Polishing composition and polishing method

Abstract

The purpose of the present invention is to provide a polishing composition capable of achieving an excellent polishing removal rate. A polishing composition containing a permanganate and an oxyzirconium salt is provided. In the polishing composition, the oxyzirconium salt has a ratio N / c, indicating the molar concentration molar concentration N of an acid and the molar concentration c of zirconium measured with respect to an aqueous solution of the oxyzirconium salt, of greater than 1.8.

Description

Polishing composition and polishing method

[0001] The present invention relates to an abrasive composition and a polishing method. This application claims priority to Japanese Patent Application No. 2024-167888, filed on 26 September 2024, the entire contents of which are incorporated herein by reference.

[0002] Polishing is performed on the surfaces of materials such as metals, metalloids, nonmetals, and their oxides using polishing compositions. For example, surfaces composed of compound semiconductor materials such as silicon carbide, boron carbide, tungsten carbide, silicon nitride, titanium nitride, and gallium nitride are processed by polishing (lapping) performed by supplying diamond abrasive grains between the surface and the polishing platen. However, lapping using diamond abrasive grains is prone to defects and distortions due to the occurrence and retention of scratches and dents. Therefore, polishing using a polishing pad and polishing composition is being considered after, or as an alternative to, lapping with diamond abrasive grains. Patent document 1 is an example of a document disclosing this type of prior art.

[0003] U.S. Patent Application Publication No. 2021 / 0238448

[0004] Generally, from the standpoint of manufacturing efficiency and cost-effectiveness, a sufficiently high polishing removal rate is desirable for practical purposes. For example, in polishing surfaces made of high-hardness materials such as silicon carbide, an improvement in the polishing removal rate is strongly desired. To address this issue, polishing compositions containing strong oxidizing agents such as permanganates have been conventionally used. For example, Patent Document 1 describes that a polishing slurry containing potassium permanganate and zirconium oxynitrate and / or zirconium oxyhydrochloride improves the material removal rate (MRR) of silicon carbide wafers.

[0005] In polishing various objects to be polished, including substrates made of high-hardness materials such as silicon carbide, it would be practically significant to be able to achieve an even higher level of polishing removal speed. The inventors of this invention have conducted a detailed analysis of oxyzirconium salts used together with permanganate salts and have found that an oxyzirconium salt having certain characteristics can achieve a higher polishing removal speed, thus completing the present invention. That is, the present invention relates to the improvement of a polishing composition containing permanganate salt and oxyzirconium salt, and aims to provide a polishing composition that can achieve an excellent polishing removal speed. Another related objective is to provide a method for polishing objects using such a polishing composition.

[0006] This specification provides an abrasive composition comprising a permanganate and an oxyzirconium salt. In this abrasive composition, the oxyzirconium salt has a molar concentration c of zirconium measured in an aqueous solution of the oxyzirconium salt, with a ratio N / c of ​​the molar concentration N of the acid being greater than 1.8. Using an oxyzirconium salt with an N / c greater than 1.8 allows for a superior abrasive removal rate compared to using an oxyzirconium salt with an N / c of ​​1.8 or less.

[0007] In some embodiments, the oxyzirconium salt is at least one selected from the group consisting of zirconium oxynitrate, zirconium oxysulfate, and zirconium oxychloride. By using the above oxyzirconium salt, a high polishing removal rate can be preferably achieved.

[0008] In some embodiments, the polishing composition further comprises abrasive grains. A polishing composition containing abrasive grains can achieve a high polishing removal rate based on the polishing action of the abrasive grains. Silica is preferably used as the abrasive grain. Silica abrasive grains can preferably achieve both a high polishing removal rate and good surface finish.

[0009] The polishing compositions disclosed herein are used, for example, for polishing materials with a Vickers hardness of 1500 Hv or higher. In polishing such high-hardness materials, the effects of the techniques disclosed herein can be preferably demonstrated. In some embodiments, the material with a Vickers hardness of 1500 Hv or higher is a non-oxide (i.e., a compound that is not an oxide). In polishing a non-oxide material to be polished, the polishing removal rate by the polishing compositions disclosed herein can be preferably achieved.

[0010] The polishing compositions disclosed herein can be used, for example, for polishing silicon carbide. In polishing silicon carbide, the effects of the techniques disclosed herein can be favorably exhibited.

[0011] This specification further provides a polishing method comprising the step of polishing an object to be polished using any of the polishing compositions disclosed herein. Such a polishing method makes it possible to achieve a high polishing removal rate even when polishing an object to be polished made of a high-hardness material. This makes it possible to increase the productivity of the target product (polished material, for example, a compound semiconductor substrate such as a silicon carbide substrate) obtained through polishing by the above polishing method.

[0012] Preferred embodiments of the present invention will be described below. Matters other than those specifically mentioned herein that are necessary for carrying out the present invention can be understood as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed herein and common technical knowledge in the art.

[0013] <Polishing Composition> (Permanganate) The polishing composition disclosed herein contains a permanganate. In polishing materials to be polished (e.g., high-hardness non-oxide materials such as silicon carbide), the permanganate typically functions as an oxidizing agent, thereby improving the polishing removal rate. As the permanganate, alkali metal permanganates such as sodium permanganate and potassium permanganate are preferred, with potassium permanganate being particularly preferred. In some embodiments, the proportion of potassium permanganate in the total permanganate may be approximately 10% by weight or more, approximately 30% by weight or more, approximately 50% by weight or more (e.g., more than 50% by weight), approximately 70% by weight or more, approximately 90% by weight or more, or 99-100% by weight. One type of permanganate can be used alone or in combination of two or more types. The permanganate may exist in an ionic state in the polishing composition.

