Abrasive slurry and grinding method with it

Abstract

To provide an abrasive slurry that can reduce friction resistance in abrasive processing.SOLUTION: An abrasive slurry of the present invention contains: abrasive grains; and a high polymer phenolic compound. The abrasive grains preferably contain manganese oxide particulates. The high polymer phenolic compound preferably contains one or more of lignin, modified lignin, a salt of lignin. More preferably, the salt of modified lignin, and the salt of lignin and / or the salt of modified lignin contain(s) at least one or more of an alkali metal salt, an alkaline earth metal salt, and an organic salt base compound. Even more preferably, the salt of modified lignin contains sodium lignin sulfonate and / or lignosulfonic acid magnesium salt. A polishing method with abrasive slurry of the present invention performs grinding using the abrasive slurry of the present invention. A SiC wafer of the present invention has been ground with the abrasive slurry of the present invention.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Among semiconductor devices, in power semiconductor elements called so-called power devices, instead of silicon conventionally used as a substrate, silicon carbide (SiC), gallium nitride, diamond, etc. are used to achieve higher breakdown voltage and larger current. Substrates made of these materials have a larger bandgap compared to conventional silicon substrates, so they can withstand higher voltages.

[0003] Among them, a substrate made of silicon carbide (hereinafter referred to as an SiC substrate) is not only excellent in hardness, heat resistance, and scientific stability, but also excellent in terms of cost. On the other hand, since the SiC substrate has a higher hardness compared to conventional silicon substrates, as an abrasive slurry used in the process of finishing the surface of the SiC substrate to a mirror surface in the manufacturing process of the SiC substrate, that is, in a polishing process such as the so-called CMP (Chemical Mechanical Polishing) method, for example, an abrasive slurry containing manganese oxide particles as abrasive grains disclosed in Patent Document 1 has been developed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the abrasive slurry containing manganese oxide particles as abrasive grains, as disclosed in Patent Document 1, has a high frictional resistance against the object to be polished during the polishing process, resulting in problems such as abnormal noise generated from the polishing machine or the wafer, which is the object to be polished, coming off.

[0006] In view of the above problems, the present invention provides an abrasive slurry and a polishing method capable of reducing the frictional resistance during the polishing process.

Means for Solving the Problems

[0007] The abrasive slurry of the present invention made to solve the above problems is characterized by having abrasive grains and a polymer phenol compound. The abrasive slurry of the present invention can reduce the frictional resistance during the polishing process by having abrasive grains and a polymer phenol compound.

[0008] The abrasive grains contained in the abrasive slurry of the present invention can prevent warping and cracking due to the Twyman effect against, for example, a SiC substrate, which is the object to be polished, without impairing this effect. Examples of the abrasive grains 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. These particles can be used alone or in a mixture of two or more. 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] Further, 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 include manganese(II) oxide (MnO), manganese(III) oxide (Mn2O3), manganese(IV) oxide (MnO2), manganese(II, III) tetraoxide (Mn3O4), etc., and more preferably manganese(IV) oxide (MnO2). The manganese oxide particles contained in the abrasive grains may be compounded with abrasive grains other than the manganese oxide particles, for example, those in which the manganese oxide particles are surface-coated with abrasive grains other than the manganese oxide particles, or those in which the manganese oxide particles coat the surface of abrasive grains other than the manganese oxide particles.

[0010] Furthermore, the content of the abrasive grains contained in the abrasive slurry of the present invention can be determined by measuring the weight of the obtained abrasive grains by filtering, washing, and drying the abrasive slurry. 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 spectrometer (AES), etc.

[0011] Also, from the viewpoint of having high polishing power, the abrasive grains contained in the abrasive slurry of the present invention are preferably those having a particle size (D50) at 50% integrated volume by laser diffraction / scattering particle size distribution measurement method of 0.1 μm or more, and from the viewpoint of suppressing roughening of the surface of the workpiece, for example, a SiC substrate, they are preferably 5.0 μm or less. Therefore, the abrasive grains are more preferably those having a particle size (D50) at 50% integrated volume by 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) at 50% cumulative volume of the abrasive grains contained in the abrasive slurry of the present invention, as measured by the laser diffraction / scattering particle size distribution measurement method, is measured by preparing a measurement sample by diluting a mixture obtained by pulverizing the abrasive grains with beads with water so that the concentration of the mixture becomes about 0.01% in the manufacturing method of the abrasive slurry of the present invention described later. Then, the measurement is carried out using a laser diffraction / scattering particle size distribution measuring device (manufactured by Microtrac Bel Co., Ltd.: MT3300EXII).

