Method for manufacturing SiC substrate, and abrasive slurry for polishing SiC substrate

Abstract

This method for producing an SiC substrate has a polishing step for polishing the main surface of an SiC substrate using a polishing material slurry containing: manganese oxide abrasive grains containing manganese oxide particles; permanganate ions; and phosphoric acids. This polishing material slurry for polishing an SiC substrate contains: manganese oxide abrasive grains containing manganese oxide particles; permanganate ions; and phosphoric acids.

Description

[Technical field]

[0001] The present invention relates to a method for producing a SiC substrate and an abrasive slurry for polishing a SiC substrate. [Background technology]

[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, making them capable of withstanding higher voltages.

[0003] Among them, substrates made of silicon carbide (hereinafter referred to as SiC substrates) are not only excellent in hardness, heat resistance, and chemical stability, but also excellent in terms of cost. On the other hand, it is known that SiC substrates are prone to defects on their surface or inside, such as crystal defects, processing damage inside the crystal called latent scratches, and scratches on the substrate surface. In this specification, "latent scratches" refers to crystal disturbances (altered layers) that do not appear on the surface of the SiC substrate.

[0004] In addition, since the SiC substrate has a higher hardness than conventional silicon substrates, the abrasive slurry most suitable for the process of manufacturing the SiC substrate, particularly the process of mirror-finishing the surface of the SiC substrate, that is, the polishing process by the so-called CMP (Chemical Mechanical Polishing) method, is limited. For example, abrasive slurries containing silica or alumina abrasive grains as the main component have been proposed as abrasive slurries used in the polishing process, and for example, Patent Document 1 discloses an abrasive slurry containing colloidal silica and a dispersion medium in which the colloidal silica is dispersed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-117027 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, because the crystal defects and latent scratches that occur in SiC substrates exist inside the substrate, they cannot be detected by observing the surface using optical inspection equipment, etc., and therefore even SiC substrates that have been confirmed to have no scratches on their surface may have crystal defects or latent scratches inside them.

[0007] In view of the above problems, the present invention provides a method for producing a SiC substrate capable of producing a SiC substrate with few latent scratches, and an abrasive slurry for polishing a SiC substrate. [Means for solving the problem]

[0008] The method for manufacturing a SiC substrate of the present invention, which has been made to solve the above-mentioned problems, is characterized by having a polishing treatment step of polishing a main surface of a SiC substrate with an abrasive slurry containing manganese oxide abrasive grains including manganese oxide particles, permanganate ions, and phosphoric acids.

[0009] The SiC substrate for power devices is manufactured from an ingot of bulk single crystal of SiC manufactured by sublimation or the like. First, the outer periphery of the ingot is ground to be cylindrical, and then sliced ​​into a thin disk shape using a wire saw or a slicer, and the outer periphery of the sliced ​​thin disk-shaped ingot is chamfered to obtain a SiC substrate of a predetermined size. The main surface of the SiC substrate thus obtained is ground by a mechanical grinding method to adjust the unevenness and parallelism of the main surface of the SiC substrate. In this specification, the main surface of the SiC substrate may be either the Si surface or the C surface.

[0010] Next, the main surface of the SiC substrate, whose unevenness and parallelism have been adjusted, is polished by a method such as CMP (Chemical Mechanical Polishing) to give the main surface of the SiC substrate a mirror finish.

[0011] The SiC substrate after the above-mentioned processing is completed is physically and chemically cleaned to remove any attached matter, dirt, etc. The SiC substrate from which the attached matter and dirt have been removed is dried, and the main surface of the SiC substrate is inspected for visible and hidden scratches.

[0012] An SiC epitaxial film may be grown by chemical vapor deposition (CVD) on the mirror-finished main surface of the SiC substrate, and the above-mentioned grinding treatment or polishing treatment may be carried out as necessary.

[0013] In this manner, a SiC substrate for a power device is manufactured.

[0014] Among the above-mentioned methods for manufacturing a SiC substrate, in the polishing treatment by the CMP method or the like, by polishing the main surface of the SiC substrate with an abrasive slurry containing manganese oxide abrasive grains including manganese oxide particles described below, permanganate ions, and phosphoric acids, it is possible to manufacture a SiC substrate with few latent scratches.

[0015] Specifically, an abrasive slurry containing manganese oxide abrasive grains containing manganese oxide particles, permanganate ions, and phosphoric acid is supplied to a polishing pad, the polished surface of a SiC substrate is brought into contact with the polishing pad, and polishing is performed by the relative movement between the two. Here, the abrasive slurry supplied to the polishing pad may be a method of pouring the abrasive slurry, or a method of circulating the abrasive slurry, in which the abrasive slurry supplied to the polishing pad and used for polishing is recovered and the recovered abrasive slurry is supplied to the polishing pad again, and the operation is repeated. By repeatedly circulating the abrasive slurry to polish the SiC substrate, the amount of the abrasive slurry used can be reduced. In addition, the polishing pad may 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 4 It is preferable that the pressure is not more than Pa in terms of the polishing force and ease of handling of the polishing jig, etc. The supply rate of the abrasive slurry is preferably 10 mL / min to 500 mL / min, and more preferably 50 mL / min to 250 mL / min.

[0016] Latent scratches on the main surface of a SiC substrate can be observed, for example, using a mirror electron inspection device (Mirelis VM1000, manufactured by Hitachi High-Tech Corporation). Specifically, a 6-inch SiC substrate is set in the mirror electron inspection device, and a 5 mm square virtual chip is placed on the set SiC substrate. Next, multiple imaging points are set for each virtual chip. Then, defects such as latent scratches can be detected from images captured based on the imaging points.

