Polishing and cleaning method, cleaning agent, and polishing and cleaning set

Abstract

The purpose of the present invention is to provide a method for satisfactorily cleaning a substrate comprising a high-hardness material after the polishing of the substrate. Provided is a method for polishing and cleaning a substrate comprising a material having a Vickers hardness of 1500 Hv or more. This method comprises: a step for polishing a substrate of interest with a polishing composition; and a step for cleaning the polished substrate with a cleaning agent. The polishing composition contains a polishing auxiliary agent. The cleaning agent contains a surfactant.　

Description

[Technical Field]

[0001] The present invention relates to a polishing and cleaning method, a cleaning agent, and a polishing and cleaning set. More specifically, the present invention relates to a method for polishing and cleaning high-hardness materials having a Vickers hardness of 1500 Hv or more, a cleaning agent used in the cleaning, a polishing and cleaning set, and a cleaning method. This application claims priority based on Japanese Patent Application No. 2020-164596, filed on September 30, 2020, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] The surfaces of substrates made of high-hardness materials such as diamond, sapphire (aluminum oxide), silicon carbide, boron carbide, tungsten carbide, silicon nitride, and titanium nitride are typically smoothed by lapping, which involves supplying diamond abrasive grains to a polishing table. However, lapping using diamond abrasive grains generates scratches that remain, limiting the improvement in surface smoothness. Therefore, polishing, which involves using a polishing pad and supplying a polishing slurry between the polishing pad and the substrate after lapping using diamond abrasive grains, or instead of lapping, has been considered. After such polishing, the substrate surface is cleaned to remove adhering materials such as polishing debris and abrasive components. Examples of technical documents disclosing cleaning of substrates after polishing include Patent Documents 1 to 4. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-523950 [Patent Document 2] Japanese Patent Application Publication No. 2013-10888 [Patent Document 3] International Publication No. 2013 / 088928 [Patent Document 4] Japanese Patent No. 5659152 Summary of the Invention Problems to be Solved by the Invention

[0004] The substrate made of the above high-hardness material is finished to a high-quality surface by polishing. Regarding the cleaning process carried out after polishing, it is also desirable that it removes the deposits on the substrate surface and realizes a high-quality and clean surface. Regarding the cleaning of a substrate made of a high-hardness material, for example, in Patent Document 1, for the purpose of removing particles after diamond polishing, a silicon carbide substrate is cleaned using a low-concentration caustic surfactant (9 < pH < 12) mixed with deionized water in an ultrasonic cleaning tank. However, in Patent Document 1, there is no disclosure regarding polishing using a polishing aid. Also, as described above, polishing using diamond abrasive grains has limitations in improving surface quality, and it is difficult to achieve a satisfactory surface quality even after cleaning. In addition, in Patent Document 2, a cleaning agent is used for the purpose of removing wax used for fixing the substrate. However, in Patent Document 2, evaluation using the polished substrate has not been performed, and the removability of deposits such as polishing debris and polishing components has not been examined.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method capable of satisfactorily cleaning a substrate made of a high-hardness material after polishing. Another related object is to provide a cleaning agent and a polishing and cleaning set used in the above method. Still another related object is to provide a method for cleaning the above substrate. Means for Solving the Problems

[0006] This specification provides a method for polishing and cleaning a substrate made of a material having a Vickers hardness of 1500 Hv or more. This method includes the steps of polishing the substrate to be polished using a polishing composition and cleaning the polished substrate using a cleaning agent. The polishing composition contains non-diamond abrasive grains and / or a grinding aid. The cleaning agent also contains a surfactant. According to this method, a substrate made of a high-hardness material can be cleaned well by performing a polishing step using a polishing composition containing non-diamond abrasive grains followed by a cleaning step using a cleaning agent containing a surfactant. Using this cleaning agent can achieve a substrate with less deposits and high surface quality.

[0007] In some preferred embodiments, the cleaning agent contains an anionic surfactant as the surfactant. A surfactant that exhibits good cleaning properties for a substrate made of a high-hardness material after polishing can be preferably selected from among anionic surfactants.

[0008] Surfactants that are preferably used in the technology disclosed herein include compounds having an oxyalkylene unit.

[0009] The surfactant concentration in the cleaning agent is preferably 1% by weight or more. By increasing the surfactant concentration, the effect of adding the surfactant can be more effectively exhibited, and a better cleaning effect can be preferably exhibited.

[0010] In some embodiments, the cleaning agent may contain water in addition to a surfactant. A cleaning agent (which may be a cleaning liquid) containing water may allow the surfactant to exert its effects more effectively.

[0011] In some preferred embodiments, the substrate made of a material having a Vickers hardness of 1500 Hv or more is a silicon carbide substrate. The effects of the technology disclosed herein are preferably exhibited in a substrate made of silicon carbide.

[0012] The present specification also provides a cleaning agent for use in any of the methods disclosed herein. The cleaning agent contains a surfactant. The cleaning agent having the above configuration can provide good cleaning effects on substrates made of high-hardness materials after polishing.

[0013] The present specification also provides a polishing and cleaning set comprising a polishing composition and a cleaning agent. This polishing and cleaning set is used in any of the methods disclosed herein. In the polishing and cleaning set, the polishing composition contains non-diamond abrasive grains and / or a polishing aid. The cleaning agent contains a surfactant. By using a polishing and cleaning set with this configuration to polish and clean a substrate made of a high-hardness material, a substrate with high surface quality and a clean surface can be obtained.

[0014] This specification also provides a method for cleaning a silicon carbide substrate after polishing with non-diamond abrasive grains. This cleaning method includes a step of cleaning the silicon carbide substrate with a cleaning agent. The cleaning agent contains a surfactant. This cleaning method results in a substrate made of a high-hardness material having a well-cleaned surface. The polishing with non-diamond abrasive grains is preferably polishing with a polishing composition containing non-diamond abrasive grains.

[0015] This specification also provides a method for cleaning a silicon carbide substrate after polishing with a polishing aid. This cleaning method includes a step of cleaning the silicon carbide substrate with a cleaning agent, wherein the cleaning agent contains a surfactant. This cleaning method results in a substrate made of a high-hardness material having a well-cleaned surface. The polishing with the polishing aid is preferably polishing with a polishing composition containing the polishing aid.

[0016] Furthermore, this specification provides a cleaning agent used for cleaning silicon carbide substrates after polishing with non-diamond abrasive grains. This cleaning agent contains a surfactant. The cleaning agent having the above configuration can exhibit a good cleaning effect on substrates made of high-hardness materials after the polishing. The polishing with non-diamond abrasive grains is preferably polishing with a polishing composition containing non-diamond abrasive grains.

