Polishing composition and polishing method

Abstract

The present invention provides a polishing composition which is capable of polishing the surface of a polycrystalline ceramic smooth. This polishing composition contains abrasive grains and water; and the average secondary particle diameter of the abrasive grains is from 5 nm to 40 nm. This polishing composition is used for polishing of a polishing object that contains a polycrystalline ceramic.

Description

[Technical field]

[0001] The present invention relates to a polishing composition and a polishing method. [Background technology]

[0002] In recent years, with the development of communication systems, ceramics have come to be used in various electronic components. Generally, substrates for electronic components are often made of single crystal ceramics (e.g., single crystal sapphire), but when substrates for electronic components are made of polycrystalline ceramics, there are cases in which superior properties can be obtained compared to single crystal ceramics, such as a high degree of freedom in shape, low manufacturing costs, and excellent optical properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-117806 Summary of the Invention [Problem to be solved by the invention]

[0004] When forming a substrate for electronic components from polycrystalline ceramics, a smooth surface is sometimes required. However, since polycrystalline ceramics have unevenness at the grain boundaries, it may not be possible to obtain a sufficiently smooth surface even when polished with a conventional polishing composition (see, for example, Patent Document 1). An object of the present invention is to provide a polishing composition and a polishing method capable of polishing the surface of polycrystalline ceramics smoothly. [Means for solving the problem]

[0005] A polishing composition according to one embodiment of the present invention is a polishing composition used for polishing an object to be polished that contains polycrystalline ceramics, and comprises abrasive grains and water, and the average secondary particle diameter of the abrasive grains is 5 nm or more and 40 nm or less. A polishing method according to another aspect of the present invention comprises polishing an object containing polycrystalline ceramics with the polishing composition according to the above aspect. Effect of the Invention

[0006] According to the present invention, it is possible to polish the surface of polycrystalline ceramics smoothly. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] An embodiment of the present invention will be described in detail. Note that the following embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications and improvements can be made to the following embodiment, and such modifications and improvements can also be included in the present invention.

[0008] The polishing composition of the present embodiment is a polishing composition used for polishing an object to be polished that contains polycrystalline ceramics, and contains abrasive grains and water. In the polishing composition of the present embodiment, the average secondary particle diameter of the abrasive grains is 5 nm or more and 40 nm or less. The polishing method of the present embodiment is a method for polishing an object containing polycrystalline ceramics by using the polishing composition of the present embodiment.

[0009] When an object to be polished containing polycrystalline ceramics is polished using the polishing composition of the present embodiment, the surface of the polycrystalline ceramics having unevenness at the grain boundaries can be polished smoothly. Therefore, for example, even when a substrate for electronic components is formed from polycrystalline ceramics, the surface can be made smooth, and compared to single crystal ceramics, it offers superior properties such as greater freedom in shape, lower manufacturing costs, and superior optical properties.

[0010] The polishing composition and polishing method of the present embodiment will be described in detail below. 1. About the object to be polished The polishing composition and polishing method of the present embodiment can be used to polish an object to be polished that contains polycrystalline ceramics. Since polycrystalline ceramics have unevenness at the grain boundaries, it is difficult to obtain a sufficiently smooth surface by polishing, but if the polishing composition and polishing method of the present embodiment are used to polish the object, a sufficiently smooth surface can be obtained.

[0011] The type of polycrystalline ceramic is not particularly limited, but examples thereof include metal-containing oxides, metal-containing nitrides, metal-containing carbides, metal-containing borides, and metal-containing fluorides. Among these, metal-containing oxides, metal-containing nitrides, and metal-containing carbides are preferred.

[0012] Among the metal-containing oxides, metal-containing nitrides, and metal-containing carbides, silicon-containing oxides, silicon-containing nitrides, silicon-containing carbides, aluminum-containing oxides, aluminum-containing nitrides, and yttrium-containing oxides are preferred. These polycrystalline ceramics are used as substrates for electronic components such as communication devices, power semiconductors, communication high-frequency devices, and pressure sensors. The substrates are particularly required to have a smooth surface.

[0013] Among the silicon-containing oxides, silicon-containing nitrides, silicon-containing carbides, aluminum-containing oxides, aluminum-containing nitrides, and yttrium-containing oxides, at least one of aluminum-containing oxides and aluminum-containing nitrides is particularly preferred.

[0014] Specific examples of oxides containing silicon include silicon oxide (SiO2) such as quartz, nitrides containing silicon include silicon nitride (SiN), and carbides containing silicon include silicon carbide (SiC). In addition, oxides containing aluminum include alumina (Al2O3) such as translucent alumina, and spinel (MgAl2O4), nitrides containing aluminum include aluminum nitride (AlN), and oxides containing yttrium include yttria (Y2O3), YAG (Y3Al5O 12 ) are mentioned.

