Polishing composition

Abstract

Provided is a polishing composition that can exhibit an excellent polishing removal rate and has a suitably suppressed combustion promoting property. A polishing composition disclosed herein comprises: sodium permanganate and potassium permanganate as an oxidizing agent; abrasive grains composed of a material having a Mohs hardness of 6 or more; and water. The ratio (CK / CS) of the concentration CK [mM] of the potassium permanganate to the concentration CS [mM] of the sodium permanganate is 0.33 or more. The content of the sodium permanganate is less than 22.5 wt%.

Description

polishing composition

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2024-53234, 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] US Patent Application Publication No. 2022 / 0306902

[0004] Generally, from the viewpoint of manufacturing efficiency and cost-effectiveness, it is desirable that the polishing removal rate be sufficiently high for practical use. For example, when polishing a surface made of a high-hardness material such as silicon carbide, an improvement in the polishing removal rate is strongly desired. In order to improve the polishing removal rate when polishing a substrate made of such a high-hardness material, 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 proposes a polishing composition containing abrasive grains, water, and an oxidizing agent such as potassium permanganate, which is used to polish a substrate made of a high-hardness material.

[0005] In polishing various objects to be polished, including substrates made of high-hardness materials as described above, if it is possible to obtain a polishing removal rate of one step higher, it would be practically meaningful.In order to further improve the polishing removal rate, for example, it is considered effective to increase the concentration of the oxidizing agent contained in the polishing composition.However, the oxidizing agents such as potassium permanganate that have been used in this field so far tend to have low solubility in water, and it is not easy to obtain a polishing composition containing a high concentration of oxidizing agent.

[0006] Sodium permanganate is an example of a salt that has a higher solubility in water than conventional oxidizing agents. By using sodium permanganate, which has excellent solubility in water, instead of conventional oxidizing agents, it is expected that the concentration of the oxidizing agent can be increased. However, sodium permanganate has the property of promoting the combustion of substances (combustion promoting property). Therefore, it would be advantageous to provide a polishing composition with reduced combustion promoting property.

[0007] 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 and has suitably suppressed combustion-supporting properties.

[0008] The polishing composition provided herein contains an oxidizing agent, abrasive grains composed of a material with a Mohs hardness of 6 or higher, and water. The oxidizing agent contains sodium permanganate and potassium permanganate. Here, the ratio (CK / CS) of the concentration of potassium permanganate CK [mM] to the concentration of sodium permanganate CS [mM] is 0.33 or higher. The content of sodium permanganate is less than 22.5 wt%. With this configuration, a polishing composition can be realized that exhibits an excellent polishing removal rate and has suitably suppressed combustion-promoting properties by increasing the concentration of the oxidizing agent.

[0009] In some embodiments, the polishing composition further contains a metal salt A. The metal salt A can be a salt of a cation a containing a metal whose hydrated metal ion has a pKa of less than 7.0 and an anion. By using the metal salt A, 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 A is a salt of a cation a containing a metal whose hydrated metal ion has a pKa of less than 7.0 and a nitrate ion.

[0010] 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.

[0011] 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.

[0012] This specification further provides a method for polishing an object to be polished. The polishing method includes a step of 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 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.

[0013] 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.

[0014] <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 and metal salt B described below.

[0015] The polishing composition disclosed herein is characterized by containing a combination of sodium permanganate and potassium permanganate as oxidizing agents. Sodium permanganate tends to exhibit higher solubility in water compared to other permanganates such as potassium permanganate. Therefore, by including sodium permanganate as an oxidizing agent, it is easy to favorably increase the oxidizing agent content in the polishing composition. On the other hand, because sodium permanganate has the property of promoting the combustion of substances (combustion-promoting property), using it at a high concentration may increase the combustion-promoting property of the polishing composition. By using a combination of sodium permanganate and potassium permanganate as oxidizing agents, it is possible to favorably suppress the combustion-promoting property while increasing the oxidizing agent concentration.

