Polishing composition

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

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2024-53232, filed on March 28, 2024, the entire contents of which are incorporated herein by reference.

[0002] Polishing using a polishing composition has been used to polish the surfaces of materials such as metals, semimetals, nonmetals, 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) by supplying diamond abrasive grains 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 a polishing composition after lapping using diamond abrasive grains, or instead of lapping, has been considered. Patent Document 1 discloses this type of prior art.

[0003] Chinese Patent Application Publication No. 101684393

[0004] Generally, from the viewpoint of manufacturing efficiency and cost-effectiveness, it is desirable that the polishing removal rate in polishing an object to be polished be sufficiently high for practical use. However, when polishing an object made of a high-hardness material such as silicon carbide, it is not easy to improve the polishing removal rate compared to polishing an object with low hardness. In order to improve the polishing removal rate, in addition to using abrasive grains that exert a physical polishing action, it is effective to chemically modify the surface to be polished to make it weak. In order to achieve such an effect, an oxidizing agent is sometimes contained in the polishing composition. For example, Patent Document 1 attempts to improve 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.

[0005] In order to further improve the polishing removal rate, it is considered effective to increase the concentration of the oxidizing agent contained in the polishing composition.However, since potassium permanganate, which is the oxidizing agent conventionally used in this field, has not high solubility in water, there is a limit to increasing the concentration of potassium permanganate in the polishing composition.

[0006] The present invention has been made in consideration of the above 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.

[0007] 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 can be improved and the concentration (content) of potassium permanganate in the polishing composition can be increased.

[0008] The polishing composition provided herein contains potassium permanganate as an oxidizing agent, a metal salt A, and water. The metal salt A satisfies the following conditions (i) and (ii): (i) it is a salt of an anion and a cation a (excluding alkaline earth metal cations) containing a metal whose hydrated metal ion has a pKa of 7.0 or higher; (ii) the permanganate of the cation a has the same or higher solubility in water at 20°C as potassium permanganate; and the content of potassium permanganate in the polishing composition is 5.0 wt% or more. Furthermore, the ratio (CA / CK) of the concentration (molar concentration) of the metal salt A CA [mM] to the concentration (molar concentration) of the potassium permanganate CK [mM] 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.

[0009] In some embodiments, the metal salt A is a salt of the cation A and an anion selected from nitrate ion, fluoride ion, and bicarbonate ion. Use of such metal salt A makes it easy to increase the concentration of potassium permanganate in the polishing composition.

[0010] In some embodiments, the polishing composition further comprises 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. By using the metal salt B, pH fluctuations in the polishing composition are suppressed during polishing of an object to be polished, and the polishing removal rate tends to be stable. In some preferred embodiments, the metal salt B is 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.

[0011] In some embodiments, the polishing composition further comprises a metal salt C selected from alkaline earth metal salts. The polishing removal rate tends to be improved by using the metal salt C. In some preferred embodiments, the metal salt C is a salt of an alkaline earth metal cation and a nitrate ion.

[0012] In some embodiments, the polishing composition further comprises abrasive grains. The use of abrasive grains can improve the polishing removal rate.

[0013] In some embodiments, the pH of the polishing composition is 1.0 or more and less than 6.0. In this pH range, the polishing composition disclosed herein tends to exhibit a high polishing removal rate.

[0014] The polishing composition disclosed herein is used, for example, for polishing materials having a Vickers hardness of 1500 Hv or more. The effects of the technology disclosed herein can be favorably exhibited when polishing such high-hardness materials. In some embodiments, the material having a Vickers hardness of 1500 Hv or more is a non-oxide (i.e., a compound that is not an oxide). When polishing a non-oxide material, the polishing composition disclosed herein is likely to favorably exhibit its effect of improving the polishing removal rate.

[0015] The polishing composition disclosed herein is used, for example, for polishing silicon carbide. In polishing silicon carbide, the effects of the technology disclosed herein can be preferably exerted.

[0016] This specification further provides a method for polishing an object to be polished. The polishing method includes polishing the object to be polished with 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 can increase 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.

[0017] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out 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 carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0018] <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 high-hardness non-oxide material such as silicon carbide) and weakening the material. Therefore, the oxidizing agent can be effective in improving the polishing 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.

[0019] 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, according to the configuration of the polishing composition disclosed herein, the solubility of potassium permanganate in water is improved, and the content of potassium permanganate in the polishing composition tends to increase.