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

[0014] The abrasive slurry of the present invention can reduce the frictional resistance by containing a polymer phenol compound.

[0015] The polymer phenol compound contained in the abrasive slurry of the present invention is more preferably any one or more selected from the group consisting of lignin, modified lignin, salts of lignin, salts of modified lignin, polyhydric phenol compounds, and phenol novolak type compounds in that it can impart low friction properties. Also, the polymer phenol compound may be one kind or a mixture of two or more polymer phenol compounds.

[0016] Here, lignin is one of the three major components of biomass and is the second most abundant organic compound on the ground. Lignin is separated in processes such as the bioethanol pretreatment process and the chemical pulping process, and is a by-product in bioethanol production and paper pulp production. However, there are few effective utilization methods other than as a heat source, and its effective utilization is being explored.

[0017] The modified lignin is not particularly limited. For example, it may include alkali lignin (lignin obtained by alkaline digestion of lignocellulose), kraft lignin, acetic acid lignin, organosolv lignin, chloro lignin, nitro lignin, lignin sulfonic acid, thio lignin, enzyme lignin (lignin obtained by enzymatic saccharification of lignocellulose), and the like. Here, it is more preferable that the modified lignin contains acid-modified lignin and / or lignin sulfonic acid.

[0018] The salt of lignin and / or the salt of modified lignin preferably contains any one or more selected from the group consisting of alkali metal salts, alkaline earth metal salts, and organic base compounds, and more preferably contains an alkali metal salt and / or an alkaline earth metal salt. For example, it may be a Na salt, K salt, Ca salt, Li salt, or Mg salt, and more preferably a Na salt or Mg salt.

[0019] Furthermore, it is more preferable that the salt of modified lignin contains sodium lignin sulfonate and / or magnesium lignin sulfonate.

[0020] The content of the polymer phenol compound contained in the abrasive slurry of the present invention is preferably 0.001% by mass or more with respect to the total amount of the abrasive slurry of the present invention from the viewpoint of friction, and preferably 0.2% by mass or less from the viewpoint of pot life. Further, the content of the polymer phenol compound is more preferably 0.002% by mass or more and 0.1% by mass or less, and even more preferably 0.0025% by mass or more and 0.05% by mass or less. Typically, the content of the polymer phenol compound may be 0.0025% by mass or more and 0.01% by mass or less, or may be 0.0025% by mass or more and 0.005% by mass or less. The presence or absence and the content of the polymer phenol compound can be measured by liquid chromatography (LC) or gel permeation chromatography (GPC).

[0021] Furthermore, when expressing the content of the polymer phenol compound contained in the abrasive slurry of the present invention as a mass ratio with respect to the abrasive grain content in the abrasive slurry of the present invention, it is preferably 0.05% or more and 10.0% or less. The mass ratio is more preferably 0.1% or more and 5% or less, and even more preferably 0.125% or more and 2.5% or less. Typically, the mass ratio may be 0.125% or more and 0.5% or less, or may be 0.125% or more and 0.25% or less.

[0022] In addition, the abrasive slurry of the present invention preferably further contains manganate ions in addition to the abrasive grains and the polymer phenol compound described above. Here, examples of the manganate ions include permanganate ions (MnO4 - ), manganate ions (MnO4 2- ), and permanganate ions are preferred.

[0023] Manganate ions, when used in combination with abrasive grains as an oxidizing agent, can have a high polishing power against high-hardness materials such as silicon carbide. Here, the source of manganate ions is preferably a manganate. Examples of manganates include alkali metal salts of manganic acid and alkaline earth metal salts of manganic acid. Further, from the viewpoints of easy availability and improvement of the polishing efficiency of the abrasive slurry of the present invention, among the manganates that are the source of manganate ions, alkali metal salts of manganic acid are preferred, and sodium manganate (Na2MnO4), potassium manganate (K2MnO4), sodium permanganate (NaMnO4), and potassium permanganate (KMnO4) are more preferred, and potassium permanganate (KMnO4) is even more preferred. Note that these manganates may be used alone or in combination of two or more.