[0016] In the polishing composition disclosed herein, the ratio (CK / CS) of the potassium permanganate concentration (molar concentration) CK [mM] to the sodium permanganate concentration (molar concentration) CS [mM] is 0.33 or more. When potassium permanganate is used in an amount relative to the content of sodium permanganate such that CK / CS is 0.33 or more, the combustion improving effect derived from the sodium permanganate contained in the polishing composition tends to be suitably suppressed. From the viewpoint of further suppressing the combustion improving effect, in some preferred embodiments, CK / CS is 0.4 or more, more preferably 0.45 or more, even more preferably 0.5 or more, and may be 0.55 or more, 0.6 or more, or 0.65 or more.

[0017] The upper limit of the CK / CS is not particularly limited. From the viewpoint of easily realizing a higher polishing removal rate by utilizing sodium permanganate, which has high solubility in water, the CK / CS is preferably 100 or less, more preferably 10 or less, and even more preferably 2.5 or less. In some embodiments, the CK / CS may be 1.5 or less, 1 or less, or 0.7 or less.

[0018] The polishing composition disclosed herein has a sodium permanganate content of less than 22.5 wt%. If the sodium permanganate content is greater than 22.5 wt%, the combustion-supporting property of the polishing composition increases, which may promote the combustion of nearby combustible materials (e.g., a cloth used to wipe the polishing composition). From the viewpoint of suitably reducing the combustion-supporting property of the polishing composition, the content of sodium permanganate in the polishing composition is preferably 20 wt% or less (approximately 1410 mM or less). In some embodiments, it may be 15 wt% or less (approximately 1060 mM or less), 13 wt% or less (approximately 920 mM or less), 10 wt% or less (approximately 700 mM or less), 8 wt% or less (approximately 560 mM or less), or 6 wt% or less (approximately 420 mM or less). Reducing the sodium permanganate content can also be advantageous from the viewpoint of reducing the occurrence of defects caused by sodium that may remain after polishing. From this perspective, in some embodiments, the content of sodium permanganate may be 5% by weight or less (approximately 350 mM or less), 4.5% by weight or less (approximately 320 mM or less), or 4% by weight or less (approximately 280 mM or less).

[0019] The content of sodium permanganate in the polishing composition disclosed herein is more than 0% by weight. From the viewpoint of utilizing the feature that sodium permanganate exhibits high solubility in water and easily realizing a higher polishing removal rate, the content of sodium permanganate is preferably 1% by weight or more (approximately 70 mM or more), more preferably 2% by weight or more (approximately 140 mM or more), even more preferably 3% by weight or more (approximately 210 mM or more), or may be 4% by weight or more (approximately 280 mM or more), 5% by weight or more (approximately 350 mM or more), or may be 5.5% by weight or more (approximately 390 mM or more).

[0020] The technology disclosed herein is characterized by using potassium permanganate together with sodium permanganate. That is, the content of potassium permanganate in the polishing composition disclosed herein is greater than 0% by weight. From the viewpoint of reducing the combustion improver of the polishing composition containing sodium permanganate, the content of potassium permanganate is preferably 0.5% by weight or more (approximately 30 mM or more), more preferably 1% by weight or more (approximately 60 mM or more), even more preferably 2% by weight or more (approximately 130 mM or more), and may be 2.5% by weight or more (approximately 160 mM or more), 3% by weight or more (approximately 190 mM or more), 3.5% by weight or more (approximately 220 mM or more), or 4% by weight or more (approximately 250 mM or more). The upper limit of the content of potassium permanganate is not particularly limited. In some embodiments, the content of potassium permanganate in the polishing composition is 6.5 wt % or less (approximately 410 mM or less), optionally 6 wt % or less (approximately 380 mM or less), optionally 5.5 wt % or less (approximately 350 mM or less), optionally 4.5 wt % or less (approximately 280 mM or less), or optionally 4 wt % or less (approximately 250 mM or less).

