WO2025205562A1 - Polishing composition - Google Patents

Abstract

The present invention provides a polishing composition with which it is possible to achieve an excellent polishing removal rate on an object to be polished through improving the solubility of potassium permanganate in the composition for polishing. A polishing composition disclosed herein includes potassium permanganate as an oxidizing agent, a metal salt A, and water. Here, the metal salt A is a salt of a cation a containing a metal having a hydrated metal ion pKa of 7.0 or more (excluding alkaline earth metal cations) and an anion, and a permanganate of the cation a has the same or larger solubility in water at 20°C than potassium permanganate. Also, the content of the potassium permanganate is 5.0 wt% or more, and the ratio (CA/CK) of the concentration CA [mM] of the metal salt A to the concentration CK [mM] of the potassium permanganate is larger than 0.1.

Description

polishing composition

The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2024-53232, filed March 28, 2024, the entire contents of which are incorporated herein by reference.

Abrasive compositions are used to polish the surfaces of materials such as metals, semi-metals, non-metals, and their oxides. For example, surfaces made of compound semiconductor materials such as silicon carbide, boron carbide, tungsten carbide, silicon nitride, titanium nitride, and gallium nitride are processed by polishing (lapping) using diamond abrasive grains supplied between the surface and a polishing table. However, lapping using diamond abrasive grains is prone to defects and distortion due to the generation and persistence of scratches and dents. Therefore, polishing (polishing) using a polishing pad and abrasive composition after lapping with diamond abrasive grains, or instead of lapping, is being considered. Patent Document 1 is an example of a document disclosing this type of prior art.

Chinese Patent Application Publication No. 101684393

In general, from the standpoint of manufacturing efficiency and cost-effectiveness, it is desirable that the polishing removal rate when polishing an object be sufficiently high for practical use. However, when polishing an object made of a high-hardness material such as silicon carbide, it is not as easy to improve the polishing removal rate compared to polishing an object with a low hardness. In order to improve the polishing removal rate, in addition to using abrasive grains that exert a physical polishing action, it is also effective to chemically modify the surface to be polished to make it weaker. In anticipation of this effect, polishing compositions sometimes contain oxidizing agents. For example, Patent Document 1 addresses improving the polishing removal rate by polishing tungsten or copper with a polishing composition containing abrasive grains, water, and various oxidizing agents such as potassium permanganate.

Increasing the concentration of the oxidizing agent contained in the polishing composition is thought to be effective in further improving the polishing removal rate. However, potassium permanganate, the oxidizing agent conventionally used in this field, does not have very high solubility in water, so there have been limits to how much the concentration of potassium permanganate in polishing compositions can be increased.

The present invention was made in consideration of these circumstances, and aims to provide a polishing composition that can exhibit an excellent polishing removal rate for the object to be polished by improving the solubility of potassium permanganate in the polishing composition.

The inventors have discovered that by further adding a specific metal salt A to a polishing composition containing potassium permanganate, the solubility of potassium permanganate is improved, and the concentration (content) of potassium permanganate in the polishing composition can be increased.

The polishing composition provided herein contains potassium permanganate as an oxidizing agent, a metal salt A, and water, wherein the metal salt A satisfies the following conditions (i) and (ii):
(i) A salt of a cation a containing a metal whose hydrated metal ion has a pKa of 7.0 or more (excluding alkaline earth metal cations) and an anion.
(ii) The permanganate of the above cation a has the same or higher solubility in water at 20° C. than potassium permanganate.
The polishing composition contains 5.0 wt % or more of potassium permanganate, and the ratio (CA/CK) of the concentration (molar concentration) CA [mM] of the metal salt A to the concentration (molar concentration) CK [mM] of the potassium permanganate in the polishing composition is greater than 0.1.
According to this configuration, the concentration (or "content"; the same applies below) of potassium permanganate in the polishing composition can be increased, and a polishing composition can be obtained that can improve the polishing removal rate for the object to be polished.

In some embodiments, the metal salt A is a salt of the cation a and an anion selected from nitrate ions, fluoride ions, and bicarbonate ions. Use of such a metal salt A makes it easier to increase the concentration of potassium permanganate in the polishing composition.

In some embodiments, the polishing composition further contains metal salt B, which is a salt of cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0 and an anion. By using metal salt B, pH fluctuations in the polishing composition are suppressed during polishing of the object to be polished, making it easier to stabilize the polishing removal rate. In some preferred embodiments, metal salt B is a salt of cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0 and a nitrate ion.

In some embodiments, the polishing composition further contains a metal salt C selected from alkaline earth metal salts. Use of the metal salt C tends to improve the polishing removal rate. In some preferred embodiments, the metal salt C is a salt of an alkaline earth metal cation and a nitrate ion.

In some embodiments, the polishing composition further contains abrasive grains. The use of abrasive grains can improve the polishing removal rate.

In some embodiments, the pH of the polishing composition is 1.0 or greater and less than 6.0. In this pH range, the polishing composition disclosed herein tends to exhibit a high polishing removal rate.

The polishing composition disclosed herein is used, for example, for polishing materials with a Vickers hardness of 1500 Hv or greater. The effects of the technology disclosed herein can be favorably exhibited when polishing such high-hardness materials. In some embodiments, the material with a Vickers hardness of 1500 Hv or greater is a non-oxide (i.e., a compound that is not an oxide). When polishing non-oxide materials, the polishing composition disclosed herein is likely to favorably exhibit its effect of improving the polishing removal rate.

The polishing composition disclosed herein is used, for example, for polishing silicon carbide. The effects of the technology disclosed herein can be effectively achieved when polishing silicon carbide.

The specification also provides a method for polishing an object to be polished. The polishing method includes polishing the object to be polished using any of the polishing compositions disclosed herein. This polishing method can increase the polishing removal rate, even when polishing an object made of a high-hardness material. This increases the productivity of the object (polished object, for example, a compound semiconductor substrate such as a silicon carbide substrate) obtained through polishing using the polishing method.

The following describes preferred embodiments of the present invention. It should be noted that matters necessary for implementing the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

<Polishing composition>
(oxidizing agent)
The polishing composition disclosed herein contains an oxidizing agent. The oxidizing agent is effective in reducing the hardness of the material to be polished (e.g., a hard non-oxide material such as silicon carbide) and weakening the material. Therefore, the oxidizing agent can be effective in improving the removal rate when polishing the material to be polished. In this specification, the oxidizing agent refers to a substance that oxidizes other substances, and refers to a substance other than metal salt A, metal salt B, and metal salt C described below.

The polishing composition disclosed herein contains potassium permanganate as an oxidizing agent. Generally, the solubility of potassium permanganate in water is limited, and it is not easy to include it in a polishing composition at a high concentration. However, the configuration of the polishing composition disclosed herein improves the solubility of potassium permanganate in water, and the potassium permanganate content in the polishing composition tends to increase.

In some embodiments, the content of potassium permanganate in the polishing composition is 5.0% by weight or more. Increasing the concentration of potassium permanganate in the polishing composition promotes the effect of chemically altering (oxidizing) the surface to be polished by potassium permanganate, thereby improving the polishing removal rate when polishing the object to be polished. To facilitate achieving a higher polishing removal rate, in some embodiments, the content of potassium permanganate is preferably 5.2% by weight or more (e.g., 5.5% by weight or more), more preferably 6% by weight or more, even more preferably 6.5% by weight or more, and may be 6.8% by weight or more, 7% by weight or more, or 7.5% by weight or more. While there is no particular upper limit for the content of potassium permanganate, from the viewpoint of ensuring the content of components other than potassium permanganate (e.g., abrasive grains), it is appropriate to set it to approximately 15% by weight or less, and it may be 12.5% by weight or less, 10% by weight or less, 9% by weight or less, or 8% by weight or less. Reducing the potassium permanganate content can also be advantageous in terms of reducing the occurrence of defects caused by potassium that may remain after polishing.

The polishing composition disclosed herein may or may not further contain an oxidizing agent other than potassium permanganate (hereinafter also referred to as "other oxidizing agent"). Specific examples of compounds that can be selected as other oxidizing agents include peroxides such as hydrogen peroxide; permanganates such as permanganic acid and its salts, such as permanganates other than potassium permanganate (e.g., sodium permanganate); periodic acids such as periodic acid and its salts, such as sodium periodate and potassium periodate; iodic acids such as iodic acid and its salt, such as ammonium iodate; bromic acids such as bromic acid and its salt, such as potassium bromate; ferric acids such as ferric acid and its salt, such as potassium ferrate; chromic acids and dichromates such as perchromic acid, chromic acid and its salt, such as potassium chromate; dichromic acid and its salt, such as potassium dichromate; vanadic acid and its salt, such as ammonium vanadate, sodium vanadate, and vanadic acid. Examples of other oxidizing agents include vanadates such as potassium; ruthenic acids such as perruthenic acid or its salts; molybdic acids such as permolybdic acid, molybdic acid, and their salts such as ammonium molybdate and disodium molybdate; rhenic acids such as perrhenic acid or its salts; tungstic acids such as pertungstic acid, tungstic acid, and their salts such as disodium tungstate; persulfates such as peroxomonosulfuric acid and peroxodisulfuric acid, and their salts such as ammonium persulfate and potassium persulfate; chloric acids and perchloric acids such as chloric acid and its salts, perchloric acid, and its salt potassium perchlorate; osmic acids such as perosmic acid and osmic acid; selenic acids such as perselenic acid and selenic acid; and cerium ammonium nitrate. These compounds may be used alone or in combination. In some embodiments, the other oxidizing agent is preferably an inorganic compound from the viewpoint of the performance stability of the polishing composition (e.g., prevention of deterioration due to long-term storage).