[0024] Also, from the viewpoint of sufficiently increasing the polishing rate, the content of manganate ions contained in the abrasive slurry of the present invention is preferably 0.5% by mass or more based on the total amount of the abrasive slurry of the present invention. Further, from the viewpoints of preventing crystal precipitation due to increasing the addition amount, ensuring the handling safety of the abrasive slurry, and the tendency that the polishing rate saturates even when the addition amount is increased, the content of manganate ions contained in the abrasive slurry of the present invention is preferably 3.2% by mass or less based on the total amount of the abrasive slurry of the present invention. That is, the content of manganate ions is preferably 0.5% by mass or more and 3.2% by mass or less based on the total amount of the abrasive slurry of the present invention, 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. Typically, the content of manganate ions 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. Note that the content of manganate ions can be determined by centrifuging the abrasive slurry of the present invention, allowing the abrasive grains in the abrasive slurry to settle, separating the supernatant liquid, diluting the supernatant liquid, and measuring the absorbance (intensity of the absorption peak appearing at a wavelength of 525 nm) of the diluted liquid by absorbance photometry.

[0025] Furthermore, it is more preferable that the abrasive slurry of the present invention further contains phosphoric acids in addition to the abrasive grains, polymer phenol compounds, and manganate ions described above. By using phosphoric acids in combination with the abrasive grains and manganate ions, the dispersibility of the abrasive slurry of the present invention can be improved.

[0026] The phosphoric acids contained in the abrasive slurry of the present invention are preferably inorganic phosphorus compounds, for example. Specifically, as the phosphate compounds, sodium phosphates (trisodium phosphate (anhydrous) (Na3PO4), CAS No.: 7601-54-9; trisodium phosphate dodecahydrate (Na3PO4·12H2O), CAS No.: 10101-89-0; sodium phosphate monobasic (NaH2PO4), CAS No.: 7558-80-7; sodium phosphate dibasic (Na2HPO4), CAS No.: 7558-79-4) and potassium phosphates (tripotassium phosphate (anhydrous) (K3PO4), CAS No.: 7778-53-2; tripotassium phosphate monohydrate (K3PO4·H2O), CAS No.: 27176-10-9; potassium phosphate dibasic trihydrate (K2HPO4·H2O), CAS No.: 16788-57-1; potassium dihydrogen phosphate (KH2PO4), CAS No.: 7778-77-0; dipotassium hydrogen phosphate (K2HPO4), CAS No.: 7758-11-4) can be mentioned.

[0027] Also, as the metaphosphate compounds, sodium metaphosphate (NaPO3) n , CAS No.: 35270-09-8) and potassium metaphosphate (KPO3) n , CAS No.: 7790-53-6 can be mentioned.

[0028] As the hexametaphosphate compounds, sodium hexametaphosphate (NaH7P6O 18 ), CAS No.: 10124-56-8 can be mentioned.

[0029] Examples of 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), potassium pyrophosphate (K4P2O7), CAS number: 7320-34-5).

[0030] Examples of polyphosphate compounds include sodium polyphosphate (Na3P3O 10 X2), CAS number: 68915-31-1; potassium polyphosphate (K3P3O 10 X2), CAS number: 68956-75-2).

[0031] Examples of tripolyphosphate compounds include sodium tripolyphosphate (Na5P3O 10 ), CAS number: 7758-29-4 and potassium tripolyphosphate (K5P3O 10 ), CAS number: 13845-36-8).

[0032] Furthermore, these salts and hydrates are included. 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 polishing abrasive slurry of the present invention, from the viewpoints of effective high dispersibility in a small amount and 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.

[0033] Furthermore, among the inorganic phosphorus compounds described above, pyrophosphate compounds are preferable from the viewpoints of high dispersibility and sufficiently enhancing the polishing rate. Among pyrophosphate compounds, alkali metal salts of pyrophosphoric acid or alkaline earth metal salts of pyrophosphoric acid are more preferable, and sodium pyrophosphate or potassium pyrophosphate is particularly preferable.

[0034] In addition, the presence or absence and the content of phosphoric acids contained in the abrasive slurry of the present invention can be measured by high performance liquid chromatography (HPLC), diffusion ordered NMR spectroscopy (DOSY method) in phosphorus-31 nuclear magnetic resonance ( 31 P-NMR), peak separation, etc. At that time, if necessary, the abrasive slurry of the present invention may be diluted with pure water and filtered, and the phosphoric acids may be analyzed in a state of being contained in the filtrate.

[0035] Furthermore, the measurement of 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 method anion analysis column, the types and weights of phosphoric acids can be measured by known methods. For example, as a non-suppressor method anion analysis column, Shodex non-suppressor method anion analysis column IC I-524A (manufactured by Shoko Science Co., Ltd.) can be mentioned. By using this non-suppressor method anion analysis column, the phosphoric acids contained in the abrasive slurry of the present invention can be separated and measured.