[0021] The polishing composition disclosed herein may or may not further contain an oxidizing agent other than sodium permanganate and 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; permanganic acids such as permanganic acid and its salts, i.e., permanganates other than sodium permanganate and potassium permanganate; periodic acids such as periodic acid and its salts, i.e., sodium periodate and potassium periodate; iodic acids such as iodic acid and its salts, i.e., ammonium iodate; bromic acids such as bromic acid and its salts, i.e., potassium bromate; ferric acids such as ferric acid and its salts, i.e., potassium ferrate; chromic acids and dichromates such as perchromic acid, chromic acid and its salts, i.e., potassium chromate; dichromic acid and its salts, i.e., potassium dichromate; vanadic acid and its salts, i.e., ammonium vanadate, sodium vanadate, potassium vanadate. Examples of the other oxidizing agent include vanadates such as ammonium vanadates, perruthenic acids or their salts; ruthenic acids such as perruthenic acids or their salts; molybdic acids such as permolybdic acid, molybdic acid, and its salts such as ammonium molybdate and disodium molybdate; rhenic acids such as perrhenic acids or their 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 ammonium cerium nitrate. As the other oxidizing agent, 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 the other oxidizing agent is an inorganic compound.

[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. ＋ , K. ＋ It is preferable that:

[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] The total content of oxidizing agents in the polishing composition disclosed herein is not particularly limited. From the viewpoint of improving the polishing removal rate, in some preferred embodiments, the total content of oxidizing agents is 200 mM or more, more preferably 300 mM or more (for example, 400 mM or more), and may be 500 mM or more, 550 mM or more, 600 mM or more, 650 mM or more, or 700 mM or more. The upper limit of the total content of oxidizing agents is not particularly limited. From the viewpoint of balancing the polishing removal rate and surface quality, the total content of oxidizing agents is usually appropriate to be 3000 mM or less, preferably 2000 mM or less, more preferably 1500 mM or less, even more preferably 1000 mM or less, and may be 900 mM or less, 800 mM or less, or 750 mM or less. In some embodiments, the total oxidizing agent content may be 700 mM or less, 650 mM or less, 600 mM or less, or 550 mM or less.

[0025] (Metal Salt A) In some preferred embodiments, the polishing composition may contain a metal salt A selected from salts of anions and cations containing poor metals, i.e., metals belonging to Groups 13 to 16 of the periodic table. The metal salts A may be used alone or in combination of two or more. By further using a metal salt A in a polishing composition containing sodium permanganate as an oxidizing agent, deterioration in the performance of the polishing composition (e.g., a decrease in the polishing removal rate) due to pH fluctuations in the polishing composition during polishing of an object to be polished can be suppressed.

[0026] The above-mentioned poor 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 of the periodic table, more preferably those belonging to Periods 3 and 4, with the poor metal belonging to Period 3, i.e., aluminum, being particularly preferred.

[0027] In some embodiments, the metal salt A is preferably a salt of an anion and a cation containing a metal whose hydrated metal ion has a pKa of less than about 7.0. The metal salt A, which is a salt of such a cation and anion, 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 is therefore likely to suppress deterioration of the performance of the polishing composition over time. From this perspective, the metal salt A can preferably be a salt of an anion and a cation containing a metal whose hydrated metal ion has a pKa of, for example, less than 7.0 or 6.0 or less. Examples of cations containing a metal whose hydrated metal ion has a pKa of 6.0 or less include Al, as described in "Inorganic Chemistry, GARY WULFBERG, University Science Books, 2000, p.59, Table 2.2 "Hydrolysis 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＋ (pKa of the hydrated metal ion is −0.3), but is not limited to these.

[0028] The type of salt in the metal salt A 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, and 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. The technology disclosed herein relates to, for example, a method for preparing a metal salt A using 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

[0029] Preferably, the metal salt A is a compound that is not oxidized by an oxidizing agent. From this perspective, by appropriately selecting the oxidizing agent and the metal salt A, it is possible to prevent the metal salt A 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 perspective, preferred examples of the metal salt A include aluminum nitrate and aluminum chloride. Here, the use of aluminum nitrate can increase the combustion promoting property of the polishing composition. According to the technology described herein, the combustion promoting property of the polishing composition can be sufficiently suppressed, so that even metal salts A that may increase the combustion promoting property, such as aluminum nitrate, can be suitably used. Among them, since nitrates have oxidizing properties, aluminum nitrate is particularly preferred as the metal salt A. When the metal salt A is used in combination with the metal salt B described below, the polishing removal rate can be further improved.

[0030] 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.

[0031] When the polishing composition contains metal salt A, the concentration (content) of metal salt A 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 A 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 A 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 A, the lower limit of the concentration of metal salt A 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 effects of use of metal salt A, preferably 5 mM or more, more preferably 10 mM or more (for example, 15 mM or more), and may be 17 mM or more, 20 mM or more, or 30 mM or more.