[0017] This specification also provides a cleaning agent used to clean silicon carbide substrates after polishing with a polishing aid. The cleaning agent contains a surfactant. The cleaning agent having the above configuration can exhibit a good cleaning effect on substrates made of high-hardness materials after the polishing. The polishing with the polishing aid is preferably polishing with a polishing composition containing the polishing aid. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an AFM image of the surface of a SiC wafer after cleaning according to Comparative Example 1. [Figure 2] 1 is an AFM image of the surface of a SiC wafer after cleaning according to Example 1. [Figure 3] 10 is an AFM image of the surface of a SiC wafer after cleaning according to Example 2. [Figure 4] 10 is an AFM image of the surface of a SiC wafer after cleaning according to Example 3. [Figure 5] 10 is an AFM image of the surface of a SiC wafer after cleaning according to Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0020] <Substrate> The technology disclosed herein includes a method for cleaning a substrate made of a material having a Vickers hardness of 1500 Hv or more (also referred to as a high-hardness material). More specifically, it includes a method for polishing and then cleaning a substrate made of the high-hardness material. Therefore, a substrate made of the high-hardness material is both a substrate to be cleaned and a substrate to be polished. According to the method disclosed herein, the surface of a substrate made of such a high-hardness material is effectively cleaned. The Vickers hardness of the high-hardness material is preferably 1800 Hv or more (e.g., 2000 Hv or more, typically 2200 Hv or more). The upper limit of the Vickers hardness is not particularly limited, but may be approximately 7000 Hv or less (e.g., 5000 Hv or less, typically 3000 Hv or less). In this specification, Vickers hardness can be measured based on JIS R 1610:2003. The international standard corresponding to the JIS standard is ISO 14705:2000.

[0021] Materials with a Vickers hardness of 1500 Hv or greater include diamond, sapphire (aluminum oxide), silicon carbide, boron carbide, tungsten carbide, silicon nitride, titanium nitride, and the like. The method disclosed herein can be applied to cleaning the mechanically and chemically stable single-crystal surfaces of the above materials after polishing. In particular, the substrate surface to be polished is preferably composed of silicon carbide. The C (carbon) face of a silicon carbide substrate tends to be more difficult to remove polishing debris and abrasive components from after polishing than the Si (silicon) face. Therefore, the cleaning method disclosed herein is particularly suitable for cleaning such C faces. Silicon carbide is also expected to be a semiconductor substrate material with low power loss and excellent heat resistance. Improving its surface quality offers significant practical benefits, and there are also significant advantages to performing a cleaning process on a surface that has been polished to a high surface quality, resulting in a clean surface. The method disclosed herein is particularly preferably applied to single-crystal silicon carbide surfaces.

[0022] <Cleaning agent> (surfactant) The cleaning agent disclosed herein is used for cleaning substrates made of high-hardness materials after polishing, and is characterized by containing a surfactant. Cleaning using a cleaning agent containing a surfactant can achieve good cleaning effects on substrates made of high-hardness materials after polishing. Specifically, it can remove particles and other deposits from the substrate surface after polishing.

[0023] The surfactant used in the cleaning agent is not particularly limited, and any of anionic, cationic, nonionic, and amphoteric surfactants can be used. A surfactant that exhibits good cleaning properties for substrate surfaces made of high-hardness materials after polishing can be preferably selected from anionic surfactants. Alternatively, nonionic surfactants are preferably used from the viewpoints of low foaming properties and ease of pH adjustment. The surfactants can be used alone or in combination of two or more.

[0024] Examples of anionic surfactants include sulfonic acid compounds such as alkanesulfonates, alkylbenzenesulfonates (e.g., nonylbenzenesulfonates, decylbenzenesulfonates, dodecylbenzenesulfonates, etc.), naphthalenesulfonates, alkyl sulfates (e.g., lauryl sulfate, octadecyl sulfate, etc.), polyoxyalkylene sulfates, α-olefinsulfonates, α-sulfofatty acid salts, α-sulfofatty acid alkyl ester salts, alkyl sulfosuccinates, and dialkyl sulfosuccinates; sulfate compounds such as alkyl sulfates, alkenyl sulfates, polyoxyalkylene alkyl ether sulfates (e.g., polyoxyethylene octadecyl ether sulfate, polyoxyethylene lauryl ether sulfate), and polyoxyalkylene alkenyl ether sulfate; carboxylic acid compounds such as alkyl ether carboxylates, amide ether carboxylates, sulfosuccinates, and amino acid surfactants; and phosphate compounds such as alkyl phosphates and alkyl ether phosphates. Among these, polyoxyalkylene alkyl ether sulfates are preferred. When the anionic surfactant forms a salt, the salt may be, for example, a metal salt (preferably a salt of a monovalent metal) such as a sodium salt, potassium salt, calcium salt, or magnesium salt, an ammonium salt, an amine salt, etc. The anionic surfactant may be used alone or in combination of two or more kinds.

[0025] Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene derivatives (e.g., polyoxyalkylene adducts) such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; copolymers of multiple types of oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers); etc. The nonionic surfactants can be used alone or in combination of two or more.

[0026] Examples of cationic surfactants include amine-type cationic surfactants such as alkylamidoamines and alkylamines; and quaternary ammonium salt-type cationic surfactants such as tetraalkyl (C1-4) ammonium salts (e.g., tetramethylammonium salts), mono-long-chain alkyl (C8-18) tri-short-chain alkyl (C1-2) ammonium salts (e.g., lauryltrimethylammonium salts, palmityltrimethylammonium salts, stearyltrimethylammonium salts), and di-long-chain alkyl (C8-18) di-short-chain alkyl (C1-2) ammonium salts. When the cationic surfactant forms a salt, the salt may be, for example, a halide such as chlorine, bromine, or iodine; a hydroxide; a sulfonate ester, sulfate ester, or nitrate ester having 1 to 5 carbon atoms. Among these, quaternary ammonium salt-type cationic surfactants (preferably mono-long-chain alkyl tri-short-chain alkyl ammonium salts, di-long-chain alkyl di-short-chain alkyl ammonium salts, etc.) are preferred. The cationic surfactants can be used alone or in combination of two or more.

[0027] The amphoteric surfactant is not particularly limited, and examples thereof include amine alkylene oxide surfactants, amine oxide surfactants, etc. These surfactants may be used alone or in combination of two or more.