The polishing composition disclosed herein may contain, as another oxidizing agent, a complex metal oxide, which is a salt of a cation selected from alkali metal ions and an anion selected from transition metal oxoacid ions. The complex metal oxide is effective in reducing the hardness of high-hardness materials, such as silicon carbide, and thereby weakening the materials. The complex metal oxides may be used singly or in combination of two or more. Specific examples of the transition metal oxoacid ions in the complex transition metal oxide include permanganate ions, ferrate ions, chromate ions, dichromate ions, vanadate ions, ruthenate ions, molybdate ions, rhenate ions, and tungstate ions. Of these, oxoacids of fourth-period transition metal elements in the periodic table are more preferred. Suitable examples of fourth-period transition metal elements in the periodic table include Fe, Mn, Cr, V, and Ti. Among these, Fe, Mn, and Cr are more preferred, with Mn being even more preferred. The alkali metal ion in the complex transition metal oxide is preferably Na ⁺ . In some embodiments, other oxidizing agents may include sodium permanganate.

In addition, when the compound used as the oxidizing agent is a salt (e.g., permanganate), the compound may be present in the polishing composition in an ionic state.

(Metal Salt A)
The polishing composition disclosed herein contains a metal salt A, which is a salt that satisfies the following conditions (i) and (ii):
(i) A salt of a cation a containing a metal whose hydrated metal ion has a pKa of 7.0 or more, and an anion, provided that alkaline earth metal cations are not included in the above cation a.
(ii) The permanganate of the above cation a has the same or higher solubility in water at 20° C. than potassium permanganate.

In this way, metal salt A, which is a salt of an anion and cation a containing a metal whose hydrated metal ion has a pKa of 7.0 or higher, and in which the solubility of the permanganate of said cation a in water at 20°C is the same as or greater than that of potassium permanganate, tends to improve the solubility of potassium permanganate when used together with potassium permanganate. Metal salt A can be used alone or in combination of two or more types.

Examples of cation a capable of forming a permanganate having the same or greater solubility in water as potassium permanganate include, but are not limited to, Na ⁺ , Li ⁺ , Zn ²⁺ , K ⁺ , etc. Metal salt A, which is a salt of an anion and cation a capable of forming a permanganate having the same or greater solubility in water as potassium permanganate, tends to improve the solubility of potassium permanganate when contained in water together with potassium permanganate.

In some embodiments, the pKa of the hydrated metal ion of the metal contained in cation a is 7.5 or greater, and may be 8.0 or greater, 8.5 or greater, 9.0 or greater, 9.5 or greater, 10.0 or greater, 10.5 or greater, 11.0 or greater, 11.5 or greater, 12.0 or greater, 12.5 or greater, 13.0 or greater, or 13.5 or greater.

There is no particular upper limit to the pKa of the hydrated metal ion of the metal contained in cation a. In some embodiments, the pKa of the hydrated metal ion of the metal contained in cation a is suitably approximately 15 or less, and may be, for example, 14.8 or less, or 14.5 or less.

Examples of metal cations whose hydrated metal ions have a pKa of 7.0 or higher include, but are not limited to, K ⁺ (whose hydrated metal ion has a pKa of 14.5), Na ⁺ (whose hydrated metal ion has a pKa of 14.2), Li + (whose hydrated metal ion has a pKa of 13.6), and Zn ²⁺ (whose hydrated metal ion has a pKa of 9.0), as described in "Inorganic Chemistry, GARY WULFBERG, University Science Books, 2000, p. ⁵⁹ , Table 2.2 "Hydrolysis Constants for Metal Cations"".

Metal salt A may be a salt of a monovalent cation and an anion, a salt of a divalent or higher polyvalent cation and an anion, or a combination of these salts. In some preferred embodiments, metal salt A is one or more salts selected from salts of a monovalent cation and an anion and salts of a divalent cation and an anion. In some embodiments, metal salt A is a salt of a monovalent cation and an anion.

The reason why the addition of metal salt A improves the solubility of potassium permanganate used in conjunction with metal salt A in water is not particularly limited, but can be thought of as follows, for example. In other words, in an environment where potassium permanganate and metal salt A are both dissolved in water, ion exchange (cation exchange) occurs between potassium ions derived from the potassium permanganate and cation a derived from metal salt A. Here, if the solubility of cation a in permanganate is high in water, it is thought that the dissolution of potassium permanganate is promoted as the above-mentioned ion exchange progresses.

In some embodiments, metal salt A may be an inorganic acid salt or an organic acid salt. Examples of inorganic acid salts include salts of hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid; halides such as chlorides, bromides, and fluorides; nitric acid, sulfuric acid, carbonic acid, bicarbonate (hydrogencarbonate), silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include salts of carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycine acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; organic sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; and organic phosphoric acids such as ethylphosphoric acid. Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and bicarbonate are preferred, and salts of nitric acid are more preferred due to their oxidizing properties.

Metal salt A is preferably a water-soluble salt. By using a water-soluble metal salt A, a good surface with few defects such as scratches can be efficiently formed.

From the viewpoint of better improving the solubility of potassium permanganate, the ratio (CA/CK) of the concentration of metal salt A in the polishing composition (when multiple metal salts A are contained, their total concentration) CA [mM] to the concentration of potassium permanganate CK [mM] is preferably greater than 0.1. From the viewpoint of further improving the content of potassium permanganate, in some embodiments, CA/CK may be 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.8 or more. There are no particular limitations on the upper limit of CA/CK, but from the viewpoint of ensuring the content of potassium permanganate as an oxidizing agent, it is appropriate that it be approximately 50 or less, and it may also be 10 or less, 7 or less, 5 or less, 4 or less, 3 or less, 2.5 or less, 2 or less, or 1 or less. At this molar concentration ratio (CA/CK) of metal salt A to potassium permanganate, the effect of metal salt A in improving the solubility of potassium permanganate can be favorably exhibited.

The concentration (content) of metal salt A in the polishing composition is not particularly limited. In some embodiments, from the viewpoint of suitably increasing the concentration of potassium permanganate in the polishing composition, the concentration of metal salt A in the polishing composition (if multiple metal salts A are contained, their total concentration) is preferably 120 mM or more (e.g., 130 mM or more), more preferably 150 mM or more, and even more preferably 190 mM or more. In some embodiments, the concentration of metal salt A in the polishing composition may be 250 mM or more, 400 mM or more, 500 mM or more, 600 mM or more, 700 mM or more, or 800 mM or more. The upper limit of the concentration of metal salt A in the polishing composition is not particularly limited. From the viewpoint of ensuring the content of other active ingredients such as an oxidizing agent and suppressing a decrease in the polishing removal rate, the concentration of metal salt A in the polishing composition (when multiple metal salts A are contained, their total concentration) is typically 3000 mM or less, and may be 2500 mM or less. In some embodiments, the concentration of metal salt A in the polishing composition may be 2000 mM or less, 1500 mM or less, 1000 mM or less, 800 mM or less, 600 mM or less, 500 mM or less, or 300 mM or less.

(Metal Salt B)
The polishing composition disclosed herein may further comprise a metal salt B, which is a salt composed of a cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0 and an anion. Such a salt of a cation and an anion, the metal salt B, forms a hydrated metal cation in water, and the hydrated metal cation acts as a pH buffer because the protons on the coordinated water are in adsorption/desorption equilibrium, and thus is likely to suppress deterioration of the performance of the polishing composition over time. From this viewpoint, a salt of a cation containing a metal whose hydrated metal ion has a pKa of, for example, less than 7.0 or 6.0 or less, and an anion can be preferably used as the metal salt B. Examples of cations containing metals whose hydrated metal ions have a pKa of 6.0 or less include, but are not limited to, Al ³⁺ (whose hydrated metal ion has a pKa of 5.0), Ga ³⁺ (whose hydrated metal ion has a pKa of 2.6), In ³⁺ (whose hydrated metal ion has a pKa of 4.0), ZrO ²⁺ and Zr ⁴⁺ (whose hydrated metal ion has a pKa of -0.3), as described in the aforementioned "Inorganic Chemistry, GARY WULFBERG, University Science Books, 2000, p. 59, Table 2.2 "Hydrolysis Constants for Metal Cations". Metal salt B can be used singly or in combination of two or more.