[0020] In some embodiments, the content of potassium permanganate in the polishing composition is 5.0 wt% or more. When the concentration of potassium permanganate in the polishing composition is increased, the effect of chemically modifying (oxidizing) the surface to be polished by potassium permanganate is promoted, thereby improving the polishing removal rate when polishing the object to be polished. From the viewpoint of easily achieving a higher polishing removal rate, in some embodiments, the content of potassium permanganate is preferably 5.2 wt% or more (e.g., 5.5 wt% or more), more preferably 6 wt% or more, even more preferably 6.5 wt% or more, and may be 6.8 wt% or more, 7 wt% or more, or even 7.5 wt% or more. The upper limit of the content of potassium permanganate is not particularly limited, but 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 wt% or less, and may be 12.5 wt% or less, 10 wt% or less, 9 wt% or less, or 8 wt% or less. Reducing the content of potassium permanganate can also be advantageous from the viewpoint of reducing the occurrence of defects caused by potassium that may remain after polishing.

[0021] 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 salts, such as ammonium iodate; bromic acids such as bromic acid and its salts, such as potassium bromate; ferric acids such as ferric acid and its salts, such as potassium ferrate; chromic acids and dichromates such as perchromic acid, chromic acid and its salts, such as potassium chromate; dichromate and its salts, such as vanadic acid and its salts, 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 its 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 its salts such as disodium tungstate; persulfates such as peroxomonosulfuric acid and peroxodisulfuric acid, and its salts such as ammonium persulfate and potassium persulfate; chloric acids and perchloric acids such as chloric acid and its salts, perchloric acid and its salts such as potassium perchlorate; osmic acids such as perosmic acid and osmic acid; selenic acids such as perselenic acid and selenic acid; and cerium ammonium nitrate.As other oxidizing agents, one or more of these compounds can be used in combination.In some embodiments, from the viewpoint of the performance stability of the polishing composition (for example, preventing deterioration due to long-term storage), it is preferable that other oxidizing agents are inorganic compounds.

[0022] 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 weakening the materials. The complex metal oxides may be used singly or in combination of two or more. Specific examples of 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, and Mn is even more preferred. The alkali metal ions in the complex transition metal oxide include Na, Mn, Cr, V, and Ti. ＋ In some embodiments, other oxidizing agents may include sodium permanganate.

[0023] When the compound used as the oxidizing agent is a salt (for example, permanganate), the compound may be present in the polishing composition in the form of ions.

[0024] (Metal Salt A) The polishing composition disclosed herein contains metal salt A, which is a salt that satisfies the following conditions (i) and (ii): (i) It is a salt of an anion and cation a, which contains a metal whose hydrated metal ion has a pKa of 7.0 or more. However, alkaline earth metal cations are not included in the cation a. (ii) The permanganate of the cation a has the same or higher solubility in water at 20°C than potassium permanganate.

[0025] Thus, 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 the solubility of a 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.

[0026] As a cation a that can form a permanganate with the same or higher solubility in water compared to potassium permanganate, Na ＋ , Li ＋ , Zn ２＋ , K. ＋ Metal salt A, which is a salt of an anion and a cation a capable of forming a permanganate having the same or higher solubility in water as potassium permanganate, tends to improve the solubility of potassium permanganate when contained in water together with potassium permanganate.

[0027] In some embodiments, the pKa of the hydrated metal ion of the metal contained in cation a is 7.5 or greater, optionally 8.0 or greater, optionally 8.5 or greater, optionally 9.0 or greater, optionally 9.5 or greater, optionally 10.0 or greater, optionally 10.5 or greater, optionally 11.0 or greater, optionally 11.5 or greater, optionally 12.0 or greater, optionally 12.5 or greater, optionally 13.0 or greater, or optionally 13.5 or greater.

[0028] 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 about 15 or less, for example, 14.8 or less, or 14.5 or less.

[0029] Examples of metal cations whose hydrated metal ions have a pKa of 7.0 or more include K, as described in "Inorganic Chemistry, Gary Wulfberg, University Science Books, 2000, p. 59, Table 2.2 "Hydrolysis Constants for Metal Cations" and the like. ＋ (pKa of hydrated metal ion is 14.5), Na ＋ (pKa of hydrated metal ion is 14.2), Li ＋ (pKa of hydrated metal ion is 13.6), Zn ２＋ (pKa of the hydrated metal ion is 9.0) and the like, but are not limited to these.

