TW201631109A - Polishing composition and manufacturing method of substrate using same - Google Patents

Abstract

Provided is a polishing composition capable of polishing a subject to be polished which has a crystalline metal compound in the surface thereof, with higher polishing efficiency. The polishing composition, used for the purpose of polishing a subject to be polished which has a crystalline metal compound in the surface thereof, contains an aluminum oxide abrasive grain, a colloidal silica abrasive grain, and water.

Description

Composition for polishing and method for producing substrate using the same

The present invention relates to a polishing composition used for polishing an object to be polished which has a crystalline metal compound on its surface, and a method for producing a substrate using the composition.

As a substrate material for an optical device or a substrate material for a power supply device, for example, an oxide such as alumina (for example, sapphire), yttrium oxide, gallium oxide, or zirconia, aluminum nitride, tantalum nitride, or gallium nitride is known. Such as nitrides, and carbides such as tantalum carbide. The substrate or film formed of these materials is generally stable because of the chemical action against oxidation or misalignment and etching, so processing by polishing is not easy. Therefore, it is generally processed by grinding or cutting using a hard material. However, a surface having high smoothness cannot be obtained by processing by grinding or cutting.

For the purpose of obtaining a smoother surface, it is known to polish a sapphire substrate using a polishing composition containing colloidal cerium oxide. For example, Patent Document 1 describes that a polishing liquid containing a high concentration of colloidal cerium oxide can improve the polishing efficiency of a sapphire substrate.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-44078

However, in the polishing liquid described in Patent Document 1, there is a problem that the improvement in polishing efficiency is insufficient.

The present invention has been made in view of the above knowledge, and an object thereof is to provide a polishing composition which can be polished at a higher polishing efficiency by polishing an object having a crystalline metal compound on its surface.

The above problems should be solved, and the inventors of the present invention repeatedly focused on research. As a result, it has been found that the above problems can be solved by a polishing composition containing alumina abrasive grains and colloidal ceria abrasive grains together. Then, based on the above knowledge, the present invention is achieved.

That is, the present invention relates to a polishing composition which is used for polishing an object to be polished which is a crystalline metal compound having a surface, and the polishing composition contains alumina abrasive grains and colloidal cerium oxide abrasive grains. And water.

According to the present invention, it is possible to provide a polishing composition which can be polished at a higher polishing efficiency by polishing an object having a crystalline metal compound on its surface.

The present invention relates to a polishing composition which is used for polishing an object to be polished which is composed of a crystalline metal compound containing alumina abrasive grains, colloidal cerium oxide abrasive grains, and water. By the polishing composition of the present invention having such a configuration, it is possible to polish the object to be polished having a crystalline metal compound on the surface with higher polishing efficiency.

On the other hand, the effect of the above-mentioned polishing composition of the present invention is not particularly known, but it can be considered as follows.

It is known that in the case where sapphire, which is an example of a crystalline metal compound, is ground by colloidal cerium oxide abrasive grains, a solid phase reaction is generated by contact of colloidal cerium oxide abrasive grains with sapphire, and a kelp is formed on the surface. The layer of stone (mullite) forms a so-called reaction layer (for example, see Henry W. Gutsche and Jerry W. Moody, Journal of Electrochemical Society, Vol. 125 (1978), No. 1, 136-138.). In addition, it is also known that a fragile layer (process-degraded layer) remaining in stress or strain is generated on the surface of the object to be polished, such as embossing or scratching of the abrasive grains of the object to be polished.

In the case where the object to be polished is polished by the polishing composition of the present invention, the colloidal cerium oxide abrasive grains and the object to be polished are used. The reaction layer and the fragile layer which are formed on the surface of the object to be polished which are in contact with each other are removed by the alumina abrasive grains, so that the surface of the object to be polished becomes reactive. By successively contacting the colloidal cerium oxide abrasive grains to the reactive surface to form a series of cycles of the reaction layer and the fragile layer, compared to the polishing composition containing only the colloidal cerium oxide abrasive grains, the present invention The polishing composition can achieve high polishing efficiency. Moreover, the above mechanism is presumed to be speculative, and the present invention does not have any ones that are subject to the above mechanism.