In some preferred embodiments, metal salt B is a salt selected from salts of a cation containing a poor metal, i.e., a metal belonging to Groups 13 to 16 of the periodic table, and an anion. The poor metal is preferably one belonging to Groups 13 to 15 of the periodic table, more preferably one belonging to Groups 13 to 14, and also preferably one belonging to Periods 3 to 5 of the periodic table, more preferably one belonging to Periods 3 and 4, with a poor metal belonging to Period 3, i.e., aluminum, being particularly preferred.

The type of salt in the metal salt B is not particularly limited, and may be an inorganic acid salt or an organic acid salt. Examples of inorganic acid salts include salts of hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, as well as salts of nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include salts of carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycine acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; organic sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; and organic phosphoric acids such as ethylphosphoric acid. Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid are preferred, and salts of hydrochloric acid and nitric acid are more preferred. In some embodiments, the metal salt B is preferably a salt of a cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0 and a nitrate ion (NO ₃ ⁻ ). The technology disclosed herein can be preferably implemented, for example, in an embodiment using, as metal salt B, a salt of a cation selected from Al ³⁺ , Ga ³⁺ , In ³⁺ , ZrO ²⁺ , and Zr ⁴⁺ and a nitrate ion (NO ₃ ⁻ ) or a chloride ion (Cl ⁻ ).

Metal salt B is preferably a compound that is not oxidized by an oxidizing agent. From this perspective, by appropriately selecting the oxidizing agent and metal salt B, it is possible to prevent deactivation of the oxidizing agent due to oxidation of metal salt B by the oxidizing agent, and to suppress deterioration of the performance of the polishing composition over time (e.g., a decrease in the polishing removal rate). From this perspective, examples of preferred metal salts B include aluminum nitrate and aluminum chloride. Of these, aluminum nitrate is a particularly preferred example of metal salt B, as nitrates have oxidizing properties. Metal salt B can improve the polishing removal rate by being used in combination with the aforementioned metal salt A or the later-described metal salt C.

Metal salt B is preferably a water-soluble salt. By using a water-soluble metal salt B, a good surface with few defects such as scratches can be efficiently formed.

When the polishing composition contains metal salt B, the concentration (content) of metal salt B in the polishing composition is not particularly limited and can be appropriately set so as to achieve the desired effect depending on the purpose and manner of use of the polishing composition. The concentration of metal salt B (if multiple metal salts B are contained, their total concentration) may be, for example, approximately 1000 mM or less (i.e., 1 mol/L or less), 500 mM or less, or 300 mM or less. In some embodiments, the concentration of metal salt B is suitably 200 mM or less, preferably 100 mM or less, more preferably 50 mM or less, and may be 30 mM or less, 20 mM or less, or 10 mM or less. When the polishing composition contains metal salt B, the lower limit of the concentration of metal salt B may be, for example, 0.1 mM or more; from the perspective of properly exerting the effects of use of metal salt B, it is advantageous to set it to 1 mM or more, preferably 5 mM or more, more preferably 10 mM or more (e.g., 15 mM or more), and may be 18 mM or more, 20 mM or more, or 30 mM or more.

When the polishing composition contains a metal salt B, the ratio (CB/Wx) of the concentration of the metal salt B (when a plurality of metal salts B are contained, the total concentration thereof) CB [mM] to the content of the oxidizing agent (typically potassium permanganate) (when a plurality of oxidizing agents are contained, the total content thereof) Wx [wt %] in the polishing composition (CB/Wx) is usually 0 or more, preferably 0.01 or more, more preferably 0.025 or more, and may be 0.05 or more, 0.1 or more, or 0.5 or more. In some embodiments, CB/Wx may be, for example, 0.8 or more, 1.0 or more, 2.0 or more, 2.5 or more, or 3.0 or more. The upper limit of CB/Wx is not particularly limited, but is suitably approximately 500 or less, and may be 300 or less, preferably 200 or less, more preferably 100 or less, and even more preferably 50 or less. In some preferred embodiments, CB/Wx may be 25 or less, 20 or less, 10 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.
In the above "CB/Wx,""CB" represents the numerical value when the concentration (content) of metal salt B in the polishing composition is expressed in units of "mM," and "Wx" represents the numerical value when the content of oxidizing agent in the polishing composition is expressed in units of "wt %," and both CB and Wx are dimensionless numbers.

When the polishing composition contains metal salt B, the relationship between the concentration CA [mM] of metal salt A and the concentration CB [mM] of metal salt B in the polishing composition is not particularly limited. For example, CA/CB can be in the range of 0.1 to 2000. From the viewpoint of improving the polishing removal rate, in some embodiments, CA/CB is suitably approximately 0.1 or greater, and may be 0.5 or greater, or 10 or greater. Furthermore, CA/CB is suitably approximately 2000 or less, and may be 1000 or less, 500 or less, 300 or less, 200 or less, or 100 or less.

(Metal Salt C)
In some preferred embodiments, the polishing composition may contain a metal salt C selected from alkaline earth metal salts. As the metal salt C, one type of alkaline earth metal salt may be used alone, or two or more types of alkaline earth metal salts may be used in combination. The use of the metal salt C tends to improve the polishing removal rate. The metal salt C preferably contains one or more of Mg, Ca, Sr, and Ba as an element belonging to the alkaline earth metals. Of these, either Ca or Sr is preferred, and Ca is more preferred.

The type of salt in metal salt C is not particularly limited and may be an inorganic or organic acid salt. Examples of inorganic acid salts include salts of hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, as well as salts of nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include salts of carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycine acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; organic sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; and organic phosphoric acids such as ethylphosphoric acid. Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid are preferred, and salts of nitric acid are more preferred due to their oxidizing properties. The technology disclosed herein can be preferably implemented, for example, in an embodiment using an alkaline earth metal nitrate or chloride as metal salt C.

Specific examples of alkaline earth metal salts that may be selected for metal salt C include chlorides such as magnesium chloride, calcium chloride, strontium chloride, and barium chloride; bromides such as magnesium bromide; fluorides such as magnesium fluoride, calcium fluoride, strontium fluoride, and barium fluoride; nitrates such as magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate; sulfates such as magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate; carbonates such as magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate; carboxylates such as calcium acetate, strontium acetate, calcium benzoate, and calcium citrate; etc.

The metal salt C is preferably a water-soluble salt. By using a water-soluble metal salt C, a good surface with few defects such as scratches can be efficiently formed.
In addition, metal salt C is preferably a compound that is not oxidized by an oxidizing agent.From this viewpoint, by appropriately selecting an oxidizing agent and metal salt C, it is possible to prevent the metal salt C from being oxidized by the oxidizing agent, thereby preventing the deactivation of the oxidizing agent, and suppress the performance deterioration of the polishing composition over time (for example, the decrease in polishing removal rate, etc.).From this viewpoint, calcium nitrate can be mentioned as a preferred metal salt C.

When the polishing composition contains metal salt C, the concentration (content) of metal salt C in the polishing composition is not particularly limited and can be appropriately set so as to achieve the desired effect depending on the purpose and manner of use of the polishing composition. The concentration of metal salt C may be, for example, approximately 1000 mM or less (i.e., 1 mol/L or less), 500 mM or less, or 300 mM or less. In some embodiments, the concentration of metal salt C is suitably 200 mM or less, preferably 100 mM or less, more preferably 50 mM or less, and may be 30 mM or less, 20 mM or less, or 10 mM or less. The lower limit of the concentration of metal salt C may be, for example, 0.1 mM or more, and from the perspective of appropriately exerting the effects of use of metal salt C, it is preferably 0.5 mM or more, more preferably 1 mM or more, and may be 2.5 mM or more, 5 mM or more, 10 mM or more, 20 mM or more, or 30 mM or more.

When the polishing composition contains a metal salt C, the ratio (CC/Wx) of the concentration of the metal salt C (if a plurality of metal salts C are contained, the total concentration thereof) CC [mM] to the content of the oxidizing agent (if a plurality of oxidizing agents are contained, the total content thereof) Wx [wt%] in the polishing composition is usually 0 or more, preferably 0.01 or more, more preferably 0.025 or more, and may be 0.05 or more, 0.1 or more, or 0.5 or more. In some embodiments, CC/Wx may be, for example, 0.8 or more, 1.0 or more, 2.0 or more, 2.5 or more, or 3.0 or more. The upper limit of CC/Wx is not particularly limited, but can be, for example, 300 or less, suitably approximately 100 or less, preferably 75 or less, more preferably 50 or less, and even more preferably 25 or less. In some preferred embodiments, CC/Wx may be 20 or less, 10 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.
In the above "CC/Wx,""CC" represents the numerical value when the concentration (content) of metal salt C in the polishing composition is expressed in units of "mM," and "Wx" represents the numerical value when the content of oxidizing agent in the polishing composition is expressed in units of "wt %," and both CC and Wx are dimensionless numbers.