[0014] The permanganate content in any of the polishing compositions disclosed herein is not particularly limited and can be appropriately set to achieve the desired effect depending on the purpose and manner of use of the polishing composition. In some embodiments, from the viewpoint of improving the polishing removal rate, the permanganate content is suitable to be approximately 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, even more preferably 2% by weight or more, even more preferably 3% by weight or more, and may be 3.5% by weight or more. Also in some embodiments, from the viewpoint of surface quality after polishing, the permanganate content in the polishing composition is suitable to be approximately 30% by weight or less, may be 20% by weight or less, or 15% by weight or less. In some other embodiments, the permanganate content may be less than 12% by weight, may be 10% by weight or less (e.g., less than 10% by weight), may be 8% by weight or less, may be 6% by weight or less, or may be 5% by weight or less. Embodiments with a content of less than 12% by weight are suitable, for example, when potassium permanganate is used. By limiting the amount of permanganate used, it is possible to sufficiently dissolve the permanganate in the polishing composition and achieve a high polishing removal rate.

[0015] (Oxyzirconium Salt) The polishing compositions disclosed herein contain oxyzirconium salts. Here, an oxyzirconium salt refers to a salt containing oxyzirconium (ZrO), and more specifically, a salt of a cation composed of ZrO and an anion. Such oxy transition metal cations are thought to easily suppress the performance degradation of the polishing composition containing them over time, thereby contributing to an improvement in the polishing removal rate. Oxyzirconium salts can be used individually or in combination of two or more. Oxyzirconium salts can typically exist in the polishing composition dissolved in a solvent such as water.

[0016] Furthermore, the oxyzirconium salt added to the polishing composition is characterized by having a ratio N / c of ​​the molar concentration c of zirconium to the molar concentration N of the acid, measured in an aqueous solution of the oxyzirconium salt, which is greater than 1.8. An oxyzirconium salt with an N / c greater than 1.8 can achieve an excellent polishing removal rate. It is thought that the oxyzirconium salt having the above characteristics better promotes oxidation of the surface of the object to be polished. However, the above considerations do not limit the scope of the present invention. The above N / c may be 1.9 or greater, 2.0 or greater (for example, greater than 2.0), 2.1 or greater, or 2.2 or greater. Also, the upper limit of the above N / c may be, for example, 2.8 or less, 2.6 or less, or 2.5 or less.

[0017] The above N / c ratio of the oxyzirconium salt can be specifically determined by the method described in the examples below. For oxyzirconium salts with an N / c ratio greater than 1.8, the N / c ratio can be measured for oxyzirconium salts obtained by known or conventional methods, and those with an N / c ratio greater than 1.8 can be selected and used. The above N / c ratio of the oxyzirconium salt can be adjusted by the synthesis conditions.

[0018] The type of salt in the oxyzirconium salt is not particularly limited and may be an inorganic salt or an organic salt. Although not particularly limited, the use of hydrohalogen acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, or inorganic salts such as nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid is preferred. Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid are more preferred, and salts of hydrochloric acid and nitric acid are particularly preferred. In some preferred embodiments, the oxyzirconium salt is an oxyzirconium cation and a nitrate ion (NO2). ３ － ), sulfate ions (SO ４ ２－ ) or chloride ions (Cl － This can preferably be carried out in a manner using a salt of ) . Specific examples of such oxyzirconium salts include zirconium oxynitrate, zirconium oxysulfate, and zirconium oxychloride.

[0019] The concentration (content) of the oxyzirconium salt in the polishing composition is not particularly limited and can be appropriately set to achieve the desired effect depending on the purpose and manner of use of the polishing composition. The concentration of the oxyzirconium salt in the polishing composition may be, for example, 0.001% by weight or more, and from the viewpoint of appropriately exhibiting the effect of using the oxyzirconium salt, it is advantageous to set it to 0.01% by weight or more, preferably 0.05% by weight or more, may be 0.1% by weight or more, may be 0.2% by weight or more, may be 0.3% by weight or more, may be 0.4% by weight or more, and may be 0.5% by weight or more. Furthermore, the upper limit of the concentration of the oxyzirconium salt may be, for example, approximately 20% by weight or less, may be 10% by weight or less, and may be 5% by weight or less. In some embodiments, the concentration of the oxyzirconium salt is appropriate to be 3% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less, and may be 0.8% by weight or less. By appropriately setting the amount of oxyzirconium salt used within the above range, the polishing removal rate improvement effect of the technology disclosed herein can be favorably achieved.

[0020] The ratio (W2 / W1) of the concentration W2 [weight%] of the oxyzirconium salt in the polishing composition to the content W1 [weight%] of the permanganate is greater than 0, may be 0.001 or greater, 0.005 or greater, or 0.01 or greater. From the viewpoint of better exhibiting the effect of including the oxyzirconium salt in the polishing composition containing the permanganate, in some embodiments, the ratio (W2 / W1) may be, for example, 0.05 or greater, 0.08 or greater, 0.10 or greater, 0.12 or greater, or 0.15 or greater. The upper limit of the ratio (W2 / W1) is not particularly limited, but it is appropriate to be approximately 30 or less, preferably 10 or less, and more preferably 5 or less. In some preferred embodiments, the ratio (W2 / W1) may be 1 or less, 0.5 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0021] (Abrasive grains) The polishing compositions disclosed herein may or may not contain abrasive grains. In some embodiments, the polishing compositions contain abrasive grains. With polishing compositions containing abrasive grains, a higher polishing rate can be achieved by providing a primarily mechanical polishing action by the abrasive grains in addition to the primarily chemical polishing action by permanganate salts and oxyzirconium salts.

[0022] The material and properties of the abrasive grains are not particularly limited. For example, the abrasive grains may be inorganic particles, organic particles, or organic-inorganic composite particles. Examples 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; diamond particles; carbonates such as calcium carbonate and barium carbonate; and abrasive grains substantially composed of any of these. The abrasive grains may be used individually or in combination of two or more types. 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. Among these, silica particles, alumina particles, zirconium oxide particles, chromium oxide particles, and iron oxide particles are more preferred, and silica particles and alumina particles are particularly preferred.