[grinding object]

The object to be polished according to the present invention is a metal compound having crystallinity on the surface. It is preferable that the surface of the object to be polished is hydrophilic because the particles are hard to adhere, and it is preferable that the surface of the object to be polished contains a single crystal material from the viewpoint of having less impurities. More specifically, examples of the crystalline metal compound to be contained on the surface of the object to be polished include oxides of aluminum oxide (for example, sapphire), cerium oxide, gallium oxide, and zirconium oxide, and aluminum nitride. A ceramic such as tantalum nitride or a nitride such as gallium nitride or a carbide such as tantalum carbide. Among them, the chemical action of oxidation or misalignment and etching is ideal for alumina of a stable material, particularly sapphire. In this case, the surface orientation of the sapphire is not particularly limited, and examples thereof include a c-plane (0001), a r-plane (-1012), and an R-plane (10-14). In addition, the so-called c-plane, r-plane, and R-face are based on the SEMI M65-0306E2 (revision of February 2006), a new specification for the SEMI standard.

The use of the object to be polished is not particularly limited, and examples thereof include materials for optical devices, materials for power supply devices, and compound semiconductors. The form of the object to be polished is not particularly limited, and examples thereof include a substrate, a film, and other molded members.

Next, the configuration of the polishing composition of the present invention will be described in detail.

[Alumina abrasive grain]

The type of the alumina abrasive grains is not particularly limited, and examples thereof include those of α-alumina, δ-alumina, θ-alumina, γ-alumina, or κ-alumina. However, in order to polish the crystalline metal compound with higher polishing efficiency, it is preferred that the alumina abrasive particles have α-alumina as a main component. Specifically, the α conversion ratio of the alumina in the alumina abrasive grains is preferably 20% or more, and more preferably 40% or more. The alpha conversion rate of the alumina in the alumina abrasive grains was determined by the integrated intensity ratio of the (113) plane-wound rays measured by X-ray diffraction.

Alumina abrasive grains, which may also contain impurities such as barium, titanium, iron, copper, chromium, sodium, potassium, calcium, magnesium, and the like. However, the purity of the alumina abrasive grains is preferably as high as possible, and specifically, it is preferably 99% by mass or more, more preferably 99.5% by mass or more, and still more preferably 99.8% by mass or more. When the purity of the alumina abrasive grains is increased in the range of 99% by mass or more, the contamination of the surface of the object to be polished after polishing using the polishing composition is less. In this point, the purity of the alumina abrasive grains is 99% by mass or more, more specifically, 99.5% by mass or more, and further, 99.8%. When the mass is at least the above, it is easy to reduce the contamination of the surface of the object to be polished which is caused by the polishing composition to a level which is particularly suitable for practical use. In addition, the content of the impurity element in the alumina abrasive grains can be calculated, for example, from a measured value obtained by an ICP emission spectroscopic analyzer such as ICPE-9000 manufactured by Shimadzu Corporation.

The average secondary particle diameter of the alumina abrasive grains is preferably 0.01 μm or more, and more preferably 0.1 μm or more. As the average secondary particle diameter of the alumina abrasive grains increases, the removal rate of the object to be polished increases.

The average secondary particle diameter of the alumina abrasive grains is preferably 20 μm or less, more preferably 15 μm or less, and more preferably 10 μm or less. As the average secondary particle diameter of the alumina abrasive grains becomes smaller, the possibility of occurrence of defects such as sudden scratches is lowered. In addition, the average secondary particle diameter of the alumina abrasive grains is measured by, for example, a laser diffraction/scattering type, and can be carried out, for example, by using "LA-950" manufactured by Horiba, Ltd.

The specific surface area of the aluminum oxide abrasive grains, which is based 5m ² / g or more is over, 7m ² / g or more is more desirable. Since the primary particle diameter of the alumina abrasive grains becomes smaller as the specific surface area of the alumina abrasive grains becomes larger, the contact area with the object to be polished becomes larger, and the polishing efficiency is improved.

Further, the specific surface area of the alumina abrasive grains is preferably 40 m ² /g or less, and more preferably 20 m ² /g or less. Since the primary particle diameter of the alumina abrasive grains becomes larger as the specific surface area of the alumina abrasive grains becomes smaller, the mechanical action becomes stronger, and the removal rate of the object to be polished becomes higher. The value of the specific surface area of the alumina abrasive grains can be determined, for example, by a nitrogen adsorption method (BET method) using Flow Sorb II 2300 manufactured by Micromeritics.