[0015] The object to be polished may be any object containing polycrystalline ceramics, and may be entirely or partially formed of polycrystalline ceramics. The object to be polished may contain one type of polycrystalline ceramics or may contain multiple types of polycrystalline ceramics. A specific example of the object to be polished is a sintered body of polycrystalline ceramic powder.

[0016] 2. About abrasive grains The type of abrasive grains contained in the polishing composition of this embodiment is not particularly limited, but for example, abrasive grains containing silica (SiO2) or diamond can be used. The type of silica is not particularly limited, but for example, colloidal silica, fumed silica, sol-gel method silica, precipitated method silica, etc. can be used. These silicas may be used alone or in combination of two or more types. Among these abrasive grains, colloidal silica is preferred from the viewpoint of more efficiently smoothing the surface of polycrystalline ceramics.

[0017] In order to sufficiently polish the surface of polycrystalline ceramics smoothly, the average secondary particle size of the abrasive grains contained in the polishing composition of this embodiment must be 5 nm or more and 40 nm or less, and preferably 7 nm or more and 35 nm or less. Conventionally, when polishing single crystal ceramics, abrasive grains with an average secondary particle diameter larger than a specific grain size (abrasive grains with an average secondary particle diameter larger than 40 nm) were used because they could easily polish the surface of the single crystal ceramics sufficiently smoothly. However, when polishing polycrystalline ceramics that have grain boundaries, it is important to use abrasive grains with an average secondary particle diameter smaller than a specific grain size (abrasive grains with an average secondary particle diameter of 5 nm or more and 40 nm or less).

[0018] If abrasive grains with an average secondary particle size larger than a specific grain size are used, the convex and concave parts of the grain boundaries are processed simultaneously, so the grain boundary steps cannot be filled and a sufficiently smooth surface cannot be obtained. However, if abrasive grains with an average secondary particle size smaller than the specific grain size are used, the abrasive grains do not come into contact with the concave parts of the grain boundary steps and only the convex parts are processed, so the grain boundary steps disappear and a sufficiently smooth surface can be obtained. The average secondary particle size of the abrasive grains can be measured, for example, using a laser diffraction / scattering type particle size distribution measuring device (for example, "LA-950" manufactured by Horiba, Ltd.).

[0019] The content of the abrasive grains in the polishing composition of the present embodiment is not particularly limited, but is preferably 1% by mass to 30% by mass, more preferably 3% by mass to 25% by mass. By using a polishing composition with an abrasive grain content within the above range, the surface of the polycrystalline ceramic can be polished more smoothly.

[0020] 3. Polishing composition The polishing composition of this embodiment is a slurry containing the above-mentioned abrasive grains and water. The water functions as a dispersion medium or solvent that disperses the abrasive grains and disperses or dissolves other components. A mixture of water and an organic solvent may be used as the dispersion medium or solvent. The water used is preferably water that contains as few impurities as possible from the viewpoint of suppressing the inhibition of the action of the other components. Specifically, it is preferable to use pure water or ultrapure water that has been filtered to remove foreign matter after removing impurity ions with an ion exchange resin, or distilled water.

[0021] The pH of the polishing composition of this embodiment is not particularly limited, but is preferably 1.5 to 9.0, more preferably 2.0 to 8.5. By using a polishing composition having a pH within the above range, the surface of polycrystalline ceramics can be polished more smoothly. The pH of the polishing composition of this embodiment may be adjusted by a pH adjuster, which is an additive. The pH adjuster may be used alone or in combination of two or more.

[0022] The polishing composition of the present embodiment may contain, in addition to abrasive grains and water, additives (eg, pH adjusters) which are the other components described above, if desired. As the pH adjuster, known acids, bases, or salts thereof can be used.Specific examples of acids that 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, and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furan carboxylic acid, 2,5-furandicarboxylic acid, 3-furan carboxylic acid, 2-tetrahydrofuran carboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, and phenoxyacetic acid.

[0023] When an inorganic acid is used as the pH adjuster, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc. are preferred from the viewpoint of improving the polishing rate, and when an organic acid is used as the pH adjuster, glycolic acid, succinic acid, maleic acid, citric acid, tartaric acid, malic acid, gluconic acid, itaconic acid, etc. are preferred.