[0028] In some preferred embodiments, the surfactant (preferably an anionic surfactant) used may be a compound having an oxyalkylene unit. Typically, it may be a compound having a polyoxyalkylene structure. The oxyalkylene unit may be composed of one oxyalkylene group or may be a repeating structure of two or more oxyalkylene units. Examples of the oxyalkylene unit include an oxyethylene unit (EO) and an oxypropylene unit (PO). Of these, an oxyethylene unit (EO) is preferred. When the surfactant has multiple oxyalkylene units, the oxyalkylene units may be of the same type (i.e., one kind) or may be composed of two or more types of oxyalkylene units. The total number of added moles of alkylene oxide contained in the surfactant may be 1 or more, 3 or more, 5 or more, 10 or more, 15 or more, 20 or more, 50 or less, 30 or less, 22 or less, 16 or less, 12 or less, 8 or less, or 4 or less (e.g., 3 or less).

[0029] The surfactant (e.g., anionic surfactant) used in some embodiments has a hydrocarbon group. The hydrocarbon group may be composed of saturated hydrocarbons such as an alkyl group, or may contain an unsaturated bond such as a carbon-carbon double bond. The hydrocarbon group (typically an alkyl group) may be either linear or branched. The number of carbon atoms contained in the hydrocarbon group (e.g., an alkyl group) may be 8 or more, 10 or more, 12 or more, 24 or less, 20 or less, 18 or less, 16 or less, or 12 or less. Specific examples of the hydrocarbon group (typically an alkyl group) include an octyl group, a decyl group, a lauryl group, a myristyl group, a palmityl group, and a stearyl group.

[0030] The pH of the surfactant (the pH of a 100% surfactant concentration by weight, or the pH of a commercially available surfactant (which may contain an appropriate amount of water, etc.)) is not particularly limited, and is, for example, suitably 5.0 or higher, preferably 6.0 or higher (e.g., greater than 6.0), more preferably 6.5 or higher, even more preferably 7.0 or higher, and particularly preferably 7.5 or higher (e.g., greater than 8.0, or even 8.2 or higher). The pH of the surfactant is suitably, for example, less than 11.0, preferably less than 9.5, more preferably 9.0 or lower (e.g., less than 9.0), and may be less than 8.0, less than 7.0, less than 6.0, or less than 5.0. High surface quality is easily achieved by performing cleaning using a surfactant in the near-neutral range.

[0031] In this specification, the pH of a liquid surfactant or cleaning agent (typically a cleaning solution) can be determined by using a pH meter (for example, a glass electrode hydrogen ion concentration indicator (model number F-23) manufactured by HORIBA, Ltd.) and performing three-point calibration using standard buffer solutions (phthalate pH buffer solution, pH: 4.01 (25°C), neutral phosphate pH buffer solution, pH: 6.86 (25°C), and carbonate pH buffer solution, pH: 10.01 (25°C)), then immersing the glass electrode in the cleaning agent to be measured and measuring the value after stabilization for at least two minutes.

[0032] The surfactant concentration in the cleaning agent is appropriately set within a range in which the effects of containing the surfactant are exhibited, and is not limited to a specific range. The surfactant concentration in the cleaning agent can be 0.01% by weight or more, and is suitably 0.1% by weight or more. In some embodiments, the surfactant concentration in the cleaning agent is 1% by weight or more, preferably 3% by weight or more, more preferably 10% by weight or more, and even more preferably 20% by weight or more, and may be 30% by weight or more, or 40% by weight or more (e.g., 50% by weight or more). In such embodiments, the upper limit of the surfactant concentration in the cleaning agent can be less than 90% by weight, may be less than 70% by weight, may be less than 50% by weight, or may be less than 35% by weight. Such a cleaning agent may be in the form of a cleaning solution containing a surfactant and water. In other embodiments, the surfactant concentration in the cleaning agent can be approximately 90% by weight or more (e.g., 90 to 100% by weight), is suitably 95% by weight or more, and may be 99% by weight or more. Such a cleaning agent may be essentially composed of a surfactant.

[0033] (water) In some embodiments, the cleaning agent contains water in addition to a surfactant. A cleaning agent containing water can enhance the effects of the surfactant. Such a cleaning agent can be a cleaning solution that is liquid at room temperature. In this specification, room temperature refers to 23°C. Suitable water for use in the cleaning agent is ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. The cleaning agent disclosed herein may further contain an organic solvent (e.g., lower alcohol, lower ketone) that is uniformly miscible with water, as needed. Preferably, 90% or more by volume of the solvent contained in the cleaning agent is water, and more preferably 95% or more by volume (e.g., 99 to 100% by volume) is water.

[0034] (Optional Additives) The cleaning agent disclosed herein may further contain, as necessary, one or more of known additives that can be used in cleaning agents, such as a chelating agent, a pH adjuster (such as an acid or a basic compound), an antioxidant, an antifoaming agent, an antiseptic, and an antifungal agent.

[0035] Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid. The chelating agents can be used alone or in combination.

[0036] The cleaning agent disclosed herein may be substantially free of a chelating agent. Here, "substantially free of a chelating agent" means that the concentration of the chelating agent in the cleaning agent is less than 1% by weight. The concentration of the chelating agent in the cleaning agent may be less than 0.3% by weight, less than 0.1% by weight, less than 0.01% by weight, or less than 0.005% by weight. The technology disclosed herein can also be preferably implemented in an embodiment where the cleaning agent does not contain a chelating agent.

[0037] The content of the optional additives can be set within an appropriate range so long as the effects of the present invention are not significantly impaired. For example, the content of the optional additives in the cleaning agent is preferably less than 30% by weight, and may be less than 10% by weight, less than 1% by weight, less than 0.1% by weight, or less than 0.01% by weight. The technology disclosed herein is preferably implemented in an embodiment in which the cleaning agent does not contain any optional additives. Note that optional additives are defined as components other than solvents such as water.

[0038] The amount of the optional additive used can also be determined based on its relative relationship with the surfactant. In a cleaning agent, the content of the optional additive per 1 part by weight of the surfactant can be less than 3 parts by weight, and preferably less than 1 part by weight. From the viewpoint of optimally exerting the effects of the surfactant, the content of the optional additive per 1 part by weight of the surfactant may be, for example, less than 0.3 parts by weight, less than 0.1 parts by weight, less than 0.03 parts by weight, or less than 0.01 parts by weight. From the viewpoint of optimally exerting the effects of the additive, the content of the optional additive per 1 part by weight of the surfactant can be 0.00001 parts by weight or more, and preferably 0.001 parts by weight or more, and may be 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more.

[0039] In some embodiments, the cleaning agent (which may be a cleaning liquid) is substantially composed of a surfactant and water. Such a cleaning agent may be in the form of an aqueous surfactant solution. In this embodiment, the total proportion of surfactant and water in the cleaning agent is, for example, 90% by weight or more (e.g., 90 to 100% by weight), preferably 95% by weight or more, and more preferably 99% by weight or more. In this way, by using a cleaning agent substantially composed of surfactant and water, the effect of the surfactant tends to be more effectively exhibited.