[0023] In this specification, "substantially consisting of X" or "substantially composed of X" means that the proportion of X in the abrasive grains (purity of X) is 90% or more by weight. Furthermore, the proportion of X in the abrasive grains is preferably 95% or more, more preferably 97% or more, even more preferably 98% or more, and for example, 99% or more.

[0024] The average primary particle diameter of the abrasive grains is not particularly limited. For example, the average primary particle diameter of the abrasive grains can be 5 nm or more, 10 nm or more is appropriate, preferably 20 nm or more, and may also be 30 nm or more. In some embodiments, the average primary particle diameter of the abrasive grains may be 50 nm or more, 80 nm or more, 150 nm or more, 250 nm or more, or 350 nm or more. From the viewpoint of improving the polishing removal speed, a larger average primary particle diameter of the abrasive grains is preferable. Also, from the viewpoint of surface quality after polishing, the average primary particle diameter of the abrasive grains can be, for example, 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less, and may also be 750 nm or less or 500 nm or less. From the viewpoint of obtaining better surface quality, in some embodiments, the average primary particle diameter of the abrasive grains may be 350 nm or less, 300 nm or less, 180 nm or less, 150 nm or less, 85 nm or less, or 50 nm or less.

[0025] In this specification, the average primary particle diameter is calculated by the following formula, derived from the specific surface area (BET value) measured by the BET method: Average primary particle diameter (nm) = 6000 / (True density (g / cm³) ３ ) × BET value (m ２ This refers to the particle diameter (BET particle diameter) calculated by the formula ( / g). The specific surface area can be measured, for example, using a surface area measuring device manufactured by Micromeritex, Inc., product name "Flow Sorb II 2300".

[0026] The average secondary particle diameter of the abrasive grains may be, for example, 10 nm or more, preferably 50 nm or more, more preferably 100 nm or more, and may also be 250 nm or more, or 400 nm or more, from the viewpoint of easily increasing the polishing removal rate. The upper limit of the average secondary particle diameter of the abrasive grains is appropriately set to approximately 10 μm or less from the viewpoint of ensuring a sufficient number of particles per unit weight. Furthermore, from the viewpoint of surface quality after polishing, the above average secondary particle diameter is preferably 5 μm or less, more preferably 3 μm or less, for example 1 μm or less. From the viewpoint of obtaining even better surface quality, in some embodiments, the average secondary particle diameter of the abrasive grains may be 600 nm or less, 300 nm or less, 170 nm or less, or 100 nm or less.

[0027] For particles smaller than 500 nm, the average secondary particle diameter of abrasive grains can be measured as the volume-average particle diameter (volume-based arithmetic mean diameter; Mv) using dynamic light scattering, for example, with a Nikkiso Co., Ltd. model "UPA-UT151". For particles larger than 500 nm, the volume-average particle diameter can be measured using methods such as the pore electrical resistance method with a Beckman Coulter model "Multisizer 3".

[0028] When using alumina particles (alumina abrasive grains) as abrasive grains, various known alumina particles can be appropriately selected and used. Examples of such known alumina particles include α-alumina and intermediate alumina. Here, intermediate alumina is a general term for alumina particles other than α-alumina, and specifically, examples include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, χ-alumina, etc. In addition, alumina called fumed alumina (typically alumina fine particles produced when alumina salt is calcined at high temperature) based on the manufacturing method may be used. Furthermore, alumina called colloidal alumina or alumina sol (for example, alumina hydrate such as boehmite) is also included in the examples of known alumina particles. From the viewpoint of processability, it is preferable to include α-alumina. The alumina abrasive grains in the technology disclosed herein may contain one type of such alumina particle alone or a combination of two or more types.

[0029] When using alumina particles as abrasive grains, it is generally advantageous for the proportion of alumina particles to the total amount of abrasive grains used to be higher. For example, the proportion of alumina particles to the total amount of abrasive grains is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more, and may even be substantially 100% by weight.

[0030] The particle size of the alumina abrasive grains is not particularly limited and can be selected to achieve the desired polishing effect. From the viewpoint of improving the polishing removal speed, the average primary particle diameter of the alumina abrasive grains is preferably 50 nm or more, more preferably 80 nm or more, and may also be 150 nm or more, 250 nm or more, 300 nm or more, or 350 nm or more. The upper limit of the average primary particle diameter of the alumina abrasive grains is not particularly limited, but from the viewpoint of surface quality after polishing, it is appropriate to be approximately 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less, and may also be 750 nm or less, 500 nm or less, 400 nm or less, or 350 nm or less.

[0031] When alumina particles are used as abrasive grains, the polishing compositions disclosed herein may further contain abrasive grains made of materials other than alumina (hereinafter also referred to as non-alumina abrasive grains), to the extent that they do not impair the effects of the present invention. Examples of such non-alumina abrasive grains include oxide particles such as silica particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide 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; diamond particles; and abrasive grains substantially composed of carbonates such as calcium carbonate and barium carbonate.

[0032] The content of the non-alumina abrasive grains is appropriately set to, for example, 30% by weight or less of the total weight of abrasive grains contained in the polishing composition, preferably 20% by weight or less, and more preferably 10% by weight or less.

[0033] In some preferred embodiments, the polishing composition contains silica particles (silica abrasive grains) as abrasive grains. The silica abrasive grains can be appropriately selected from various known silica particles. Examples of such known silica particles include colloidal silica and dry-processed silica. Among these, the use of colloidal silica is preferred. With silica abrasive grains containing colloidal silica, good surface accuracy can be suitably achieved.