In some preferred embodiments, the polishing composition may contain a combination of metal salt B and metal salt C. In some preferred embodiments when a combination of metal salt B and metal salt C is contained, metal salt B and metal salt C have the same anion species. The anion species common to metal salt B and metal salt C may be, for example, nitric acid, hydrochloric acid, phosphoric acid, etc. From the viewpoint of obtaining a higher effect, a polishing composition in which metal salt B and metal salt C are all nitrates is particularly preferred. In some preferred embodiments, metal salt A, metal salt B, and metal salt C have the same anion species. In some embodiments, metal salt A, metal salt B, and metal salt C are all nitrates.

When the polishing composition contains a combination of metal salt B and metal salt C, the relationship between the concentration CB [mM] of metal salt B and the concentration CC [mM] of metal salt C in the polishing composition is not particularly limited and can be set so that the effect of using them in combination is appropriately exhibited. For example, CB/CC may be in the range of 0.001 to 1000. From the viewpoint of improving the polishing removal rate, in some embodiments, CB/CC is suitably approximately 0.01 or more, and preferably 0.05 or more (e.g., 0.1 or more). Furthermore, CB/CC is suitably approximately 100 or less, preferably 50 or less, and may be 30 or less, and more preferably 25 or less (e.g., 10 or less).

When the polishing composition contains metal salt C, the relationship between the concentration CA [mM] of metal salt A and the concentration CC [mM] of metal salt C in the polishing composition is not particularly limited. For example, CA/CC can be in the range of 0.1 to 2000. From the viewpoint of improving the polishing removal rate, in some embodiments, CA/CB is suitably approximately 0.1 or more, and may be 0.5 or more (e.g., 5 or more). Furthermore, CA/CB is suitably approximately 2000 or less, and may be 1000 or less, 500 or less, 200 or less, or 100 or less.

(abrasive grains)
In some embodiments of the presently disclosed technology, the polishing composition contains abrasive grains. A polishing composition containing abrasive grains can achieve a higher polishing removal rate by exerting a primarily mechanical polishing action due to the abrasive grains in addition to a primarily chemical polishing action due to an oxidizing agent or the like.

The material and properties of the abrasive grains are not particularly limited. For example, the abrasive grains can be inorganic particles, organic particles, or organic-inorganic composite particles. Examples include abrasive grains essentially composed of oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. One type of abrasive grain may be used alone, or two or more types may be used in combination. Among these, oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, zirconium oxide particles, manganese dioxide particles, and iron oxide particles are preferred because they can form a good surface. Among these, silica particles, alumina particles, zirconium oxide particles, chromium oxide particles, and iron oxide particles are more preferred, with silica particles and alumina particles being even more preferred, and alumina particles being particularly preferred. In embodiments using alumina particles as abrasive grains, the technology disclosed herein can be applied to suitably achieve an improved polishing removal rate.

In this specification, the terms "consisting essentially of X" or "consisting essentially of X" in relation to the composition of abrasive grains mean that the proportion of X in the abrasive grains (purity of X) is 90% or more by weight. Furthermore, the proportion of X in the abrasive grains is preferably 95% or more, more preferably 97% or more, even more preferably 98% or more, for example, 99% or more.

The average primary particle size of the abrasive grains is not particularly limited. From the viewpoint of improving the polishing removal rate, the average primary particle size of the abrasive grains can be, for example, 5 nm or more, suitably 10 nm or more, preferably 20 nm or more, or even 30 nm or more. From the viewpoint of further improving the polishing removal rate, in some embodiments, the average primary particle size of the abrasive grains may be 50 nm or more, 80 nm or more, 150 nm or more, 250 nm or more, or 350 nm or more. Furthermore, from the viewpoint of surface quality after polishing, the average primary particle size of the abrasive grains can be, for example, 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less, or may be 750 nm or less, or may be 500 nm or less. From the viewpoint of further improving surface quality after polishing, in some embodiments, the average primary particle size of the abrasive grains may be 350 nm or less, 180 nm or less, 85 nm or less, or 50 nm or less.

In this specification, the average primary particle size refers to the particle size (BET particle size) calculated from the specific surface area (BET value) measured by the BET method using the formula: average primary particle size (nm) = 6000/(true density (g/ ^cm3 ) x BET value ( ^m2 /g)). The specific surface area can be measured, for example, using a surface area measuring device manufactured by Micromeritics, product name "Flow Sorb II 2300".

The average secondary particle diameter of the abrasive grains may be, for example, 10 nm or more, and from the viewpoint of easily increasing the polishing removal rate, it is preferably 50 nm or more, more preferably 100 nm or more, and may be 250 nm or more, or 400 nm or more. The upper limit of the average secondary particle diameter of the abrasive grains is appropriately set to approximately 10 μm or less, from the viewpoint of ensuring a sufficient number per unit weight. Furthermore, from the viewpoint of surface quality after polishing, the average secondary particle diameter is preferably 5 μm or less, more preferably 3 μm or less, for example 1 μm or less. From the viewpoint of further improving surface quality after polishing, in some embodiments, the average secondary particle diameter of the abrasive grains may be 600 nm or less, 300 nm or less, 170 nm or less, or 100 nm or less.

The average secondary particle diameter of abrasive grains can be measured as the volume average particle diameter (arithmetic mean diameter by volume; Mv) for particles less than 500 nm using dynamic light scattering with, for example, a Nikkiso Co., Ltd. model "UPA-UT151." Furthermore, for particles 500 nm or larger, the volume average particle diameter can be measured using, for example, the pore electrical resistance method with a Beckman Coulter Co., Ltd. model "Multisizer 3."

When using alumina particles (alumina abrasive grains) as abrasive grains, they can be appropriately selected from various known alumina particles. Examples of such known alumina particles include α-alumina and intermediate alumina. Intermediate alumina is a general term for alumina particles other than α-alumina, and specific examples include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and χ-alumina. Fumed alumina (typically fine alumina particles produced by high-temperature calcination of alumina salts) may also be used, based on classification by production method. Furthermore, alumina known as colloidal alumina or alumina sol (e.g., alumina hydrates such as boehmite) is also included as an example of the known alumina particles. From the standpoint of processability, it is preferable to use α-alumina. The alumina abrasive grains in the technology disclosed herein may contain one type of such alumina particle alone or a combination of two or more types.

When using alumina particles as abrasive grains, it is generally advantageous to have a higher proportion of alumina particles in the total abrasive grains used. For example, the proportion of alumina particles in the total abrasive grains is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more, and may be substantially 100% by weight.

The particle size of the alumina abrasive grains is not particularly limited and can be selected so as to achieve the desired polishing effect. From the perspective of improving the polishing removal rate, the average primary particle diameter of the alumina abrasive grains is preferably 50 nm or more, more preferably 80 nm or more, and may be 150 nm or more, 250 nm or more, or 300 nm or more. There is no particular upper limit to the average primary particle diameter of the alumina abrasive grains, but from the perspective of surface quality after polishing, it is appropriate to set it to approximately 5 μm or less. From the perspective of further improving surface quality after polishing, it is preferably 3 μm or less, more preferably 1 μm or less, and may be 750 nm or less, 500 nm or less, 400 nm or less, or 350 nm or less.

When alumina particles are used as abrasive grains, the polishing composition disclosed herein may further contain abrasive grains made of a material other than alumina (hereinafter also referred to as non-alumina abrasive grains) to the extent that the effects of the present invention are not impaired. Examples of such non-alumina abrasive grains include abrasive grains essentially composed of any of the following: oxide particles such as silica particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide particles, zinc oxide particles, and iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate.

The content of the non-alumina abrasive grains is suitably, for example, 30% by weight or less of the total weight of the abrasive grains contained in the polishing composition, preferably 20% by weight or less, and more preferably 10% by weight or less.

In another preferred embodiment of the technology disclosed herein, the polishing composition contains silica particles (silica abrasive grains) as abrasive grains. The silica abrasive grains can be appropriately selected from various known silica particles. Examples of such known silica particles include colloidal silica and dry-process silica. Of these, the use of colloidal silica is preferred. Silica abrasive grains containing colloidal silica can suitably achieve good surface precision.