[0030] The 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, the metal salt A is one or more selected from salts of a monovalent cation and an anion and salts of a divalent cation and an anion. In some embodiments, the metal salt A is a salt of a monovalent cation and an anion.

[0031] The reason why the addition of metal salt A improves the solubility in water of potassium permanganate used together with metal salt A is not particularly limited, but can be thought of as follows, for example: In an environment in which potassium permanganate and metal salt A are both dissolved in water, ion exchange (cation exchange) occurs between potassium ions derived from potassium permanganate and cation a derived from metal salt A. Here, it is thought that if the solubility of cation a in permanganate is high in water, the dissolution of potassium permanganate is promoted as the ion exchange proceeds.

[0032] In some embodiments, the 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.

[0033] The 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.

[0034] 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 a plurality of 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. The upper limit of CA / CK is not particularly limited, but from the viewpoint of ensuring the content of potassium permanganate as an oxidizing agent, it is appropriate that it is approximately 50 or less, and may 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 such a 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 preferably exhibited.

[0035] 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 (when multiple metal salts A are contained, their total concentration) is preferably 120 mM or more (for example, 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 the metal salt A in the polishing composition (when a plurality of metal salts A are contained, their total concentration) is usually suitably 3000 mM or less, and may be 2500 mM or less. In some embodiments, the concentration of the 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.

[0036] (Metal Salt B) The polishing composition disclosed herein may further contain 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. Metal salt B, which is a salt of such a cation and an anion, forms a hydrated metal cation in water, and since the protons on the coordinated water are in adsorption / desorption equilibrium with each other, the hydrated metal cation acts as a pH buffer and easily suppresses deterioration of the performance of the polishing composition over time. From this perspective, 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 metal salt B. Examples of cations containing a metal whose hydrated metal ion has a pKa of 6.0 or less include Al, as described in the aforementioned "Inorganic Chemistry, GARY WULFBERG, University Science Books, 2000, p. 59, Table 2.2 "Hydrology Constants for Metal Cations"" and the like. ３＋ (pKa of hydrated metal ion is 5.0), Ga ３＋ (pKa of hydrated metal ion is 2.6), In ３＋ (pKa of hydrated metal ion is 4.0), ZrO ２＋ and Zr ４＋ (The pKa of the hydrated metal ion is -0.3) can be mentioned, but is not limited to these. The metal salt B can be used alone or in combination of two or more.

[0037] In some preferred embodiments, metal salt B is a salt selected from salts of anions and cations containing impoverished metals, i.e., metals belonging to Groups 13 to 16 of the periodic table. The impoverished metals are preferably those belonging to Groups 13 to 15 of the periodic table, more preferably those belonging to Groups 13 to 14, and also preferably those belonging to Periods 3 to 5, more preferably those belonging to Periods 3 and 4, with aluminum being particularly preferred as a impoverished metal belonging to Period 3.

[0038] 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 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 － In the technology disclosed herein, for example, the metal salt B is preferably a salt of Al ３＋ , Ga ３＋ , In ３＋ , ZrO ２＋ or Zr ４＋ and nitrate ions (NO ３ － ) or chloride ions (Cl － The method can be preferably carried out in an embodiment using a salt of

[0039] Preferably, metal salt B is a compound that is not oxidized by an oxidizing agent. From this viewpoint, by appropriately selecting the oxidizing agent and metal salt B, it is possible to prevent the metal salt B from being oxidized by the oxidizing agent, thereby preventing the deactivation of the oxidizing agent, and to suppress deterioration of the performance of the polishing composition over time (for example, a decrease in the polishing removal rate). From this viewpoint, preferred examples of metal salt B include aluminum nitrate and aluminum chloride. Among them, since nitrates have oxidizing properties, aluminum nitrate is particularly preferred as metal salt B. Metal salt B can improve the polishing removal rate by being used in combination with the above-mentioned metal salt A or the below-mentioned metal salt C.

[0040] The 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.