[0032] When the polishing composition contains a metal salt A, although it is not particularly limited, from the viewpoint of better exerting the effect of adding a metal salt A to a polishing composition containing sodium permanganate, the ratio (CA / CS) of the concentration of the metal salt A in the polishing composition (when a plurality of metal salts A are contained, their total concentration) CA [mM] to the content CS [mM] of sodium permanganate is usually 0 or more, preferably 0.005 or more, more preferably 0.01 or more, may be 0.02 or more, may be 0.03 or more, may be 0.04 or more, may be 0.05 or more, may be 0.055 or more, may be 0.06 or more, may be 0.065 or more, may be 0.07 or more. The upper limit of CA / CS is not particularly limited, but is suitably 0.5 or less, may be 0.4 or less, preferably 0.3 or less, more preferably 0.2 or less, may be 0.1 or less. In the above "CA / CS", "CA" represents the numerical portion when the concentration (content) of metal salt A in the polishing composition is expressed in units of "mM", and "CS" represents the numerical portion when the concentration (content) of sodium permanganate in the polishing composition is expressed in units of "mM", and both CA and CS are dimensionless numbers.

[0033] When the polishing composition contains a metal salt A, although it is not particularly limited, from the viewpoint of better exerting the effect of adding a metal salt A to a polishing composition containing potassium permanganate, the ratio (CA / CK) of the concentration of the metal salt A in the polishing composition (when a plurality of metal salts A are contained, their total concentration) CA [mM] to the content CK [mM] of potassium permanganate is usually 0 or more, preferably 0.005 or more, more preferably 0.01 or more, may be 0.02 or more, may be 0.03 or more, may be 0.04 or more, may be 0.05 or more, may be 0.06 or more, may be 0.07 or more, may be 0.08 or more. The upper limit of CA / CK is not particularly limited, but is suitably 1 or less, may be 0.5 or less, preferably 0.4 or less, more preferably 0.3 or less, may be 0.2 or less. In the above "CA / CK", "CA" represents the numerical portion when the concentration (content) of metal salt A in the polishing composition is expressed in units of "mM", and "CK" represents the numerical portion when the concentration (content) of potassium permanganate in the polishing composition is expressed in units of "mM", and both CA and CK are dimensionless numbers.

[0034] When the polishing composition contains a metal salt A, although it is not particularly limited, from the viewpoint of better exerting the effect of containing a metal salt A in an oxidizing agent-containing polishing composition, the ratio (CA / Wx) of the concentration of the metal salt A in the polishing composition (when a plurality of metal salts A are contained, their total concentration) CA [mM] to the content of the oxidizing agent (total content of a plurality of oxidizing agents) Wx [wt%] 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, CA / 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 CA / 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, CA / 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 "CA / Wx," "CA" represents the numerical value when the concentration (content) of metal salt A 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 CA and Wx are dimensionless numbers.

[0035] (Metal Salt B) In some preferred embodiments, the polishing composition may contain a metal salt B selected from alkaline earth metal salts. As the metal salt B, 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 B tends to improve the polishing removal rate. The metal salt B preferably contains one or more of Mg, Ca, Sr, and Ba as an element belonging to the alkaline earth metals. Among them, either Ca or Sr is preferred, and Ca is more preferred.

[0036] The type of salt in 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 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 B.

[0037] Specific examples of alkaline earth metal salts that can be selected for the metal salt B 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;

[0038] 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. In addition, the metal salt B 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 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 suppress deterioration of the performance of the polishing composition over time (for example, a decrease in the polishing removal rate). From this viewpoint, calcium nitrate is a preferred metal salt B.

[0039] 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 mode of use of the polishing composition. The concentration of metal salt B 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 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. The lower limit of the concentration of metal salt B may be, for example, 0.1 mM or more, and from the viewpoint of appropriately exerting the effects of use of metal salt B, 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.

[0040] 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 (the total content of the plurality of oxidizing agents) 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, 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 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, CB / 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 "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.