[0036] In addition, from the perspective of frictional resistance, the content of phosphoric acids contained in the abrasive slurry of the present invention is preferably 0.001% by mass or more based on the total amount of the abrasive slurry of the present invention. Further, from the perspective that the polishing rate tends to saturate even if the addition amount is increased, the content of phosphoric acids contained in the abrasive slurry of the present invention is preferably 0.2% by mass or less based on the total amount of the abrasive slurry of the present invention. That is, the content of phosphoric acids is preferably 0.001% by mass or more and 0.2% by mass or less based on the total amount of the abrasive slurry of the present invention, more preferably 0.002% by mass or more from the perspective of frictional resistance, and more preferably 0.1% by mass or less from the perspective of sufficiently increasing the polishing rate. The content of phosphoric acids is more preferably 0.002% by mass or more and 0.05% by mass or less. Typically, the content of phosphoric acids may be 0.002% by mass or more and 0.02% by mass or less. In the present specification, the content of phosphoric acids is the total amount of substances classified as phosphoric acids unless otherwise specified.

[0037] Furthermore, when expressing the content of phosphoric acids contained in the abrasive slurry of the present invention as a mass ratio to the abrasive grain content in the abrasive slurry of the present invention, it 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 0.1% or more and 2.5% or less. Typically, the mass ratio may be 0.1% or more and 1.0% or less.

[0038] In addition, the abrasive slurry of the present invention may contain a polymer additive containing at least one water-soluble organic polymer selected from the group consisting of polycarboxylic acids, polycarboxylates, salts of naphthalenesulfonic acid formalin condensates, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and copolymers thereof, in addition to the above-described abrasive grains, polymer phenol compounds, manganate ions, and phosphoric acids. By containing the above-described polymer additive, the pot life of the abrasive slurry of the present invention can be extended.

[0039] Further, in the abrasive slurry of the present invention, it is more preferable that the polymer additive is at least one water-soluble organic polymer selected from polycarboxylic acids, polycarboxylates, and copolymers thereof. It is even more preferable that the polymer additive is at least one water-soluble organic polymer selected from polyacrylic acid, polymaleic acid, polyacrylate, polymaleate, 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 salt.

[0040] Also, from the viewpoint of dispersibility, the content of the polymer additive contained in the abrasive slurry of the present invention is preferably 0.006% by mass or more based on the total amount of the abrasive slurry of the present invention. Further, from the viewpoint of sufficiently increasing the polishing rate, the content of the polymer additive in the abrasive slurry of the present invention is preferably 0.05% by mass or less based on the total amount of the abrasive slurry of the present invention. 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 based on 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 the present specification, the content of the polymer additive is the total amount of those classified into the above-described polymer additives unless otherwise specified.

[0041] Furthermore, when expressing the content of the polymer additive in the abrasive slurry of the present invention as a mass ratio to the abrasive grain content contained in the abrasive slurry of the present invention, it is preferably 0.3% or more and 2.5% or less, more preferably 0.5% or more and 1.5% or less, and even more preferably 0.5% or more and 1.0% or less. Typically, the mass ratio may be 0.5% or more and 0.75% or less.

[0042] Here, the abrasive slurry of the present invention contains the above-described abrasive grains, polymer phenol compound, manganate ions, and phosphoric acids, as well as a dispersion medium for dissolving or dispersing them. The dispersion medium is preferably water, a water-soluble organic solvent such as alcohol or ketone, or a mixture thereof, in terms of sufficiently increasing 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 99.9% by mass or less, based on the total amount of the abrasive slurry of the present invention. The content of the dispersion medium 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.

[0043] Furthermore, the abrasive slurry of the present invention may contain optional additives other than the above-described abrasive grains, polymer phenol compound, manganate ions, phosphoric acids, and dispersion medium. Here, the optional additives are a dispersant, a pH adjuster, a viscosity adjuster, a chelating agent, a rust inhibitor, and the like. 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.

[0044] In addition, the abrasive slurry of the present invention can be in a form where the above-described abrasive grains, polymer phenol compound, manganate ions, phosphoric acids, dispersion medium, and optional additives are appropriately mixed. For example, it may be in the form of a kit in which these components are divided into two or more agents. The configuration of the kit may be in a form such that the polishing ability is sufficiently exhibited when the abrasive slurry of the present invention is adjusted.

[0045] The dispersibility of the abrasive slurry of the present invention described above can be evaluated by the following method. Dilute the abrasive slurry of the present invention with water so that the concentration becomes about 0.01% by mass to prepare a sample for measurement. Then, using a laser diffraction / scattering particle size distribution measuring device (manufactured by Microtrac Bell Co., Ltd.: MT3300EXII), measure the particle size (D50) at a volume-based cumulative fraction of 50%, and evaluate the measured particle size (D50) to evaluate the dispersibility of the abrasive slurry of the present invention.

