Polishing material slurry and polishing method using same

Abstract

A polishing material slurry according to the present invention has abrasive grains and a nonionic surfactant. The abrasive grains preferably each include a manganese oxide particle. The nonionic surfactant preferably contains a polyalkylene glycol and / or a compound having a polyalkylene glycol moiety, and more preferably contains a polyethylene glycol and / or a compound having a polyethylene glycol moiety. It is even more preferable that the compound having a polyethylene glycol moiety contains a polyethylene glycol alkyl ether. The polishing material slurry according to the present invention preferably further contains manganate ions, and phosphoric acid or the like. A polishing method using the polishing material slurry according to the present invention involves performing polishing by using the polishing material slurry according to the present invention. An SiC wafer of the present invention is obtained by polishing using the polishing material slurry according to the present invention.

Description

Abrasive slurry and polishing method using the same

[0001] The present invention relates to an abrasive slurry and a polishing method using the same.

[0002] Among semiconductor devices, power semiconductor elements known as power devices are being required to withstand higher voltages and currents by using silicon carbide (SiC), gallium nitride, diamond, etc. instead of the silicon that has traditionally been used as a substrate. Substrates made of these materials have a larger band gap than conventional silicon substrates, and are therefore able to withstand higher voltages.

[0003] Among these, substrates made of silicon carbide (hereinafter referred to as SiC substrates) are excellent not only in hardness, heat resistance, and chemical stability, but also in cost. On the other hand, since SiC substrates have a higher hardness than conventional silicon substrates, abrasive slurries containing manganese oxide particles as abrasive grains have been developed as disclosed in Patent Document 1, for example, as abrasive slurries used in a polishing step by a so-called CMP (Chemical Mechanical Polishing) method or the like, which is a step of mirror-finishing the surface of a SiC substrate during the manufacturing process of the SiC substrate.

[0004] Patent No. 6744295

[0005] However, there is a concern that the abrasive slurry containing manganese oxide particles as abrasive grains as disclosed in Patent Document 1 has high friction resistance with respect to the workpiece during polishing. On the other hand, when the slurry is left to stand, the abrasive grains precipitate, making it difficult to maintain a constant concentration of the abrasive slurry, and causing variations in polishing precision.

[0006] In view of the above problems, the present invention provides an abrasive slurry and a polishing method that can reduce frictional resistance during polishing and suppress the deposition of abrasive grains.

[0007] The abrasive slurry of the present invention, which has been made to solve the above problems, is characterized by comprising abrasive grains and a nonionic surfactant. By comprising abrasive grains and a nonionic surfactant, the abrasive slurry of the present invention can reduce frictional resistance during polishing and suppress precipitation of abrasive grains.

[0008] The abrasive particles contained in the abrasive slurry of the present invention include manganese oxide particles, alumina particles, silica particles, cerium oxide particles, zirconium oxide particles, titanium oxide particles, chromium oxide particles, iron oxide particles, magnesium hydroxide particles, cerium hydroxide particles, silicon carbide particles, boron carbide particles, and diamond particles, so long as the effect of preventing warpage and cracking due to the Twyman effect on the object to be polished, for example, a SiC substrate, is not impaired. These particles can be used alone or in combination of two or more types, and for example, a mixture of manganese oxide particles and silica particles may be used, or a mixture of manganese oxide particles, silica particles, and alumina particles may be used.

[0009] The abrasive grains contained in the abrasive slurry of the present invention preferably contain manganese oxide particles. The manganese oxide particles contained in the abrasive grains are manganese oxide (II) (MnO), dimanganese trioxide (III) (Mn ２ O ３ ), manganese dioxide (IV) (MnO ２ ), trimanganese(II,III) tetroxide (Mn ３ O ４ ), and manganese dioxide (IV) (MnO ２ The manganese oxide particles contained in the abrasive grains may be composited with abrasive grains other than manganese oxide particles, for example, manganese oxide particles may be surface-coated with abrasive grains other than manganese oxide particles, or manganese oxide particles may coat the surfaces of abrasive grains other than manganese oxide particles.

[0010] Furthermore, the content of abrasive grains contained in the abrasive slurry of the present invention can be measured as follows. Specifically, the abrasive slurry is filtered, washed, and dried, and the weight of the resulting abrasive grains is measured to determine the content of abrasive grains. Furthermore, the composition of the abrasive grains contained in the abrasive slurry of the present invention can be measured by energy dispersive X-ray spectroscopy (SEM-EDX), electron probe microanalyzer (EPMA), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), etc.

[0011] Furthermore, the abrasive grains contained in the abrasive slurry of the present invention preferably have a particle size (D50) at 50% of the cumulative volume measured by a laser diffraction / scattering particle size distribution measurement method of 0.1 μm or more from the viewpoint of having high polishing power, and preferably have a particle size of 5.0 μm or less from the viewpoint of suppressing roughness of the surface of the workpiece to be polished, such as a SiC substrate. Therefore, the abrasive grains preferably have a particle size (D50) at 50% of the cumulative volume measured by a laser diffraction / scattering particle size distribution measurement method of 0.15 μm or more and 4.5 μm or less, and even more preferably 0.2 μm or more and 4.0 μm or less.

[0012] Here, the particle size (D50) of the abrasive grains contained in the abrasive slurry of the present invention at 50% of the cumulative volume as measured by the laser diffraction / scattering particle size distribution measurement method is prepared by preparing a sample by pulverizing the abrasive grains with beads in the method for producing an abrasive slurry of the present invention described later, and diluting the mixture with water so that the concentration of this mixture becomes about 0.01%. Then, the measurement is carried out using a laser diffraction / scattering particle size distribution measurement device (manufactured by Microtrackbell Co., Ltd.: MT3300EXII).