[0034] When using silica abrasive grains, a higher proportion of silica abrasive grains to the total abrasive grains used is generally advantageous. For example, the proportion of silica abrasive grains to the total abrasive grains is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more, and may be substantially 100% by weight. In an abrasive composition that substantially does not contain abrasive grains other than silica abrasive grains, for example, if it substantially does not contain abrasive grains with a higher hardness than silica abrasive grains (e.g., alumina particles, zirconium oxide particles, chromium oxide particles), scratches and dents on the polished surface caused by the inclusion of such high-hardness abrasive grains are less likely to occur, and a better surface accuracy can be suitably achieved. Note that substantially not containing abrasive grains other than silica abrasive grains means that the proportion of abrasive grains other than silica abrasive grains in the total weight of abrasive grains contained in the abrasive composition is 1% by weight or less, for example 0.5% by weight or less, and even more preferably 0.1% by weight or less, and includes the case where the proportion of abrasive grains other than silica abrasive grains is 0% by weight.

[0035] The shape (outer form) of silica abrasive grains may be spherical or non-spherical. For example, specific examples of non-spherical silica abrasive grains include peanut shape (i.e., the shape of a peanut shell), cocoon shape, konpeito shape, rugby ball shape, etc. In the technology disclosed herein, silica abrasive grains may be in the form of primary particles or in the form of secondary particles formed by the association of multiple primary particles. Furthermore, silica abrasive grains in the form of primary particles and silica abrasive grains in the form of secondary particles may be mixed. In one preferred embodiment, at least some of the silica abrasive grains are included in the polishing composition in the form of secondary particles.

[0036] As the silica abrasive grains, those having an average primary particle diameter larger than 5 nm can be preferably adopted. From the viewpoint of polishing efficiency and the like, the average primary particle diameter of the silica abrasive grains is preferably 15 nm or more, more preferably 20 nm or more, still more preferably 25 nm or more, and particularly preferably 30 nm or more. The upper limit of the average primary particle diameter of the silica abrasive grains is not particularly limited, but it is appropriate to make it generally 120 nm or less, preferably 100 nm or less, and more preferably 85 nm or less. For example, from the viewpoint of achieving both higher polishing efficiency and surface quality, silica abrasive grains having an average primary particle diameter of 12 nm or more and 80 nm or less are preferable, and silica abrasive grains having an average primary particle diameter of 15 nm or more and 75 nm or less are preferable.

[0037] The average secondary particle diameter of the silica abrasive grains is not particularly limited, but from the viewpoint of polishing efficiency and the like, it is preferably 20 nm or more, more preferably 5 nm or more, and still more preferably 70 nm or more. Also, from the viewpoint of obtaining a higher-quality surface, the average secondary particle diameter of the silica abrasive grains is appropriately 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less, still more preferably 130 nm or less, and particularly preferably 110 nm or less (for example, 100 nm or less).

[0038] The true specific gravity (true density) of the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and still more preferably 1.7 or more. With an increase in the true specific gravity of the silica particles, the physical polishing ability tends to increase. The upper limit of the true specific gravity of the silica particles is not particularly limited, but typically it is 2.3 or less, for example, 2.2 or less, 2.0 or less, 1.9 or less. As the true specific gravity of the silica particles, a measured value by the liquid displacement method using ethanol as the displacement liquid can be adopted.

[0039] The shape (outer shape) of the silica particles is preferably spherical. Although not particularly limited, the average value (average aspect ratio) of the major axis / minor axis ratio of the particles is theoretically 1.00 or more, and from the viewpoint of improving the polishing removal rate, for example, it may be 1.05 or more, or 1.10 or more. Also, the average aspect ratio of the particles is suitably 3.0 or less, and may be 2.0 or less. From the viewpoints of improving the smoothness of the polished surface and reducing scratches, the average aspect ratio of the particles is preferably 1.50 or less, and may be 1.30 or less, or 1.20 or less.

[0040] The shape (outer shape) and average aspect ratio of the particles can be grasped, for example, by electron microscope observation. As a specific procedure for grasping the average aspect ratio, for example, using a scanning electron microscope (SEM), the shapes of a predetermined number (for example, 200) of particles are extracted. Draw the smallest rectangle that circumscribes the shape of each of the extracted particles. Then, for the rectangle drawn for the shape of each particle, the value obtained by dividing the length of the long side (value of the major axis) by the length of the short side (value of the minor axis) is calculated as the major axis / minor axis ratio (aspect ratio). The average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the above-mentioned predetermined number of particles.

[0041] In an embodiment where the polishing composition contains silica abrasive grains, the polishing composition may further contain abrasive grains made of a material other than silica (hereinafter also referred to as non-silica abrasive grains). Examples of the particles constituting such non-silica abrasive grains include oxide particles such as alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide particles, zinc oxide particles, iron oxide particles; nitride particles such as silicon nitride particles, boron nitride particles; carbide particles such as silicon carbide particles, boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; and particles substantially composed of any of these.

[0042] In an embodiment using silica abrasive grains, the content of non-silica abrasive grains in the total weight of the abrasive grains contained in the polishing composition may be, for example, 30% by weight or less, 20% by weight or less, or 10% by weight or less.