The method for producing the alumina abrasive grains is not particularly limited. The alumina abrasive grain is an alumina refined from alumina bauxite by the Bayer process, or may be melted and pulverized. Alternatively, alumina obtained by heat-treating aluminum hydroxide hydrothermally synthesized using an aluminum compound as a raw material, or alumina synthesized by an aluminum compound by a vapor phase method. Alumina synthesized from an aluminum compound is characterized by higher purity than usual alumina.

[colloidal cerium oxide abrasive grains]

The type of the colloidal cerium oxide abrasive grains is not particularly limited, and those obtained by various conventionally known production methods can be used. Further, commercially available products can also be used as the colloidal cerium oxide abrasive grains. As an example of the commercial product, the company is manufactured by Nissan Chemical Industry Co., Ltd., manufactured by Nippon Chemical Industry Co., Ltd., manufactured by Japan Chemical Industry Co., Ltd., manufactured by Fusang Chemical Industry Co., Ltd., manufactured by ADEKA Co., Ltd., manufactured by Akzo Nobel Co., Ltd., and manufactured by AZ Electronic Materials Co., Ltd. Colloidal cerium oxide manufactured by Nalco Corporation and manufactured by WR Grace. Further, two or more kinds of colloidal cerium oxide particles having different preparation methods or manufacturers are prepared, and by mixing these components in an arbitrary ratio, suitable colloidal cerium oxide abrasive grains can be obtained.

The average secondary particle diameter of the colloidal cerium oxide abrasive grains is preferably 5 nm or more, and more preferably 10 nm or more. As the average secondary particle diameter of the colloidal cerium oxide abrasive grains becomes larger, the impedance during polishing becomes smaller, and the polishing becomes stable.

In addition, the average secondary particle size of the colloidal cerium oxide abrasive particles, It is preferably 500 nm or less, more preferably 200 nm or less, and more preferably 120 nm or less. As the average secondary particle diameter of the colloidal cerium oxide abrasive grains becomes smaller, the surface area per unit mass of the colloidal cerium oxide abrasive grains becomes larger, the contact frequency with the object to be polished is increased, and the polishing efficiency is improved. In addition, the average secondary particle diameter of the colloidal cerium oxide abrasive particles is measured by, for example, a dynamic light scattering method, and can be carried out, for example, by using "UPA-UT151" manufactured by Nikkiso Co., Ltd.

[other abrasive grains]

The polishing composition of the present invention may further comprise the above-mentioned alumina abrasive grains and other abrasive grains other than the colloidal cerium oxide abrasive grains. Examples of the other abrasive grains include cerium oxide other than colloidal cerium oxide particles such as cerium oxide, or zirconia, cerium oxide, titanium oxide, cerium carbide, aluminum hydroxide, and the like.

The shape of the abrasive grains (alumina abrasive grains, colloidal cerium oxide abrasive grains, and other abrasive grains) may be spherical or non-spherical. As a specific example of the non-spherical shape, a polygonal columnar shape, a cylindrical shape, and a central portion of a column such as a triangular column or a quadrangular column are formed in a straw shape which is more swollen than the end portion, and the center portion of the disk is a through-dough shape or a plate shape. The so-called 茧-shaped shape having a neck-down shape at the center portion, a so-called ginseng shape having a plurality of protrusions on the surface, a rugby shape, and the like can be exemplified by various shapes, and is not particularly limited.

The total content of the abrasive in the polishing composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, more preferably 0.5% by mass or more. As the content of the abrasive grains increases, the polishing rate of the surface of the object to be polished according to the polishing composition is improved.

Further, the content of the abrasive grains in the polishing composition is preferably 50% by mass or less, and preferably 40% by mass or less. As the content of the abrasive grains decreases, the manufacturing cost of the polishing composition decreases. Further, in the present specification, the content of the above-mentioned abrasive grains is the total content of all the abrasive component (alumina abrasive grains, colloidal cerium oxide abrasive grains, and other abrasive grains).

