishing)] by the polishing time.

[0182] <Number of scratches>

[0183] For the number of scratches on the surface of the ground silicon oxide film, a wafer inspection device "Surfscan (registered trademark) SP2" manufactured by KLA-Tencor Corporation is used to measure the coordinates of the entire surface of both sides of the grinding object (except for the outer periphery of 2 mm), and all measured coordinates are observed with Review-SEM (RS-6000, Hitachi High-Technologies Corporation), thereby measuring the number of scratches. It should be noted that for scratches, damage to the surface of the substrate having a depth of more than 10 nm and less than 100 nm, a width of more than 100 nm and less than 500 nm, and a length of more than 80 nm is counted as scratches. The fewer the number of scratches, the more preferred. When the number of scratches is less than 25, it is practical, preferably less than 20, more preferably less than 15, more preferably less than 10, and particularly preferably less than 10.

[0184] The evaluation results of the abrasive aggregation rate, polishing rate, and number of scratches are shown in Table 2 below.

[0185] [Table 2]

[0186] [Table 2]

[0187]

[0188] As is clear from Table 2, the polishing compositions of the Examples provide a high polishing rate for silicon oxide films and reduce scratches on the surface of the polished silicon oxide films. It is also clear that the polishing compositions of Comparative Examples 1 and 2, which have high abrasive aggregation rates, increase scratches on the surface of the silicon oxide films. Furthermore, the polishing composition of Comparative Example 3, which has a low abrasive aggregation rate, reduces the polishing rate for silicon oxide films.

[0189] This application is based on Japanese Patent Application No. 2024-036950 filed on March 11, 2024, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A polishing composition comprising abrasive particles having an average primary particle size of 1 nm to 150 nm and a dispersion medium, The abrasive grains have an aggregation rate of 40% or more and less than 75%.

2. The polishing composition according to claim 1, wherein The abrasive grains have an aggregation rate of 40% or more and 55% or less. The polishing composition according to claim 1 , further comprising an inorganic salt.

4. The polishing composition according to claim 3, wherein The inorganic salt is at least one selected from the group consisting of ammonium sulfate, ammonium nitrate, ammonium carbonate, potassium sulfate, potassium nitrate, and potassium carbonate. The polishing composition according to claim 1 , further comprising an organic onium salt.

6. The polishing composition according to claim 5, wherein The organic onium salt is 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, [NR 1 R 2 R 3 R 4 ] + A - Chemical formula 1 [PR 5 R 6 R 7 R 8 ] + X - Chemical formula 2 In the 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 - Each is independently a monovalent anion.

7. The polishing composition according to claim 6, wherein The organic onium salt is a tetraalkylammonium salt represented by Chemical Formula 1.

8. The polishing composition according to claim 6, wherein A in the chemical formula 1 and the chemical formula 2 - and X - It is a hydroxide ion.

9. The polishing composition according to claim 6, wherein The tetraalkylammonium salt represented by Chemical Formula 1 is at least one selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetra-n-butylammonium hydroxide.

10. The polishing composition according to claim 1, wherein The abrasive in the polishing composition has a negative zeta potential.

11. The polishing composition according to claim 10, wherein The abrasive particles are anion-modified colloidal silica. The polishing composition according to claim 1 , wherein the pH thereof is less than 7.

0. 13 . The polishing composition according to claim 1 , which is used for polishing an object to be polished containing silicon oxide. 14 . A polishing method comprising the step of polishing an object to be polished containing silicon oxide using the polishing composition according to claim 1 . 15 . A method for producing a semiconductor substrate, comprising the step of polishing a semiconductor substrate made of silicon oxide by the polishing method according to claim 14 .

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