[0043] The content of abrasive grains (e.g., silica abrasive grains) in the polishing compositions disclosed herein is not particularly limited and can be appropriately set to achieve the desired effect depending on the purpose and manner of use of the polishing composition. The content of abrasive grains may be, for example, less than 5% by weight, less than 3% by weight, or less than 2% by weight. In some embodiments, the content of abrasive grains in the polishing composition is preferably less than 1% by weight, more preferably less than 0.5% by weight, more preferably 0.4% by weight or less, may be 0.3% by weight or less, or 0.2% by weight or less. In some embodiments, the content of abrasive grains in the polishing composition may be 0.1% by weight or less or less, 0.05% by weight or less or less, 0.04% by weight or less or less, or 0.03% by weight or less or less. The lower limit of the abrasive content is not particularly limited and may be, for example, 0.000001% by weight or more (i.e., 0.01 ppm or more). From the viewpoint of enhancing the effectiveness of using abrasive grains, in some embodiments, the abrasive content in the polishing composition may be 0.00001% by weight or more, 0.0001% by weight or more, 0.001% by weight or more, 0.002% by weight or more, or 0.005% by weight or more. In some preferred embodiments, the abrasive content in the polishing composition may be 0.01% by weight or more, 0.02% by weight or more, 0.03% by weight or more, 0.05% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or 0.8% by weight or more. When the polishing composition disclosed herein contains multiple types of abrasive grains, the abrasive content in the polishing composition refers to the total content of the above multiple types of abrasive grains.

[0044] The polishing compositions disclosed herein preferably contain substantially no diamond particles. Diamond particles have high hardness and can be a limiting factor in improving smoothness. Furthermore, since diamond particles are generally expensive, they are not a cost-effective material, and from a practical standpoint, the degree of reliance on high-priced materials such as diamond particles may be low. Here, "substantially containing no diamond particles" means that the proportion of diamond particles in the total particles is 1% by weight or less, more preferably 0.5% by weight or less, and typically 0.1% by weight or less, and includes the case where the proportion of diamond particles is 0% by weight. In such embodiments, the effects of the present invention can be suitably demonstrated.

[0045] In embodiments of the polishing composition containing abrasive grains, the relationship between the abrasive grain content and the permanganate content is not particularly limited and can be appropriately set to achieve the desired effect depending on the purpose and manner of use. The ratio of the permanganate content W1 [weight%] to the abrasive grain content Wa [weight%] (W1 / Wa) can be, for example, approximately 0.01 or more, preferably 0.1 or more, and may also be 1 or more. As the ratio (W1 / Wa) increases, the contribution of chemical polishing tends to increase relative to the contribution of mechanical polishing. In some embodiments, the ratio (W1 / Wa) is preferably 5 or more, may be 10 or more, may be 20 or more, and may also be 30 or more. There is no particular upper limit to the ratio (W1 / Wa), but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 5000 or less, 1500 or less, 1000 or less, 800 or less, 400 or less, 250 or less, 100 or less, 80 or less, or 50 or less. In some embodiments, the ratio (W1 / Wa) can be 30 or less, 20 or less, or 10 or less.

[0046] In embodiments of the polishing composition containing abrasive grains, the relationship between the abrasive grain content and the oxyzirconium salt concentration is not particularly limited and can be appropriately set to achieve the desired effect depending on the purpose and manner of use. The ratio of the concentration of the oxyzirconium salt W2 [weight%] to the abrasive grain content Wa [weight%] (W2 / Wa) is appropriately set to 0.001 or higher, preferably 0.01 or higher, more preferably 0.1 or higher, and may also be 0.5 or higher. As the ratio (W2 / Wa) increases, the contribution of chemical polishing tends to increase relative to the contribution of mechanical polishing. In some embodiments, the ratio (W2 / Wa) may be 1.0 or higher, 2.0 or higher, 3.0 or higher, 4.0 or higher, 5 or higher, or 10 or higher. There is no particular upper limit to the ratio (W2 / Wa), but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 500 or less, 1000 or less, 50 or less, 25 or less, or 10 or less. In some embodiments, the ratio (W2 / Wa) may be 5 or less, 3 or less, 2 or less, or 1 or less.

[0047] (Water) The polishing compositions disclosed herein typically contain water. Deionized water, pure water, ultrapure water, distilled water, etc., can be preferably used as the water. The polishing compositions disclosed herein may further contain, if necessary, an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water. Typically, 90% by volume or more of the solvent in the polishing composition is water, preferably 95% by volume or more, and more preferably 99-100% by volume.

[0048] (Acid) The polishing composition may contain an acid as needed for purposes such as pH adjustment or improving the polishing removal rate. Both inorganic and organic acids can be used. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of organic acids include aliphatic carboxylic acids such as formic acid, acetic acid, and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acid, and organic phosphonic acid. These can be used individually or in combination of two or more. When using an acid, the amount used is not particularly limited and can be adjusted according to the purpose of use (e.g., pH adjustment). Alternatively, some embodiments of the polishing composition disclosed herein may have a composition that is substantially free of acid.

[0049] (Basic Compounds) The polishing composition may contain basic compounds as needed for purposes such as pH adjustment or improving the polishing removal rate. Here, a basic compound refers to a compound that, when added to the polishing composition, has the function of increasing the pH of the composition. Examples of basic compounds include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates and bicarbonates such as ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate; ammonia; quaternary ammonium compounds, such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; and others such as amines, phosphates, hydrogen phosphates, and organic acid salts. Basic compounds can be used individually or in combination of two or more. When using basic compounds, the amount used is not particularly limited and can be adjusted according to the purpose of use (e.g., pH adjustment). Alternatively, some embodiments of the polishing compositions disclosed herein may have a composition that substantially does not contain basic compounds.

[0050] (Optional Oxidizing Agents) The polishing compositions disclosed herein may contain oxidizing agents other than permanganates, to the extent that they do not impair the effects of the present invention. Examples of compounds that may be selected as oxidizing agents other than permanganates include peroxides such as hydrogen peroxide, periodic acids, iodic acids, bromic acids, iron acids, chromic acids and dichromates, vanadic acids, ruthenic acids, molybdic acids, perrhenic acids, tungstic acids, persulfates, chloric acids and perchloric acids, osmium acids, selenic acids, cerium ammonium nitrate, and the like. Oxidizing agents other than permanganates may be used individually or in combination of two or more.