Further, the ratio of the total amount of the alumina abrasive grains to the colloidal cerium oxide abrasive grains of the abrasive is preferably 20% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, and 70% by mass. More than % is particularly preferable, and 80% by mass or more is more particularly desirable, and 100% by mass, that is, the abrasive grains are preferably formed of alumina abrasive grains and colloidal cerium oxide abrasive grains.

In addition, the mass ratio of the alumina abrasive grains to the colloidal cerium oxide abrasive grains in the polishing composition is ideal for the alumina abrasive grains: colloidal cerium oxide abrasive grains = 1:9 to 9:1. Alumina abrasive grains: colloidal cerium oxide abrasive grains = 2.1: 7.9 ~ 6: 4 is more desirable. For this range, the grinding efficiency is further improved.

〔water〕

The polishing composition of the present invention contains water as a dispersion medium or a solvent for dispersing or dissolving each component. From the viewpoint of suppressing the action of the other components, it is preferable that water containing no impurities is contained as much as possible. Specifically, after removing the impurity ions by the ion exchange resin, the pure water or ultrapure water of the foreign matter is removed by a filter. Or distilled water is ideal.

[other ingredients]

The polishing composition of the present invention may further contain an additive for adjusting the dispersibility of the abrasive particles, or a preservative, a mold inhibitor, and a pH adjuster, such as a surfactant, a water-soluble polymer, or a dispersing aid. Other ingredients. These other components may be used alone or in combination of two or more.

Examples of the surfactant include a nonionic surfactant, an anionic surfactant, a cationic surfactant, and the like. Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and sorbitan monooleate. Specific examples of the anionic surfactant include a carboxylic acid compound, a sulfonic acid compound, a sulfate compound, and a phosphate compound. Specific examples of the cationic surfactant include a quaternary ammonium salt and the like.

Examples of the water-soluble polymer include polycarboxylic acids, polyphosphonic acids, polysulfonic acids, polysaccharides, cellulose derivatives, oxygen alkylene polymers, or copolymers of these components or salts thereof. Derivatives, etc.

Examples of the dispersing aid include condensed phosphates such as pyrophosphate or hexametaphosphate.

Examples of the preservative and the antifungal agent include, for example, 2-methyl-4-isothiazolin-3-one or 5-chloro-2-methyl-4-isothiazolin-3-one. Thiazoline-based preservatives, parabens, and phenoxyethanol.

Hereinafter, a pH adjuster for other desirable components will be described.

[pH adjuster]

The polishing composition of the present invention is preferably a pH adjusting agent. The pH adjuster adjusts the pH of the polishing composition, and when the pH adjuster is added to the polishing composition, the dispersibility of the abrasive grains is improved as compared with the unadded polishing composition. The polishing efficiency is further improved by promoting ionization of the surface of the object to be polished. Further, in the high pH range, the surface of the colloidal cerium oxide abrasive grains is hydrolyzed to activate the reaction with the object to be polished, thereby improving the polishing efficiency.

As the pH adjuster, a generally known acid, a base, or a salt thereof can be used. Specific examples of the acid which can be used as the pH adjuster include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid, or formic acid and acetic acid. , propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, caproic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, heptanoic acid, 2- Methylhexanoic acid, octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, cis-butyl Aenedioic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid An organic acid such as methoxyacetic acid, methoxyphenylacetic acid, or phenoxyacetic acid. When a mineral acid is used as a pH adjuster, in particular, sulfuric acid, nitric acid, phosphoric acid, etc. are particularly preferable from the viewpoint of improving the polishing rate, and when an organic acid is used as a pH adjuster, glycolic acid, succinic acid, Maleic acid, citric acid, tartaric acid, apple Acid, gluconic acid, and itaconic acid are ideal.

Examples of the base which can be used as the pH adjuster include an amine such as an aliphatic amine or an aromatic amine, an organic base such as quaternary ammonium hydroxide, or a hydroxide of an alkali metal such as potassium hydroxide or a group 2 element. Hydroxide, ammonia, etc.

Among them, nitric acid, potassium hydroxide, potassium carbonate, phosphoric acid, sulfuric acid, and sodium hydroxide are preferred in terms of availability.