[0017] The inspection technology used in the mirror electron inspection device described above applies a negative potential close to the acceleration voltage of the irradiated electron beam to the substrate surface, inverts the electron beam irradiated over the entire inspection field on the substrate surface near the substrate surface, and forms an image of the inverted electrons (hereinafter referred to as mirror electrons) using an electron lens to obtain an electron image for inspection. In addition, a defect inspection device using a mirror electron microscope simultaneously irradiates the substrate with ultraviolet light, which excites electric charges over a certain depth from the sample surface. This electric charge inside the sample is captured in the crystal defect portion, causing localized charging and distorting the equipotential surface of the surface. In the mirror electron microscope, even a slight distortion of the equipotential generates shading in the mirror electron image, so threading dislocations, basal plane dislocations, stacking faults, etc. can be detected with high sensitivity. In addition, because an electron beam is used for imaging, the resolution of the optical system is several tens of nanometers, which is much higher than that of optical inspection technology.

[0018] The abrasive slurry for polishing SiC substrates of the present invention is characterized by comprising manganese oxide abrasive grains containing manganese oxide particles, permanganate ions, and phosphoric acids. The abrasive slurry for polishing SiC substrates of the present invention contains manganese oxide abrasive grains containing manganese oxide particles, permanganate ions, and phosphoric acids, and therefore has excellent dispersibility and exhibits a high polishing rate.

[0019] Examples of manganese oxide particles contained in the manganese oxide abrasive grains include manganese oxide (II) (MnO), dimanganese trioxide (III) (Mn2O3), manganese dioxide (IV) (MnO2), trimanganese tetroxide (II, III) (Mn3O4), etc. The manganese oxide abrasive grains may be a mixture of one type or two or more types of manganese oxide particles.

[0020] In addition, the manganese oxide abrasive grains may contain abrasive grains other than the above-mentioned manganese oxide grains, within a range that does not impair the effect of preventing warpage and cracking due to the Twyman effect on the SiC substrate, which is the object to be polished by the abrasive slurry for polishing SiC substrates of the present invention. Examples of abrasive grains other than manganese oxide grains include compounds such as oxides, hydroxides, and carbides of at least one element selected from Mg, B, Si, Ce, Al, Zr, Fe, Ti, and Cr, and other carbon materials. Specifically, alumina, silica, cerium oxide, zirconium oxide, titanium oxide, chromium oxide, iron oxide, magnesium hydroxide, cerium hydroxide, silicon carbide, boron carbide, and diamond may be mentioned. These may be used alone or in combination of two or more. In addition, the manganese oxide grains may be composited with abrasive grains other than manganese oxide grains, for example, manganese oxide grains may be surface-coated with abrasive grains other than manganese oxide grains, or manganese oxide grains may be surface-coated with abrasive grains other than manganese oxide grains.

[0021] Moreover, it is preferable that the manganese oxide abrasive grains have a particle size (D50) at 50% of the cumulative volume as measured by a laser diffraction / scattering particle size distribution measurement method of 0.1 μm or more in terms of having a high polishing power, and it is preferable that the particle size is 5.0 μm or less in terms of suppressing roughness of the surface of the workpiece to be polished, such as a SiC substrate. Therefore, it is more preferable that the manganese oxide abrasive grains have a particle size (D50) at 50% of the cumulative volume as 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 preferable that the particle size is 0.2 μm or more and 4.0 μm or less.

[0022] Here, the particle size at 50% cumulative volume (D50) of manganese oxide abrasive grains measured by a laser diffraction / scattering particle size distribution measurement method is prepared by diluting a mixture of manganese oxide abrasive grains pulverized with beads in the manufacturing method of the abrasive slurry for polishing SiC substrates of the present invention described later with water to a concentration of about 0.01% to prepare a measurement sample. Then, the measurement is carried out using a laser diffraction / scattering particle size distribution measurement device (MT3300EXII manufactured by Microtrackbell Co., Ltd.).

[0023] Furthermore, the content of manganese oxide abrasive grains contained in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.5% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, based on the total amount of the polishing slurry, from the viewpoint of sufficiently increasing the polishing rate of high hardness materials such as silicon carbide, from the viewpoint of ensuring the suitable fluidity of abrasive grains in the polishing slurry, and from the viewpoint of preventing aggregation.In addition, the content of manganese oxide particles contained in the manganese oxide abrasive grains is more preferably 1% by mass or more and 5% by mass or less, from the viewpoint of sufficiently increasing the polishing rate.In addition, in this specification, the content in the abrasive slurry for polishing SiC substrate of the present invention is the content in the polishing slurry before starting polishing, unless otherwise specified.

[0024] Furthermore, the abrasive slurry for polishing SiC substrates of the present invention contains, in addition to the manganese oxide abrasive grains described above, permanganate ions (MnO4 - ) The permanganate ion can have a high polishing power for high hardness materials such as silicon carbide by using it together with manganese oxide abrasive grains as an oxidizing agent. Here, the source of the permanganate ion is preferably a permanganate. Examples of the permanganate include an alkali metal salt of permanganate and an alkaline earth metal salt of permanganate. Furthermore, from the viewpoint of easy availability and improvement of the polishing efficiency of the abrasive slurry for polishing SiC substrates of the present invention, among the permanganates that are the source of the permanganate ion, an alkali metal salt of permanganate is preferred, and sodium permanganate or potassium permanganate is more preferred. Note that these permanganates may be used alone or in combination of two or more kinds.

[0025] In addition, the content of permanganate ions in the abrasive slurry for polishing SiC substrates of the present invention is preferably 0.5% by mass or more based on the total amount of the abrasive slurry for polishing SiC substrates of the present invention from the viewpoint of sufficiently increasing the polishing rate.In addition, the content of permanganate ions in the abrasive slurry for polishing SiC substrates of the present invention is preferably 3.2% by mass or less based on the total amount of the abrasive slurry for polishing SiC substrates of the present invention from the viewpoint of preventing crystal precipitation due to increasing the amount of addition, from the viewpoint of ensuring the safety of handling the abrasive slurry, and from the viewpoint that the polishing rate tends to saturate even if the amount of addition is increased.That is, the content of permanganate ions is preferably 0.5% by mass or more to 3.2% by mass or less based on the total amount of the abrasive slurry for polishing SiC substrates of the present invention, and more preferably 1.0% by mass or more to 2.1% by mass or less based on the total amount of the abrasive slurry for polishing SiC substrates of the present invention.The content of permanganate ions is measured by ion chromatography or absorptiometry.