The shape (external shape) of the silica abrasive grains may be spherical or non-spherical. Specific examples of non-spherical silica abrasive grains include peanut-shaped (i.e., peanut shell-shaped), cocoon-shaped, confetti-shaped, and rugby ball-shaped. In the technology disclosed herein, the silica abrasive grains may be in the form of primary particles, or in the form of secondary particles formed by aggregation of multiple primary particles. Furthermore, silica abrasive grains in the form of primary particles and silica abrasive grains in the form of secondary particles may be present together. In one preferred embodiment, at least a portion of the silica abrasive grains are contained in the polishing composition in the form of secondary particles.

Silica abrasive grains with an average primary particle diameter of greater than 5 nm are preferably used. From the viewpoint of polishing efficiency, etc., the average primary particle diameter of the silica abrasive grains is preferably 15 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, and particularly preferably 30 nm or more. There is no particular upper limit to the average primary particle diameter of the silica abrasive grains, but it is appropriate to set it to approximately 120 nm or less, preferably 100 nm or less, and more preferably 85 nm or less. For example, from the viewpoint of achieving a higher level of both polishing efficiency and surface quality, silica abrasive grains with a BET diameter of 12 nm or more and 80 nm or less are preferred, and silica abrasive grains with a BET diameter of 15 nm or more and 75 nm or less are preferred.

The average secondary particle diameter of the silica abrasive grains is not particularly limited, but from the viewpoint of polishing efficiency, etc., it is preferably 20 nm or more, more preferably 50 nm or more, and even more preferably 70 nm or more. Furthermore, from the viewpoint of obtaining a higher-quality surface, the average secondary particle diameter of the silica abrasive grains is appropriately 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less, even more preferably 130 nm or less, and particularly preferably 110 nm or less (e.g., 100 nm or less).

The true specific gravity (true density) of the silica particles is preferably 1.5 or higher, more preferably 1.6 or higher, and even more preferably 1.7 or higher. Increasing the true specific gravity of silica particles tends to increase their physical polishing ability. There is no particular upper limit for the true specific gravity of silica particles, but it is typically 2.3 or lower, for example, 2.2 or lower, 2.0 or lower, or 1.9 or lower. The true specific gravity of silica particles can be measured using a liquid displacement method using ethanol as the displacement liquid.

The shape (external shape) of the silica particles is preferably spherical. Although not particularly limited, the average value of the particle's long axis/short axis ratio (average aspect ratio) is, in principle, 1.00 or more, and from the viewpoint of improving the polishing removal rate, it may be, for example, 1.05 or more, or 1.10 or more. Furthermore, the average aspect ratio of the particles is suitably 3.0 or less, and may be 2.0 or less. From the viewpoint of improving the smoothness of the polished surface and reducing scratches, the average aspect ratio of the particles is preferably 1.50 or less, and may be 1.30 or less, or 1.20 or less.

The shape (external shape) and average aspect ratio of particles can be determined, for example, by observation using an electron microscope. A specific procedure for determining the average aspect ratio involves, for example, using a scanning electron microscope (SEM) to extract the shapes of a predetermined number of particles (e.g., 200 particles). The smallest rectangle circumscribing the shape of each extracted particle is then drawn. Then, for the rectangle drawn for each particle shape, the length of its long side (long diameter value) is divided by the length of its short side (short diameter value) to calculate the long diameter/short diameter ratio (aspect ratio). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

In embodiments in which the polishing composition contains silica abrasive grains, the polishing composition may further contain abrasive grains made of a material other than silica (hereinafter also referred to as non-silica abrasive grains). Examples of particles that make up such non-silica abrasive grains include particles that are essentially composed of any of the following: oxide particles such as alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide particles, zinc oxide particles, and iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; etc.

The content of the non-silica abrasive grains is suitably, for example, 30% by weight or less of the total weight of the abrasive grains contained in the polishing composition, preferably 20% by weight or less, and more preferably 10% by weight or less.

From the viewpoint of surface quality after polishing, the content of abrasive grains (e.g., alumina abrasive grains) in the polishing composition disclosed herein is suitably less than 10 wt%, advantageously less than 6 wt%, preferably less than 3 wt%, more preferably less than 2 wt%, and may be less than 1.5 wt%, 1.3 wt% or less, 1.2 wt% or less, 1.1 wt% or less, or 1.0 wt% or less. In some embodiments, the content of abrasive grains in the polishing composition may be 0.5 wt% or less or less than 0.5 wt%, 0.1 wt% or less or less than 0.1 wt%, 0.05 wt% or less or less than 0.05 wt%, or 0.04 wt% or less or less than 0.04 wt%. The lower limit of the abrasive grain content is not particularly limited and may be, for example, 0.000001 wt% or more (i.e., 0.01 ppm or more). In order to enhance the effectiveness of the abrasive grains, in some embodiments, the content of abrasive grains in the polishing composition may be 0.00001 wt % or more, 0.0001 wt % or more, 0.001 wt % or more, 0.002 wt % or more, or 0.005 wt % or more. In some embodiments, the content of abrasive grains in the polishing composition may be 0.01 wt % or more, 0.02 wt % or more, 0.03 wt % or more, more than 0.1 wt %, more than 0.3 wt %, 0.5 wt % or more, or 0.8 wt % or more. When the polishing composition disclosed herein contains multiple types of abrasive grains, the content of abrasive grains in the polishing composition refers to the total content of the multiple types of abrasive grains.

The polishing composition disclosed herein preferably contains substantially no diamond particles as particles. Diamond particles have a high hardness, which can be a limiting factor in improving smoothness. Furthermore, diamond particles are generally expensive, so they are not an advantageous material in terms of cost-effectiveness. From a practical standpoint, it is preferable to have less reliance on expensive materials such as diamond particles. Here, "particles substantially free of diamond particles" means that the proportion of diamond particles in the total particles is 1% by weight or less, more preferably 0.5% by weight or less, and typically 0.1% by weight or less, and includes cases where the proportion of diamond particles is 0% by weight. In such an embodiment, the effects of applying the present invention can be preferably exerted.

In a polishing composition containing abrasive grains, the relationship between the content of the oxidizing agent (typically potassium permanganate) and the content of the abrasive grains is not particularly limited and can be appropriately set to achieve the desired effect depending on the purpose and mode of use. The ratio of the content of the oxidizing agent (if a plurality of oxidizing agents are included, the total content) Wx [wt %] to the content of the abrasive grains (if a plurality of abrasive grains are included, the total content) Wp [wt %], i.e., Wx/Wp, can be, for example, approximately 0.01 or more, suitably 0.025 or more, may be 0.05 or more, 0.1 or more, 0.2 or more, or 1 or more, advantageously 1.4 or more, preferably 2.5 or more, and more preferably 3.5 or more. The larger Wx/Wp, the greater the contribution of chemical polishing to the contribution of mechanical polishing tends to be. In some embodiments, Wx/Wp may be 5 or more, 6 or more, even 6.5 or more, 7 or more, 8 or more, or 9 or more. In some preferred embodiments, Wx/Wp may be, for example, approximately 10 or more, 30 or more, 50 or more, 70 or more, 90 or more, 120 or more, 150 or more, or 180 or more. The upper limit of Wx/Wp is not particularly limited, but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 5000 or less, 1500 or less, 1000 or less, 800 or less, 400 or less, 250 or less, 100 or less, 80 or less, or 40 or less. In some embodiments, Wx/Wp may be 30 or less, 20 or less, or 10 or less.
In the above "Wx/Wp,""Wx" represents the numerical portion when the content of oxidizing agent in the polishing composition is expressed in units of "weight percent," and "Wp" represents the numerical portion when the content of abrasive grains in the polishing composition is expressed in units of "weight percent," and both Wx and Wp are dimensionless numbers.

In the polishing composition containing abrasive grains and metal salt A, the relationship between the concentration of metal salt A and the content of abrasive grains is not particularly limited, and can be appropriately set so as to achieve the desired effect according to the purpose of use and the mode of use.The ratio of the concentration CA of metal salt A (if a plurality of metal salts A are contained, the total concentration thereof) [mM] to the content Wp of abrasive grains (if a plurality of abrasive grains are contained, the total content thereof) [wt%], that is, CA/Wp, can be, for example, 0.5 or more, suitably 1 or more, may be 2 or more, preferably 10 or more, more preferably 30 or more, may be 50 or more, or may be 100 or more.When CA/Wp is larger, the contribution of chemical polishing to the contribution of mechanical polishing tends to be larger.In some embodiments, CA/Wp may be 120 or more, may be 150 or more, or may be 180 or more. In some other embodiments, CA/Wp may be 500 or more, 1000 or more, 1500 or more, 2000 or more, or 2500 or more. The upper limit of CA/Wp is not particularly limited, but from the viewpoint of storage stability of the polishing composition, it can be, for example, about 300,000 or less, 100,000 or less, 50,000 or less, 25,000 or less, or 10,000 or less. In some embodiments, CA/Wp may be 1,000 or less, 500 or less, 400 or less, or 300 or less.
In the above "CA/Wp,""CA" represents the numerical portion when the concentration of metal salt A in the polishing composition is expressed in units of "mM," and "Wp" represents the numerical portion when the content of abrasive grains in the polishing composition is expressed in units of "weight %," and both Wp and CA are dimensionless numbers.