[0040] (pH) The pH of the cleaning agent disclosed herein is not particularly limited. For example, the pH of the cleaning agent may be 0.5 or higher, 1.0 or higher, 2.0 or higher, 3.0 or higher, or 4.0 or higher. In some preferred embodiments, the pH of the cleaning agent is suitably 5.0 or higher, preferably 6.0 or higher (e.g., greater than 6.0), 6.5 or higher, 7.0, 7.5 or higher, or 8.0 or higher. The pH of the cleaning agent may be, for example, 13.0 or lower, 12.5 or lower, 12.0 or lower, or less than 12.0. In some embodiments, the pH of the cleaning agent is, for example, less than 11.0, preferably less than 9.5, more preferably 9.0 or lower (e.g., less than 9.0), and may be less than 8.0, less than 7.0, less than 6.0, or less than 5.0. High surface quality is easily achieved by performing cleaning using a cleaning agent in the near-neutral range.

[0041] <Cleaning method> The cleaning method disclosed herein includes a step (cleaning step) of cleaning a substrate made of a high-hardness material after polishing using a cleaning agent. The cleaning agent used is one of the cleaning agents described above. The cleaning method is not particularly limited and can be performed by any appropriate means depending on the purpose. For example, one or more cleaning processes selected from immersion cleaning, spray cleaning, scrubbing cleaning, ultrasonic cleaning, etc. can be employed. Scrubbing cleaning is preferred from the perspective of cleanability. Note that scrubbing refers to cleaning in which the substrate surface is wiped or rubbed using a cleaning tool such as a sponge, brush, or nonwoven fabric. For example, by applying a cleaning agent to the surface of a cleaning tool such as a sponge, brush, or nonwoven fabric, and then abutting the cleaning tool with the cleaning agent applied to the substrate surface and moving it relative to the substrate surface, particles and other deposits attached to the substrate surface can be removed. Furthermore, from the perspective of removability of attached particles, the cleaning step is preferably performed before the substrate surface dries after polishing. Note that the cleaning step disclosed herein can be preferably performed in an embodiment that does not include ultrasonic cleaning or microwave cleaning.

[0042] From the viewpoint of removing adhering particles, scrubbing using a sponge (e.g., a polyvinyl alcohol (PVA) sponge) is preferred as a cleaning method. This type of cleaning is also called sponge cleaning. In addition, in the cleaning process (typically scrubbing), water (deionized water, pure water, ultrapure water, distilled water, etc.) or an organic solvent (lower alcohol, lower ketone, etc.) may or may not be additionally supplied to the substrate surface as needed.

[0043] The time for the cleaning step using the cleaner is not particularly limited, but from the viewpoint of particle removal performance on the substrate surface, it is appropriate to set it to 10 seconds or more, preferably 30 seconds or more, more preferably 1 minute or more. From the viewpoint of cleaning efficiency, it is appropriate to set it to about 30 minutes or less, preferably 10 minutes or less, more preferably 3 minutes or less (for example, 1 to 2 minutes).

[0044] The temperature of the detergent in the washing step can usually be room temperature (typically 10°C or higher and lower than 40°C, for example, about 20 to 30°C). Washing may also be performed by heating the detergent (for example, heating to 40°C or higher or about 50 to 80°C).

[0045] In some preferred embodiments, preliminary cleaning (also referred to as pre-cleaning) is performed before the cleaning step using the cleaning agent. The preliminary cleaning is cleaning without using the cleaning agent, and may be one or more methods selected from the group consisting of immersion cleaning, running water cleaning, spray cleaning, scrubbing cleaning, and ultrasonic cleaning. For example, preliminary cleaning may be immersion in water (deionized water, pure water, ultrapure water, distilled water, etc.; the same applies hereinafter unless otherwise specified), running water cleaning, water spray cleaning, scrubbing cleaning using water, ultrasonic cleaning in a water tank, etc. The water immersion may be batch immersion, in which the substrate is immersed in a water tank containing water, overflow immersion, or quick dump immersion. From the viewpoint of cleaning performance, scrubbing is preferred. Scrubbing using water is preferably performed while supplying water (running water) to the substrate surface. The scrubbing method used in the preliminary cleaning is preferably scrubbing using a sponge (e.g., a PVA sponge). From the viewpoint of removability of adhered particles, the pre-cleaning step is preferably carried out before the substrate surface dries after polishing, and the cleaning step is preferably carried out after the pre-cleaning step is completed and before the substrate surface dries. The water may contain an appropriate amount of an organic solvent (such as a lower alcohol or a lower ketone).

[0046] The time for the preliminary cleaning step is not particularly limited, but from the viewpoint of cleaning performance, it is appropriate to set it to 10 seconds or more, preferably 30 seconds or more, and from the viewpoint of cleaning efficiency, it is appropriate to set it to about 10 minutes or less, preferably 3 minutes or less (for example, 1 to 2 minutes).

[0047] In some embodiments, a post-cleaning step is carried out after the cleaning step using the above-mentioned cleaning agent. The post-cleaning step can be carried out in the same manner as the pre-cleaning step described above, except that it is carried out after the above-mentioned cleaning step, so a duplicated explanation will be omitted. For the post-cleaning step, a method that combines running water cleaning and immersion cleaning (e.g., overflow immersion) can be preferably used. When immersion cleaning is used, the time for the post-cleaning step is suitably 1 minute or more, and preferably 10 minutes or more (e.g., about 10 to 30 minutes).

[0048] The cleaning method disclosed herein can achieve good cleaning effects on substrates made of high-hardness materials by using a surfactant and, in a preferred embodiment, by scrubbing with a sponge, and therefore can be preferably carried out in an embodiment that does not include ultrasonic cleaning or microwave cleaning, which are commonly used in conventional cleaning methods.

[0049] The surface roughness Ra of the substrate cleaned as described above is not particularly limited, but can be, for example, approximately 3 nm or less. The surface roughness Ra is preferably approximately 1 nm or less, more preferably approximately 0.3 nm or less, and even more preferably less than 0.10 nm (for example, approximately 0.01 to 0.07 nm). Furthermore, the Rmax of the substrate after cleaning is not particularly limited, but is preferably less than 30 nm, more preferably less than 20 nm, and even more preferably less than 10 nm. Cleaning using the cleaning agent disclosed herein achieves a high-quality, clean surface as described above. The Ra and Rmax are measured using an atomic force microscope (AFM), as described in the Examples below.

[0050] The substrate made of the cleaned high-hardness material is naturally dried or forcedly dried using a dryer or the like, and is then preferably used as, for example, a semiconductor substrate material for various device applications such as optical devices and power devices.