[0041] When the polishing composition contains a metal salt B, the concentration (content) of the 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 mode of use of the polishing composition. The concentration of the metal salt B (when a plurality of metal salts B are contained, their total concentration) may be, for example, approximately 1000 mM or less (i.e., 1 mol / L or less), may be 500 mM or less, or may be 300 mM or less. In some embodiments, the concentration of the metal salt B is suitably 200 mM or less, preferably 100 mM or less, more preferably 50 mM or less, may be 30 mM or less, may be 20 mM or less, or may be 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, and it is advantageous to make it 1 mM or more from the viewpoint of properly exerting the use effect of metal salt B, preferably 5 mM or more, more preferably 10 mM or more (for example, 15 mM or more), and may be 18 mM or more, 20 mM or more, or 30 mM or more.

[0042] 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, 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.

[0043] 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 may 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 about 0.1 or more, may be 0.5 or more, or may be 10 or more. Furthermore, CA / CB is suitably about 2000 or less, may be 1000 or less, may be 500 or less, may be 300 or less, may be 200 or less, or may be 100 or less.

[0044] (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 kind of alkaline earth metal salt may be used alone, or two or more kinds of alkaline earth metal salts may be used in combination. When the metal salt C is used, the polishing removal rate is likely to be improved. As an element belonging to alkaline earth metals, the metal salt C preferably contains one or more of Mg, Ca, Sr, and Ba. Among them, either Ca or Sr is preferred, and Ca is more preferred.

[0045] The type of salt in the metal salt C 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 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 the metal salt C.

[0046] Specific examples of alkaline earth metal salts that can be selected for the 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;

[0047] 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, the metal salt C is preferably a compound that is not oxidized by an oxidizing agent. From this viewpoint, by appropriately selecting the oxidizing agent and the 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 suppressing deterioration of the performance of the polishing composition over time (for example, a decrease in the polishing removal rate). From this viewpoint, calcium nitrate can be mentioned as a preferred metal salt C.

[0048] 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 according to the purpose and mode 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), may be 500 mM or less, or may be 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, may be 30 mM or less, may be 20 mM or less, or may be 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 viewpoint 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.

[0049] 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.

[0050] In some preferred embodiments, the polishing composition may contain a combination of metal salt B and metal salt C. In some preferred embodiments when the polishing composition contains a combination of metal salt B and metal salt C, the 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, the anion species of metal salt A, metal salt B, and metal salt C are the same. In some embodiments, metal salt A, metal salt B, and metal salt C are all nitrates.

[0051] 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 can 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, 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).

[0052] 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 may 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 about 0.1 or more, and may be 0.5 or more (e.g., 5 or more). Furthermore, CA / CB is suitably about 2000 or less, and may be 1000 or less, 500 or less, 200 or less, or 100 or less.

[0053] (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.

[0054] The material and properties of the abrasive grains are not particularly limited. For example, the abrasive grains can be any of inorganic particles, organic particles, and organic-inorganic composite particles. Examples include 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; carbonates such as calcium carbonate and barium carbonate; and the like. The abrasive grains may be used alone or in combination of two or more. Among them, 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, silica particles and alumina particles are even more preferred, and alumina particles are particularly preferred. In an embodiment in which alumina particles are used as abrasive grains, the technique disclosed herein can be applied to suitably exhibit the effect of improving the polishing removal rate.

[0055] In this specification, the phrase "consisting essentially of X" or "consisting essentially of X" in relation to the composition of the abrasive grains means that the proportion of X in the abrasive grains (purity of X) is 90% or more by weight. 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.

[0056] 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 even 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.

[0057] In this specification, the average primary particle diameter is calculated from the specific surface area (BET value) measured by the BET method by the following formula: average primary particle diameter (nm) = 6000 / (true density (g / cm ３ ) × BET value (m ２ The specific surface area is the particle size (BET particle size) calculated by the formula: (1 / g / g) The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, Inc., under the trade name "Flow Sorb II 2300."

[0058] 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 even 400 nm or more. From the viewpoint of ensuring a sufficient number per unit weight, the upper limit of the average secondary particle diameter of the abrasive grains is suitably set to approximately 10 μm or less. 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.

[0059] The average secondary particle diameter of the abrasive grains can be measured as the volume average particle diameter (volume-based arithmetic mean diameter; Mv) for particles less than 500 nm by dynamic light scattering using, for example, a model "UPA-UT151" manufactured by Nikkiso Co., Ltd. Furthermore, for particles 500 nm or larger, the volume average particle diameter can be measured by, for example, a pore electrical resistance method using a model "Multisizer 3" manufactured by Beckman Coulter.