[0013] Furthermore, the content of abrasive grains contained in the abrasive slurry of the present invention is preferably 0.5% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, and from the viewpoint of sufficiently increasing the polishing rate of high-hardness materials such as silicon carbide, ensuring the suitable fluidity of abrasive grains in the abrasive slurry, and preventing aggregation, based on the total amount of the abrasive slurry of the present invention, and from the viewpoint of sufficiently increasing polishing rate, more preferably 1.0% by mass or more and 2.5% by mass or less.In addition, in this specification, the content in the abrasive slurry of the present invention is the content in the abrasive slurry before starting polishing, unless otherwise specified.

[0014] The abrasive slurry of the present invention contains a nonionic surfactant, thereby reducing frictional resistance during polishing and suppressing deposition of abrasive grains.

[0015] The nonionic surfactant contained in the abrasive slurry of the present invention preferably contains polyalkylene glycol and / or a compound having a polyalkylene glycol moiety, since this reduces frictional resistance during polishing and inhibits the deposition of abrasive grains. The nonionic surfactant may be a mixture of one type or two or more types of nonionic surfactants.

[0016] Here, examples of polyalkylene glycol include polyethylene glycol (PEG), polypropylene glycol (PPG), and polyethylene glycol-polypropylene glycol (PEG-PPG).

[0017] Examples of compounds having a polyalkylene glycol moiety include compounds having a polyethylene glycol moiety, compounds having a polypropylene glycol moiety, and compounds having a polyethylene glycol-polypropylene glycol copolymer moiety, such as polyoxyalkylene alkyl ethers, polyoxyalkylene phenol ethers, polyoxyalkylene carboxylic acid esters, polyoxyalkylene polyhydric alcohol ethers, and polyoxyalkylene polycarboxylic acid esters.

[0018] Examples of polyoxyalkylene alkyl ethers include polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, and polyoxyethylene polyoxypropylene alkyl ethers. Examples of polyoxyethylene alkyl ethers include polyoxyethylene methyl ether, polyoxyethylene ethyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene palmitoleyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene linoleyl ether, and polyoxyethylene stearyl ether.

[0019] Examples of polyoxyalkylene carboxylic acid esters include polyoxyethylene fatty acid esters, polyoxypropylene fatty acid esters, and polyoxyethylene polyoxypropylene fatty acid esters. Examples of polyoxyethylene fatty acid esters include polyoxyethylene oleic acid esters, polyoxyethylene palmitic acid esters, polyoxyethylene linoleic acid esters, polyoxyethylene linolenic acid esters, and polyoxyethylene stearate esters.

[0020] Examples of polyoxyalkylene polyhydric alcohol ethers include polyoxyethylene polyhydric alcohol ethers, polyoxypropylene polyhydric alcohol ethers, and polyoxyethylene polyoxypropylene polyhydric alcohol ethers. Examples of polyoxyethylene polyhydric alcohol ethers include polyoxyethylene glycerin ethers. Examples of polyoxyethylene glycerin ethers include polyoxyethylene sorbitan ether, polyoxyethylene glycerin ether, polyoxyethylene diglycerin ether, polyoxyethylene pentaerythritol ether, and polyoxyethylene dipentaerythritol ether.

[0021] Examples of the polyoxyalkylene polycarboxylic acid ester include polyoxyethylene polycarboxylic acid ester, polyoxypropylene polycarboxylic acid ester, and polyoxyethylene polyoxypropylene polycarboxylic acid ester.

[0022] Furthermore, it is more preferable that the nonionic surfactant contained in the abrasive slurry of the present invention contains polyethylene glycol and / or a compound having a polyethylene glycol moiety, and it is even more preferable that the compound having a polyethylene glycol moiety contains a polyethylene glycol alkyl ether.

[0023] The content of the nonionic surfactant contained in the abrasive slurry of the present invention can be measured as follows. Specifically, the abrasive slurry can be diluted with pure water and filtered to collect the nonionic surfactant in a filtrate. This filtrate is then separated using preparative gel permeation chromatography (preparative GPC) or preparative liquid chromatography (preparative LC) to prepare a dispersion of the nonionic surfactant. The content of the nonionic surfactant contained in the abrasive slurry of the present invention per unit weight can then be measured. Furthermore, the type of nonionic surfactant contained in the abrasive slurry of the present invention can be identified by subjecting this dispersion of the nonionic surfactant to matrix-assisted laser desorption / ionization.

[0024] The content of the nonionic surfactant contained in the abrasive slurry of the present invention is preferably more than 0% by mass and not more than 1.0% by mass relative to the total amount of the abrasive slurry of the present invention from the viewpoint of friction characteristics.Moreover, the content of the nonionic surfactant is more preferably 0.001% by mass or more and not more than 0.5% by mass, and preferably 0.002% by mass or more and not more than 0.25% by mass.Typically, the content of the nonionic surfactant may be 0.001% by mass or more and not more than 0.05% by mass, or may be 0.1% by mass or more and not more than 0.2% by mass.

[0025] Furthermore, the content of the nonionic surfactant contained in the abrasive slurry of the present invention, expressed as a mass ratio to the abrasive grain content in the abrasive slurry of the present invention, is preferably 0% to 50% and more preferably 0.05% to 25%. Typically, the mass ratio may be 0.05% to 2.5%, or 5% to 10%.

[0026] The abrasive slurry of the present invention preferably further contains manganate ions in addition to the abrasive grains and nonionic surfactant. ４ － ), manganate ions (MnO ４ ２－ ) and permanganate ion is preferred.