[0041] In some preferred embodiments, the polishing composition may contain a combination of metal salt A and metal salt B. In some preferred embodiments when the polishing composition contains a combination of metal salt A and metal salt B, the metal salt A and metal salt B have the same anion species. The anion species common to metal salt A and metal salt B may be, for example, nitric acid, hydrochloric acid, phosphoric acid, etc. From the viewpoint of obtaining a higher effect, a polishing composition in which both metal salt A and metal salt B are nitrates is particularly preferred.

[0042] When the polishing composition contains a combination of metal salt A and 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 and can be set so that the effect of using them in combination is appropriately exhibited. For example, CA / CB can be in the range of 0.001 to 1000. From the viewpoint of improving the polishing removal rate, in some embodiments, CA / CB is suitably approximately 0.01 or more, preferably 0.05 or more (e.g., 0.1 or more). Furthermore, CA / CB 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).

[0043] (Abrasive grains) The polishing composition disclosed herein 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.

[0044] 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.

[0045] From the viewpoint of improving the polishing removal rate, in some preferred embodiments, the polishing composition contains abrasive grains made of a material having a Mohs hardness of 6 or more. Here, when the abrasive grains are made of two or more materials, the hardness of the abrasive grains can be determined by calculating the product of the Mohs hardness and the mass ratio for each material and adding them up. The abrasive grains made of a material having a Mohs hardness of 6 or more may be used alone or in combination of two or more. The technology disclosed herein can be implemented in an embodiment in which only abrasive grains made of a material having a Mohs hardness of 6 or more are used as abrasive grains.

[0046] Examples of materials with a Mohs hardness of 6 or higher include alumina, zirconia, ceria, titania, silica, chromium oxide, iron oxide, silicon carbide, boron carbide, silicon nitride, manganese oxide, etc. Among these, alumina and silica are preferred from the viewpoint of achieving both a high polishing removal rate and reduced scratches. In some embodiments, the abrasive grains disclosed herein are composed of one or more types of particles selected from alumina and silica having a Mohs hardness of 6 or higher.

[0047] 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.

[0048] 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.

[0049] 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 / 2) / (2 / g). The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300."

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The content of abrasive grains (e.g., alumina abrasive grains, silica abrasive grains, etc.) in the polishing composition disclosed herein is suitably less than 10 wt % from the viewpoint of surface quality after polishing, 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.

[0067] 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.

[0068] In a polishing composition containing abrasive grains, the relationship between the content of the oxidizing agent and the content of the 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 content of the oxidizing agent (the total content of multiple oxidizing agents) Wx [wt%] to the content of the abrasive grains (the total content of multiple abrasive grains when multiple abrasive grains are included) 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.

[0069] 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, 0.05 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.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 can be 12 or more, 15 or more, or 18 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 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, CA / Wp may be 100 or less, 50 or less, 40 or less, or 30 or less. In the above "CA / Wp", "CA" represents the numerical value when the concentration of metal salt A 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 CA are both dimensionless numbers.

[0070] 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 20 or more, 50 or more, 100 or more, or 300 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, or may be 5,000 or less, or 2,500 or less. In some embodiments, CB / Wp may be 1,000 or less, 800 or less, or 600 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 %." CB and Wp are both dimensionless numbers.

[0071] (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.

[0072] (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.

[0073] (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.

[0074] (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.

[0075] (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.

[0076] 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.

[0077] 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 optionally 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 mixed, water for dilution or the like may be further added. In a preferred embodiment, the multi-component polishing composition disclosed herein contains an oxidizing agent and water in Part A, a metal salt (e.g., metal salt A, metal salt B, etc.) and water in Part B, and an abrasive in Part C. This embodiment can improve the storage stability of the polishing composition.

[0078] <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.

[0079] 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.

[0080] 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.

[0081] <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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] <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.