[0051] <Substrate manufacturing method> The present specification also provides a method for manufacturing a substrate made of a high-hardness material, including the cleaning method. The substrate manufacturing method is, for example, a method for manufacturing a silicon carbide substrate. The technology disclosed herein may include a method for manufacturing a substrate made of a high-hardness material and providing a substrate made of a high-hardness material manufactured by the method. That is, the technology disclosed herein provides a method for manufacturing a substrate made of a high-hardness material, including a cleaning step of supplying any of the cleaning agents disclosed herein to a substrate made of a high-hardness material to clean the substrate, and a substrate made of a high-hardness material manufactured by the method. The manufacturing method can be carried out by preferably applying the content of any of the cleaning methods disclosed herein. The manufacturing method can efficiently provide a clean substrate with improved surface quality, such as a silicon carbide substrate.

[0052] Furthermore, the method for manufacturing a substrate made of a high-hardness material may include a step of polishing the substrate made of a high-hardness material to be polished (polishing step) before the cleaning step. Specifically, the polishing step is a step of polishing the surface of the substrate made of a high-hardness material using a polishing composition described below. The cleaning agent and cleaning method disclosed herein can be applied to a substrate made of a high-hardness material after polishing in the polishing step described below, thereby achieving the desired effect. The cleaning agent and cleaning method disclosed herein are preferably implemented in a mode in which they are combined with the polishing process described below. Thus, this specification provides a method for polishing and cleaning a substrate made of a high-hardness material. The polishing composition and polishing method are described below.

[0053] <Polishing composition> (abrasive grain) The polishing composition disclosed herein typically contains abrasive grains. It is preferable for the polishing composition to contain abrasive grains in order to efficiently achieve excellent smoothness. The type of abrasive grains that can be contained in the polishing composition is not particularly limited. For example, the abrasive grains can be any of inorganic particles, organic particles, and organic-inorganic composite particles. Examples of abrasive grains include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; and carbonates such as calcium carbonate and barium carbonate. Abrasive grains may be used alone or in combination. Among these, oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, zirconium oxide particles, manganese dioxide particles, and iron oxide particles are preferred because they can form a good surface. In some embodiments, alumina particles, zirconium oxide particles, chromium oxide particles, and iron oxide particles are more preferred, with alumina particles being particularly preferred, while in other embodiments, silica particles, cerium oxide particles, and manganese dioxide particles are more preferred, with silica particles being particularly preferred.

[0054] In this specification, the phrase "consisting essentially of X" or "consisting essentially of X" in relation to the composition of an abrasive grain means that the proportion of X in the abrasive grain (purity of X) is 90% or more by weight (preferably 95% or more, more preferably 97% or more, even more preferably 98% or more, for example 99% or more).

[0055] In some embodiments, alumina particles are used as abrasive grains. The alumina particles can be used singly or in combination of two or more types. When using alumina particles as abrasive grains, it is generally advantageous to have a higher proportion of alumina particles in the total abrasive grains contained in the polishing composition. For example, the proportion of alumina particles in the total abrasive grains contained in the polishing composition is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more (e.g., 95 to 100% by weight).

[0056] In some preferred embodiments, silica particles are used as abrasive grains. Examples of silica particles include colloidal silica, fumed silica, and precipitated silica. From the viewpoint of improving smoothness, preferred silica particles include colloidal silica and fumed silica. Among these, colloidal silica is particularly preferred. The technology disclosed herein is suitable for a method including polishing using a polishing composition containing silica particles. When polishing a substrate using silica particles, if the silica particles adhere to the substrate surface, their removal is often more difficult than with other particles. According to the technology disclosed herein, such silica particles adhered to the substrate surface can be preferably removed using the above-mentioned cleaning agent. The silica particles can be used alone or in combination of two or more types.

[0057] Abrasive grain A FIN When silica particles are used as the abrasive, it is generally advantageous to have a higher proportion of silica particles in the total abrasive grains contained in the polishing composition. For example, the proportion of silica particles in the total abrasive grains contained in the polishing composition is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more (e.g., 95 to 100% by weight).

[0058] In addition, the polishing composition disclosed herein preferably uses non-diamond abrasive grains that are substantially free of diamond grains as abrasive grains.Diamond grains have high hardness, which can be a limiting factor in improving smoothness.In addition, diamond grains are generally expensive, so they are not considered to be advantageous materials in terms of cost-effectiveness.From a practical standpoint, it is desirable to have a low dependency on expensive materials such as diamond grains.

[0059] The average primary particle diameter of the abrasive grains (e.g., silica particles) is not particularly limited, and from the viewpoint of improving the polishing removal rate, it is 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and may be 50 nm or more, or even 60 nm or more. By increasing the average primary particle diameter, a higher polishing removal rate can be realized. Furthermore, from the viewpoint of surface quality after polishing, the average primary particle diameter is usually 500 nm or less, and is suitably 300 nm or less, preferably 150 nm or less, more preferably 100 nm or less, even more preferably 80 nm or less, and may be, for example, 60 nm or less.

[0060] In the technology disclosed herein, the average primary particle size of the abrasive grains is calculated from the specific surface area (BET value) measured by the BET method as follows: average primary particle size (nm) = 6000 / (true density (g / cm 3 )×BET value(m 2 The specific surface area refers to the particle diameter (BET particle diameter) calculated by the formula: (1) Specific surface area = (1 / 2) / (g) The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0061] When the polishing composition contains abrasive grains, the abrasive grain concentration in the polishing composition is typically 0.01 wt % or more, from the viewpoint of polishing removal rate, and may be 0.1 wt % or more, 1 wt % or more, or 3 wt % or more. From the viewpoint of efficiently improving smoothness, the abrasive grain concentration is preferably 10 wt % or more, and more preferably 20 wt % or more. Furthermore, from the viewpoint of obtaining good dispersibility, the abrasive grain concentration in the finish polishing composition is typically 50 wt % or less, and preferably 40 wt % or less, and may be 20 wt % or less, 10 wt % or less, or 8 wt % or less. In some other embodiments, from the viewpoint of obtaining the desired surface quality, the polishing composition may not contain abrasive grains.

[0062] (grinding aid) The polishing composition disclosed herein preferably contains a polishing aid. The polishing aid is a component that enhances the effect of polishing, and is typically water-soluble. The polishing aid is not particularly limited, but it is thought that it acts to alter (typically oxidize) the substrate surface during polishing, weakening the substrate surface and contributing to polishing by abrasive grains. For example, taking silicon carbide (SiC), a typical example of a high-hardness material, as an example, the polishing aid acts to oxidize SiC, i.e., to SiO x C y It is believed that this contributes to the x C y The hardness of SiC is lower than that of single crystal SiC. Furthermore, in high-hardness materials with a Vickers hardness of 1500 Hv or more, oxidation reactions generally result in a decrease in hardness and embrittlement. For these reasons, it is believed that the addition of polishing aids improves the polishing removal rate and the surface quality of the substrate.