[0027] Manganate ions, when used as an oxidizing agent in combination with abrasive grains, can have a high polishing power for high-hardness materials such as silicon carbide. Here, manganate salts are preferred as the source of manganate ions. Examples of manganate salts include alkali metal salts of manganate and alkaline earth metal salts of manganate. Furthermore, from the viewpoint of easy availability and improving the polishing efficiency of the abrasive slurry of the present invention, alkali metal salts of manganate are preferred among the manganate salts that are the source of manganate ions, and sodium manganate (Na ２ MnO ４ ), potassium manganate (K ２ MnO ４ ), sodium permanganate (NaMnO ４ ), potassium permanganate (KMnO ４ ) is more preferred, and potassium permanganate (KMnO ４ These manganates may be used alone or in combination of two or more.

[0028] The manganate ion content of the abrasive slurry of the present invention is preferably 0.5% by mass or more relative to the total amount of the abrasive slurry of the present invention, from the viewpoint of sufficiently increasing the polishing rate. Furthermore, the manganate ion content of the abrasive slurry of the present invention is preferably 3.2% by mass or less relative to the total amount of the abrasive slurry of the present invention, from the viewpoint of preventing crystal precipitation due to increased addition amounts, ensuring safety in handling the abrasive slurry, and the tendency for the polishing rate to saturate even when increased addition amounts are used. That is, the manganate ion content is preferably 0.5% by mass or more and 3.2% by mass or less, more preferably 1.0% by mass or more and 2.5% by mass or less, and even more preferably 1.0% by mass or more and 2.1% by mass or less relative to the total amount of the abrasive slurry of the present invention. Typically, the manganate ion content may be 1.0% by mass or more and 1.2% by mass or less, or 1.7% by mass or more and 2.1% by mass or less. The manganate ion content can be determined by centrifuging the abrasive slurry of the present invention to allow the abrasive grains in the abrasive slurry to settle, collecting the supernatant, diluting the supernatant, and measuring the absorbance (intensity of the absorption peak appearing at a wavelength of 525 nm) of the diluted solution by absorptiometry.

[0029] Furthermore, the abrasive slurry of the present invention preferably further contains a phosphoric acid compound in addition to the abrasive grains, nonionic surfactant, and manganate ions described above. The phosphoric acid compound can improve the dispersibility of the abrasive slurry of the present invention by using it in combination with the abrasive grains and manganate ions.

[0030] The phosphoric acid compound contained in the abrasive slurry of the present invention is preferably, for example, an inorganic phosphorus compound. Specifically, the phosphoric acid compound is preferably sodium phosphate (trisodium phosphate (anhydrous) (Na ３ P.O. ４ ), CAS number: 7601-54-9; trisodium phosphate dodecahydrate (Na ３ P.O. ４ ・12H ２ O), CAS number: 10101-89-0; Sodium phosphate monobasic (NaH ２ P.O. ４), CAS number: 7558-80-7; Sodium phosphate dibasic (Na ２ HPO ４ ), CAS number: 7558-79-4) and potassium phosphate (tripotassium phosphate (anhydrous) (K ３ P.O. ４ ), CAS number: 7778-53-2; Potassium phosphate tripotassium phosphate monohydrate (K ３ P.O. ４ ・H ２ O), CAS number: 27176-10-9; Potassium phosphate dibasic trihydrate (K ２ HPO ４ ・H ２ O), CAS number: 16788-57-1; monobasic potassium phosphate (KH ２ P.O. ４ ), CAS number: 7778-77-0; dipotassium phosphate (K ２ HPO ４ ), CAS number: 7758-11-4).

[0031] Furthermore, as the metaphosphate compound, sodium metaphosphate (NaPO ３ ) ｎ , CAS number: 35270-09-8) and potassium metaphosphate (KPO ３ ) ｎ , CAS number: 7790-53-6.

[0032] As a hexametaphosphate compound, sodium hexametaphosphate (NaH ７ P ６ O １８ ), CAS number: 10124-56-8.

[0033] As the pyrophosphate compound, sodium pyrophosphate (sodium pyrophosphate (anhydrous) (Na ４ P ２ O ７ ), CAS number: 7722-88-5; Sodium pyrophosphate decahydrate (Na ４ P ２ O ７ ・10H ２ O), CAS number: 13472-36-1; Sodium acid pyrophosphate (Na ２ H ２ P２ O ７ ), CAS number: 7758-16-9) and potassium pyrophosphate (K ４ P ２ O ７ ), CAS number: 7320-34-5.

[0034] As the polyphosphate compound, sodium polyphosphate (Na ３ P ３ O １０ X ２ ), CAS number: 68915-31-1; potassium polyphosphate (K ３ P ３ O １０ X ２ ), CAS number: 68956-75-2.

[0035] As a tripolyphosphate compound, sodium tripolyphosphate (Na ５ P ３ O １０ ), CAS number: 7758-29-4, potassium tripolyphosphate (K ５ P ３ O １０ ), CAS number: 13845-36-8.

[0036] Further examples include salts and hydrates thereof. In the case of these salts, alkali metal salts and alkaline earth metal salts are preferred, and sodium salts and potassium salts are particularly preferred. In particular, in the abrasive slurry of the present invention, from the viewpoint of effective high dispersibility with a small amount and from the viewpoint of sufficiently increasing the polishing rate, metaphosphate compounds, hexametaphosphate compounds, pyrophosphate compounds (sodium pyrophosphate and potassium pyrophosphate), polyphosphate compounds (sodium polyphosphate and potassium polyphosphate), and tripolyphosphate compounds are more preferred. These phosphoric acids may be used alone or in combination of two or more.

[0037] Furthermore, among the inorganic phosphorus compounds described above, pyrophosphate compounds are preferred from the viewpoints of high dispersibility and sufficiently increasing the polishing rate. Among the pyrophosphate compounds, alkali metal salts of pyrophosphate and alkaline earth metal salts of pyrophosphate are more preferred, and sodium pyrophosphate and potassium pyrophosphate are particularly preferred.