The pH of the polishing composition of the present invention is preferably 2 or more, and more preferably 8 or more. On the other hand, from the viewpoint of polishing efficiency, the pH is higher, but the safety of the operator may decrease as the pH becomes higher. Therefore, the upper limit of pH is preferably 13.5 or less.

The pH adjuster may be used alone or in combination of two or more. In this case, it is preferred to use a pH adjusting agent in combination of two or more types to exhibit a buffering effect and to maintain the pH in the above range. Further, by adding a pH adjuster at the appropriate time during polishing, the same effect can be obtained by maintaining the pH in the above range. In particular, in the case where a weak acid and a strong base, a strong acid and a weak base, or a combination of a weak acid and a weak base are used, a pH buffering action can be obtained.

The amount of the pH adjuster to be added is not particularly limited, and is preferably adjusted so that the polishing composition has a desired pH.

[Method for Producing Composition for Grinding]

The method for producing the polishing composition of the present invention is not particularly limited For example, alumina abrasive grains, colloidal cerium oxide abrasive grains, and other components such as a pH adjuster may be stirred and mixed in water as necessary.

The order in which the components are mixed, the temperature at the time of mixing, or the mixing time is also not particularly limited.

It is also preferable that each component contained in the polishing composition is filtered by a filter immediately before the polishing composition is produced. Further, the polishing composition of the present invention is preferably subjected to filtration treatment by a filter before use. By applying a filtration treatment, coarse foreign matter in the polishing composition is removed to improve the quality.

[Grinding method and method of manufacturing substrate]

As described above, the polishing composition of the present invention is applied to an object to be polished which is polished to a metal compound having a crystalline surface. Therefore, the present invention provides a polishing method for polishing an object to be polished which has a crystalline metal compound on the surface thereof, using the polishing composition of the present invention. Moreover, the present invention provides a method for producing a substrate which is a substrate which has a crystalline metal compound on its surface and is polished by the above-described polishing method.

When the polishing composition of the present invention is used to polish a substrate having a crystalline metal compound on its surface, an apparatus or condition used for polishing a normal substrate can be used. As a general polishing apparatus, there is a single-side polishing apparatus or a double-side polishing apparatus, and in a single-side polishing apparatus, a substrate is held by using a holder called a carrier, and is supplied for polishing. The composition simultaneously presses a platen to which a polishing cloth is adhered on one surface of the substrate to rotate the platen to polish one side of the substrate. In the double-side polishing apparatus, the substrate is held by using a holder called a carrier, and the polishing composition is supplied from above, and the pressure plate to which the polishing cloth is adhered is pressed against the opposite surface of the substrate. The two sides of the substrate are polished by rotating in opposite directions. At this time, polishing is performed by the physical action of the polishing pad, the polishing composition, the friction with the substrate, and the chemical composition of the polishing composition.

The polishing pad used in the present invention is not particularly limited. For example, in addition to materials such as a polyurethane type, a non-woven type, and a suede type, physical properties such as hardness and thickness are different, and those containing or not containing abrasive grains may be used, but these types may be used. Any kind of pad.

When the object to be polished is polished by using the polishing composition described above, the polishing composition used once for polishing can be recovered and used again for polishing. An example of a method of reusing the polishing composition is a method in which the polishing composition discharged from the polishing apparatus is collected in a tank and recycled to the polishing apparatus for use. By recycling the polishing composition, the amount of the polishing composition discharged as the waste liquid can be reduced, and the environmental load can be reduced, and the amount of the polishing composition can be reduced to suppress the polishing of the polishing target. The point of manufacturing cost is useful.

When the polishing composition is recycled, alumina abrasive grains or colloidal cerium oxide abrasive grains which are consumed by polishing, and one or all of the additives may be added to the recycling agent as a composition adjusting agent. In this case, the composition adjusting agent may be a mixture of alumina abrasive grains, colloidal cerium oxide abrasive grains, and one or all of the additives in an arbitrary mixing ratio. It is added by the addition of the composition adjusting agent, and the polishing composition can be adjusted to a suitable composition, and the polishing can be suitably maintained. The concentration of the alumina abrasive grains, the colloidal cerium oxide abrasive grains, and the additive contained in the composition adjusting agent is not particularly limited, but is preferably adjusted in accordance with the size of the circulation tank or the polishing conditions.