In a polishing composition containing abrasive grains and metal salt B, the relationship between the concentration of metal salt B and the content of abrasive grains is not particularly limited, and can be appropriately set so as to achieve the desired effect depending on the purpose and mode of use. The ratio of the concentration of metal salt B CB (if a plurality of metal salts B are contained, the total concentration thereof) [mM] to the content of abrasive grains Wp (if a plurality of abrasive grains are contained, the total content thereof) [wt%], i.e., CB/Wp, can be, for example, 0.05 or more, suitably 0.1 or more, may be 0.2 or more, preferably 1 or more, more preferably 3 or more, may be 5 or more, or may be 10 or more. The larger CB/Wp, the greater the contribution of chemical polishing to the contribution of mechanical polishing tends to be. In some embodiments, CB/Wp may be 12 or more, 15 or more, or 18 or more. The upper limit of CB/Wp is not particularly limited, but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 30,000 or less, or may be 10,000 or less, 5,000 or less, 2,500 or less, or 1,000 or less. In some embodiments, CB/Wp may be 100 or less, 50 or less, 40 or less, or 30 or less.
In the above "CB/Wp,""CB" represents the numerical portion when the concentration of metal salt B in the polishing composition is expressed in units of "mM," and "Wp" represents the numerical portion when the content of abrasive grains in the polishing composition is expressed in units of "weight %," and both Wp and CB are dimensionless numbers.

In a polishing composition containing abrasive grains and metal salt C, the relationship between the concentration of metal salt C and the content of abrasive grains is not particularly limited, and can be appropriately set so as to achieve the desired effect depending on the purpose and mode of use. The ratio of the concentration CC of metal salt C (if a plurality of metal salts C are contained, the total concentration thereof) [mM] to the content Wp of abrasive grains (if a plurality of abrasive grains are contained, the total content thereof) [wt%], i.e., CC/Wp, can be, for example, 0.05 or more, suitably 0.1 or more, may be 0.2 or more, preferably 1 or more, more preferably 3 or more, may be 5 or more, or may be 10 or more. The larger CC/Wp, the greater the contribution of chemical polishing to the contribution of mechanical polishing tends to be. In some embodiments, CC/Wp may be 20 or more, 50 or more, 100 or more, or 300 or more. The upper limit of CC/Wp is not particularly limited, but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 30,000 or less, or may be 5,000 or less, or may be 2,500 or less. In some embodiments, CC/Wp may be 1,000 or less, 800 or less, or 600 or less.
In the above "CC/Wp,""CC" represents the numerical portion when the concentration of metal salt B in the polishing composition is expressed in units of "mM," and "Wp" represents the numerical portion when the content of abrasive grains in the polishing composition is expressed in units of "wt %," and both CC and Wp are dimensionless numbers.

The polishing composition disclosed herein can also be preferably implemented in an embodiment that does not contain abrasive grains. Even in such an embodiment, the use of potassium permanganate and metal salt A as oxidizing agents effectively improves the solubility of potassium permanganate and the polishing removal rate.

(water)
The polishing composition disclosed herein contains water. Ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used as the water. The polishing composition disclosed herein may further contain, as necessary, an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water. Generally, it is appropriate that 90% by volume or more of the solvent contained in the polishing composition is water, preferably 95% by volume or more, and more preferably 99 to 100% by volume.

(acid)
The polishing composition may contain an acid as needed for purposes such as adjusting the pH or improving the polishing removal rate. Both inorganic and organic acids can be used as the acid. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of organic acids include aliphatic carboxylic acids such as formic acid, acetic acid, and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acids, and organic phosphonic acids. These acids can be used alone or in combination of two or more. When an acid is used, the amount used is not particularly limited and can be determined according to the purpose of use (e.g., pH adjustment). Alternatively, some embodiments of the polishing composition disclosed herein may be substantially acid-free.

(Basic Compound)
The polishing composition may contain a basic compound as needed for purposes such as adjusting pH or improving the polishing removal rate. Here, the term "basic compound" refers to a compound that, when added to a polishing composition, increases the pH of the composition. Examples of basic compounds include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates and bicarbonates such as ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate; ammonia; quaternary ammonium compounds, such as quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; and amines, phosphates, hydrogen phosphates, and organic acid salts. The basic compound may be used alone or in combination with two or more. When a basic compound is used, its amount is not particularly limited and can be adjusted depending on the purpose of use (e.g., pH adjustment). Alternatively, some embodiments of the polishing composition disclosed herein may be substantially free of a basic compound.

(Other ingredients)
The polishing composition disclosed herein may further contain, as needed, known additives that can be used in polishing compositions (for example, polishing compositions used for polishing high-hardness materials such as silicon carbide), such as chelating agents, thickeners, dispersants, surface protective agents, wetting agents, surfactants, rust inhibitors, preservatives, and antifungal agents, within the scope that does not impair the effects of the present invention. The content of the above additives may be appropriately set depending on the purpose of their addition, and detailed explanations are omitted because they do not characterize the present invention.

(pH)
The pH of the polishing composition is suitably about 1 to 12. When the pH is in the above range, a practical polishing removal rate is likely to be achieved. In some embodiments, the pH may be 12.0 or less, 11.0 or less, 10.0 or less, 9.0 or less, less than 9.0, 8.0 or less, less than 8.0, 7.0 or less, less than 7.0, or 6.0 or less. From the viewpoint of improving the polishing removal rate, in some embodiments, the pH of the polishing composition is preferably less than 6.0, 5.0 or less, less than 5.0, 4.0 or less, or less than 4.0. The pH may be, for example, 1.0 or more, 1.5 or more, 2.0 or more, or 2.5 or more.

The method for preparing the polishing composition disclosed herein is not particularly limited. For example, the components contained in the polishing composition may be mixed using a well-known mixing device such as a blade mixer, ultrasonic disperser, or homomixer. The manner in which these components are mixed is not particularly limited; for example, all components may be mixed at once, or they may be mixed in an appropriately set order.

The polishing composition disclosed herein may be a single-component type or a multi-component type, such as a two-component type. For example, the polishing composition may be configured such that Part A, which contains some of the components (e.g., components other than water), and Part B, which contains the remaining components, are mixed together and used to polish an object to be polished. The multi-component polishing composition may further contain Part C in addition to Part A and Part B. These may be stored separately before use, for example, and mixed at the time of use to prepare a single-component polishing composition. When mixing, water for dilution may also be added. In a preferred embodiment, the multi-component polishing composition disclosed herein contains an oxidizing agent and water in Part A, and a metal salt (e.g., metal salt A, metal salt B, metal salt C) and water in Part B. This embodiment improves the storage stability of the polishing composition. The optional Part C may or may not contain abrasive grains.

<Object to be polished>
The object to be polished with the polishing composition disclosed herein is not particularly limited. For example, the polishing composition disclosed herein can be used to polish a substrate having a surface composed of a compound semiconductor material, i.e., a compound semiconductor substrate. The constituent material of the compound semiconductor substrate is not particularly limited and may be, for example, II-VI compound semiconductors such as cadmium telluride, zinc selenide, cadmium sulfide, cadmium mercury telluride, or zinc cadmium telluride; III-V compound semiconductors such as gallium nitride, gallium arsenide, gallium phosphide, indium phosphide, aluminum gallium arsenide, gallium indium arsenide, indium gallium nitride arsenide, or aluminum gallium indium phosphide; or IV-IV compound semiconductors such as silicon carbide or germanium silicide. The object to be polished may be composed of multiple materials selected from these. In a preferred embodiment, the polishing composition disclosed herein can be used to polish a substrate having a surface composed of a non-oxide (i.e., non-oxide) chemical semiconductor material. When polishing a substrate having a surface made of a non-oxide chemical semiconductor material, the polishing-accelerating effect of the oxidizing agent contained in the polishing composition disclosed herein is likely to be favorably exhibited.

The polishing composition disclosed herein can be preferably used for polishing a workpiece surface having a Vickers hardness of, for example, 500 Hv or more. The Vickers hardness is preferably 700 Hv or more, for example, 1000 Hv or more, or 1500 Hv or more. The Vickers hardness of the material to be polished may be 1800 Hv or more, 2000 Hv or more, or 2200 Hv or more. There is no particular upper limit to the Vickers hardness of the workpiece surface, and it may be, for example, approximately 7000 Hv or less, 5000 Hv or less, or 3000 Hv or less. In this specification, Vickers hardness can be measured based on JIS R 1610:2003. The international standard corresponding to the above JIS standard is ISO 14705:2000.