[0026] Furthermore, the abrasive slurry for polishing SiC substrate of the present invention contains phosphoric acid in addition to the above-mentioned manganese oxide abrasive grains and permanganate ion. By using phosphoric acid in combination with manganese oxide abrasive grains and permanganate ion, the dispersibility of the abrasive slurry for polishing SiC substrate of the present invention can be improved.

[0027] The phosphoric acid contained in the abrasive slurry for polishing SiC substrates of the present invention is preferably, for example, an inorganic phosphorus compound. Specifically, the phosphoric acid compound may be sodium phosphate (trisodium phosphate (anhydrous) (Na3PO4), CAS number: 7601-54-9; trisodium phosphate·12-hydrate (Na3PO4·12H2O), CAS number: 10101-89-0; sodium phosphate monobasic (NaH2PO4), CAS number: 7558-80-7; sodium phosphate dibasic (Na2HPO4), CAS number: 7558-79-4), potassium phosphate (phosphorus Potassium phosphate, tripotassium phosphate (anhydrous) (K3PO4), CAS number: 7778-53-2; potassium phosphate, tripotassium phosphate, monohydrate (K3PO4·H2O), CAS number: 27176-10-9; potassium phosphate, dibasic, trihydrate (K2HPO4·H2O), CAS number: 16788-57-1; potassium phosphate, monobasic (KH2PO4), CAS number: 7778-77-0; potassium phosphate, dibasic (K2HPO4), CAS number: 7758-11-4).

[0028] As a metaphosphate compound, sodium metaphosphate (NaPO3) n , CAS number: 35270-09-8) and potassium metaphosphate (KPO3) n , CAS number: 7790-53-6.

[0029] The hexametaphosphate compound is sodium hexametaphosphate (NaHPO 18 ), CAS number: 10124-56-8.

[0030] Pyrophosphate compounds include sodium pyrophosphate (Sodium pyrophosphate, anhydrous (Na4P2O7), CAS number: 7722-88-5; Sodium pyrophosphate decahydrate (Na4P2O7 10H2O), CAS number: 13472-36-1; Sodium acid pyrophosphate (Na2H2P2O7), CAS number: 7758-16-9) and potassium pyrophosphate (K4P2O7), CAS number: 7320-34-5.

[0031] As a polyphosphate compound, sodium polyphosphate (Na3P3O 10 X2), CAS number: 68915-31-1; Potassium polyphosphate (K3P3O 10 X2), CAS number: 68956-75-2.

[0032] As a tripolyphosphate compound, sodium tripolyphosphate (Na5P3O 10 ), CAS number: 7758-29-4, potassium tripolyphosphate (K5P3O 10 ), CAS number: 13845-36-8.

[0033] Further, salts and hydrates thereof may be mentioned. In the case of these salts, alkali metal salts and alkaline earth metal salts are preferred, and sodium salts and potassium salts are more preferred. In particular, in the abrasive slurry of the present invention, from the viewpoint of effective high dispersibility in a small amount and 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.

[0034] The abrasive slurry for polishing SiC substrates of the present invention is characterized in that the phosphoric acid contained therein is a pyrophosphate compound. The phosphoric acid contained in the abrasive slurry for polishing SiC substrate of the present invention is preferably pyrophosphate compound, from the viewpoint of high dispersibility and sufficient improvement of polishing rate.In the pyrophosphate compound, more preferably alkali metal salt of pyrophosphate or alkaline earth metal salt of pyrophosphate, particularly preferably sodium pyrophosphate or potassium pyrophosphate.

[0035] In addition, the content of phosphoric acid in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.01 mass% or more based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention from the viewpoint of dispersibility.In addition, the content of phosphoric acid in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.1 mass% or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention, because the polishing rate tends to saturate even if the amount of addition is increased.That is, the content of phosphoric acid is preferably 0.01 mass% or more and 0.1 mass% or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention, more preferably 0.02 mass% or more from the viewpoint of improving dispersibility, and more preferably 0.05 mass% or less from the viewpoint of sufficiently increasing the polishing rate.In addition, the content of phosphoric acid in this specification is the total amount of those classified as phosphoric acid, unless otherwise specified.

[0036] Furthermore, the content of phosphoric acid in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.5% or more and 5.0% or less, more preferably 0.8% or more and 3.0% or less, and even more preferably 1.0% or more and 2.0% or less, when expressed as a mass ratio to the content of manganese oxide abrasive grain in the abrasive slurry for polishing SiC substrate of the present invention.

[0037] The abrasive slurry for polishing SiC substrates of the present invention is characterized in that it further contains a cellulose-based surfactant and / or a cationic surfactant. The abrasive slurry for polishing SiC substrates of the present invention can have improved low friction properties by further containing a cellulose-based surfactant and / or a cationic surfactant.

[0038] As the cellulose-based surfactant, anionic surfactants, cationic surfactants, and nonionic surfactants are all known. First, anionic surfactants include those in which a negative group, such as a carboxyl group, an alkoxyl group, or a hydroxyl group, is introduced into the cellulose skeleton. In addition, cationic surfactants include cationic cellulose. Furthermore, nonionic groups include alkyl celluloses such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose.

[0039] Among these cellulose surfactants, anionic surfactants are preferred, and those containing a carboxyl group are more preferred, and carboxymethylcellulose and its derivatives are preferred from the viewpoint of low friction. Carboxymethylcellulose is a compound in which a carboxymethyl group is bonded to a part of the hydroxyl group of a glucopyranose monomer constituting a cellulose skeleton. In addition, examples of the carboxymethylcellulose derivative include alkali metal salts of carboxymethylcellulose, specifically salts such as sodium or potassium salts. Furthermore, examples of the carboxymethylcellulose derivative include those in which a hydroxyl group, an alkyl group, or the like is bonded to the side chain of carboxymethylcellulose within a range that does not lose the surfactant effect of carboxymethylcellulose. Other examples of the cellulose surfactant include crystalline cellulose and its modified products (for example, Avicel manufactured by Asahi Kasei Corporation). It should be noted that one or more of these cellulose surfactants may be used in combination.