[0046] The polishing method for polishing an object to be polished using the abrasive slurry of the present invention described above will be described below.

[0047] Examples of the polishing method include a method of supplying the abrasive slurry of the present invention to a polishing pad, bringing the polished surface of the object to be polished into contact with the polishing pad, and performing polishing by relative movement between the two. Here, a method of flowing the abrasive slurry of the present invention, or an operation of collecting the abrasive slurry of the present invention supplied to the polishing pad and used for polishing, and repeatedly supplying the collected abrasive slurry of the present invention to the polishing pad may be used. Since the abrasive slurry of the present invention can circulate and repeatedly polish the object to be polished, the amount used can be suppressed. Here, as the polishing pad, for example, a conventionally used non-woven fabric, a pad impregnated with a resin such as polyurethane or epoxy, and a suede material can be used. The polishing pressure is preferably 0.5×10 4 Pa or more and 1.0×10 5 Pa or less, particularly preferably 1.0×10 4 Pa or more and 5.0×10 4 Pa or less from the viewpoints of polishing force and ease of handling of the polishing tool. The supply amount 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.

[0048] The object to be polished by the abrasive slurry of the present invention is, for example, a high-hardness material having a Mohs hardness of 8 or more. Here, the Mohs hardness is a quantification of hardness based on the way of scratching against a standard substance, and can be measured by a conventional method using a Mohs hardness tester. The Mohs hardness is specified with standard substances from 1 to 10 in order from the softest. The specific standard substances are talc for Mohs hardness 1, gypsum for 2, calcite for 3, fluorite for 4, apatite for 5, orthoclase for 6, quartz for 7, topaz for 8, corundum for 9, and diamond for 10. High-hardness materials with a Mohs hardness of 8 or more include, for example, silicon carbide (Mohs hardness of about 9), gallium nitride (Mohs hardness of about 9), diamond, etc.

[0049] And the abrasive slurry of the present invention can be used in a finishing CMP (Chemical Mechanical Polishing) process or the like after lapping of a substrate made of a high-hardness material. In particular, the abrasive slurry of the present invention can be used for polishing a substrate made of silicon carbide (SiC), that is, an SiC substrate, can sufficiently increase the polishing rate, and can effectively prevent the occurrence of warping and cracking due to the Twyman effect. As the SiC substrate, a single-crystalline silicon carbide substrate is usually used. As its crystal system, hexagonal or rhombohedral crystals are usually mentioned, and hexagonal crystals are preferable from the viewpoint of exerting the effect of the abrasive slurry capable of preventing the occurrence of warping and cracking due to the Twyman effect. The polymorphs of hexagonal crystals are 2H, 4H, 6H, 8H, 10H. The polymorph of rhombohedral crystals is 15R.

[0050] Next, the manufacturing method of the abrasive slurry of the present invention described above will be described below.

[0051] First, pure water, manganese dioxide (abrasive grains, MnO2), phosphoric acids (for example, sodium salt of pyrophosphoric acid), and beads (zirconia-made φ0.4 mm) are put into a container, the container is set on a paint shaker (60 Hz), the container is rotated at a high speed, and manganese dioxide (abrasive grains, MnO2) is mixed and pulverized.

[0052] The mixture containing the mixed and ground manganese dioxide (abrasive grains, MnO2) in the container 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.

[0053] The collected supernatant is measured for the solid content concentration in the supernatant, that is, the manganese dioxide abrasive grain concentration, using a heating type moisture meter, and pure water is added to reach a predetermined concentration to obtain an intermediate abrasive slurry.

[0054] A high molecular phenolic compound is added to and mixed with the obtained intermediate abrasive slurry.

[0055] Then, by mixing the intermediate abrasive slurry added with the high molecular phenolic compound and potassium permanganate (KMnO4), the abrasive slurry of the present invention is obtained.

[0056] Further, the SiC wafer of the present invention is characterized in that it is polished using the abrasive slurry of the present invention described above. The SiC wafer of the present invention has no warpage and cracks due to the Twyman effect because it is polished using the abrasive slurry of the present invention described above. Also, the SiC wafer of the present invention is polished by the polishing method of the abrasive slurry of the present invention described above.

[0057] In this specification, when expressed as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", and also the meaning of "preferably greater than X" or "preferably less than Y". Also, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the intention of "preferably greater than X" or "preferably less than Y".