[0024] Examples of bases that can be used as pH adjusters include amines such as aliphatic amines and aromatic amines, organic bases such as quaternary ammonium hydroxide, alkali metal hydroxides such as potassium hydroxide, alkaline earth metal hydroxides, ammonia, etc. Among these bases, potassium hydroxide and ammonia are preferred because of their ease of availability.

[0025] Alternatively, instead of or in combination with the above acids, salts such as ammonium salts or alkali metal salts of the above acids may be used as pH adjusters. In particular, salts of weak acids and strong bases, salts of strong acids and weak bases, or salts of weak acids and weak bases can be expected to have a pH buffering effect, and in the case of salts of strong acids and strong bases, it is possible to adjust not only the pH but also the electrical conductivity with a small amount of the salt. The amount of the pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH.

[0026] The polishing composition of the present embodiment may further contain additives other than the pH adjuster as necessary, but from the viewpoint of polishing the surface of the polycrystalline ceramic more smoothly, it is preferable that the composition does not contain additives other than the pH adjuster. For example, the polishing composition may contain additives having the effect of further increasing the polishing rate, such as a complexing agent, an etching agent, or an oxidizing agent. The polishing composition may also contain a water-soluble polymer (which may be a copolymer, a salt thereof, or a derivative) that acts on the surface of the object to be polished or the surface of the abrasive grains. Furthermore, the polishing composition may contain additives such as a dispersant that improves the dispersibility of the abrasive grains or a dispersion aid that facilitates the redispersion of the aggregates of the abrasive grains. Furthermore, the polishing composition may contain known additives such as an antiseptic, an antifungal agent, and an antirust agent.

[0027] These various additives are known in many patent documents as those that can be added in polishing compositions, and the type and amount of additives are not particularly limited.However, when these additives are added, the amount of each of them is preferably less than 1 mass% relative to the entire polishing composition, and more preferably less than 0.5 mass%.These additives may be used alone or in combination of two or more.

[0028] Examples of complexing agents include inorganic acids, organic acids, amino acids, nitrile compounds, and chelating agents. Specific examples of inorganic acids include sulfuric acid, nitric acid, boric acid, and carbonic acid. Specific examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid. Organic sulfuric acids such as methanesulfonic acid, ethanesulfonic acid, and isethionic acid can also be used. In place of or in combination with an inorganic or organic acid, a salt such as an alkali metal salt of an inorganic or organic acid may be used. Of these complexing agents, glycine, alanine, malic acid, tartaric acid, citric acid, glycolic acid, isethionic acid, or salts thereof are preferred.

[0029] Examples of the chelating agent include carboxylic acid-based chelating agents such as gluconic acid, amine-based chelating agents such as ethylenediamine, diethylenetriamine, and trimethyltetraamine, and polyaminopolycarboxylic acid-based chelating agents such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, and diethylenetriaminepentaacetic acid. Examples of the chelating agent include organic phosphonic acid-based chelating agents such as 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, methanehydroxyphosphonic acid, and 1-phosphonobutane-2,3,4-tricarboxylic acid, as well as phenol derivatives and 1,3-diketones.

[0030] Examples of etching agents include inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and hydrofluoric acid; organic acids such as acetic acid, citric acid, tartaric acid, and methanesulfonic acid; inorganic alkalis such as potassium hydroxide, sodium hydroxide, and ammonia; and organic alkalis such as amines and quaternary ammonium hydroxides. Examples of the oxidizing agent include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, perchlorate, persulfate, nitric acid, potassium permanganate, and the like.

[0031] Examples of water-soluble polymers (which may be copolymers, salts, or derivatives thereof) include polycarboxylic acids such as polyacrylates, polyphosphonic acids, polysulfonic acids such as polystyrene sulfonic acid, polysaccharides such as xanthan gum and sodium alginate, and cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose. Other examples of water-soluble polymers include polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, sorbitan monooleate, and oxyalkylene polymers having a single or multiple oxyalkylene units.

[0032] Examples of the dispersion aid include pyrophosphates and condensed phosphates such as hexametaphosphates. Examples of the preservatives include sodium hypochlorite. Examples of the antifungal agents include oxazolines such as oxazolidine-2,5-dione. Examples of the anticorrosive agent include surfactants, alcohols, polymers, resins, amines, pyridines, tetraphenylphosphonium salts, benzotriazoles, triazoles, tetrazoles, and benzoic acid.

[0033] The surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.The nonionic surfactants include ether type, ether ester type, ester type, and nitrogen-containing type, and the anionic surfactants include carboxylates, sulfonates, sulfates, and phosphates.The cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts, and the amphoteric surfactants include carboxybetaine type, aminocarboxylates, imidazolinium betaines, lecithin, and alkylamine oxides.