[0063] Examples of polishing aids include peroxides such as hydrogen peroxide; nitric acid, its salts such as iron nitrate, silver nitrate, aluminum nitrate, and its complexes such as cerium ammonium nitrate; persulfates such as potassium peroxomonosulfate and peroxodisulfate, and persulfate compounds such as ammonium persulfate and potassium persulfate; chlorine compounds such as chloric acid and its salts, perchloric acid and its salt, potassium perchlorate; bromine compounds such as bromic acid and its salt, potassium bromate; iodine compounds such as ammonium iodate and its salt, periodic acid and its salt, sodium periodate and potassium periodate; and iron compounds such as ferric acid and its salt, potassium ferrate. Acids include permanganic acid and its salts, such as sodium permanganate and potassium permanganate; chromic acid and its salts, such as potassium chromate and potassium dichromate; vanadic acid and its salts, such as ammonium vanadate, sodium vanadate, and potassium vanadate; ruthenic acids, such as perruthenic acid and its salts; molybdic acid and its salts, such as ammonium molybdate and disodium molybdate; rhenic acids, such as perrhenium and its salts; and tungstic acids, such as tungstic acid and its salt, disodium tungstate. These may be used alone or in combination of two or more. In some embodiments, permanganic acid or its salts, chromic acid or its salts, and ferric acid or its salts are preferred, with sodium permanganate and potassium permanganate being particularly preferred. In some other embodiments, vanadic acid or a salt thereof, an iodine compound, molybdic acid or a salt thereof, or tungstic acid or a salt thereof is preferred, with sodium metavanadate, sodium vanadate, and potassium vanadate being particularly preferred.

[0064] In some preferred embodiments, the polishing composition contains a complex metal oxide as a polishing aid. Examples of the complex metal oxide include metal nitrates, ferric acids, permanganic acids, chromic acids, vanadates, ruthenic acids, molybdic acids, rhenic acids, and tungstic acids. Among these, ferric acids, permanganic acids, chromic acids, vanadates, molybdic acids, and tungstic acids are more preferred, and permanganic acids and vanadates are even more preferred.

[0065] The polishing composition disclosed herein may or may not further contain an oxidizing agent other than the composite metal oxide. The technology disclosed herein can be preferably implemented in an embodiment in which the oxidizing agent contains the composite metal oxide and an oxidizing agent other than the composite metal oxide (e.g., hydrogen peroxide). The technology disclosed herein can also be implemented in an embodiment in which the polishing aid does not substantially contain a polishing aid other than the composite metal oxide (e.g., hydrogen peroxide).

[0066] The content of the grinding aid in the polishing composition is usually suitably 0.005 mol / L or more. From the viewpoint of improving the polishing removal rate, the content of the grinding aid in the polishing composition is preferably 0.008 mol / L or more, more preferably 0.01 mol / L or more, and may be 0.03 mol / L or more, 0.05 mol / L or more, 0.06 mol / L or more, or even 0.07 mol / L or more. From the viewpoint of improving smoothness, the content of the grinding aid in the polishing composition is usually suitably 0.5 mol / L or less, preferably 0.3 mol / L or less, more preferably 0.2 mol / L or less, and may be 0.1 mol / L or less, or may be 0.09 mol / L or less.

[0067] (Other ingredients) The polishing composition disclosed herein may further contain, as needed, known additives that can be used in polishing compositions (typically compositions for polishing high-hardness materials, for example, compositions for polishing silicon carbide substrates), such as metal salts, alkali metal salts, alkaline earth metal salts, chelating agents, thickeners, dispersants, pH adjusters, surfactants, inorganic polymers, organic polymers, organic acids, organic acid salts, inorganic acids, inorganic acid salts, rust inhibitors, preservatives, and antifungal agents, within the scope that does not impair the effects of the present invention. The content of the above additives may be appropriately set depending on the purpose of their addition, and detailed description thereof will be omitted because they do not characterize the present invention.

[0068] (dispersion medium) The dispersion medium used in the polishing composition is not particularly limited as long as it can disperse abrasive grains. Ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used as the dispersion medium. The polishing composition disclosed herein may further contain, as necessary, an organic solvent (such as a lower alcohol or a lower ketone) that is uniformly miscible with water. Generally, it is preferable that 90% by volume or more of the dispersion medium contained in the polishing composition is water, and more preferably 95% by volume or more (typically 99 to 100% by volume) is water.

[0069] The pH of the polishing composition is not particularly limited. It is usually appropriate for the polishing composition to have a pH of about 2 to 12. When the pH of the polishing composition is within the above range, a practical polishing removal rate is likely to be achieved. The pH of the polishing composition is preferably 2 to 10, more preferably 3 to 9.5, and may be 4 to 8. In some embodiments, the pH of the polishing composition may be, for example, 6 to 10, or 8.5 to 9.5.

[0070] The method for preparing the polishing composition disclosed herein is not particularly limited. For example, the components contained in the polishing composition may be mixed using a well-known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all of the components may be mixed at once, or they may be mixed in an appropriately selected order.

[0071] The polishing composition disclosed herein may be a single-component type or a multi-component type, such as a two-component type. For example, the polishing composition may be stored in such a manner that a liquid A containing some of the components constituting the polishing composition and a liquid B containing the remaining components are separately stored, and the liquids A and B are mixed and used when polishing a substrate.

[0072] The polishing composition disclosed herein may be in a concentrated form (i.e., in the form of a concentrated polishing liquid) before being used for polishing. Such a concentrated polishing composition is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc.

[0073] <Polishing and cleaning set> As described above, this specification provides a polishing and cleaning set used for polishing and cleaning substrates made of high-hardness materials. This polishing and cleaning set includes a polishing composition and a cleaning agent. The polishing composition is used to polish substrates made of high-hardness materials, and the cleaning agent is used to clean the substrates made of high-hardness materials after polishing with the polishing composition. More specifically, the polishing and cleaning set is used in a method for manufacturing substrates made of high-hardness materials. The polishing composition is the polishing composition disclosed herein. The cleaning agent is the cleaning agent disclosed herein. Specifically, the polishing composition may contain, for example, a polishing aid. It may also contain, for example, abrasive grains (preferably non-diamond abrasive grains). The cleaning agent also contains a surfactant. The polishing composition and the cleaning agent are typically stored separately. Substrates produced using the polishing and cleaning set can have high surface quality after polishing and can be cleaned to have a clean surface. Details of the polishing composition and the cleaning agent are as described above, and therefore will not be described here.