[0051] The content of oxidizing agents other than permanganate in the polishing composition is, for example, less than 100% by weight, less than 50% by weight, less than 30% by weight, less than 10% by weight, less than 3% by weight, or less than 1% by weight, when the content of permanganate is taken as 100% by weight. The techniques disclosed herein can preferably be carried out using polishing compositions that do not contain oxidizing agents other than permanganate.

[0052] (Optional Salts) The polishing compositions disclosed herein may contain various salts other than permanganates and oxyzirconium salts, as long as they do not impair the effects of the present invention. Any salt other than permanganates and oxyzirconium salts is, for example, a metal salt. Examples of such optional metal salts (e.g., alkali metal salts, alkaline earth metal salts) include chlorides such as magnesium chloride, calcium chloride, strontium chloride, and barium chloride; bromides such as magnesium bromide; fluorides such as magnesium fluoride, calcium fluoride, strontium fluoride, and barium fluoride; nitrates such as magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate; sulfates such as magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate; carbonates such as magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate; carboxylates such as calcium acetate, strontium acetate, calcium benzoate, and calcium citrate; and the like. Other examples of the above metal salts include aluminum salts such as aluminum hydrochloride, aluminum nitrate, and aluminum sulfate; rare earth salts such as scandium nitrate, yttrium nitrate, lanthanum nitrate, cerium nitrate, and gadolinium nitrate; indium salts; gallium salts; and so on.

[0053] (Other Components) The polishing compositions disclosed herein may further contain, as necessary, known additives that can be used in polishing compositions (for example, polishing compositions used for polishing high-hardness materials such as silicon carbide), such as chelating agents, thickeners, dispersants, surface protectants, wetting agents, surfactants, rust inhibitors, preservatives, and fungicides, to the extent that they do not impair the effects of the present invention. The content of the above additives can be appropriately set according to their purpose of addition and does not characterize the present invention, so a detailed explanation is omitted.

[0054] (pH) The pH of the polishing composition is preferably around 1 to 12. When the pH is within the above range, a practical polishing removal rate is easily achieved. In some embodiments, the above pH may be 12.0 or less, 11.0 or less, 10.0 or less, 9.0 or less, less than 9.0, 8.0 or less, less than 8.0, 7.0 or less, less than 7.0, or 6.0 or less. From the viewpoint of making it easier to exhibit the polishing removal rate improvement effect of permanganate and oxyzirconium salt, in some embodiments, the pH of the polishing composition is preferably less than 6.0, may be 5.0 or less, less than 5.0, may be 4.0 or less, or less than 4.0. The above pH may be, for example, 1.0 or higher, 1.5 or higher, 1.7 or higher, or 2.0 or higher.

[0055] <Method for preparing the polishing composition> 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 vane stirrer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited; for example, all components may be mixed at once, or they may be mixed in an order set as appropriate. For example, the polishing composition disclosed herein can be prepared by preparing a permanganate (for example, in the form of an aqueous solution) and an aqueous solution of oxyzirconium salt with an N / c ratio greater than 1.8, and mixing the permanganate and the aqueous solution of oxyzirconium salt. In such preparation, abrasive particles such as silica particles and other optional components may be mixed at an appropriate time. A pH adjusting agent may be added at an appropriate time simultaneously with or before / after the mixing of the above components for the purpose of pH adjustment, or it may not be necessary to add a pH adjusting agent.

[0056] The polishing compositions disclosed herein may be mono-component or multi-component, including two-component types. For example, the polishing composition may be configured such that part A, containing some of the components (e.g., components other than water), and part B, containing the remaining components, are mixed together for use in polishing an object. These can be stored separately before use, for example, and mixed at the time of use to prepare a one-component polishing composition. During mixing, water or other diluents may be added.

[0057] <Concentrated Solution> The polishing composition disclosed herein may be in a concentrated form (i.e., in the form of a concentrated polishing solution) before being supplied to the object to be polished. Such a concentrated form of the polishing composition is advantageous in terms of convenience and cost reduction during manufacturing, distribution, and storage. The concentration ratio is not particularly limited and can be, for example, 1.1 to 50 times in terms of volume, and is usually appropriate at about 1.5 to 40 times (for example, 2 to 30 times). Such a concentrated solution can be used by diluting it at a desired timing to prepare a polishing solution (working slurry) and supplying the polishing solution to the substrate. The above dilution can be performed, for example, by adding water to the concentrated solution and mixing it.

[0058] <Objects to be Polished> The objects to be polished with the polishing compositions disclosed herein are not particularly limited. For example, the polishing compositions disclosed herein can be applied to polishing substrates having a surface made of compound semiconductor material, i.e., compound semiconductor substrates. The constituent materials of the compound semiconductor substrate are not particularly limited and may include, for example, II-VI compound semiconductors such as cadmium telluride, zinc selenide, cadmium sulfide, cadmium mercury telluride, zinc cadmium telluride; III-V compound semiconductors such as gallium nitride, gallium arsenide, gallium phosphide, indium phosphide, aluminum gallium arsenide, indium gallium arsenide, indium nitrogen gallium arsenide, and aluminum gallium phosphide; IV-IV compound semiconductors such as silicon carbide (SiC) and germanium silicide; and so on. These materials may be conductive with impurities doped, or insulating or semi-insulating without impurities doped. The object to be polished may be composed of a plurality of these materials. In a preferred embodiment, the polishing composition disclosed herein may be applied to polishing a substrate having a surface composed of a non-oxide (i.e., non-oxide) chemical semiconductor material. In polishing a substrate having a surface composed of a non-oxide chemical semiconductor material, the polishing-promoting effect of the oxidizing agent (typically a permanganate) contained in the polishing composition disclosed herein is readily exhibited.