[0038] The presence or absence of phosphoric acid contained in the abrasive slurry of the present invention and its content can be determined by high performance liquid chromatography (HPLC), phosphorus-31 nuclear magnetic resonance ( ３１ The measurement can be carried out by peak separation using the DOSY (Diffusion Ordered NMR Spectroscopy) method in P-NMR. In this case, the abrasive slurry of the present invention may be diluted with pure water and filtered, if necessary, to analyze the phosphoric acid contained in the filtrate.

[0039] Furthermore, the measurement of the phosphoric acids contained in the abrasive slurry of the present invention is preferably performed by high performance liquid chromatography. In high performance liquid chromatography, by using a non-suppressor anion analysis column, the type and weight of phosphoric acids can be measured by a known method. For example, an example of a non-suppressor anion analysis column is Shodex non-suppressor anion analysis column IC I-524A (manufactured by Shoko Science Co., Ltd.). By using this non-suppressor anion analysis column, the phosphoric acids contained in the abrasive slurry of the present invention can be separated and measured.

[0040] Furthermore, from the viewpoint of frictional resistance, the content of phosphoric acid contained in the abrasive slurry of the present invention is preferably 0.001 mass% or more relative to the total amount of the abrasive slurry of the present invention. Furthermore, since the polishing rate tends to saturate even when the added amount is increased, the content of phosphoric acid contained in the abrasive slurry of the present invention is preferably 0.2 mass% or less relative to the total amount of the abrasive slurry of the present invention. That is, the content of phosphoric acid is preferably 0.001 mass% or more and 0.2 mass% or less relative to the total amount of the abrasive slurry of the present invention, and from the viewpoint of frictional resistance, it is more preferably 0.002 mass% or more, and from the viewpoint of sufficiently increasing the polishing rate, it is more preferably 0.1 mass% or less. The content of phosphoric acid is more preferably 0.002 mass% or more and 0.05 mass% or less. Typically, the content of phosphoric acid may be 0.002 mass% or more and 0.02 mass% or less. In this specification, the content of phosphoric acid is the total amount of those classified as phosphoric acid, unless otherwise specified.

[0041] Furthermore, the content of phosphoric acid contained in the abrasive slurry of the present invention, expressed as a mass ratio relative to the abrasive grain content in the abrasive slurry of the present invention, is preferably 0.05% or more and 10.0% or less. More preferably, it is 0.1% or more and 5.0% or less, and even more preferably, it is 0.1% or more and 2.5% or less. Typically, the mass ratio may be 0.1% or more and 1.0% or less.

[0042] Furthermore, the abrasive slurry of the present invention may contain, in addition to the above-mentioned abrasive grains, nonionic surfactant, manganate ions, and phosphoric acids, a polymer additive containing one or more water-soluble organic polymers selected from the group consisting of polycarboxylic acids, polycarboxylates, salts of naphthalenesulfonic acid-formalin condensates, polyvinyl alcohols, polyvinylpyrrolidones, and copolymers thereof. By containing the above-mentioned polymer additives, the pot life of the abrasive slurry of the present invention can be extended.

[0043] Furthermore, in the abrasive slurry of the present invention, it is more preferable that the polymer additive is one or more water-soluble organic polymers selected from polycarboxylic acids, polycarboxylates, and copolymers thereof, it is even more preferable that the polymer additive is one or more water-soluble organic polymers selected from polyacrylic acid, polymaleic acid, polyacrylates, polymaleates, and copolymers thereof, it is particularly preferable that the polymer additive is a polyacrylate, and it is even more particularly preferable that the polymer additive is an ammonium polyacrylate.

[0044] Furthermore, the content of the polymer additive contained in the abrasive slurry of the present invention is preferably 0.006% by mass or more relative to the total amount of the abrasive slurry of the present invention from the viewpoint of dispersibility. Furthermore, the content of the polymer additive in the abrasive slurry of the present invention is preferably 0.05% by mass or less relative to the total amount of the abrasive slurry of the present invention from the viewpoint of sufficiently increasing the polishing rate. That is, the content of the polymer additive is preferably 0.006% by mass or more and 0.05% by mass or less, more preferably 0.01% by mass or more and 0.03% by mass or less, and even more preferably 0.01% by mass or more and 0.02% by mass or less relative to the total amount of the abrasive slurry of the present invention. Typically, the content of the polymer additive may be 0.01% by mass or more and 0.015% by mass or less. In this specification, the content of the polymer additive is the total amount of those classified as the above-mentioned polymer additives, unless otherwise specified.

[0045] Furthermore, the content of the polymer additive in the abrasive slurry of the present invention, expressed as a mass ratio relative to the abrasive grain content in the abrasive slurry of the present invention, is preferably 0.3% to 2.5%, more preferably 0.5% to 1.5%, and even more preferably 0.5% to 1.0%. Typically, the mass ratio may be 0.5% to 0.75%.

[0046] The abrasive slurry of the present invention contains a dispersant for dissolving or dispersing the abrasive grains, nonionic surfactant, manganate ions, and phosphates. The dispersant is preferably water, a water-soluble organic solvent such as an alcohol or a ketone, or a mixture thereof, in order to sufficiently increase the polishing rate, and more preferably water. The content of the dispersant is preferably 60% by mass or more and 99.9% by mass or less, and more preferably 80% by mass or more and 99.9% by mass or less, based on the total amount of the abrasive slurry of the present invention. The content of the dispersant may be 99% by mass or less, 98% by mass or less, 97% by mass or less, 95% by mass or less, or 90% by mass or less, based on the total amount of the abrasive slurry of the present invention.