The polishing conditions of the polishing method of the present invention include the amount of the polishing composition. The amount of supply varies depending on the type of the substrate to be polished, the polishing apparatus, and the polishing conditions. However, the polishing composition may be supplied in a sufficient amount so that the polishing composition is not uniformly distributed between the substrate and the polishing pad. When the amount of the polishing composition is small, the polishing composition is not supplied to the entire substrate, or the polishing composition is dried and solidified to cause defects on the surface of the substrate. On the other hand, in the case where the amount of supply is large, in addition to being uneconomical, there is a case where the polishing composition, particularly water, or the like, interferes with the friction and hinders the polishing.

The polishing composition of the present invention may be a one-liquid type, and for example, a two-liquid type multi-liquid type in which part or all of the polishing composition is mixed at an arbitrary mixing ratio. In addition, in the case of using a polishing apparatus having a supply path of a plurality of polishing compositions, two or more polishing compositions adjusted in advance by mixing the polishing composition on the polishing apparatus may be used.

Further, the polishing composition of the present invention may be in the form of a stock solution, or may be prepared by diluting a stock solution of the polishing composition with water. system. In the case where the polishing composition is a two-component type, the order of mixing and dilution is arbitrary, and for example, a case where one of the components is diluted with water and then the component is mixed, or a mixture is diluted with water, and The case where the mixed polishing composition is diluted with water.

[Examples]

The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following embodiments. In addition, the average secondary particle diameter of the alumina abrasive grain is measured by "LA-950" manufactured by Horiba, Ltd., and the average secondary particle diameter of the colloidal cerium oxide abrasive grain is made by Nikkiso Co., Ltd. "UPA-UT151" is measured. Further, the specific surface area of the alumina abrasive grains was determined by a nitrogen adsorption method (BET method) using Flow Sorb II 2300 manufactured by Micromeritics Co., Ltd.

(Experimental Example 1: Relationship between content ratio of abrasive grains in the composition and polishing efficiency)

The relationship between the content ratio of the alumina abrasive grains and the colloidal cerium oxide abrasive grains in the polishing composition and the polishing efficiency was evaluated.

A suspension containing alumina abrasive grains (specific surface area: 12.3 m ² /g) having an average secondary particle diameter of 0.3 μm and a suspension containing colloidal ceria abrasive grains having an average secondary particle diameter of 112 nm were used. The mixing ratio of the abrasive grains was mixed as shown in Table 2, and the polishing composition (Examples 1-1 to 1-2) was prepared. The concentration of the total abrasive grains in the polishing compositions of the respective Examples and Comparative Examples was 10% by mass. Potassium hydroxide was used as a pH adjuster, and the pH of the polishing composition was adjusted to 10.

Then, using the polishing compositions of the respective Examples and Comparative Examples, the surface (c surface) of the sapphire substrate was polished under the conditions shown in Table 1 below. The sapphire substrates used were all of the same type with a diameter of 52 mm (about 2 inches).

The polishing rate was determined by measuring the difference between the masses of the sapphire substrates before and after the polishing, and the difference between the masses of the sapphire substrates before and after the polishing. The results are shown in Table 2.

As shown in the above Table 2, when the polishing composition of the example was used, the polishing efficiency was improved.

(Experimental Example 2: Relationship between particle diameter of colloidal cerium oxide abrasive grains and polishing efficiency)

The relationship between the average secondary particle size of the colloidal cerium oxide abrasive grains and the grinding efficiency was evaluated.

The alumina abrasive grains (specific surface area: 12.3 m ² /g) having an average secondary particle diameter of 0.3 μm and the colloidal ceria abrasive grains having an average secondary particle diameter shown in Table 4 below were 3: A mass ratio of 7 is used to prepare a polishing composition. The concentration of the total abrasive grains in the polishing composition of each of the examples was 10% by mass. Potassium hydroxide was used as a pH adjuster, and the pH of the composition was adjusted to 10 (Examples 2-1 to 2-3).

Then, using the polishing composition of each example, the following The surface (c surface) of the sapphire substrate was polished under the conditions shown in Table 3. The sapphire substrates used were all of the same type with a diameter of 52 mm (about 2 inches).