[0040] The cationic surfactant may be an amine salt surfactant or a quaternary ammonium salt surfactant, and is preferably one having a quaternary ammonium ion site. Here, the cationic surfactant having a quaternary ammonium ion site may be, for example, a salt represented by the following general formula (1):

[0041] [ka] (In the above general formula (1), R1, R2, R3, and R4 are each independently an alkyl group, an aryl group, or an arylalkyl group, or R1, R2, and R3 are bonded to form a pyridine ring, and R4 is an alkyl group, an aryl group, or an arylalkyl group; X - is a monovalent anion.)

[0042] In the above general formula (1), the alkyl group represented by R1, R2, R3, and R4 preferably has 1 to 20 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, t-amyl group, hexyl group, heptyl group, isoheptyl group, t-heptyl group, n-octyl group, isooctyl group, 2-ethylhexyl group, t-octyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, dodecyl group, tridecyl group, isotridecyl group, tetradecyl group, hexadecyl group, octadecyl group, icosyl group, etc., and linear group is preferable. The aryl group represented by R1, R2, R3, and R4 is preferably a phenyl group. The arylalkyl group represented by R1, R2, R3, and R4 is preferably a benzyl group, a phenethyl group, or the like. - The monovalent anion represented by is preferably a halide ion. The halide ion is preferably a chloride ion or a bromide ion. The aromatic ring in the aryl group or arylalkyl group represented by R1, R2, R3, and R4 and the pyridine ring formed by bonding R1, R2, and R3 may be substituted with an alkyl group or an amino group, and the methylene group in the arylalkyl group may be replaced with -O-. The pyridine ring formed by bonding R1, R2, and R3 may be condensed with a benzene ring.

[0043] The cationic surfactant represented by the above general formula (1) is, for example, distearyldimethylammonium chloride (rational formula C 18 H 37 N + C 18 H 37 (CH3)2 Cl -), benzalkonium chloride (chemical formula C6H5CH2N + (CH3)2RCl - (R=C8H 17 ~C 18 H 37 , long chain alkyl), benzethonium chloride (molecular formula C 27 H 42 ClNO2), cetylpyridinium chloride (molecular formula C 21 H 38 NCl), hexadecyltrimethylammonium bromide (with rational formula (C 16 H 33 )N + (CH3)3Br - ), dequalinium chloride (molecular formula C 30 H 40 C l2 N4) etc.

[0044] In addition, the total content of the cellulose surfactant and / or cationic surfactant in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.1 mass% or more based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention from the viewpoint of improving low friction.In addition, the total content of the cellulose surfactant and / or cationic surfactant in the abrasive slurry for polishing SiC substrate of the present invention is preferably 1 mass% or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention from the viewpoint of sufficiently increasing the polishing rate.That is, the total content of the cellulose surfactant and / or cationic surfactant is preferably 0.1 mass% or more to 1 mass% or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention, and more preferably 0.1 mass% or more to 0.5 mass% or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention.In addition, in this specification, the total content of the cellulose surfactant and / or cationic surfactant is the content of only one of the cellulose surfactant and / or cationic surfactant when it contains only one of them, and is the total amount when it contains both of them, unless otherwise specified.

[0045] In addition, the abrasive slurry for polishing SiC substrates of the present invention is characterized by further containing a polymer additive containing one or more water-soluble organic polymers selected from the group consisting of polycarboxylic acids, polycarboxylates, salts of naphthalenesulfonic acid-formaldehyde condensates, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and copolymers thereof. The abrasive slurry for polishing SiC substrates of the present invention can extend the pot life after mixing by further containing, in addition to the above-mentioned manganese oxide abrasive grains, permanganate ions, and phosphoric acids, a polymer additive containing one or more water-soluble organic polymers selected from the group including polycarboxylic acids, polycarboxylates, salts of naphthalenesulfonic acid-formalin condensates, polyvinyl alcohols, polyethylene glycols, polyvinylpyrrolidone, and copolymers thereof.

[0046] Furthermore, the water-soluble organic polymer preferably has a number average molecular weight (Mn) of 1000 to 10000, a weight average molecular weight (Mw) of 1000 to 1000000, a z-average molecular weight (Mz) of 5000 to 1000000, a dispersity (Mw / Mn) of 0.1 to 150, and a ratio of Mz to Mw (Mz / Mw) of 0.1 to 20. Here, the number average molecular weight (Mn) is more preferably 2000 to 8000. Typically, the number average molecular weight (Mn) may be 3000 to 6000. The weight average molecular weight (Mw) is more preferably 3500 to 100000, and even more preferably 4000 to 50000. Typically, the weight average molecular weight (Mw) may be 5000 or more and 20000 or less. More preferably, the z-average molecular weight (Mz) is 6000 or more and 100000 or less. Typically, the z-average molecular weight (Mz) may be 6500 or more and 75000 or less, or 7000 or more and 50000 or less. More preferably, the dispersity (Mw / Mn) is 0.5 or more and 75 or less, and even more preferably, 0.8 or more and 10 or less. Typically, the dispersity (Mw / Mn) may be 0.9 or more and 5 or less. More preferably, the ratio of Mz to Mw (Mz / Mw) is 0.5 or more and 15 or less, and even more preferably, 0.8 or more and 10 or less. Typically, the ratio of Mz to Mw (Mz / Mw) may be 0.9 or more and 5 or less. On the other hand, when CMC (carboxymethyl cellulose) is contained as a polymer additive, the pot life of the abrasive slurry for polishing SiC substrates tends to be shortened.