[0060] When alumina particles (alumina abrasive grains) are used 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. Here, 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 alumina fine particles produced by high-temperature calcination of alumina salts) may also be used, based on classification by production method. Furthermore, alumina called colloidal alumina or alumina sol (e.g., alumina hydrates such as boehmite) also fall within the scope of the known alumina particles. From the viewpoint of processability, α-alumina is preferred. The alumina abrasive grains disclosed herein may contain one type of such alumina particles alone or in combination of two or more types.

[0061] When alumina particles are used 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, even more preferably 95% by weight or more, and may be substantially 100% by weight.

[0062] 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 viewpoint 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. The upper limit of the average primary particle diameter of the alumina abrasive grains is not particularly limited, but from the viewpoint of the surface quality after polishing, it is appropriate to set it to approximately 5 μm or less. From the viewpoint of further improving the 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.

[0063] When using alumina particles as abrasive grains, the polishing composition disclosed herein may further contain abrasive grains made of materials other than the above-mentioned alumina (hereinafter also referred to as non-alumina abrasive grains) within the scope that does not impair the effects of the present invention.Examples of such non-alumina abrasive grains include abrasive grains that are substantially composed of any of 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, iron oxide particles, etc.; nitride particles such as silicon nitride particles, boron nitride particles, etc.; carbide particles such as silicon carbide particles, boron carbide particles, etc.; diamond particles; carbonates such as calcium carbonate, barium carbonate, etc.

[0064] 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.

[0065] In another preferred embodiment of the technology disclosed herein, the polishing composition contains silica particles (silica abrasive particles) as abrasive particles. The silica abrasive particles can be appropriately selected from various known silica particles. Examples of such known silica particles include colloidal silica and dry process silica. Among these, colloidal silica is preferably used. Silica abrasive particles containing colloidal silica can suitably achieve good surface precision.

[0066] 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 in which a plurality of primary particles are aggregated. 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 a preferred embodiment, at least a portion of the silica abrasive grains are contained in the polishing composition in the form of secondary particles.

[0067] As the silica abrasive grains, those having an average primary particle diameter of more than 5 nm can be 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. The upper limit of the average primary particle diameter of the silica abrasive grains is not particularly limited, but it is appropriate to set it to approximately 120 nm or less, preferably 100 nm or less, more preferably 85 nm or less. For example, from the viewpoint of achieving both polishing efficiency and surface quality at a higher level, silica abrasive grains having a BET diameter of 12 nm or more and 80 nm or less are preferred, and silica abrasive grains having a BET diameter of 15 nm or more and 75 nm or less are preferred.

[0068] The average secondary particle size of the silica abrasive grains is not particularly limited, but is preferably 20 nm or more, more preferably 50 nm or more, and even more preferably 70 nm or more, from the viewpoint of polishing efficiency, etc. Furthermore, from the viewpoint of obtaining a higher quality surface, the average secondary particle size of the silica abrasive grains is suitably 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).

[0069] The true specific gravity (true density) of the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. An increase in the true specific gravity of the silica particles tends to increase the physical polishing ability. The upper limit of the true specific gravity of the silica particles is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less, 2.0 or less, or 1.9 or less. The true specific gravity of the silica particles can be measured by a liquid substitution method using ethanol as the substitution liquid.

[0070] The shape (outer shape) of silica particles is preferably spherical.Although not particularly limited, the average value of the long diameter / short diameter ratio of particles (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.In addition, the average aspect ratio of 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 particles is preferably 1.50 or less, may be 1.30 or less, or may be 1.20 or less.

[0071] The particle shape (external shape) and average aspect ratio can be determined, for example, by observation with 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 each extracted particle shape is then drawn. The length of the long side (major axis value) of the rectangle drawn for each particle shape is then divided by the length of the short side (minor axis value) to calculate the major axis / minor axis ratio (aspect ratio). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

[0072] In the embodiment where the polishing composition comprises silica abrasive grains, the polishing composition may further comprise abrasive grains made of materials other than silica (hereinafter also referred to as non-silica abrasive grains).The examples of the particles that constitute such non-silica abrasive grains include 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, iron oxide particles; nitride particles such as silicon nitride particles, boron nitride particles; carbide particles such as silicon carbide particles, boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; etc.

[0073] 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.