Materials with a Vickers hardness of 1500 Hv or greater include silicon carbide, silicon nitride, titanium nitride, and gallium nitride. The object to be polished in the technology disclosed herein can have a single crystal surface of the above materials, which is mechanically and chemically stable. In particular, the surface of the object to be polished is preferably composed of either silicon carbide or gallium nitride, and more preferably silicon carbide. Silicon carbide is expected to be a compound semiconductor substrate material with low power loss and excellent heat resistance, and the practical benefit of improving productivity by increasing the polishing removal rate is particularly great. The technology disclosed herein can be particularly preferably applied to polishing the single crystal surface of silicon carbide.

<Polishing method>
The polishing composition disclosed herein can be used to polish an object to be polished, for example, in an embodiment including the following steps.
That is, a polishing liquid (slurry) containing any of the polishing compositions disclosed herein is prepared.Preparing the polishing liquid may include adjusting the concentration (e.g., diluting), adjusting the pH, etc. of the polishing composition to prepare the polishing liquid.Alternatively, the polishing composition may be used as is as the polishing liquid.In addition, in the case of a multi-agent polishing composition, preparing the polishing liquid may include mixing the agents, diluting one or more agents before the mixing, or diluting the mixture after the mixing.
The polishing liquid is then supplied to the object to be polished, and polishing is carried out by a conventional method used by those skilled in the art. For example, the object to be polished is placed in a general polishing device, and the polishing liquid is supplied to the surface of the object to be polished through the polishing pad of the polishing device. Typically, while the polishing liquid is continuously supplied, the polishing pad is pressed against the surface of the object to be polished, and the two are moved relative to each other (e.g., rotated). Polishing of the object to be polished is completed through this polishing process.

Note that the above-mentioned contents (concentrations) and content (concentration) ratios for each component that may be contained in the polishing composition in the technology disclosed herein typically refer to the contents and content ratios in the polishing composition when it is actually supplied to the object to be polished (i.e., at the point of use), and can therefore be interpreted as the contents and content ratios in the polishing liquid.

This specification provides a polishing method for polishing an object to be polished (typically, a material to be polished), and a method for manufacturing an object to be polished using the polishing method. The polishing method is characterized by including a step of polishing the object to be polished using the polishing composition disclosed herein. A preferred embodiment of the polishing method includes a step of performing preliminary polishing (preliminary polishing step) and a step of performing finish polishing (finish polishing step). In a typical embodiment, the preliminary polishing step is a polishing step that is located immediately before the finish polishing step. The preliminary polishing step may be a single-stage polishing step, or may be a multi-stage polishing step consisting of two or more stages. Furthermore, the finish polishing step referred to here is a step of performing finish polishing on an object to be polished that has been pre-polished, and is the polishing step that is located last (i.e., furthest downstream) among polishing steps that are performed using a polishing slurry containing abrasive grains. In such a polishing method that includes a preliminary polishing step and a finish polishing step, the polishing composition disclosed herein may be used in the preliminary polishing step, the finish polishing step, or both the preliminary polishing step and the finish polishing step.

Preliminary polishing and finish polishing can be applied to both polishing using a single-sided polishing machine and polishing using a double-sided polishing machine. With a single-sided polishing machine, the object to be polished is attached to a ceramic plate with wax or held using a holder called a carrier. A polishing composition is supplied while a polishing pad is pressed against one side of the object to be polished and the two are moved relative to one another to polish one side of the object to be polished. This movement can be, for example, rotational movement. With a double-sided polishing machine, the object to be polished is held using a holder called a carrier, and a polishing pad is pressed against the opposing side of the object to be polished while a polishing composition is supplied from above. The two are then rotated relative to one another to polish both sides of the object to be polished simultaneously.

The polishing conditions are not limited to specific conditions and are appropriately set based on the type of material being polished, the desired surface properties (specifically, smoothness), the polishing removal rate, and other factors. For example, the polishing composition disclosed herein can be used over a wide range of processing pressures, for example, from 10 kPa to 150 kPa. To improve the polishing removal rate, in some embodiments, the processing pressure may be, for example, 5 kPa or more, 10 kPa or more, 20 kPa or more, 30 kPa or more, or 40 kPa or more, and may be 100 kPa or less, 80 kPa or less, or 60 kPa or less. The polishing composition disclosed herein can also be preferably used for polishing under processing conditions of, for example, 30 kPa or more or higher, which can increase the productivity of the target object (polished object) obtained through such polishing. Note that the processing pressure herein is synonymous with the polishing pressure.

The polishing pad used in each polishing process disclosed herein is not particularly limited. For example, any of nonwoven fabric, suede, and hard foam polyurethane types may be used. In some embodiments, hard foam polyurethane type polishing pads may be preferably used. Note that the polishing pads used in the technology disclosed herein do not contain abrasive grains.

The object to be polished using the method disclosed herein is typically washed after polishing. This washing can be carried out using an appropriate cleaning liquid. There are no particular restrictions on the cleaning liquid used, and any known, commonly used liquid can be selected and used as appropriate.

The polishing method disclosed herein may include any other process in addition to the preliminary polishing process and the finish polishing process. Examples of such processes include a mechanical polishing process or a lapping process carried out before the preliminary polishing process. The mechanical polishing process involves polishing the object to be polished using a liquid in which diamond abrasive grains are dispersed in a solvent. In some preferred embodiments, the dispersion does not contain an oxidizing agent. The lapping process involves pressing the surface of a polishing platen, such as a cast iron platen, against the object to be polished to polish it. Therefore, a polishing pad is not used in the lapping process. The lapping process is typically carried out by supplying abrasive grains between the polishing platen and the object to be polished. The abrasive grains are typically diamond abrasive grains. The polishing method disclosed herein may also include an additional process before the preliminary polishing process or between the preliminary polishing process and the finish polishing process. Examples of such additional processes include a cleaning process or a polishing process.

<Method of manufacturing polished object>
The technology disclosed herein may include a method for manufacturing a polishing object, which includes a polishing step using any of the polishing methods described above, and the provision of a polishing object manufactured by the method. The method for manufacturing a polishing object is, for example, a method for manufacturing a silicon carbide substrate. That is, the technology disclosed herein provides a method for manufacturing a polishing object, which includes polishing an object having a surface made of a high-hardness material using any of the polishing methods disclosed herein, and a polishing object manufactured by the method. The manufacturing method described above can efficiently provide a substrate manufactured through polishing, such as a silicon carbide substrate.

The matters disclosed by this specification include the following:
[1] A method for producing a catalyst comprising: potassium permanganate as an oxidizing agent; a metal salt A; and water;
wherein the metal salt A is:
A salt of a cation a (excluding alkaline earth metal cations) containing a metal whose hydrated metal ion has a pKa of 7.0 or more, and an anion; and
The permanganate of the cation a has the same or higher solubility in water at 20°C than potassium permanganate;
The content of potassium permanganate is 5.0% by weight or more,
The polishing composition has a ratio (CA/CK) of the concentration CA [mM] of the metal salt A to the concentration CK [mM] of the potassium permanganate greater than 0.1.
[2] The polishing composition according to [1], wherein the metal salt A is a salt of the cation a selected from potassium ion, zinc ion, lithium ion, and sodium ion and an anion.
[3] The polishing composition according to [1] or [2], wherein the metal salt A is a salt of the cation a and an anion selected from the group consisting of a nitrate ion, a fluoride ion, and a bicarbonate ion.
[4] The polishing composition according to any one of [1] to [3], wherein the metal salt A is a salt of the cation a selected from potassium ion, zinc ion, lithium ion, and sodium ion and an anion selected from nitrate ion, fluoride ion, and bicarbonate ion.
[5] The polishing composition according to any one of [1] to [4] above, further comprising a metal salt B which is a salt of a cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0 and an anion.
[6] The polishing composition according to [5], wherein the metal salt B is a salt of the cation b and a nitrate ion.
[7] The polishing composition according to any one of [1] to [6] above, further comprising a metal salt C selected from alkaline earth metal salts.
[8] The polishing composition according to [7], wherein the metal salt C is a salt of an alkaline earth metal cation and a nitrate ion.
[9] The polishing composition according to any one of [1] to [8] above, further comprising abrasive grains.
[10] The polishing composition according to any one of [1] to [9] above, which has a pH of 1.0 or more and less than 6.0.
[11] The polishing composition according to any one of [1] to [10] above, which is used for polishing a material having a Vickers hardness of 1500 Hv or more.
[12] The polishing composition according to any one of [1] to [11] above, which is used for polishing silicon carbide.
[13] A polishing method, comprising polishing an object to be polished with the polishing composition according to any one of [1] to [12] above.

Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "%" is by weight unless otherwise specified.