Advantages of the Invention

[0058] The abrasive slurry of the present invention can reduce the frictional resistance during the polishing process.

Brief Description of the Drawings

[0059]

Figure 1

Best Mode for Carrying Out the Invention

[0060] Hereinafter, the abrasive slurry of the embodiment according to the present invention will be further described with reference to the following examples. However, the following examples do not limit the present invention.

[0061] (Example 1) Into a container, put pure water, manganese dioxide (MnO2) as abrasive grains, sodium pyrophosphate as phosphoric acids (specifically, sodium pyrophosphate decahydrate (Na4P2O7·10H2O), CAS number: 13472-36-1), ammonium polyacrylate salt as a polymer additive, and beads (zirconia φ0.4 mm), set the container on a paint shaker (60 Hz), rotate the container at high speed, and mix and grind manganese dioxide.

[0062] The mixture containing the mixed and ground manganese dioxide in the container was separated from the beads using a centrifuge (himac CT 6E manufactured by Hitachi Koki Co., Ltd., etc.), and the supernatant was collected. The solid content concentration in the supernatant, that is, the manganese oxide abrasive grain concentration, of the collected supernatant was measured with a heating moisture meter, and pure water was added to reach a predetermined concentration to obtain an abrasive slurry intermediate.

[0063] A salt of modified lignin as a polymer phenol compound (manufactured by Nippon Paper Industries Co., Ltd., product name: Vanirex N, main component: high-purity partially desulfonated lignin sulfonic acid sodium) was added to the abrasive slurry intermediate and mixed.

[0064] Then, the abrasive slurry intermediate to which the polymer phenol compound was added and an aqueous potassium permanganate (KMnO4) solution with a KMnO4 mass% concentration of 3.2 mass% were mixed to obtain the abrasive slurry according to Example 1.

[0065] Regarding the content of each component with respect to the total amount of the abrasive slurry according to the above-described Example 1, the total content of abrasive grains was 2.0% by mass, the content of permanganate ions was 1.2% by mass, the total content of phosphoric acids was 0.002% by mass, the total content of the polymer phenol compound was 0.0025% by mass, and the total content of the polymer additive was 0.01% by mass.

[0066] Also, regarding the mass ratio of the content of each component with respect to the total content of abrasive grains according to Example 1, the mass ratio of the total content of phosphoric acids was 0.1%, the mass ratio of the total content of the polymer phenol compound was 0.125%, and the mass ratio of the total content of the polymer additive was 0.5%.

[0067] (Example 2) In Example 2, instead of the polymer phenol compound used in Example 1, a salt of modified lignin (manufactured by Nippon Paper Industries Co., Ltd., product name: Sun Extract P252, main component: sodium lignin sulfonate) was added, and the content of the polymer phenol compound according to Example 2 was adjusted to 0.005% by mass with respect to the total amount of the abrasive slurry according to Example 2. Except for this, the same manufacturing method as in Example 1 was carried out to obtain the abrasive slurry according to Example 2.

[0068] Regarding the content of each component with respect to the total amount of the abrasive slurry according to the above-described Example 2, the total content of abrasive grains was 2.0% by mass, the content of permanganate ions was 1.2% by mass, the total content of phosphoric acids was 0.002% by mass, the total content of the polymer phenol compound was 0.005% by mass, and the total content of the polymer additive was 0.01% by mass.

[0069] Also, regarding the mass ratio of the content of each component with respect to the total content of abrasive grains according to Example 2, the mass ratio of the total content of phosphoric acids was 0.1%, the mass ratio of the total content of the polymer phenol compound was 0.25%, and the mass ratio of the total content of the polymer additive was 0.5%.

[0070] (Example 3) In Example 3, instead of the polymer phenol compound used in Example 1, a salt of modified lignin (manufactured by Nippon Paper Industries Co., Ltd., product name: Sun Extract P321, main component: magnesium lignosulfonate) was added, and the content of the polymer phenol compound according to Example 3 was adjusted to 0.005% by mass based on the total amount of the abrasive slurry according to Example 3. Otherwise, the same manufacturing method as in Example 1 was carried out to obtain the abrasive slurry according to Example 3.

[0071] Regarding the content of each component with respect to the total amount of the abrasive slurry according to Example 3 described above, the total content of abrasive grains was 2.0% by mass, the content of permanganate ions was 1.2% by mass, the total content of phosphoric acids was 0.002% by mass, the total content of the polymer phenol compound was 0.005% by mass, and the total content of the polymer additive was 0.01% by mass.