[0074] 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 0.5 wt %, 0.1 wt % or less or 0.1 wt %, 0.05 wt % or less or 0.05 wt %, or 0.04 wt % or less or 0.04 wt %. The lower limit of the content of abrasive grains 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 effect of using the abrasive grains, in some embodiments, the content of the 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 the 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 the abrasive grains in the polishing composition refers to the total content of the multiple types of abrasive grains.

[0075] The polishing composition disclosed herein preferably does not substantially contain diamond particles as particles.Diamond particles have high hardness, which can be a limiting factor in improving smoothness.In addition, diamond particles are generally expensive, so they are not considered to be an advantageous material in terms of cost-effectiveness, and from a practical standpoint, it is acceptable to have a low dependency on expensive materials such as diamond particles.Here, "particles substantially do not contain 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, typically 0.1% by weight or less, and includes the case where the proportion of diamond particles is 0% by weight.In such an embodiment, the application effect of the present invention can be suitably exhibited.

[0076] 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.

[0077] 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 the storage stability of the polishing composition, it can be, for example, approximately 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 "wt%", and Wp and CA are both dimensionless numbers.

[0078] 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 the storage stability of the polishing composition, it can be, for example, approximately 30,000 or less, and 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 value when the concentration of metal salt B in the polishing composition is expressed in units of "mM," and "Wp" represents the numerical value when the content of abrasive grains in the polishing composition is expressed in units of "wt%," and Wp and CB are both dimensionless numbers.

[0079] 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 the 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 value when the concentration of metal salt B in the polishing composition is expressed in units of "mM," and "Wp" represents the numerical value when the content of abrasive grains in the polishing composition is expressed in units of "wt%." CC and Wp are both dimensionless numbers.

[0080] The polishing composition disclosed herein can also be preferably used in an embodiment that does not contain abrasive grains. Even in such an embodiment, the effects of improving the solubility of potassium permanganate and improving the polishing removal rate due to the use of potassium permanganate and metal salt A as oxidizing agents are well exhibited.

[0081] (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 water. The polishing composition disclosed herein may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water, as needed. 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.

[0082] (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.

[0083] (Basic Compound) The polishing composition may contain a basic compound as needed for purposes such as adjusting the 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 other compounds such as 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.

[0084] (Other Components) 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-mentioned additives can be appropriately set according to the purpose of addition, and since they do not characterize the present invention, detailed explanations will be omitted.

[0085] (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 easily 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.

[0086] 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 known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or may be mixed in an appropriately set order.

[0087] The polishing composition disclosed herein may be a single-component type or a multi-component type, such as a two-component type. For example, Part A containing some of the components of the polishing composition (e.g., components other than water) and Part B containing the remaining components may be mixed 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 be further 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 can improve the storage stability of the polishing composition. The optional Part C may or may not contain abrasive grains.

[0088] <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 group compound semiconductors such as cadmium telluride, zinc selenide, cadmium sulfide, cadmium mercury telluride, or zinc cadmium telluride; III-V group 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 group 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.

[0089] The polishing composition disclosed herein can be preferably used for polishing a 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. The upper limit of the Vickers hardness of the surface of the object to be polished is not particularly limited, and 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.

[0090] Examples of materials having a Vickers hardness of 1500 Hv or more include silicon carbide, silicon nitride, titanium nitride, and gallium nitride. The object to be polished in the technology disclosed herein may have a single crystal surface of the above material, which is mechanically and chemically stable. 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 advantage of improving productivity by improving the polishing removal rate is particularly great. The technology disclosed herein is particularly suitable for polishing the single crystal surface of silicon carbide.

[0091] <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 the case of a multi-component polishing composition, preparing the polishing liquid may include mixing the components, diluting one or more components before mixing, or diluting the mixture after mixing. The polishing liquid is then supplied to the object to be polished, and polishing is performed using a method commonly used by those skilled in the art. For example, the polishing liquid may be placed in a conventional polishing apparatus, and the polishing liquid is supplied to the surface of the object to be polished via the polishing pad of the polishing apparatus. Typically, the polishing liquid is continuously supplied, while the polishing pad is pressed against the surface of the object to be polished, causing relative movement (e.g., rotational movement) between the two. Polishing of the object to be polished is completed through this polishing process.

[0092] In addition, the above-mentioned content (concentration) and content (concentration) ratio of each component that may be contained in the polishing composition in the technology disclosed herein typically mean the content and content ratio in the polishing composition when actually supplied to the object to be polished (i.e., at the point of use), and therefore can be read as the content and content ratio in the polishing liquid.