[0047] Here, the number average molecular weight (Mn), weight average molecular weight (Mw), and z average molecular weight (Mz) calculated as polyethylene glycol (PEG) measured by GPC can be measured and analyzed under the following conditions. From the obtained number average molecular weight (Mn), weight average molecular weight (Mw), and z average molecular weight (Mz), the dispersity (Mw / Mn) and the ratio of Mz to Mw (Mz / Mw) are calculated. =Molecular weight measurement conditions= Measurement equipment: HPLC Prominence series (Shimadzu Corporation) Equipment configuration: CBM20A, DGU-20A3R, LC-20AD, SIL-20ACHT, CTO-20AC, RID-10A Column: Shodex OHpak SB-803 HQ (Resonac Co., Ltd.) Temperature: 40℃ Flow rate: 1.0ml / min Detector: Differential refractive index detector Eluent: 0.1M sodium chloride aqueous solution =Analysis software= Software: LabSolutions / LCsolution GPC (Shimadzu Corporation) Version: 1.25 SP2

[0048] Furthermore, when the aqueous solution in which the water-soluble organic polymer is dissolved in water has a high viscosity, it is difficult to measure each molecular weight by the GPC. In that case, it is preferable that the viscosity of the aqueous solution containing 1% by mass of the water-soluble organic polymer at a liquid temperature of 25°C is 10000 mPa·s or more and 30000 mPa·s or less. Typically, the viscosity may be 11000 mPa·s or more and 27000 mPa·s or less, 12000 mPa·s or more and 24000 mPa·s or less, or 13000 mPa·s or more and 21000 mPa·s or less. The viscosity of the water-soluble organic polymer is measured using a digital rotational viscometer DV3T (manufactured by Eiko Seiki Co., Ltd.) and is a value measured under the condition of a rotation speed of 0.01 rpm.

[0049] In addition, in the abrasive slurry for polishing SiC substrates of the present invention, the polymer additive is preferably one or more water-soluble organic polymers selected from polycarboxylic acids, polycarboxylates, and copolymers thereof, more preferably one or more water-soluble organic polymers selected from polyacrylic acid, polymaleic acid, polyacrylates, polymaleates, and copolymers thereof, particularly preferably one or more water-soluble organic polymers selected from polyacrylic acid, polymaleic acid, polyacrylates, polymaleates, and copolymers thereof, particularly preferably one or more polyacrylates, and even more particularly preferably one or more polyammonium acrylates.

[0050] In addition, the content of polymer additive in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.006% by mass or more based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention from the viewpoint of dispersibility.In addition, the content of polymer additive in the abrasive slurry for polishing SiC substrate of the present invention is preferably 0.05% by mass or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention from the viewpoint of sufficiently increasing the polishing rate.That is, the content of polymer additive is preferably 0.006% by mass or more and 0.05% by mass or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention, and more preferably 0.01% by mass or more and 0.03% by mass or less based on the total amount of the abrasive slurry for polishing SiC substrate of the present invention.In addition, the content of polymer additive in this specification is the total amount of the polymer additives classified as the above-mentioned polymer additives, unless otherwise specified.

[0051] Furthermore, the content of the polymer additive in the abrasive slurry for polishing SiC substrates of the present invention, expressed as a mass ratio relative to the content of manganese oxide abrasive grains in the abrasive slurry for polishing SiC substrates of the present invention, is preferably 0.3% or more and 2.5% or less, more preferably 0.4% or more and 2.0% or less, and even more preferably 0.5% or more and 1.0% or less.

[0052] Here, the abrasive slurry for polishing SiC substrate of the present invention contains the above-mentioned manganese oxide abrasive grains, permanganate ions, phosphoric acids, cellulose surfactants, and / or cationic surfactants, or a dispersion medium for dissolving or dispersing polymer additives. The dispersion medium is preferably water, water-soluble organic solvents such as alcohols and ketones, or mixtures thereof, in order to sufficiently increase the polishing rate, and more preferably water. The content of the dispersion medium is preferably 60% by mass or more and 99.9% by mass or less, and more preferably 80% by mass or more and 90% by mass or less, based on the total amount of the abrasive slurry for polishing SiC substrate.

[0053] Furthermore, the abrasive slurry for polishing SiC substrates of the present invention may contain any additive other than the above-mentioned manganese oxide abrasive grains, permanganate ions, phosphoric acids, cellulose surfactants, and / or cationic surfactants, or polymer additives, and dispersion medium. Here, the optional additives are 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 for polishing SiC substrates of the present invention.

[0054] The abrasive slurry for polishing SiC substrate of the present invention can be in the form of appropriately mixing the above-mentioned manganese oxide abrasive grains, permanganate ions, phosphoric acids, cellulose surfactant, and / or cationic surfactant, and / or polymer additive, dispersion medium, and any additive, and can be, for example, a kit in which these components are divided into two or more agents. The composition of the kit may be in such a form that the polishing ability of the abrasive slurry for polishing SiC substrate is fully exhibited when the abrasive slurry for polishing SiC substrate is prepared.

[0055] The above-mentioned abrasive slurry for polishing SiC substrates of the present invention can be used in a finishing CMP (Chemical Mechanical Polishing) process after lapping of a SiC substrate. It can sufficiently increase the polishing rate and effectively prevent warping and cracking caused by the Twyman effect. A single crystal silicon carbide substrate is usually used as a SiC substrate, and its crystal system is usually hexagonal or rhombohedral, and hexagonal is preferred in terms of exerting the effect of the abrasive slurry that can prevent warping and cracking caused by the Twyman effect. Polymorphs of hexagonal crystals include 2H, 4H, 6H, 8H, and 10H. Polymorphs of rhombohedral crystals include 15R.