[0090] The matters disclosed by this specification include the following. [1] A polishing composition comprising an oxidizing agent, abrasive grains composed of a material having a Mohs hardness of 6 or more, and water, wherein the oxidizing agent comprises sodium permanganate and potassium permanganate, the ratio (CK / CS) of the concentration of the sodium permanganate CS [mM] to the concentration of the potassium permanganate CK [mM] is 0.33 or more, and the content of the sodium permanganate is less than 22.5 wt%. [2] The polishing composition according to [1] above, further comprising a metal salt A. [3] The polishing composition according to [2] above, wherein the metal salt A is a salt of an anion and a cation a containing a metal whose hydrated metal ion has a pKa of less than 7.0. [4] The polishing composition according to [3] above, wherein the metal salt A is a salt of the cation a and a nitrate ion. [5] The polishing composition according to any one of [1] to [4] above, which has a pH of 1.0 or more and less than 6.0. [6] The polishing composition according to any one of [1] to [5] above, which is used for polishing a material having a Vickers hardness of 1500 Hv or more. [7] The polishing composition according to any one of [1] to [6] above, which is used for polishing silicon carbide. [8] A polishing method comprising a step of polishing an object to be polished with the polishing composition according to any one of [1] to [7] above.

[0091] 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.

[0092] <Preparation of Polishing Composition>

[0093] (Example 1) Alumina abrasive grains, sodium permanganate and potassium permanganate as oxidizing agents, aluminum 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, 420 mM sodium permanganate, 280 mM potassium permanganate, and 30 mM aluminum nitrate.

[0094] Example 2 Polishing compositions of each example were prepared in the same manner as in Example 1, except that the concentrations of sodium permanganate and potassium permanganate were set as shown in Table 1, respectively.

[0095] (Example 3) Alumina abrasive grains, sodium permanganate as an oxidizing agent, aluminum 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, 700 mM sodium permanganate, and 30 mM aluminum nitrate.

[0096] In the polishing compositions of 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 Examples 1 to 3. The pH of each of the polishing compositions of Examples 1 to 3 was within the range of 3.7 to 3.8.

[0097] (Example 4) Silica abrasive grains, sodium permanganate and potassium permanganate as oxidizing agents, aluminum nitrate, and deionized water were mixed to prepare a polishing composition containing 0.1% silica abrasive grains, 420 mM sodium permanganate, 280 mM potassium permanganate, and 30 mM aluminum nitrate at concentrations.

[0098] Example 5 Polishing compositions of each example were prepared in the same manner as in Example 4, except that the concentrations of sodium permanganate and potassium permanganate were set as shown in Table 1, respectively.

[0099] (Example 6) Silica abrasive grains, sodium permanganate as an oxidizing agent, aluminum nitrate, and deionized water were mixed to prepare a polishing composition containing 0.1% silica abrasive grains, 700 mM sodium permanganate, and 30 mM aluminum nitrate.

[0100] In the polishing compositions of Examples 4 to 6, colloidal silica having an average primary particle size of 35 nm was used as the silica abrasive grains. No pH adjuster was used in preparing the polishing compositions of Examples 4 to 6. The pH of each of the polishing compositions of Examples 4 to 6 was within the range of 3.7 to 3.8.

[0101] Examples 7 to 9 Polishing compositions of each example were prepared in the same manner as in Example 1, except that the concentrations of sodium permanganate and potassium permanganate were as shown in Table 2.

[0102] (Example 10) Alumina abrasive grains, sodium permanganate as an oxidizing agent, aluminum 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, 540 mM sodium permanganate, and 30 mM aluminum nitrate.

[0103] In the polishing compositions of Examples 7 to 10, 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 7 to 10. The pH of each of the polishing compositions of Examples 7 to 10 was within the range of 3.7 to 3.8.

[0104] Examples 11 to 13 Polishing compositions of each example were prepared in the same manner as in Example 4, except that the concentrations of sodium permanganate and potassium permanganate were set as shown in Table 2, respectively.

[0105] (Example 14) Silica abrasive grains, sodium permanganate as an oxidizing agent, aluminum nitrate, and deionized water were mixed to prepare a polishing composition containing 0.1% silica abrasive grains, 540 mM sodium permanganate, and 30 mM aluminum nitrate.

[0106] In the polishing compositions of Examples 11 to 14, colloidal silica having an average primary particle size of 35 nm was used as the silica abrasive grains. No pH adjuster was used in preparing the polishing compositions of Examples 11 to 14. The pH of each of the polishing compositions of Examples 11 to 14 was within the range of 3.7 to 3.8.

[0107] <Solubility> The solubility of the polishing compositions of Examples 1 to 14 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). The results are shown in the corresponding columns in Tables 1 and 2.