[0034] 4. Manufacturing method of polishing composition The method of producing the polishing composition of the present embodiment is not particularly limited, and can be produced by stirring and mixing abrasive grains and various additives as required in water.The temperature when mixing each component is not particularly limited, but is preferably 10°C or more and 40°C or less, and may be heated to improve dissolution rate.In addition, the mixing time is also not particularly limited.

[0035] The polishing composition of this embodiment may be a one-component type, or may be a two-component or more multi-component type in which a part or all of the components of the polishing composition are mixed at any ratio. The polishing composition of this embodiment may also be prepared by diluting the stock solution of the polishing composition with water, for example, 10 times or more. When the polishing composition is a two-component type, the order of mixing and diluting the two raw material compositions that are the raw materials of the polishing composition is arbitrary. For example, one raw material composition may be diluted with water and then mixed with the other raw material composition, or both raw material compositions may be mixed and diluted with water at the same time, or both raw material compositions may be mixed and then diluted with water.

[0036] 5. Polishing Equipment and Method The polishing composition of the present embodiment can be used with a polishing device and under polishing conditions that are generally used for polishing objects made of, for example, single crystal ceramics or polycrystalline ceramics. As the polishing device, a general single-sided polishing device or double-sided polishing device can be used. When polishing using a single-sided polishing device, the object to be polished is held using a holder called a carrier, and while supplying a polishing composition, a platen with a polishing pad affixed thereto is pressed against one side of the object to be polished, and the platen is rotated to polish one side of the object to be polished.

[0037] When polishing using a double-sided polishing machine, the object to be polished is held using a carrier, and a polishing composition is supplied while a platen with an abrasive pad attached is pressed against both sides of the object to be polished, and the abrasive pad and the object to be polished are rotated in opposite directions to polish both sides of the object to be polished. Regardless of which polishing device is used, the object to be polished is polished by the physical action of friction between the polishing pad and polishing composition and the object to be polished, and by the chemical action of the polishing composition on the object to be polished.

[0038] The type of polishing pad is not particularly limited, and polishing pads having various different physical properties such as material, thickness, hardness, etc. Examples of the material of the polishing pad include polyurethane, epoxy resin, nonwoven fabric, suede, etc. Of the surfaces of the polishing pad, the polishing surface that comes into contact with the object to be polished and polishes it preferably has a C hardness of 94 or more. C hardness is the hardness measured immediately after the pressure surface is brought into contact with the surface, as determined by the test method specified in Appendix 2 of JIS K7312:1996, "Type C spring hardness test method." In this test method, a spring hardness tester is used that, when the pressure surface of the tester is brought into contact with the surface of a test piece, displays on its scale the distance that the indenter, which protrudes from a hole in the center of the pressure surface under spring pressure, is pushed back by the test piece, as the hardness. The measurement surface of the test piece should be at least as large as the pressure surface of the tester. In addition, the surface of the polishing pad preferably has grooves in a grid pattern, etc. If the surface of the polishing pad has grooves, the smoothness of the surface to be polished of the object to be polished is improved.

[0039] The polishing pad preferably has a surface roughness Ra of 0.75 μm or less, more preferably 0.1 μm or less. When the surface roughness of the polishing pad is in this range, the thickness variation (TTV) of the polished object in the polishing batch is reduced.

[0040] The method for reducing the surface roughness Ra of the polishing pad is not particularly limited, but a method of dressing between batches using a dresser containing abrasive grains such as diamond is preferred. The average grain size of the abrasive grains such as diamond contained in the dresser is preferably 10 μm or less, more preferably 5 μm or less, and most preferably 2 μm or less. When the average grain size of the abrasive grains of the dresser is within this range, the thickness variation (TTV) of the polished object in the polishing batch is reduced.

[0041] The amount of the polishing composition to be supplied is not particularly limited, but is preferably 20 mL or more per minute, and more preferably 100 mL or more. When the amount of the polishing composition to be supplied is within this range, the smoothness of the polished surface of the object to be polished is improved.

[0042] [Example] The present invention will be described in more detail below with reference to examples and comparative examples. Abrasive grains made of colloidal silica were mixed with water to disperse the abrasive grains in the water to produce polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 7. The average secondary particle size of the abrasive grains used in each Example and Comparative Example and the content of the abrasive grains in the polishing composition are as shown in Table 1. The average secondary particle size of the colloidal silica was measured using a laser diffraction / scattering type particle size distribution measuring device LA-950 manufactured by Horiba, Ltd.