[0093] This specification provides a polishing method for polishing an object to be polished (typically, a material to be polished) and a method for manufacturing a polished product 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 pre-polishing (pre-polishing step) and a step of performing finish polishing (finish polishing step). In a typical embodiment, the pre-polishing step is a polishing step arranged immediately before the finish polishing step. The pre-polishing step may be a single-stage polishing step or may be a multi-stage polishing step consisting of two or more stages. The finish polishing step referred to here is a step of finish polishing the object to be polished after pre-polishing, and refers to the polishing step arranged last (i.e., most downstream) among polishing steps performed using a polishing slurry containing abrasive grains. In such a polishing method including a pre-polishing step and a finish polishing step, the polishing composition disclosed herein may be used in the pre-polishing step, in the finish polishing step, or in both the pre-polishing step and the finish polishing step.

[0094] 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. In 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. While supplying a polishing composition, a polishing pad is pressed against one side of the object to be polished, and the two are moved relative to each other, thereby polishing one side of the object to be polished. The movement is, for example, rotational movement. In a double-sided polishing machine, the object to be polished is held using a holder called a carrier, and while supplying a polishing composition from above, a polishing pad is pressed against the opposing side of the object to be polished, and the two are rotated relative to each other, thereby simultaneously polishing both sides of the object to be polished.

[0095] The polishing conditions are not limited to specific conditions and are appropriately set based on the type of material to be polished, the desired surface properties (specifically, smoothness), the polishing removal rate, etc. For example, the polishing composition disclosed herein can be used over a wide pressure range, for example, from 10 kPa to 150 kPa. From the viewpoint of improving 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, and can increase the productivity of the target object (polished object) obtained through such polishing. Note that the processing pressure here is synonymous with the polishing pressure.

[0096] The polishing pad used in each polishing step 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 pad used in the technology disclosed herein is a polishing pad that does not contain abrasive grains.

[0097] The object to be polished by the method disclosed herein is typically washed after polishing. This washing can be carried out using an appropriate washing liquid. The washing liquid to be used is not particularly limited, and a known or commonly used one can be appropriately selected and used.

[0098] The polishing method disclosed herein may include any other process in addition to the pre-polishing process and the finish polishing process. Examples of such processes include a mechanical polishing process or a lapping process performed before the pre-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 performed 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 pre-polishing process or between the pre-polishing process and the finish polishing process. The additional process may be, for example, a cleaning process or a polishing process.

[0099] <Method for manufacturing a polished product> The technology disclosed herein may include a method for manufacturing a polished product, which includes a polishing step using any of the polishing methods described above, and the provision of a polished product manufactured by this method. The method for manufacturing the polished product is, for example, a method for manufacturing a silicon carbide substrate. That is, the technology disclosed herein provides a method for manufacturing a polished product, which includes polishing an object having a surface made of a high-hardness material using any of the polishing methods disclosed herein, and a polished product manufactured by this method. The manufacturing method described above can efficiently provide a substrate manufactured through polishing, such as a silicon carbide substrate.

[0100] The subject matter disclosed by this specification includes the following: [1] A polishing composition 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 higher, and an anion; and the permanganate of the cation a has the same or higher solubility in water at 20°C as potassium permanganate; the potassium permanganate content 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 greater than 0.1. [2] The polishing composition according to [1] above, wherein the metal salt A is a salt of the cation a selected from potassium ions, zinc ions, lithium ions, and sodium ions, and an anion. [3] The polishing composition according to [1] or [2] above, wherein the metal salt A is a salt of the cation a and an anion selected from nitrate ion, fluoride ion, and bicarbonate ion. [4] The polishing composition according to any of [1] to [3] above, 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 of [1] to [4] above, further comprising metal salt B which is a salt of an anion and cation b containing a metal whose hydrated metal ion has a pKa of less than 7.0. [6] The polishing composition according to [5] above, wherein metal salt B is a salt of the cation b and nitrate ion. [7] The polishing composition according to any of [1] to [6] above, further comprising metal salt C selected from alkaline earth metal salts. [8] The polishing composition according to [7] above, 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, wherein the pH is 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.

[0101] 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 based on weight unless otherwise specified.

[0102] 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.