[0108] <Combustion Improver Test> Approximately 10 mL of the polishing compositions of Examples 1 to 14 obtained was placed on a stainless steel tray and dried in an oven heated to 110°C for 1 hour to obtain a powdery dry product. The obtained powder was heated by placing it on a hot plate heated to 60°C. Under an environment of 23°C and 50% RH, a Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.) soaked with 1 g of deionized water was prepared, and 0.2 g of the powder heated to 60°C was placed on it. Immediately after placing the powder, the temperature of the Kimwipe surface was measured with a radiation thermometer (manufactured by A&D Co., Ltd., model number AD-5611A). The maximum temperature of the Kimwipe surface measured within 10 minutes after placing the powder was recorded as the reached temperature. The results are shown in the corresponding columns in Tables 1 and 2. In Tables 1 and 2, ">60°C" indicates that the reached temperature was higher than 60°C. If the temperature reached is 60° C. or less, it can be determined that the combustion-supporting effect is sufficiently suppressed.

[0109] Although not shown in Tables 1 and 2, a polishing composition was prepared in the same manner as in Example 3, except that the content of sodium permanganate was 22.5% by weight. 2 mL of the polishing composition was taken and dropped onto a Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.). Immediately after dropping, the temperature of the Kimwipe surface was measured with a radiation thermometer (manufactured by A&D Co., Ltd., model number AD-5611A). Within 10 minutes after dropping, the temperature of the Kimwipe surface exceeded 60°C.

[0110] <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 a polishing liquid as is to polish the object to be polished 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

[0111] 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.

[0112] <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 [μm / h] = polishing removal amount [cm] x 10 ４ / Polishing time (= 5 / 60 hours)

[0113] The polishing removal rates obtained for each example are shown in the corresponding columns of Tables 1 and 2.

[0114]

[0115]

[0116] As is clear from the results shown in Table 1, the polishing composition of Example 1, which contains sodium permanganate and potassium permanganate as oxidizing agents and has a molar ratio of potassium permanganate to sodium permanganate (CK / CS) of 0.33 or more, exhibits a superior polishing removal rate and significantly reduces combustion promoting properties compared to the polishing compositions of Example 2, which has a CK / CS ratio of less than 0.33, and Example 3, which does not contain potassium permanganate. Similarly, the polishing composition of Example 4, which has a molar ratio of potassium permanganate to sodium permanganate (CK / CS) of 0.33 or more, exhibits a superior polishing removal rate and significantly reduces combustion promoting properties compared to the polishing compositions of Example 5, which has a CK / CS ratio of less than 0.33, and Example 6, which does not contain potassium permanganate.

[0117] The same tendency was also confirmed from the results shown in Table 2. That is, it was confirmed that the polishing compositions of Examples 7 to 9, which contained sodium permanganate and potassium permanganate as oxidizing agents and had a molar ratio of potassium permanganate to sodium permanganate (CK / CS) of 0.33 or more, exhibited superior polishing removal rates and significantly reduced combustion promoting properties compared to the polishing composition of Example 10, which did not contain potassium permanganate. It was also confirmed that the polishing compositions of Examples 11 to 13, which had a molar ratio of potassium permanganate to sodium permanganate (CK / CS) of 0.33 or more, exhibited superior polishing removal rates and significantly reduced combustion promoting properties compared to the polishing composition of Example 14, which did not contain potassium permanganate.

[0118] 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 an oxidizing agent, abrasive grains made of a material with a Mohs hardness of 6 or more, and water, wherein the oxidizing agent comprises sodium permanganate and potassium permanganate, the ratio (CK / CS) of the concentration of potassium permanganate CK [mM] to the concentration of sodium permanganate CS [mM] is 0.33 or more, and the content of sodium permanganate is less than 22.5 wt%.

2. The polishing composition according to claim 1, further comprising a metal salt A.

3. The polishing composition according to claim 2, wherein the metal salt A is a salt of an anion and a cation a containing a metal whose hydrated metal ion has a pKa of less than 7.

0.

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

5. The polishing composition according to any one of claims 1 to 4, which is used for polishing a material having a Vickers hardness of 1500 Hv or more.

6. The polishing composition according to any one of claims 1 to 4, which is used for polishing silicon carbide.

7. A polishing method comprising a step of polishing an object to be polished with the polishing composition according to any one of claims 1 to 4.

Images