[0056] In addition, the object to be polished by the abrasive slurry for polishing SiC substrates of the present invention is not limited to SiC substrates, and may be, for example, a high-hardness material with a Mohs hardness of 8 or more. Here, the Mohs hardness is a numerical value of hardness based on how a standard material is scratched, and can be measured by a conventional method using a Mohs hardness meter. Standard materials are designated in order of Mohs hardness from 1 to 10, from softest to softest, and specific standard materials are Mohs hardness 1 for talc, 2 for gypsum, 3 for calcite, 4 for fluorite, 5 for apatite, 6 for orthoclase, 7 for quartz, 8 for topaz, 9 for corundum, and 10 for diamond. As for the Mohs hardness, examples of high-hardness materials with a Mohs hardness of 8 or more include silicon carbide (Mohs hardness about 9), gallium nitride (Mohs hardness about 9), diamond, etc.

[0057] Next, a method for producing the above-mentioned abrasive slurry for polishing SiC substrates of the present invention will be described below.

[0058] First, pure water, manganese dioxide (abrasive grains, MnO2), phosphoric acid (e.g., sodium salt of pyrophosphate), and beads (zirconia, φ0.4 mm) are placed in a container, and the container is set on a paint shaker (60 Hz) and rotated at high speed to mix and grind the manganese dioxide (abrasive grains, MnO2). When mixing and grinding the manganese dioxide (abrasive grains, MnO2), a polymer additive may be added.

[0059] The mixture containing the mixed and ground manganese dioxide (abrasive grains, MnO2) in the container is separated from the beads using a centrifuge (Hitachi Koki himac CT 6E) or the like, and the supernatant liquid is collected.

[0060] The solids concentration in the collected supernatant, i.e., the manganese oxide abrasive grain concentration, is measured using a heating moisture meter, and pure water is added to the supernatant to obtain a predetermined concentration, thereby obtaining an abrasive slurry intermediate. Furthermore, if necessary, a cellulose-based surfactant and / or a cationic surfactant may be added to and mixed with the obtained abrasive slurry intermediate.

[0061] Then, the abrasive slurry intermediate and potassium permanganate (KMnO4) are mixed to obtain the abrasive slurry for polishing SiC substrates of the present invention.

[0062] In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably greater than X" or "preferably smaller than Y". In addition, when "X or more" (X is any number) or "Y or less" (Y is any number), it also includes the meaning of "preferably greater than X" or "preferably less than Y". Effect of the Invention

[0063] The method for producing a SiC substrate and the abrasive slurry for polishing a SiC substrate of the present invention can produce a SiC substrate with few latent scratches. [Brief description of the drawings]

[0064] [Figure 1] 1 is a table showing the physical property values ​​and measurement results of abrasive slurries according to Example 1 and Comparative Example 1. BEST MODE FOR CARRYING OUT THEINVENTION

[0065] Hereinafter, the SiC substrate produced by the SiC substrate production method according to the embodiment of the present invention and the abrasive slurry for polishing SiC substrate used in the polishing process of the production method will be described in more detail with the following examples. However, the following examples do not limit the present invention.

[0066] Example 1 First, an abrasive slurry for polishing a SiC substrate used in the polishing treatment step of the manufacturing method of a SiC substrate according to Example 1 was manufactured as follows.

[0067] Pure water, manganese dioxide (MnO2) as abrasive grains, sodium pyrophosphate as phosphoric acid (specifically, sodium pyrophosphate decahydrate (Na4P2O7·10H2O), CAS number: 13472-36-1), and beads (zirconia, φ0.4 mm) were placed in a container, and the container was set on a paint shaker (60 Hz) and rotated at high speed to mix and grind the manganese dioxide. The contents of these components were adjusted so that the manganese dioxide content was 30 mass% and the sodium pyrophosphate content was 0.3 mass% relative to the total amount of the abrasive slurry for polishing SiC substrates according to Example 1.

[0068] The mixture containing the mixed and ground manganese dioxide in the container was separated from the beads using a centrifuge (Hitachi Koki Himac CT 6E) or the like, and the supernatant was collected. Note that the supernatant obtained in this process will be the measurement sample before the addition of potassium permanganate in the dispersibility test described below.

[0069] The solid content concentration in the collected supernatant, i.e., manganese oxide abrasive grain concentration, was measured using a heating moisture meter, and pure water was added to the collected supernatant to obtain a predetermined concentration, thereby obtaining an intermediate abrasive slurry. Carboxymethylcellulose, a cellulose-based surfactant, was added to the intermediate abrasive slurry obtained so that the content was 0.25 mass% relative to the total amount of the abrasive slurry for polishing SiC substrates according to Example 1, and mixed.

[0070] Then, the abrasive slurry intermediate and an aqueous potassium permanganate (KMnO4) solution with a KMnO4 mass% concentration of 3.2 mass% were mixed to obtain an abrasive slurry for polishing SiC substrates according to Example 1. The content of permanganate ions was adjusted to 2.1 mass% with respect to the total amount of the abrasive slurry for polishing SiC substrates according to Example 1. The mass ratio of the total content of phosphoric acids to the manganese oxide abrasive grain content according to Example 1 was 1%. The abrasive slurry for polishing SiC substrates according to Example 1 obtained in this process is the measurement sample after the addition of potassium permanganate in the dispersibility test described later. The composition of the abrasive slurry for polishing SiC substrates shown in FIG. 1 is the composition in the final product.

[0071] Next, the abrasive slurry for polishing SiC substrates according to Example 1 was supplied to a polishing pad (Nitta DuPont: IC1000), the main surface of the SiC substrate was brought into contact with the polishing pad, and polished by relative movement between the two to obtain the SiC substrate according to Example 1. Here, the polishing device used was a single-sided polisher ARW-681M manufactured by MAT Corporation. The rotation speed of the surface plate was set to 40 rpm, and the outer peripheral speed was set to 7,665 cm / min. The rotation speed of the carrier was also set to 40 rpm, and the outer peripheral speed was set to 641 cm / min. Furthermore, the load during polishing was 4.3 psi (approximately 2.94×10 4 The supply rate of 1 L of the abrasive slurry for polishing SiC substrates according to Example 1 was set to 250 mL / min, and the slurry was supplied to the polishing pad in a circulating manner.