[0059] The polishing compositions disclosed herein can be preferably used, for example, for polishing the surface of an object to be polished having a Vickers hardness of 500 Hv or more. The Vickers hardness is preferably 700 Hv or more, for example, 1000 Hv or more, or 1500 Hv or more. The Vickers hardness of the material to be polished may be 1800 Hv or more, 2000 Hv or more, or 2200 Hv or more. The upper limit of the Vickers hardness of the surface of the object to be polished is not particularly limited, and may be approximately 7000 Hv or less, 5000 Hv or less, or 3000 Hv or less. In this specification, Vickers hardness can be measured in accordance with JIS R 1610:2003. The international standard corresponding to the above JIS standard is ISO 14705:2000.

[0060] Materials having a Vickers hardness of 1500 Hv or higher include silicon carbide, silicon nitride, titanium nitride, and gallium nitride. The object to be polished in the technology disclosed herein may have a single-crystal surface of the above material that is mechanically and chemically stable. In particular, the surface of the object to be polished is preferably composed of either silicon carbide or gallium nitride, and more preferably of silicon carbide. Silicon carbide is expected to be a compound semiconductor substrate material with low power loss and excellent heat resistance, and the practical advantage of improving productivity by improving the polishing removal speed is particularly great. The technology disclosed herein can be particularly preferably applied to the polishing of a single-crystal surface of silicon carbide.

[0061] <Polishing Method> The polishing compositions disclosed herein can be used to polish an object to be polished in a manner that includes, for example, the following operations: a polishing solution (slurry) is prepared using any of the polishing compositions disclosed herein. Preparing the polishing solution may include adjusting the concentration (e.g., dilution) or pH of the polishing composition to prepare the polishing solution. Alternatively, the polishing composition may be used as is as the polishing solution. In the case of a multi-component polishing composition, preparing the polishing solution may include mixing the agents, diluting one or more agents before mixing, or diluting the mixture after mixing. The polishing solution is then supplied to the object to be polished and polished in a manner that is common to those skilled in the art. For example, the object to be polished is set in a general polishing apparatus, and the polishing solution is supplied to the surface of the object to be polished through the polishing pad of the apparatus. Typically, the polishing solution is supplied continuously, while the polishing pad is pressed against the surface of the object to be polished and the two are moved relative to each other (e.g., rotated). Polishing of the object to be polished is completed through this polishing process.

[0062] Furthermore, the above-mentioned content and content ratio for each component that may be included in the polishing composition in the technology disclosed herein typically refers to the content and content ratio in the polishing composition when actually supplied to the object to be polished (i.e., at the point of use), and therefore can be interpreted as the content and content ratio in the polishing solution.

[0063] This specification provides a polishing method for polishing an object to be polished (typically, a material to be polished) and a method for manufacturing a polished object using the polishing method. The polishing method is characterized by including a step of polishing the object to be polished using the polishing composition disclosed herein. A polishing method according to a preferred embodiment includes a step of performing pre-polishing (pre-polishing step) and a step of performing finish polishing (finish polishing step). In a typical embodiment, the pre-polishing step is a polishing step that is placed immediately before the finish polishing step. The pre-polishing step may be a single polishing step or a multi-step polishing step of two or more steps. The finish polishing step, as used herein, is a step of performing finish polishing on the object to be polished that has been pre-polished, and is the last (i.e., furthest downstream) polishing step among the polishing steps that are performed using a polishing slurry containing abrasive particles. In a polishing method including a pre-polishing step and a finish polishing step, the polishing composition disclosed herein may be used in the pre-polishing step, in the finish polishing step, or in both the pre-polishing step and the finish polishing step.

[0064] Pre-polishing and finish polishing are applicable to both single-sided and double-sided polishing. In a single-sided polishing device, the object to be polished is attached to a ceramic plate with wax, or held using a holder called a carrier. Polishing is performed by supplying a polishing composition and pressing a polishing pad against one side of the object, then moving the two relative to each other. This movement is, for example, rotational movement. In a double-sided polishing device, the object to be polished is held using a holder called a carrier. Polishing composition is supplied from above, and polishing pads are pressed against opposing sides of the object. Both sides of the object are polished simultaneously by rotating them in relative directions.

[0065] The polishing conditions described above are not limited to specific conditions, as they are appropriately set based on the type of material to be polished, the target surface properties (specifically smoothness), the polishing removal rate, etc. For example, regarding the processing pressure, the polishing composition disclosed herein can be used in a wide pressure range of, for example, 10 kPa to 150 kPa. From the viewpoint of improving the polishing removal rate, in some embodiments, the processing pressure may be, for example, 20 kPa or more, 30 kPa or more, or 40 kPa or more, and may also be 100 kPa or less, 80 kPa or less, or 60 kPa or less. The polishing composition disclosed herein can also be preferably used for polishing at processing conditions of, for example, 30 kPa or more or higher, and the productivity of the target product (polished product) obtained through such polishing can be increased. Note that the processing pressure as used herein is synonymous with polishing pressure.

[0066] The polishing pads used in each polishing step disclosed herein are not particularly limited. For example, nonwoven fabric type, suede type, or rigid foamed polyurethane type may be used. In some embodiments, a rigid foamed polyurethane type polishing pad may be preferred. The polishing pads used in the technologies disclosed herein are polishing pads that do not contain abrasive particles.

[0067] Workpieces polished by the methods disclosed herein are typically cleaned after polishing. This cleaning can be carried out using a suitable cleaning solution. The cleaning solution used is not particularly limited, and known and conventional solutions can be appropriately selected and used.

[0068] The polishing method disclosed herein may include any other steps in addition to the pre-polishing and finish-polishing steps described above. Such steps include mechanical polishing and lapping steps performed before the pre-polishing step. The mechanical polishing step involves polishing the workpiece using a solution in which diamond abrasive particles are dispersed in a solvent. In some preferred embodiments, the dispersion does not contain an oxidizing agent. The lapping step involves polishing the workpiece by pressing the surface of a polishing plate, such as a cast iron plate, against it. Therefore, no polishing pad is used in the lapping step. The lapping step is typically performed by supplying abrasive particles between the polishing plate and the workpiece. The abrasive particles are typically diamond abrasive particles. The polishing method disclosed herein may also include additional steps before the pre-polishing step or between the pre-polishing and finish-polishing steps. Additional steps may include, for example, cleaning and polishing steps.