[0103] Reference Examples 2 and 3 Polishing compositions of the present examples were prepared in the same manner as in Reference Example 1, except that the content of potassium permanganate was set as shown in Table 1.

[0104] An outline of Reference Examples 1 to 3 is shown in Table 1. Note that, since undissolved matter was generated in the polishing composition of Reference Example 3 as described below, the concentration (content) of the dissolved component 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.

[0105] In the polishing compositions of Reference Examples 1 to 3, α-alumina abrasive grains having an average primary particle size of 300 nm were used as the alumina abrasive grains. No pH adjuster was used in preparing the polishing compositions of Reference Examples 1 to 3. The pH of each of the polishing compositions of Reference Examples 1 to 3 was within the range of 3.7 to 3.8.

[0106] <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 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 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.

[0107] <Polishing of object to be polished> A SiC wafer was pre-polished using a preliminary polishing composition containing alumina abrasive grains. This pre-polished SiC wafer was used as the object to be polished, and the polishing composition according to each example was used as the polishing liquid to polish the object under the following polishing conditions. [Polishing conditions] Polishing apparatus: Fujikoshi Machinery Co., Ltd., model "RDP-500" Polishing pad: Nitta DuPont "IC-1000" (made of hard polyurethane) Processing pressure: 490 gf / cm ２ 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

[0108] As mentioned above, the polishing composition of Reference Example 3 contained undissolved matter, so the polishing composition was passed through a polypropylene mesh with a mesh size of 100 μm to remove the undissolved matter, and the resulting liquid (filtrate) was used as the polishing liquid.

[0109] 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 were performed before the polishing.

[0110] <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 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 ](=3.21g / cm ３ ) / polished area [cm ２ ] (=78.54cm 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 better polishing removal rate.

[0111] The polishing removal rates obtained for Reference Examples 1 to 3 are shown in the corresponding columns in Table 1.

[0112]

[0113] 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 content of potassium permanganate to 7.5% reduced the solubility and produced undissolved material.

[0114] 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.

[0115] (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 the mixture was 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) of 0.4 to potassium permanganate.

[0116] (Examples 2 to 4) The polishing compositions of the present examples were prepared in the same manner as in Example 1, except that the molar content ratio (CA / CK) of sodium nitrate to potassium permanganate was set as shown in Table 2.

[0117] Table 2 shows an overview of Examples 1 to 4 and Comparative Example 1. Note that, since the polishing composition of Comparative Example 1 contained undissolved matter as described below, 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.

[0118] In the polishing compositions of Examples 1 to 4 and Comparative Example 1, α-alumina abrasive grains having an average primary particle size of 300 nm were used as the alumina abrasive grains. 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.

[0119] <Solubility> The obtained polishing compositions of Examples 1 to 4 and Comparative Example 1 were 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 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.

[0120]

[0121] As is clear from the results shown in Table 2, when sodium nitrate as metal salt A is used in an amount such that the molar content ratio CA / CK of metal salt A to potassium permanganate exceeds 0.1, it has been confirmed that the solubility is improved and no undissolved matter is generated, even if the potassium permanganate content is 7.5%. A high content of potassium permanganate in the polishing composition can contribute to an improvement in the polishing removal rate.

[0122] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A polishing composition 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 as potassium permanganate; the potassium permanganate content is 5.0 wt% or more; and the ratio (CA / CK) of the concentration of the metal salt A CA [mM] to the concentration of the potassium permanganate CK [mM] is greater than 0.

1.

2. The polishing composition according to claim 1, 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.

3. 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.

4. The polishing composition according to claim 3, wherein the metal salt B is a salt of the cation b and a nitrate ion.

5. The polishing composition according to claim 1 or 2, further comprising a metal salt C selected from alkaline earth metal salts.

6. The polishing composition according to claim 5, wherein said metal salt C is a salt of an alkaline earth metal cation and a nitrate ion.

7. The polishing composition according to claim 1 or 2, further comprising abrasive grains.

8. The polishing composition according to claim 1 or 2, having a pH of 1.0 or more and less than 6.

0.

9. The polishing composition according to claim 1 or 2, which is used for polishing a material having a Vickers hardness of 1500 Hv or more.

10. The polishing composition according to claim 1 or 2, which is used for polishing silicon carbide.

11. A polishing method comprising polishing an object to be polished with the polishing composition according to claim 1 or 2.

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