[0043] [Table 1]

[0044] Next, the polishing composition of Examples 1 to 10 and Comparative Examples 1 to 7 was used to polish the object to be polished. The object to be polished was a plate-shaped member formed of a sintered body of translucent alumina, aluminum nitride, or silicon nitride powder, which is a polycrystalline ceramic. Before polishing, the polishing pad was dressed using a dresser containing diamond with a grain size of #270 (53 μm), and the surface roughness Ra of the polishing pad was set to 1.1 μm. Then, the surface roughness Ra of the polished surface of the polished object to be polished and the step (uneven step at the grain boundary) of the polished surface were measured, and the polishing speed was calculated.

[0045] The polishing conditions are as follows. Polishing device: Engis single-sided polishing device EJ-380IN (surface plate diameter 380mm) Polishing pad: Epoxy resin polishing pad Polishing load: 29.4kPa (300gf / cm 2 ) Rotation speed of the plate: 110 min -1 Polishing speed (linear speed): 84m / min Polishing time: 30 minutes Supply rate of polishing composition: 20 mL / min

[0046] The surface roughness Ra of the polished surface of the polished object after polishing was measured under the condition of a viewing angle of 143×107 μm using a measuring device NewView5032 manufactured by Zygo. The step of the polished surface of the polished object after polishing was measured as follows. That is, the step of the polished surface of the polished object after polishing was evaluated by the PV value using a measuring device NewView5032 manufactured by Zygo. The PV value is a value indicating the maximum height and maximum depth in the measurement range, but since the viewing angle in this case (viewing angle 143×107 μm) is not affected by waviness, the maximum height is the remaining part of the crystal (convex part), and the maximum depth is the part of the crystal that has fallen off (concave part), and the grain boundary step is correlated with the PV value. However, in silicon nitride, the correlation between the PV value and the grain boundary step is low, and since this method cannot accurately measure the grain boundary step, it was not evaluated. The polishing speed was calculated by measuring the mass of the polished object before and after polishing, and calculating the difference, the polishing time, and the area of ​​the polished surface. The results are shown in Table 1 (silicon nitride steps are indicated as "ND").

[0047] As can be seen from the results shown in Table 1, in Examples 1 to 10, the average secondary particle size of the abrasive grains was 5 nm or more and 40 nm or less, so that the step on the polished surface of the object to be polished after polishing was small, and the surface of the object to be polished made of polycrystalline ceramics could be polished smoothly. In addition, the surface roughness Ra of the polished surface of the object to be polished after polishing was small, and the polishing rate was sufficiently high.

[0048] In contrast, in Comparative Examples 2 to 7, the average secondary particle diameter of the abrasive grains exceeded 40 nm, so that the surface of the object to be polished after polishing was large in steps, and the surface of the object to be polished made of polycrystalline ceramics could not be polished smoothly. In addition, since it is difficult to stably manufacture abrasive grains having an average secondary particle diameter of less than 5 nm, Comparative Example 1 could not be compared and examined.

[0049] In addition, in each embodiment, a dresser containing diamonds with a grain size of #270 (53 μm) was used as the dresser between polishing batches, but when a dresser containing diamonds with a grain size of 1 μm was used to dress the polishing pad and the surface roughness Ra of the polishing pad was set to 0.05 μm, and polishing was performed in the same manner.Compared to when the surface roughness Ra of the polishing pad was 1.1 μm and a dresser containing diamonds with a grain size of #270 (53 μm) was used, the surface roughness Ra and step of the polishing object were maintained, while the thickness variation (TTV) of the polishing object within the polishing batch was reduced to 60 to 80%.

Claims

1. A polishing composition used for polishing an object to be polished that contains polycrystalline ceramics, the polishing composition containing abrasive grains and water, the abrasive grains having an average secondary particle diameter of 5 nm or more and 40 nm or less, and the abrasive grains being colloidal silica.

2. 2. The polishing composition according to claim 1, wherein the polycrystalline ceramic is at least one of an oxide containing aluminum and a nitride containing aluminum.

3. 3. The polishing composition according to claim 1, wherein the object to be polished is a sintered body of the polycrystalline ceramic powder.

4. 4. The polishing composition according to claim 1, wherein the content of the abrasive grains is 1% by mass or more and 30% by mass or less.

5. A polishing method for polishing an object containing polycrystalline ceramics by using the polishing composition according to any one of claims 1 to 4.

6. 6. The polishing method according to claim 5, wherein the surface roughness Ra of the polishing pad before polishing is 0.75 [mu]m or less.

7. 7. The polishing method according to claim 5, wherein the polishing pad before polishing is dressed using a dresser containing abrasive grains having an average grain size of 10 [mu]m or less.

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