[0074] <Polishing method> The polishing composition disclosed herein can be used to polish a substrate, for example, in an embodiment including the following steps. That is, a polishing liquid (slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include adjusting the concentration of the polishing composition (e.g., diluting the polishing composition) or adjusting the pH of the polishing composition to prepare the polishing liquid. Alternatively, the polishing composition may be used as is as the polishing liquid. In the case of a multi-component polishing composition, preparing the polishing liquid may include mixing the components, diluting one or more components before mixing, or diluting the mixture after mixing. The polishing liquid is then supplied to the polishing surface, and polishing is carried out using a conventional method known to those skilled in the art. For example, a substrate is placed in a conventional polishing apparatus, and the polishing liquid is supplied to the polishing surface of the substrate via the polishing pad of the polishing apparatus. Typically, the polishing liquid is continuously supplied, while the polishing pad is pressed against the polishing surface of the substrate, causing relative movement (e.g., rotational movement) between the two. Substrate polishing is completed through this polishing process.

[0075] This specification provides a polishing method for polishing a substrate and a method for manufacturing a substrate using the polishing method. The polishing method is characterized by including a step of polishing a substrate using the polishing composition disclosed herein. Some preferred embodiments of the polishing method include a pre-polishing step (pre-polishing step) and a finish-polishing step (finish-polishing step). In some preferred embodiments, the pre-polishing step is a polishing step located immediately before the finish-polishing step. The pre-polishing step may be a single-stage polishing step or a multi-stage polishing step consisting of two or more stages. The finish-polishing step here refers to a step of finish-polishing a substrate that has been pre-polished, and is the final (i.e., most downstream) polishing step among polishing steps performed using a polishing slurry containing abrasive grains. In such a polishing method including a pre-polishing step and a finish-polishing step, the polishing composition disclosed herein may be used in one of the pre-polishing steps, in the finish-polishing step, or in both the pre-polishing step and the finish-polishing step.

[0076] Preliminary polishing and finish polishing can be performed using either a single-sided polishing machine or a double-sided polishing machine. In a single-sided polishing machine, a substrate is attached to a ceramic plate with wax, and the substrate is held using a holder called a carrier. A polishing composition is supplied while a polishing pad is pressed against one side of the substrate, and the two are moved relative to each other to polish one side of the object to be polished. The movement is, for example, rotational movement. In a double-sided polishing machine, a substrate is held using a holder called a carrier, and a polishing pad is pressed against the opposing side of the substrate while a polishing composition is supplied from above. The two are rotated relative to each other to polish both sides of the substrate simultaneously.

[0077] The polishing pad used in each polishing step disclosed herein is not particularly limited. For example, any of nonwoven fabric, suede, hard foam polyurethane, abrasive grains, and non-abrasive grains may be used. In some embodiments, nonwoven fabric and hard foam polyurethane non-abrasive grain polishing pads may be preferably used.

[0078] Substrates polished by the methods disclosed herein are typically cleaned after polishing, and the cleaning step is a cleaning method disclosed herein (a cleaning method using a cleaning agent containing a surfactant).

[0079] The polishing method disclosed herein may include any other steps in addition to the pre-polishing step and the finish polishing step. Examples of such steps include a mechanical polishing step or a lapping step performed before the pre-polishing step. The mechanical polishing step involves polishing the substrate using a liquid in which diamond abrasive grains are dispersed in a solvent. In some preferred embodiments, the dispersion does not contain an oxidizing agent. The lapping step involves pressing the surface of a polishing platen, such as a cast iron platen, against the substrate to polish it. Therefore, a polishing pad is not used in the lapping step. The lapping step is typically performed by supplying abrasive grains between the polishing platen and the substrate. The abrasive grains are typically diamond abrasive grains. The polishing method disclosed herein may also include an additional step before the pre-polishing step or between the pre-polishing step and the finish polishing step. [Example]

[0080] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in the examples. In the following description, "%" is by weight unless otherwise specified.

[0081] <Comparative Example 1> [Polishing test] (Preparation of Polishing Composition) A polishing slurry was prepared by mixing colloidal silica as abrasive grains, hydrogen peroxide and vanadates as polishing aids, and deionized water. The average primary particle diameter of the colloidal silica used was approximately 80 nm. The abrasive grain concentration in the polishing slurry was 23%.

[0082] (Policing conditions) An SiC wafer was prepared by previously lapping using diamond abrasive grains with an average particle size of 5 μm and then pre-polishing using a polishing liquid containing alumina abrasive grains. The prepared polishing slurry was used to polish the surface of a pre-polished SiC wafer under the following polishing conditions. Polishing device: Fujikoshi Machinery Co., Ltd. single-sided polishing device, model "RDP-500" Polishing pad: Nitta Haas "SUBA800" Polishing pressure: 300g / cm 2 Plate rotation speed: 80 rpm Head rotation speed: 40 rpm Slurry supply rate: 20 mL / min (flowing) Slurry temperature: 25℃ Substrate: SiC wafer (conductivity type: n-type, crystal type 4H-SiC, off-angle of the main surface (0001) relative to the C-axis: 4°) 2 inches Polishing time: 1 minute

[0083] [Cleaning test] After polishing, the SiC wafers were removed from the polishing machine and transferred to a clean room. They were then scrubbed with running water (pure water) for 1 minute using a commercially available PVA (polyvinyl alcohol) sponge at room temperature, followed by another 1 minute of running water (pure water) rinsing (overflow immersion) for 15 minutes or more.

[0084] [AFM observation] The surface (C-plane) of a SiC wafer that had been naturally dried overnight in a clean room was observed at three 10 μm × 10 μm areas using an atomic force microscope (AFM; manufactured by Bruker, model: Nanoscope V), and particle adhesion was confirmed over the entire surface. An AFM image of the SiC wafer surface after cleaning in Comparative Example 1 is shown in Figure 1.

[0085] Example 1 [Polishing test] A polishing test was carried out in the same manner and under the same conditions as in Comparative Example 1.

[0086] [Cleaning test] (Preparation of cleaning solution) As surfactant A, sodium polyoxyethylene lauryl ether sulfate (average number of moles of ethylene oxide added: 3, number of carbon atoms in the alkyl group: 12 to 14, concentration 27% aqueous solution; stock solution pH: 8.6) was diluted 5 times with water (pure water) to obtain a cleaning solution.