[0047] Furthermore, the abrasive slurry of the present invention may contain any additive other than the above-mentioned abrasive grains, nonionic surfactant, manganate ions, phosphates, and dispersion medium. Here, the optional additives include dispersants, pH adjusters, viscosity adjusters, chelating agents, and rust inhibitors. The content of the optional additives is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total amount of the abrasive slurry of the present invention.

[0048] The abrasive slurry of the present invention can be in the form of a suitable mixture of the above-mentioned abrasive grains, nonionic surfactant, manganate ions, phosphoric acid compounds, dispersion medium, and any additives, and may be, for example, a kit in which these components are divided into two or more agents. The kit may be configured in any form so long as the abrasive slurry of the present invention can fully exhibit its polishing ability when prepared.

[0049] The dispersibility of the abrasive slurry of the present invention can be evaluated by the following method. The abrasive slurry of the present invention is diluted with water so that the concentration becomes about 0.01% by mass, and a measurement sample is prepared. Then, using a laser diffraction / scattering particle size distribution analyzer (manufactured by Microtrackbell Co., Ltd.: MT3300EXII), the particle size (D50) at a volume-based cumulative fraction of 50% is measured, and the measured particle size (D50) can be evaluated to evaluate the dispersibility of the abrasive slurry of the present invention.

[0050] The polishing rate of the above-mentioned abrasive slurry of the present invention can be evaluated by the following method. A CMP-processed 4H-SiC substrate having a diameter of 4 inches and an off-angle of 4° is used as the polishing object, and a polishing test is carried out on the Si surface of the substrate under the following conditions. The polishing apparatus used is a single-side polisher BC-15 manufactured by MAT Corporation. The polishing pad attached to the surface plate is an IC1000 manufactured by Nitta DuPont. The rotation speed of the surface plate is set to 60 rpm, and the peripheral speed is set to 7,136 cm / min. The rotation speed of the carrier is also set to 60 rpm, and the peripheral speed is set to 961 cm / min. Furthermore, the load during polishing is 2.8 psi (approximately 1.96 x 10 ４ The polishing rate is calculated from the difference in the mass of the substrate to be polished before and after polishing, with the supply rate of the abrasive slurry of the present invention set to 200 mL / min. The polishing rate is calculated from the difference in the mass of the substrate to be polished before and after polishing for 1 hour. The polishing rate of the abrasive slurry of the present invention is preferably high, and is preferably 0.10 μm / h or higher. The polishing rate is more preferably 0.20 μm / h or higher, even more preferably 0.30 μm / h or higher, particularly preferably 0.40 μm / h or higher, and particularly preferably 0.50 μm / h or higher.

[0051] The pot life of the abrasive slurry of the present invention can be evaluated by the following method. First, the abrasive slurry of the present invention is left standing at room temperature (25° C.) for a certain period of time. Next, the MnO content in the abrasive slurry after the certain period of time is measured. ４ － The concentration of MnO in the abrasive slurry before standing for a certain period of time ４ － Compared with the concentration, MnO ４ － The maintenance rate of the concentration of MnO before standing for a certain period of time is calculated. ４ － MnO concentration after standing for a certain period of time ４ － A concentration retention rate of 50% or more is preferable in terms of excellent pot life of the abrasive slurry of the present invention. Here, the certain period is preferably 1 hour, 2 hours, 6 hours, 12 hours, 24 hours, 2 days, or 3 days, and the MnO concentration after being left standing for a longer certain period is４ － The higher the retention rate of the concentration, the more preferable. ４ － The concentration can be evaluated as follows. First, the abrasive slurry is centrifuged (4,000 rpm x 20 min) to allow the manganese oxide abrasive grains in the abrasive slurry to settle. Next, 1.0 g of the supernatant is taken and diluted with 109 g of pure water to prepare a diluted solution. Then, using a spectrophotometer (UH-4150 manufactured by Hitachi High-Tech Science Corporation), the MnO ４ － The absorbance (intensity of the absorption peak appearing at a wavelength of 525 nm) of MnO was measured, and the absorbance was calculated using a calibration curve prepared in advance. ４ － Calculate the concentration.

[0052] A polishing method for polishing an object to be polished using the above-described abrasive slurry of the present invention will be described below.

[0053] The polishing method includes supplying the abrasive slurry of the present invention to a polishing pad, contacting the polished surface of the workpiece with the polishing pad, and polishing by the relative movement between them. Here, the abrasive slurry of the present invention may be a method of pouring the abrasive slurry, or a method of circulating the abrasive slurry of the present invention, in which the abrasive slurry of the present invention supplied to the polishing pad and used for polishing is recovered, and the recovered abrasive slurry of the present invention is repeatedly supplied to the polishing pad. Since the abrasive slurry of the present invention can be circulated and repeatedly used to polish the workpiece, the amount used can be reduced. Here, the polishing pad can be, for example, a pad made of a conventionally used nonwoven fabric, a pad impregnated with a resin such as polyurethane or epoxy, or a suede material. The polishing pressure is 0.5 × 10 ４ Pa or more 1.0×10 ５ Pa or less, especially 1.0 × 10 ４ Pa or more 5.0×10 ４It is preferable that the abrasive pressure is 100 Pa or less in terms of polishing force and ease of handling of the polishing jig. The supply rate of the abrasive slurry is preferably 10 mL / min or more and 500 mL / min or less, and more preferably 50 mL / min or more and 250 mL / min or less.