[0072] Comparative Example 1 In Comparative Example 1, (i) instead of manganese dioxide (MnO2) used in Example 1, alumina (Al2O3) was used in an amount of 6.5 mass% based on the total amount of the abrasive slurry of Comparative Example 1, (ii) the content of potassium permanganate (KMnO4) mixed with the abrasive slurry intermediate was adjusted to 1.3 mass% based on the total amount of the abrasive slurry for SiC substrate polishing of Example 1, (iii) the content of sodium pyrophosphate was adjusted to 0.046 mass% based on the total amount of the abrasive slurry for SiC substrate polishing of Comparative Example 1, and (iv) a cellulose-based surfactant was not added. Except for this, a manufacturing method similar to that of Example 1 was carried out to obtain an abrasive slurry for SiC substrate polishing of Comparative Example 1.

[0073] Next, similarly to Example 1, the abrasive slurry for polishing the SiC substrate of Comparative Example 1 was supplied to a polishing pad, the main surface of the SiC substrate was brought into contact with the polishing pad, and polished by relative movement between the two to obtain the SiC substrate of Comparative Example 1.

[0074] Then, the physical properties of the abrasive slurries for polishing SiC substrates according to Example 1 and Comparative Example 1, and the physical properties of the SiC substrates according to Example 1 and Comparative Example 1 were measured. The measured physical properties and the measurement methods of the physical properties are shown below, and the measurement results are shown in Table 1.

[0075] <Particle size evaluation> The mixture containing the abrasive grains mixed and ground in a paint shaker in the abrasive slurry for polishing SiC substrates according to Example 1 and Comparative Example 1 was diluted with water so that the concentration of the mixture was about 0.01%, to prepare a measurement sample. Then, the particle size at a cumulative volume fraction of 50% (D50) was measured using a laser diffraction / scattering particle size distribution measuring device (MT3300EXII manufactured by Microtrackbell Co., Ltd.).

[0076] <Dispersibility evaluation> The dispersibility of the abrasive slurries for polishing SiC substrates according to Example 1 and Comparative Example 1 was evaluated before and after the addition of potassium permanganate, which is a source of permanganate ions.

[0077] First, the dispersibility before the addition of potassium permanganate was evaluated as follows. The mixture containing the abrasive grains mixed and ground by a paint shaker in the abrasive slurry for polishing SiC substrates according to Example 1 and Comparative Example 1 was diluted with water so that the concentration of the mixture was about 0.01 mass %, to prepare a measurement sample. Then, using a laser diffraction / scattering particle size distribution measuring device (Microtrackbell Co., Ltd.: MT3300EXII), the particle size (D50) at a volume-based cumulative fraction of 50% was measured, and if D50 was 0.6 μm or less, it was evaluated as "◯ (Good)", and if D50 was more than 0.6 μm, it was evaluated as "× (Bad)".

[0078] Next, the dispersibility after the addition of potassium permanganate was evaluated as follows. Measurement samples were prepared by diluting the abrasive slurries for polishing SiC substrates according to Example 1 and Comparative Example 1 with water so that the concentration was about 0.01% by mass. Then, the particle size (D50) at a volume-based cumulative fraction of 50% was measured using a laser diffraction / scattering particle size distribution measuring device (Microtrackbell Corporation: MT3300EXII). If D50 was 0.6 μm or less, it was evaluated as "Good", and if D50 was more than 0.6 μm, it was evaluated as "Bad".

[0079] Adhesion Evaluation The adhesion of the abrasive slurries for polishing SiC substrates according to Example 1 and Comparative Example 1 was judged by a tester by visually checking the adhesion state of each abrasive slurry to the container (wide-mouthed bottle made by AS ONE, Eye Boy 250 ml) containing the sample used in the above-mentioned evaluation of dispersibility after the addition of potassium permanganate, when the container was inverted, as follows: If the sample did not adhere to the container when the container containing the sample was inverted, it was evaluated as "〇〇 (Very Good)", if the sample adhered only to the bottom of the container, it was evaluated as "〇 (Good)", and if the sample adhered to the bottom and sides or sides of the container, it was evaluated as "× (Bad)".

[0080] <Polishing test> The polishing rates of the abrasive slurries for polishing SiC substrates according to Example 1 and Comparative Example 1 were evaluated by the following procedure. The polishing target was a CMP-processed 4H-SiC substrate with a diameter of 6 inches and an off angle of 4°. The polishing test was performed on the Si surface of the substrate. The polishing device used was a single-sided polisher ARW-681M manufactured by MAT Corporation. The polishing pad attached to the platen was an IC1000 manufactured by Nitta DuPont. The platen rotation speed was set to 40 rpm, and the outer peripheral speed was set to 7,665 cm / min. The carrier rotation speed was set to 40 rpm, and the outer peripheral speed was set to 641 cm / min. Furthermore, the load during polishing was 4.3 psi (approximately 2.94×10 4 The polishing rate was calculated from the difference in the mass of the substrate before and after polishing, after polishing for 1 hour, as shown in Fig. 1. If the polishing rate was 0.10 μm / h or more, it was evaluated as "Good", and if the polishing rate was less than 0.10 μm / h, it was evaluated as "Bad".

[0081] <Crystallization test> Each sample of the abrasive slurry for polishing SiC substrate according to Example 1 and Comparative Example 1 was prepared. Each prepared sample was stored in a refrigerator set at 10°C for 24 hours. Then, each sample was taken out of the refrigerator, and the solid content concentration in each sample, that is, the total value of the manganese oxide abrasive grain concentration and the potassium permanganate concentration, was obtained using a heating moisture meter. If the solid content concentration after storage was 90% or more of the solid content concentration before storage, it was evaluated as "Good (◯)", and if the solid content concentration after storage was less than 90% of the solid content concentration before storage, it was evaluated as "Bad (×)".