[0072] Also, the mass ratio of the content of each component with respect to the total content of abrasive grains according to Example 3 was such that the mass ratio of the total content of phosphoric acids was 0.1%, the mass ratio of the total content of the polymer phenol compound was 0.25%, and the mass ratio of the total content of the polymer additive was 0.5%.

[0073] (Comparative Example 1) In Comparative Example 1, the same manufacturing method as in Example 1 was carried out except that no polymer phenol compound was added to obtain the abrasive slurry according to Comparative Example 1.

[0074] Regarding the content of each component with respect to the total amount of the abrasive slurry according to Comparative Example 1 described above, the total content of abrasive grains was 2.0% by mass, the content of permanganate ions was 1.2% by mass, the total content of phosphoric acids was 0.002% by mass, the total content of the polymer phenol compound was 0.0% by mass, and the total content of the polymer additive was 0.01% by mass.

[0075] Also, the mass ratio of the content of each component with respect to the total content of abrasive grains according to Comparative Example 1 was such that the mass ratio of the total content of phosphoric acids was 0.1%, the mass ratio of the total content of the polymer phenol compound was 0.0%, and the mass ratio of the total content of the polymer additive was 0.5%.

[0076] Then, for the abrasive slurries according to Examples 1 to 3 and Comparative Example 1, the following physical property values were measured. Hereinafter, the measured physical property values and the measurement methods thereof are shown, and the measurement results are shown in FIG. 1. Note that the compositions of the abrasive slurries according to Examples 1 to 3 and Comparative Example 1 shown in FIG. 1 are the compositions in the final products.

[0077] 〈Friction Characteristic Evaluation〉 The friction characteristics of the abrasive slurries according to Examples 1 to 3 and Comparative Example 1 were evaluated as follows. A polishing pad (IC1000 manufactured by Nitto DuPont) was attached and fixed on the surface plate of the polishing machine. The supply rate of 1 L of the abrasive slurries according to Examples 1 to 3 and Comparative Example 1 was set to 200 mL / min, and the slurries were supplied in a circulating manner onto the polishing pad. Further, a work as an object to be polished was placed on the polishing pad. Furthermore, with a spring scale hooked to the work, the surface plate of the polishing machine was rotated, and the work was rotated in the same direction as the surface plate by a forced driving unit. Here, the forced driving unit is provided with a rotating roller capable of contacting the work, and the work is rotated by rotating the rotating roller. Then, the spring scale was pulled in the direction in which the work was separated from the forced driving unit, and when the rotating roller was separated from the work by the forced driving unit, the rotation of the work was stopped. The digital display value (i.e., the pulling force) indicated on the spring scale 30 seconds after the rotation of the work stopped was measured. The pulling force measured in this way was divided by the load of the work to obtain the friction coefficient of the abrasive slurries according to Examples 1 to 3 and Comparative Example 1. 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 0.39 or less, it was evaluated as "〇 (GOOD)". If the friction coefficient was more than 0.39, it was evaluated as "× (BAD)".

[0078] 〈Polishing Test〉 The polishing rates of the abrasive slurries according to Examples 1 to 3 and Comparative Example 1 were evaluated by the following procedure. As the polishing target, a 4H-SiC substrate after CMP processing with a diameter of 4 inches and an off-angle of 4° was used. The polishing test was performed on the Si surface of the substrate. As the polishing apparatus, a single-sided polishing machine BC-15 manufactured by M.A.T. was used. As the polishing pad attached to the platen, IC1000 manufactured by Nitto Denko was used. The rotation speed of the platen was set at 60 rpm, and the peripheral speed was set at 7,136 cm / min. Also, the carrier rotation speed was set at 60 rpm, and the peripheral speed was set at 961 cm / min. Furthermore, the load during polishing was 2.8 psi (about 1.96×10 4 Pa). The supply rate of the abrasive slurry was 200 mL / min, and polishing was performed for 1 hour. The polishing rate was determined from the mass difference of the substrate, which was the polishing target, before and after polishing. If the polishing rate was 0.10 μm / h or more, it was evaluated as "〇 (GOOD)", and if the polishing rate was less than 0.10 μm / h, it was evaluated as "× (BAD)".