[0054] The object to be polished with the abrasive slurry of the present invention is a high-hardness material, for example, having a Mohs hardness of 8 or more. Here, Mohs hardness is a numerical value that represents hardness based on the degree of scratching relative to a standard material, and can be measured by a conventional method using a Mohs hardness scale. Standard materials are designated on the Mohs hardness scale, ranging from 1 to 10, in order of softest to softest. Specific standard materials are: Mohs hardness 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 5: apatite, 6: orthoclase, 7: quartz, 8: topaz, 9: corundum, and 10: diamond. Examples of high-hardness materials with a Mohs hardness of 8 or more include silicon carbide (Mohs hardness approximately 9), gallium nitride (Mohs hardness approximately 9), and diamond.

[0055] The abrasive slurry of the present invention can be used in a finishing CMP (Chemical Mechanical Polishing) process after lapping of a substrate made of a high-hardness material. In particular, the abrasive slurry of the present invention can be used to polish a substrate made of silicon carbide (SiC), i.e., a SiC substrate, and can sufficiently increase the polishing rate and effectively prevent warping and cracking due to the Twyman effect. Single-crystal silicon carbide substrates are usually used for SiC substrates, and their crystal systems are usually hexagonal or rhombohedral. Hexagonal crystals are preferred in terms of demonstrating the effect of the abrasive slurry, which can prevent warping and cracking due to the Twyman effect. Polymorphs of hexagonal crystals include 2H, 4H, 6H, 8H, and 10H. Polymorphs of rhombohedral crystals include 15R.

[0056] Next, a method for producing the above-mentioned abrasive slurry of the present invention will be described below.

[0057] First, put pure water and manganese dioxide (abrasive grains, MnO ２), phosphoric acid (e.g., sodium salt of pyrophosphate), and beads (zirconia, φ0.4 mm) were placed in the container, which was then placed on a paint shaker (60 Hz). The container was rotated at high speed, and manganese dioxide (abrasive grains, MnO ２ ) are mixed and ground.

[0058] The mixed and crushed manganese dioxide (abrasive grains, MnO ２ The mixture containing the beads is separated from the beads using a centrifuge (himac CT 6E manufactured by Hitachi Koki Co., Ltd.) or the like, and the supernatant is collected.

[0059] The solids concentration in the collected supernatant, ie, the manganese oxide abrasive grain concentration, is measured using a heating moisture meter, and pure water is added to the supernatant to reach a predetermined concentration, thereby obtaining an intermediate abrasive slurry.

[0060] A nonionic surfactant is added to the obtained abrasive slurry intermediate and mixed.

[0061] Then, abrasive slurry intermediate to which a nonionic surfactant was added and potassium permanganate (KMnO ４ ) to obtain the abrasive slurry of the present invention.

[0062] The SiC wafer of the present invention is characterized by being polished using the above-described abrasive slurry of the present invention. The SiC wafer of the present invention is free from warpage and cracking due to the Twyman effect because it has been polished using the above-described abrasive slurry of the present invention. The SiC wafer of the present invention is also polished by the above-described polishing method using the abrasive slurry of the present invention.

[0063] In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number), it also means "preferably larger than X" or "preferably smaller than Y".

[0064] The abrasive slurry of the present invention can reduce frictional resistance during polishing and suppress the deposition of abrasive grains.

[0065] 1 is a table showing the physical properties and measurement results of the abrasive slurries according to Examples 1 to 8 and Comparative Examples 1 and 2.

[0066] The abrasive slurry according to the embodiment of the present invention will be further described below with reference to the following examples, although the present invention is not limited to these examples.

[0067] (Example 1) A container was charged with pure water and manganese dioxide (MnO ２ ), as a phosphoric acid, sodium pyrophosphate (specifically, sodium pyrophosphate decahydrate (Na ４ P ２ O ７ ・10H ２ 0), CAS number: 13472-36-1), ammonium polyacrylate as a polymer additive, and beads (zirconia, φ0.4 mm) were placed in the container, and the container was set on a paint shaker (60 Hz). The container was rotated at high speed to mix and grind the manganese dioxide.

[0068] The mixture containing the mixed and pulverized manganese dioxide in the container was separated from the beads using a centrifuge (himac CT 6E manufactured by Hitachi Koki Co., Ltd.) or the like, and the supernatant was collected. The solids concentration in the collected supernatant, i.e., the manganese oxide abrasive grain concentration, was measured using a heating moisture meter, and pure water was added to reach a predetermined concentration, thereby obtaining an abrasive slurry intermediate.

[0069] Polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox L-11) was added as a nonionic surfactant to the abrasive slurry intermediate and mixed.

[0070] Then, abrasive slurry intermediate to which a nonionic surfactant is added and KMnO ４ Potassium permanganate (KMnO) with a mass % concentration of 3.2 mass % ４ ) aqueous solution to obtain an abrasive slurry according to Example 1.

[0071] The content of each component relative to the total amount of the abrasive slurry in Example 1 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.250 mass%, and total polymer additive content 0.01 mass%.

[0072] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 1 was 0.1% for the total content of phosphoric acids, 12.5% ​​for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0073] The polishing rate of the abrasive slurry according to Example 1 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 1 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0074] (Example 2) In Example 2, the abrasive slurry of Example 2 was obtained by carrying out the same manufacturing method as in Example 1, except that polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox CP-B1) was added instead of the nonionic surfactant used in Example 1, and the content of the nonionic surfactant in Example 2 was adjusted to be 0.250 mass% with respect to the total amount of the abrasive slurry in Example 2.

[0075] The content of each component relative to the total amount of the abrasive slurry in Example 2 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.250 mass%, and total polymer additive content 0.01 mass%.