[0082] <Damage assessment> The entire Si surface of the SiC substrates according to Example 1 and Comparative Example 1 was observed using a SiC wafer defect device (WASAVI series SICA6X, manufactured by Lasertec Corporation) using a confocal differential interference method to perform a damage evaluation. Specifically, the Si surface area of ​​a 6-inch SiC substrate excluding a 5 mm peripheral portion was imaged in SD mode, and scratches were detected by line detection using a probabilistic Hough transform. The number of detected scratches was then divided by the area of ​​the SiC substrate to calculate the scratch density. When the calculated scratch density on the entire Si surface of the SiC substrate was 5 scratches / cm 2 If the density of scratches was less than 5 / cm2, the evaluation was made as "Good". 2 If the damage was more than 100%, it was judged to have many scratches and was rated as "Bad".

[0083] <Latent Damage Assessment> The entire Si surface of the SiC substrate according to Example 1 and Comparative Example 1 was observed using a mirror electron inspection device (Mirelis VM1000, manufactured by Hitachi High-Tech Corporation) to perform latent scratch evaluation. Specifically, a 6-inch SiC substrate was set in the mirror electron inspection device (Mirelis VM1000, manufactured by Hitachi High-Tech Corporation), and a 5 mm square virtual chip was placed in an area on the set SiC substrate excluding the outer periphery of 5 mm. For each virtual chip, a total of 64 imaging points of 80 μm × 80 μm were set, and defects such as latent scratches were detected from images captured based on the imaging points by automatic defect classification. The latent scratch density was calculated by dividing the total number of latent scratches detected at all imaging points (35,904 points) by the total area captured. If the calculated latent scratch density was 1,300 pieces / cm 2 If the density was less than 1,300 / cm, the number of latent scratches was considered small and the evaluation was "Good". 2 If the damage was more than 100%, it was judged to have many latent scratches and was rated as "Bad".

[0084] As shown in FIG. 1, the abrasive slurry for polishing SiC substrates in Example 1 had excellent dispersibility, since the particle size at 50% cumulative volume fraction (D50) in the particle size distribution, measured by laser diffraction / scattering method, was 0.6 μm or less both before and after the addition of potassium permanganate, which is a source of permanganate ions.

[0085] In Example 1, when the adhesion state of the abrasive slurry for polishing SiC substrates to a container containing a sample was checked when the container was inverted, the sample did not adhere to the container, and the adhesion was very good.

[0086] The abrasive slurry for polishing SiC substrates according to Example 1 exhibited a high polishing rate, since the polishing rate was 0.10 μm / h or more.

[0087] The density of scratches on the entire Si surface of the SiC substrate according to Example 1 is 0 scratches / cm 2 The density of latent scratches on the entire Si surface of the SiC substrate according to Example 1 was 131 / cm 2 This reduced the number of latent injuries.

[0088] The inventions disclosed in this specification include, in addition to the configurations of each invention or embodiment, those that are specified by changing these partial configurations to other configurations disclosed in this specification, to the extent applicable, or those that are specified by adding other configurations disclosed in this specification to these configurations, or those that are specified as higher-level concepts by deleting these partial configurations to the extent that partial action and effects are obtained. [Industrial Applicability]

[0089] The manufacturing method of the SiC substrate and the abrasive slurry for polishing the SiC substrate according to the present invention can manufacture a SiC substrate with few latent scratches. In addition, the manufacturing method of the SiC substrate and the abrasive slurry for polishing the SiC substrate according to the present invention have excellent dispersibility, so that the SiC substrate and the polishing pad, which are the object to be polished, can be easily washed, and the amount of washing water used can be reduced, the washing time can be shortened, and the amount of wastewater treatment can be reduced, which leads to a reduction in environmental load. Furthermore, the manufacturing method of the SiC substrate and the abrasive slurry for polishing the SiC substrate according to the present invention show a high polishing rate, so that the polishing process time can be shortened.

Claims

1. A method for manufacturing a SiC substrate, comprising a polishing treatment step of polishing a main surface of a SiC substrate with an abrasive slurry containing manganese oxide abrasive grains including manganese oxide particles, permanganate ions, and phosphoric acids which are one or more of a metaphosphate compound, a hexametaphosphate compound, a pyrophosphate compound, a polyphosphate compound, a tripolyphosphate compound, or salts or hydrates thereof.

2. manganese oxide abrasive grains containing manganese oxide particles; Permanganate ions, a phosphoric acid compound selected from the group consisting of a metaphosphate compound, a hexametaphosphate compound, a pyrophosphate compound, a polyphosphate compound, a tripolyphosphate compound, and salts or hydrates thereof; 1. An abrasive slurry for polishing a SiC substrate, comprising:

3. 3. The abrasive slurry for polishing SiC substrates according to claim 2, wherein the phosphoric acid is a pyrophosphate compound.

4. 4. The abrasive slurry for polishing SiC substrates according to claim 3, wherein the pyrophosphate compound is a metal salt of pyrophosphate.

5. 4. The abrasive slurry for polishing SiC substrates according to claim 2, further comprising a cellulose-based surfactant and / or a cationic surfactant.

6. 6. The abrasive slurry for polishing SiC substrates according to claim 5, wherein the cellulose-based surfactant contains carboxymethyl cellulose.

7. 4. The abrasive slurry for polishing SiC substrates according to claim 2 or 3, further comprising a polymer additive comprising one or more water-soluble organic polymers selected from the group consisting of polycarboxylic acids, polycarboxylates, salts of naphthalenesulfonic acid-formaldehyde condensates, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and copolymers thereof.

8. 8. The abrasive slurry for polishing SiC substrates according to claim 7, wherein the polymer additive is one or more water-soluble organic polymers selected from the group consisting of polycarboxylic acids, polycarboxylates, and copolymers thereof.

9. 8. The abrasive slurry for polishing SiC substrates according to claim 7, wherein the polymer additive is one or more water-soluble organic polymers selected from the group consisting of polyacrylic acid, polymaleic acid, polyacrylates, polymaleates, and copolymers thereof.

10. 8. The abrasive slurry for polishing SiC substrates according to claim 7, wherein the polymer additive is an ammonium salt of polyacrylic acid.

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