[0079] 〈Pot life evaluation〉 The pot lives of Examples 1 to 3 and Comparative Example 1 were evaluated as follows. The abrasive slurries according to Examples 1 to 3 and Comparative Example 1 were allowed to stand at room temperature (25°C) for 3 days. The MnO4 - concentration in the abrasive slurry after standing for 3 days was compared with the MnO4 - concentration in the abrasive slurry before standing for 3 days, and the retention rate of the MnO4 - concentration was calculated. Then, if the retention rate of the MnO4 - concentration after standing for 3 days with respect to the MnO4 - concentration before standing for 3 days was 50% or more, it was evaluated as "〇 (GOOD)", and if the retention rate of the MnO4 - concentration after standing for 3 days with respect to the MnO4 - concentration before standing for 3 days was less than 50%, it was evaluated as "× (BAD)". Here, the MnO4 -The concentration was evaluated as follows. First, the abrasive slurry was centrifuged (4,000 rpm × 20 min) to precipitate the manganese oxide abrasive grains in the abrasive slurry. Next, 1.0 g of the supernatant was collected, 109 g of pure water was added, and it was diluted to prepare a diluted solution. Then, using a spectrophotometer (manufactured by Hitachi High-Tech Science Corporation: UH-4150), the absorbance of MnO4 - in the diluted solution (the intensity of the absorption peak appearing at a wavelength of 525 nm) was measured, and the MnO4 - concentration was calculated using a calibration curve prepared in advance.

[0080] 〈Crystal Precipitation Test〉 Samples of the abrasive slurries according to Examples 1 to 3 and Comparative Example 1 were prepared. Each adjusted sample was stored in a refrigerator set at 10°C for 24 hours. Then, each sample was taken out of the refrigerator, and using a heating moisture meter, the solid content concentration in each sample, that is, the total value of the abrasive grain concentration and the potassium permanganate concentration, was determined. And if the solid content concentration after storage was 90% or more of the maintenance rate of the solid content concentration before storage, it was evaluated as "〇 (GOOD)", and if the solid content concentration after storage was less than 90% of the maintenance rate of the solid content concentration before storage, it was evaluated as "× (BAD)".

[0081] As shown in FIG. 1, since the abrasive slurries according to Examples 1 to 3 had a friction coefficient of 0.38 or less, they achieved low friction.

[0082] Since the abrasive slurries according to Examples 1 to 3 had a polishing rate of 0.10 μm / h or more, they showed a high polishing rate.

[0083] Since the solid content concentration after storing the abrasive slurries according to Examples 1 to 3 in a refrigerator set at 10°C for 24 hours was 90% or more of the maintenance rate of the solid content concentration before storage, it was found that crystals did not precipitate.

[0084] Since the maintenance rate of the MnO4 - concentration after standing at room temperature (25°C) for 3 days of the abrasive slurries according to Examples 1 to 3 was 50% or more, the pot life could be extended.

[0085] In addition to the configurations of each invention and embodiment, the invention disclosed in this specification includes, within the applicable scope, those obtained by modifying these partial configurations into other configurations disclosed in this specification, or those obtained by adding other configurations disclosed in this specification to these configurations, or those obtained by deleting these partial configurations to the extent that partial operational effects can be obtained and generalizing them to a higher concept.

Industrial Applicability

[0086] Since the abrasive slurry according to the present invention can reduce the frictional resistance during the polishing process, the generation of abnormal noise from the polishing machine can be suppressed due to the frictional resistance generated during the polishing process. Further, since the abrasive slurry according to the present invention can reduce the frictional resistance during the polishing process, the problem of the SiC substrate, which is the object to be polished, coming off can be reduced due to the frictional resistance generated during the polishing process. Furthermore, since the abrasive slurry according to the present invention can reduce the frictional resistance during the polishing process, the polishing process time can be shortened.

Claims

1. An abrasive slurry comprising abrasive grains and a polymeric phenolic compound.

2. The abrasive slurry according to claim 1, wherein the polymeric phenolic compound comprises any one or more selected from the group consisting of lignin, modified lignin, salts of lignin, salts of modified lignin, polyhydric phenolic compounds, and phenol novolak type compounds.

3. The abrasive slurry according to claim 2, wherein the modified lignin comprises acid-modified lignin and / or lignin sulfonic acid.

4. The abrasive slurry according to claim 2, wherein the salt of lignin and / or the salt of modified lignin comprises any one or more selected from the group consisting of alkali metal salts, alkaline earth metal salts, and organic base compounds.

5. The abrasive slurry according to claim 2, wherein the salt of modified lignin comprises sodium lignin sulfonate and / or magnesium lignin sulfonate.

6. The abrasive slurry according to claim 1, wherein the abrasive grains comprise manganese oxide particles.

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

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

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

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

11. A SiC wafer characterized by being polished using the abrasive slurry according to any one of claims 1 to 9.

Images