[0076] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 2 was 0.1% for the total content of phosphoric acids, 12.5% ​​for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0077] The polishing rate of the abrasive slurry according to Example 2 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 2 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0078] (Example 3) In Example 3, the same manufacturing method as in Example 1 was carried out to obtain the abrasive slurry of Example 3, except that polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox EP1010N) was added instead of the nonionic surfactant used in Example 1, and the nonionic surfactant of Example 3 was adjusted to be 0.250 mass % relative to the total amount of the abrasive slurry of Example 3.

[0079] The content of each component relative to the total amount of the abrasive slurry in Example 3 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.250 mass%, and total polymer additive content 0.01 mass%.

[0080] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 3 was 0.1% for the total content of phosphoric acids, 12.5% ​​for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0081] The polishing rate of the abrasive slurry according to Example 3 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 3 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0082] (Example 4) In Example 4, the abrasive slurry of Example 4 was obtained by carrying out the same manufacturing method as in Example 1, except that polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox E-60) was added instead of the nonionic surfactant used in Example 1, and the content of the nonionic surfactant in Example 4 was adjusted to be 0.005 mass % with respect to the total amount of the abrasive slurry in Example 4.

[0083] The content of each component relative to the total amount of the abrasive slurry in Example 4 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.005 mass%, and total polymer additive content 0.01 mass%.

[0084] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 4 was 0.1% for the total content of phosphoric acids, 0.25% for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0085] The polishing rate of the abrasive slurry according to Example 4 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 4 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0086] (Example 5) In Example 5, the abrasive slurry of Example 5 was obtained by carrying out the same manufacturing method as in Example 1, except that polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox E-60) was added instead of the nonionic surfactant used in Example 1, and the content of the nonionic surfactant in Example 5 was adjusted to be 0.050 mass% with respect to the total amount of the abrasive slurry in Example 5.

[0087] The content of each component relative to the total amount of the abrasive slurry in Example 5 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.05 mass%, and total polymer additive content 0.01 mass%.

[0088] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 5 was 0.1% for the total content of phosphoric acids, 2.5% for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0089] The polishing rate of the abrasive slurry according to Example 5 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 5 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0090] (Example 6) In Example 6, the abrasive slurry of Example 6 was obtained by carrying out the same manufacturing method as in Example 1, except that polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox E-300) was added instead of the nonionic surfactant used in Example 1, and the content of the nonionic surfactant in Example 6 was adjusted to be 0.005 mass % with respect to the total amount of the abrasive slurry in Example 6.

[0091] The content of each component relative to the total amount of the abrasive slurry in Example 6 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.005 mass%, and total polymer additive content 0.01 mass%.

[0092] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 5 was 0.1% for the total content of phosphoric acids, 0.25% for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0093] The polishing rate of the abrasive slurry according to Example 6 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 6 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0094] (Example 7) In Example 7, the abrasive slurry of Example 7 was obtained by carrying out the same manufacturing method as in Example 1, except that polyethylene glycol (manufactured by Meisei Chemical Industry Co., Ltd., product name: Alcox E-300) was added instead of the nonionic surfactant used in Example 1, and the content of the nonionic surfactant of Example 7 was adjusted to be 0.050 mass% with respect to the total amount of the abrasive slurry of Example 7.

[0095] The content of each component relative to the total amount of the abrasive slurry in Example 7 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.05 mass%, and total polymer additive content 0.01 mass%.

[0096] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 7 was 0.1% for the total content of phosphoric acids, 2.5% for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0097] The polishing rate of the abrasive slurry according to Example 7 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 7 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0098] (Example 8) In Example 8, a polyoxyalkylene-type nonionic surfactant (manufactured by San Nopco Ltd., product name: SN Wet 980) was added instead of the nonionic surfactant used in Example 1, and the content of the nonionic surfactant in Example 8 was adjusted to be 0.002 mass % relative to the total amount of the abrasive slurry in Example 8. The same manufacturing method as in Example 1 was carried out to obtain the abrasive slurry in Example 8.

[0099] The content of each component relative to the total amount of the abrasive slurry in Example 8 described above was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.002 mass%, and total polymer additive content 0.01 mass%.

[0100] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Example 8 was 0.1% for the total content of phosphoric acids, 0.1% for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0101] The polishing rate of the abrasive slurry according to Example 8 was evaluated by the above-mentioned method, and the polishing rate was found to be high. The pot life of the abrasive slurry according to Example 8 was also evaluated by the above-mentioned method, and the pot life was found to be excellent.

[0102] (Comparative Example 1) In Comparative Example 1, the same manufacturing method as in Example 1 was carried out, except that no nonionic surfactant was added and the content of the nonionic surfactant in Comparative Example 1 was 0.0 mass% relative to the total amount of the abrasive slurry in Comparative Example 1, to obtain the abrasive slurry in Comparative Example 1.

[0103] The content of each component relative to the total amount of the abrasive slurry in the above-mentioned Comparative Example 1 was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 1.2 mass%, total phosphoric acid content 0.002 mass%, total nonionic surfactant content 0.0 mass%, and total polymer additive content 0.01 mass%.

[0104] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Comparative Example 1 was 0.1% for the total content of phosphoric acids, 0.0% for the total content of nonionic surfactants, and 0.5% for the total content of polymer additives.

[0105] Comparative Example 2 In Comparative Example 2, (1) the content of permanganate ions was adjusted to 2.2% by mass relative to the total amount of the abrasive slurry according to Comparative Example 2, (2) the content of sodium pyrophosphate was adjusted to 0.02% by mass relative to the manganese dioxide abrasive grains, (3) no polymer additive was added, (4) carboxymethyl cellulose (CMC) was added instead of the nonionic surfactant used in Example 1, and (5) the content of the carboxymethyl cellulose was adjusted to 0.250% by mass relative to the total amount of the abrasive slurry according to Comparative Example 2, using the same manufacturing method as in Example 1 to obtain an abrasive slurry according to Comparative Example 2. Here, the carboxymethyl cellulose added instead of the nonionic surfactant used in Example 1 is an anionic water-soluble polymer.