<Experiment 1>
<Preparation of Polishing Composition>
(Reference example 1)
Alumina abrasive grains, potassium permanganate as an oxidizing agent, aluminum nitrate, calcium nitrate, and deionized water were mixed and stirred at room temperature at 500 rpm using a stirrer to prepare a polishing composition containing 0.1% alumina abrasive grains, 1.4% potassium permanganate, 10 mM aluminum nitrate, and 10 mM calcium nitrate.

(Reference examples 2 and 3)
The polishing composition of this example was prepared in the same manner as in Reference Example 1, except that the content of potassium permanganate was set as shown in Table 1.

Table 1 shows an overview of Reference Examples 1 to 3. Note that, as described below, undissolved matter was generated in the polishing composition of Reference Example 3, so the concentration (content) of the dissolved components in the composition differs from the value shown in Table 1. However, for convenience, Table 1 shows the amount based on the added amount of the raw materials used as the content.

In the polishing compositions of Reference Examples 1 to 3, α-alumina abrasive grains with an average primary particle size of 300 nm were used as the alumina abrasive grains. Furthermore, no pH adjuster was used in preparing the polishing compositions of Reference Examples 1 to 3. The pH of the polishing compositions of Reference Examples 1 to 3 was all within the range of 3.7 to 3.8.

<Solubility>
The solubility of the polishing compositions of Reference Examples 1 to 3 obtained was examined. Specifically, each polishing composition was passed through a polypropylene mesh with a mesh size of 100 μm, and the presence or absence of residue (undissolved matter) on the mesh was visually confirmed. If there was no residue, the solubility was evaluated as good (OK), and if there was residue, the solubility was evaluated as poor (NG). As a result, the solubility of the polishing compositions of Reference Examples 1 and 2 was OK, but the solubility of the polishing composition of Reference Example 3 was NG. The results are shown in the corresponding columns in Table 1.

<Polishing of object to be polished>
A SiC wafer was pre-polished using a preliminary polishing composition containing alumina abrasive grains. The pre-polished SiC wafer was used as an object to be polished, and the polishing composition according to each example was used as a polishing liquid to polish the object under the following polishing conditions.
[Polishing conditions]
Polishing machine: Fujikoshi Machinery Industry Co., Ltd., model "RDP-500"
Polishing pad: Nitta DuPont "IC-1000" (hard polyurethane)
Processing pressure: 490 gf/ ^cm2
Platen rotation speed: 130 rpm Head rotation speed: 130 rpm Polishing liquid supply rate: 20 mL/min Polishing liquid usage method: Disposable Polishing time: 5 minutes Polishing object: 4-inch SiC wafer (conductivity type: n-type, crystal type 4H-SiC, off angle of main surface (0001) to the C-axis: 4°), 1 wafer/batch Polishing liquid temperature: 23°C

As mentioned above, the polishing composition of Reference Example 3 contained undissolved matter, so the polishing composition was passed through a polypropylene mesh with 100 μm openings to remove the undissolved matter, and the resulting liquid (filtrate) was used as the polishing liquid.

The polishing pad used had its polishing surface brush-dressed for 5 minutes, then diamond-dressed for 3 minutes, and then brush-dressed for another 5 minutes. The brush-dressing and diamond-dressing processes were performed before the polishing process.

<Measurement and Evaluation>
(Polishing removal rate)
Under the above polishing conditions, a SiC wafer was polished using the polishing composition of each example, and then the polishing removal rate was calculated according to the following calculation formulas (1) and (2).
(1) Polishing stock removal [cm] = difference in weight of SiC wafer before and after polishing [g] / density of SiC [g/cm ³ ] (= 3.21 g/cm ³ ) / area to be polished [cm ² ] (= 78.54 cm ² )
(2) Polishing removal rate [nm/h] = polishing removal amount [cm] × 10 ⁷ / polishing time (= 5/60 hours)
The obtained results were converted into relative values, with the polishing removal rate for Reference Example 1 taken as 100%. A larger value indicates a more excellent polishing removal rate.

The polishing removal rates obtained for Reference Examples 1 to 3 are shown in the corresponding columns in Table 1.

As is clear from the results shown in Table 1, it was confirmed that increasing the content of potassium permanganate as an oxidizing agent tends to improve the polishing removal rate. On the other hand, it was confirmed that increasing the potassium permanganate content to 7.5% reduced solubility and resulted in the generation of undissolved material.

<Experiment 2>
<Preparation of Polishing Composition>
(Comparative Example 1)
Alumina abrasive grains, potassium permanganate as an oxidizing agent, sodium nitrate as metal salt A, aluminum nitrate, calcium nitrate, and deionized water were mixed and stirred at room temperature at 500 rpm using a stirrer to prepare a polishing composition containing 0.1% alumina abrasive grains, 7.5% potassium permanganate, 10 mM aluminum nitrate, and 10 mM calcium nitrate, and containing sodium nitrate at a molar content ratio (CA/CK) to potassium permanganate of 0.1.

Example 1
Alumina abrasive grains, potassium permanganate as an oxidizing agent, sodium nitrate as metal salt A, aluminum nitrate, calcium nitrate, and deionized water were mixed and stirred at room temperature at 500 rpm using a stirrer to prepare a polishing composition containing 0.1% alumina abrasive grains, 7.5% potassium permanganate, 10 mM aluminum nitrate, and 10 mM calcium nitrate, and containing sodium nitrate at a molar content ratio (CA/CK) to potassium permanganate of 0.4.

(Examples 2 to 4)
The polishing composition of this example was prepared in the same manner as in Example 1, except that the molar content ratio of sodium nitrate to potassium permanganate (CA/CK) was set as shown in Table 2.

Table 2 shows an overview of Examples 1 to 4 and Comparative Example 1. As described below, the polishing composition of Comparative Example 1 contained undissolved matter, so the concentration (content) of the dissolved components in the composition differs from the value shown in Table 2. However, for convenience, Table 2 shows the amount based on the added amount of the raw materials used as the content.

In the polishing compositions of Examples 1 to 4 and Comparative Example 1, α-alumina abrasive grains with an average primary particle size of 300 nm were used as the alumina abrasive grains. Furthermore, no pH adjuster was used in preparing the polishing compositions of Examples 1 to 4 and Comparative Example 1. The pH of the polishing compositions of Examples 1 to 4 and Comparative Example 1 was all within the range of 3.7 to 3.8.

<Solubility>
The obtained polishing compositions of Examples 1 to 4 and Comparative Example 1 were passed through a polypropylene mesh with an opening of 100 μm, and the presence or absence of residue (undissolved matter) on the mesh was visually confirmed. If no residue was found, the solubility was evaluated as good (OK), and if residue was found, the solubility was evaluated as poor (NG). As a result, the solubility of the polishing compositions of Examples 1 to 4 was good, but the solubility of the polishing composition of Comparative Example 1 was poor. The results are shown in Table 2.

As is clear from the results shown in Table 2, when sodium nitrate is used as metal salt A in an amount such that the molar content ratio of metal salt A to potassium permanganate, CA/CK, exceeds 0.1, it was confirmed that solubility is improved and no undissolved material is generated, even if the potassium permanganate content is 7.5%. A high potassium permanganate content in the polishing composition can contribute to an improved polishing removal rate.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above.

Claims (11)

The composition contains potassium permanganate as an oxidizing agent, a metal salt A, and water,
wherein said metal salt A is:
A salt of a cation a (excluding alkaline earth metal cations) containing a metal whose hydrated metal ion has a pKa of 7.0 or more, and an anion; and
The permanganate of the cation a has the same or higher solubility in water at 20°C than potassium permanganate;
The content of potassium permanganate is 5.0% by weight or more,
A polishing composition in which the ratio (CA/CK) of the concentration CA [mM] of the metal salt A to the concentration CK [mM] of the potassium permanganate is greater than 0.1. The polishing composition according to claim 1, wherein the metal salt A is a salt of the cation a and an anion selected from nitrate ions, fluoride ions, and bicarbonate ions. The polishing composition according to claim 1 or 2, further comprising a metal salt B which is a salt of a cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0 and an anion. The polishing composition according to claim 3, wherein the metal salt B is a salt of the cation b and a nitrate ion. The polishing composition according to claim 1 or 2, further comprising a metal salt C selected from alkaline earth metal salts. The polishing composition according to claim 5, wherein the metal salt C is a salt of an alkaline earth metal cation and a nitrate ion. The polishing composition according to claim 1 or 2, further comprising abrasive grains. The polishing composition according to claim 1 or 2, having a pH of 1.0 or greater and less than 6.0. The polishing composition according to claim 1 or 2, which is used for polishing materials having a Vickers hardness of 1500 Hv or more. The polishing composition according to claim 1 or 2, which is used for polishing silicon carbide. A polishing method comprising polishing an object to be polished using the polishing composition according to claim 1 or 2.