The polishing rate was determined by measuring the difference between the masses of the sapphire substrates before and after the polishing, and the difference between the masses of the sapphire substrates before and after the polishing. The results are shown in Table 4 below.

As shown in the above Table 4, in the case of the comparison of Examples 2-1 to 2-3, when the polishing composition of Example 2-1 having an average secondary particle diameter of 23 nm of colloidal cerium oxide abrasive grains was used, The grinding efficiency is further improved.

(Experimental Example 3: Relationship between pH of polishing composition and polishing efficiency)

The relationship between the polishing composition and the polishing efficiency was evaluated.

The alumina abrasive grains (specific surface area: 12.3 m ² /g) having an average secondary particle diameter of 0.3 μm and the colloidal ceria abrasive grains having an average secondary particle diameter of 23 nm were prepared and mixed at a mass ratio of 3:7. The concentration of the total abrasive grains was 10% by mass of the polishing composition. Further, nitric acid and potassium hydroxide were used as the pH adjuster, and they were adjusted so as to have pHs shown in the following Table 6 (Examples 3-1 to 3-4).

Then, using the polishing compositions of the respective Examples and Comparative Examples, the surface of the sapphire substrate was polished under the conditions shown in Table 5 below (c). surface). The sapphire substrates used were all of the same type with a diameter of 52 mm (about 2 inches).

The polishing rate was determined by measuring the difference between the masses of the sapphire substrates before and after the polishing, and the difference between the masses of the sapphire substrates before and after the polishing. The results are shown in Table 6 below.

As shown in the above Table 6, it was confirmed that the higher the pH of the polishing composition, the higher the polishing efficiency.

(Experimental Example 4: Grinding test of R surface of sapphire substrate)

A grinding test of the R surface of the sapphire substrate was performed.

The alumina abrasive grains (specific surface area: 12.3 m ² /g) having an average secondary particle diameter of 0.3 μm and the colloidal ceria abrasive grains having an average secondary particle diameter of 23 nm were prepared and mixed at a mass ratio of 3:7. The polishing composition was a concentration of the entire abrasive grains of 10% by mass. Further, potassium hydroxide was used as the pH adjuster, and the pH was adjusted so as to be in the following Table 8 (Example 4-1).

Then, using the polishing compositions of the respective Examples and Comparative Examples, the surface (R surface) of the sapphire substrate was polished under the conditions shown in Table 7 below. The sapphire substrates used are all 52mm in diameter (about 2 inches). The same kind.

The polishing rate was determined by measuring the difference between the masses of the sapphire substrates before and after the polishing, and the difference between the masses of the sapphire substrates before and after the polishing. The results are shown in Table 8 below.

As shown in the above Table 8, even when the object to be polished is the R surface of the sapphire substrate, when the polishing composition of the example is used, the effect of improving the polishing efficiency can be obtained. Therefore, the polishing composition of the present invention can be said to have an effect of improving the polishing efficiency regardless of the surface orientation of the sapphire substrate.

Claims (8)

A polishing composition comprising an alumina abrasive grain, a colloidal cerium oxide abrasive grain, and water, and is used for polishing an object to be polished on a metal compound having crystallinity on its surface. The polishing composition according to claim 1, wherein the mass ratio of the alumina abrasive grains to the colloidal ceria abrasive grains in the polishing composition is from 2.1:7.9 to 6:4. The polishing composition according to claim 1 or 2, wherein the content of the abrasive grains in the polishing composition is 0.5% by mass or more and 50% by mass or less. The polishing composition according to claim 1 or 2, wherein the colloidal ceria abrasive grains have an average secondary particle diameter of 10 nm or more and 200 nm or less. The polishing composition according to claim 1 or 2, wherein the alumina abrasive grains have an average secondary particle diameter of 0.1 μm or more and 15 μm or less. The polishing composition according to claim 1 or 2, wherein the alumina abrasive grains have a specific surface area of from 5 m ² /g to 20 m ² /g. The polishing composition according to claim 1 or 2, wherein the crystalline metal compound is sapphire. A method for producing a substrate, comprising the step of polishing a substrate having a crystalline metal compound on the surface by using the polishing composition according to any one of claims 1 to 7.