[0106] The content of each component relative to the total amount of the abrasive slurry in the above-mentioned Comparative Example 2 was as follows: total abrasive grain content 2.0 mass%, total permanganate ion content 2.2 mass%, total phosphoric acid content 0.020 mass%, total carboxymethylcellulose content 0.25 mass%, and total polymer additive content 0.0 mass%.

[0107] In addition, the mass ratio of the content of each component to the total content of the abrasive grains in Comparative Example 2 was 1.0% for the total content of phosphoric acids, 12.5% ​​for the total content of carboxymethylcellulose, and 0.0% for the total content of polymer additives.

[0108] The following physical properties were measured for the abrasive slurries of Examples 1 to 8 and Comparative Examples 1 and 2. The measured physical properties and the methods for measuring the physical properties are shown below, and the measurement results are shown in Figure 1. The compositions of the abrasive slurries of Examples 1 to 8 and Comparative Examples 1 and 2 shown in Figure 1 are the compositions of the final products.

[0109] <Friction Property Evaluation> The friction properties of the abrasive slurries according to Examples 1 to 8 and Comparative Examples 1 and 2 were evaluated as follows. A polishing pad (IC1000 manufactured by Nitta DuPont) was attached and fixed to the platen of a polishing machine, and 1 L of the abrasive slurries according to Examples 1 to 8 and Comparative Examples 1 and 2 was supplied to the polishing pad at a supply rate of 200 mL / min in a circulating manner. A workpiece was placed on the polishing pad as the object to be polished. Furthermore, with a spring balance hooked onto the workpiece, the platen of the polishing machine was rotated, and the workpiece was rotated in the same direction as the platen by a forced drive unit. Here, the forced drive unit was provided with a rotating roller that could contact the workpiece, and the workpiece was rotated by rotating the rotating roller. The spring balance was then pulled in a direction that moved the workpiece away from the forced drive unit, and the forced drive unit separated the rotating roller from the workpiece, thereby stopping the rotation of the workpiece. The digital display value (i.e., tensile force) displayed on the spring balance was measured 30 seconds after the rotation of the workpiece had stopped. The tensile force measured in this manner was divided by the load of the workpiece to determine the friction coefficient of the abrasive slurries of Examples 1 to 8 and Comparative Examples 1 and 2. If the friction coefficient was 0.38 or less, it was evaluated as "〇〇 (VERY GOOD)", if the friction coefficient was more than 0.38 and less than 0.40, it was evaluated as "〇 (GOOD)", and if the friction coefficient was more than 0.40, it was evaluated as "× (BAD)".

[0110] <Crystallization Test> Samples of abrasive slurries according to Examples 1 to 8 and Comparative Examples 1 and 2 were prepared. Each prepared sample was stored in a refrigerator set at 10°C for 24 hours. Thereafter, each sample was removed from the refrigerator, and the solids concentration in each sample, i.e., the sum of the abrasive grain concentration and the potassium permanganate concentration, was determined using a heating moisture meter. If the solids concentration after storage maintained 90% or more of the solids concentration before storage, the sample was evaluated as "Good (◯)." If the solids concentration after storage maintained less than 90% of the solids concentration before storage, the sample was evaluated as "Bad (×)."

[0111] As shown in FIG. 1, the abrasive slurries according to Examples 1 to 8 had a friction coefficient of 0.40 or less, and therefore achieved low friction.

[0112] The abrasive slurries of Examples 1 to 8 were stored in a refrigerator set at 10°C for 24 hours, and the solid content concentration after storage maintained 90% or more of the solid content concentration before storage, indicating that no crystals precipitated.

[0113] The inventions disclosed in this specification include, in addition to the configurations of each invention and embodiment, those specified by changing these partial configurations to other configurations disclosed in this specification, to the extent applicable, or those specified by adding other configurations disclosed in this specification to these configurations, or those specified as higher-level concepts specified by deleting these partial configurations to the extent that partial effects can be obtained.

[0114] The abrasive slurry of the present invention reduces frictional resistance and inhibits the precipitation of abrasive grains, making it suitable as an abrasive for polishing objects made of high-hardness materials. Furthermore, the abrasive slurry of the present invention has excellent dispersibility, making it easy to clean the objects to be polished, such as SiC substrates and polishing pads, and thus reduces the amount of cleaning water used, shortens cleaning time, and reduces the amount of wastewater to be treated, thereby reducing the environmental impact. Furthermore, the abrasive slurry of the present invention exhibits a high polishing rate, thereby shortening the polishing process time.

Claims

1. An abrasive slurry comprising abrasive grains and a nonionic surfactant.

2. The abrasive slurry according to claim 1, wherein the nonionic surfactant contains polyalkylene glycol and / or a compound having a polyalkylene glycol moiety.

3. The abrasive slurry according to claim 2, wherein the nonionic surfactant contains polyethylene glycol and / or a compound having a polyethylene glycol moiety.

4. The abrasive slurry according to claim 3, wherein the compound having a polyethylene glycol moiety contains polyethylene glycol alkyl ether.

5. The abrasive slurry according to claim 1, wherein the abrasive grains contain manganese oxide particles.

6. The abrasive slurry according to claim 1, further comprising manganate ions.

7. The abrasive slurry according to claim 1, further comprising phosphoric acids.

8. The abrasive slurry according to claim 1, wherein the solvent is water.

9. A polishing method characterized by polishing using the abrasive slurry according to any one of claims 1 to 8.

10. A SiC wafer characterized by being polished using the abrasive slurry according to any one of claims 1 to 8.

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