[0087] (Washing) The polished SiC wafer was removed from the polishing machine and transferred to a clean room. It was then scrubbed with running water (pure water) for 1 minute using a commercially available PVA sponge at room temperature. It was then immersed in the cleaning solution prepared above and ultrasonically cleaned for 1 minute. It was then washed with running water (pure water) for 1 minute. It was then washed with running water (pure water) for 15 minutes or more (overflow immersion).

[0088] [AFM observation] When the surface (C-face) of the SiC wafer after cleaning was observed with an AFM in the same manner as in Comparative Example 1, a small amount of particles was observed on the surface, but the amount of particles was clearly less than that in Comparative Example 1. The same was true for the Si-face. An AFM image of the surface of the SiC wafer after cleaning in Example 1 is shown in FIG. 2.

[0089] <Example 2> [Polishing test] A polishing test was carried out in the same manner and under the same conditions as in Comparative Example 1.

[0090] [Cleaning test] (Preparation of cleaning solution) As surfactant A, sodium polyoxyethylene lauryl ether sulfate (average number of moles of ethylene oxide added: 3, number of carbon atoms in alkyl group: 12 to 14, concentration 27% aqueous solution, stock solution pH: 8.6) was prepared and used as a cleaning agent.

[0091] (Washing) The polished SiC wafer was removed from the polishing machine and transferred to a clean room. It was then scrubbed for 1 minute with running water (pure water) using a commercially available PVA sponge at room temperature. The wafer was then scrubbed for 1 minute with a PVA sponge coated with the cleaning agent. The wafer was then rinsed for 1 minute with running water (pure water), followed by an additional 15 minutes or more of rinsing (overflow immersion) in running water (pure water).

[0092] [AFM observation] When the surface (C-face) of the SiC wafer after cleaning was observed with an AFM using the same method as in Comparative Example 1, no particles were found to be attached to the surface, and no other deposits were found. The same was true for the Si-face. An AFM image of the surface of the SiC wafer after cleaning in Example 2 is shown in Figure 3. Furthermore, the Ra of the surface (C-face) of the SiC wafer after cleaning, measured using the AFM, was 0.0497 nm, and the Rmax was 8.54 nm.

[0093] Example 3 [Polishing test] A polishing test was carried out in the same manner and under the same conditions as in Comparative Example 1.

[0094] [Cleaning test] Polyoxyethylene alkyl ether (ethylene oxide addition mole number: 9, alkyl group: isotridecyl group (carbon number: 13)) was prepared as surfactant B and used as a cleaning agent. The pH of this cleaning agent was 6.6. Cleaning was performed in the same manner as in Example 2, except for using this cleaning agent.

[0095] [AFM observation] When the surface (C-face) of the SiC wafer after cleaning was subjected to AFM observation using the same method as in Comparative Example 1, adhesion of particles was confirmed on the surface, but the amount of adhesion of particles was less than in Comparative Example 1. Adhesion other than particles was also observed. A small amount of adhesion of particles was also observed on the Si-face, and adhesion other than particles was also observed. An AFM image of the surface of the SiC wafer after cleaning in Example 3 is shown in Figure 4.

[0096] Example 4 [Polishing test] A polishing test was carried out in the same manner and under the same conditions as in Comparative Example 1.

[0097] [Cleaning test] Alkyltrimethylammonium chloride (alkyl groups: hexadecyl group, stearyl group (carbon number 16 to 18)) was used as surfactant C to prepare an aqueous solution containing the surfactant at a concentration of 28%. This was used as a cleaning agent. The pH of this cleaning agent was 7.1. Cleaning was carried out in the same manner as in Example 2, except that this cleaning agent was used.

[0098] [AFM observation] When the surface (C-face) of the SiC wafer after cleaning was observed with an AFM in the same manner as in Comparative Example 1, a small amount of particles was observed on the surface, but the amount of particles was clearly less than that in Comparative Example 1. No particles were observed on the Si-face. An AFM image of the surface of the SiC wafer after cleaning in Example 4 is shown in FIG.

[0099] The results of Examples 1 to 4 and Comparative Example 1 are summarized in Table 1. In Table 1, the product with the best cleaning ability was marked with "◎", the product with good cleaning ability was marked with "◯", the product with a certain cleaning effect was marked with "△", and the product with no cleaning effect was marked with "×".

[0100] [Table 1]

[0101] The above experimental results confirmed that the cleaning agent containing the surfactant has a cleaning effect on polished SiC wafers.

[0102] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. 1. A method for polishing and cleaning a substrate made of a material having a Vickers hardness of 1500 Hv or more, comprising: polishing a substrate with the polishing composition; cleaning the polished substrate with a cleaning agent; Including, where: the polishing composition contains a grinding aid; The cleaning agent contains an anionic surfactant as a surfactant, The anionic surfactant is a compound having an oxyalkylene unit and a hydrocarbon group, and the hydrocarbon group has 8 or more carbon atoms.

2. The method of claim 1 , wherein the concentration of the surfactant in the cleaning agent is 1% by weight or more.

3. The method of claim 1 or 2, wherein the cleaning agent further comprises water.

4. The method of any one of claims 1 to 3, wherein the polishing composition comprises non-diamond abrasive grains.

5. The method according to claim 1 , wherein the substrate made of a material having a Vickers hardness of 1500 Hv or more is a silicon carbide substrate.

6. A cleaning agent for use in the method according to any one of claims 1 to 5, The surfactant contains an anionic surfactant, A cleaning agent, wherein the anionic surfactant is a compound having an oxyalkylene unit and a hydrocarbon group, and the hydrocarbon group has 8 or more carbon atoms.

7. A polishing and cleaning set for use in the method according to any one of claims 1 to 5, a polishing composition and a cleaning agent, The polishing composition contains non-diamond abrasive grains and / or grinding aids, The cleaning agent contains an anionic surfactant as a surfactant, The polishing and cleaning set, wherein the anionic surfactant is a compound having an oxyalkylene unit and a hydrocarbon group, and the hydrocarbon group has 8 or more carbon atoms.

8. 1. A method for cleaning a silicon carbide substrate after polishing with a non-diamond abrasive and / or grinding aid, comprising: cleaning the silicon carbide substrate with a cleaning agent; The cleaning agent contains an anionic surfactant as a surfactant, A cleaning method, wherein the anionic surfactant is a compound having an oxyalkylene unit and a hydrocarbon group, and the hydrocarbon group has 8 or more carbon atoms.

9. A cleaning agent used to clean silicon carbide substrates after polishing with non-diamond abrasive grains and / or grinding aids, comprising: The surfactant contains an anionic surfactant, A cleaning agent, wherein the anionic surfactant is a compound having an oxyalkylene unit and a hydrocarbon group, and the hydrocarbon group has 8 or more carbon atoms.

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