[0069] <Method for Manufacturing Polished Products> The technologies disclosed herein may include a method for manufacturing polished products, which includes a polishing step by any of the polishing methods described herein, and a polished product manufactured by said method. The method for manufacturing polished products is, for example, a method for manufacturing a silicon carbide substrate. That is, the technologies disclosed herein provide a method for manufacturing polished products, which includes polishing an object to be polished having a surface made of a high-hardness material by applying any of the polishing methods disclosed herein, and a polished product manufactured by said method. According to the manufacturing method, a substrate manufactured through polishing, such as a silicon carbide substrate, can be efficiently provided.

[0070] The matters disclosed in this specification include: [1] an abrasive composition comprising a permanganate and an oxyzirconium salt, wherein the oxyzirconium salt has a ratio N / c of ​​the molar concentration c of zirconium to the molar concentration N of the acid, measured in an aqueous solution of the oxyzirconium salt, greater than 1.8. [2] the abrasive composition according to [1], wherein the oxyzirconium salt is at least one selected from the group consisting of zirconium oxynitrate, zirconium oxysulfate, and zirconium oxychloride. [3] the abrasive composition according to [1] or [2], further comprising abrasive grains. [4] the abrasive composition according to [3], wherein the abrasive grains contain silica. [5] the abrasive composition according to any one of [1] to [4], used for polishing materials with a Vickers hardness of 1500 Hv or higher. [6] the abrasive composition according to any one of [1] to [5], used for polishing silicon carbide. [7] A polishing method comprising the step of polishing an object to be polished using any of the polishing compositions described in [1] to [6] above.

[0071] The following describes some embodiments of the present invention, but the present invention is not intended to be limited to those shown in these embodiments.

[0072] <Preparation of Polishing Composition> (Example 1) A polishing composition was prepared by mixing silica abrasive grains, potassium permanganate, zirconium oxynitrate A, and deionized water to a concentration of 0.1% by weight of silica abrasive grains, 4% by weight of potassium permanganate, and 0.69% by weight of zirconium oxynitrate A. The pH of the polishing composition was 2.19. Colloidal silica with an average primary particle diameter of 35 nm and an average secondary particle diameter of 70 nm was used as the silica abrasive grains.

[0073] (Comparative Example 1) A polishing composition according to this example was prepared in the same manner as in Example 1, except that zirconium oxynitrate B was used instead of zirconium oxynitrate A. The pH of the polishing composition was 1.25.

[0074] <Calculation of N / c of ​​oxyzirconium salt> Using aqueous solutions (concentration approximately 20% by weight) of zirconium oxynitrate A or B used in the examples and comparative examples as measurement samples, the molar concentration c of zirconium and the molar concentration N of the acid were measured, and N / c was determined. Specifically, the molar concentration c of zirconium was calculated by measuring the zirconium weight concentration in the measurement sample by ICP-AES (inductively coupled plasma emission spectrometry), measuring the specific gravity of the measurement sample by a hydrometer, and then using the obtained zirconium weight concentration and specific gravity and the zirconium atomic weight (91.224). For the ICP-AES measurement, an ICP emission spectrometer (model number "ICPS-8100") manufactured by Shimadzu Corporation was used. As the hydrometer, a portable densimeter (product name "DMA-35") manufactured by Anton Paar was used. Furthermore, the molar concentration N of the acid was measured by pH titration using an automatic titrator (product name "COM-A19") manufactured by HIRANUMA Corporation. The measured values ​​are shown in Table 1.

[0075]

[0076] <Polishing of the object to be polished> A SiC wafer was pre-polished using a pre-polishing composition containing alumina abrasive grains. This pre-polished SiC wafer was used as the object to be polished, and the polishing composition according to each example was used as the polishing fluid to polish the object under the following polishing conditions. [Polishing conditions] Polishing equipment: Fujikoshi Machinery Co., Ltd., model "RDP-500" Polishing pad: Nitta DuPont "IC-1000" (made of hard polyurethane) Processing pressure: 490 gf / cm ２ Plate rotation speed: 130 rpm Head rotation speed: 130 rpm Polishing fluid supply rate: 20 mL / min Polishing fluid usage method: Discard polishing time: 10 minutes Polishing object: 4-inch SiC wafer (conductive type: n-type, crystalline type 4H-SiC, off-angle of main surface (0001) relative to the C axis: 4°), 1 wafer / batch Polishing fluid temperature: 23°C

[0077] As the polishing pad, one that was subjected to brush dressing treatment for 5 minutes, then diamond dressing treatment for 3 minutes, and further brush dressing treatment for 5 minutes on the polishing surface of the pad was used. The brush dressing treatment and the diamond dressing treatment were performed before the above polishing.

[0078] <Polishing removal rate> Under the above polishing conditions, after polishing the SiC wafer using the polishing composition of each example, the polishing removal rate was calculated according to the following calculation formulas (1) and (2). (1) Polishing allowance [cm] = difference in weight [g] of the SiC wafer before and after polishing / density of SiC [g / cm ３ ] (= 3.21 g / cm ３ ) / polishing target area [cm ２ ] (= 78.54 cm ２ ) (2) Polishing removal rate [nm / h] = polishing allowance [cm] × 10 ７ / polishing time (= 10 / 60) The polishing removal rate obtained in Example 1 was converted to a relative value when Comparative Example 1 was set to 100 and shown in Table 2.

[0079]

[0080] As shown in Table 2, according to the polishing composition according to Example 1 containing permanganate and zirconium oxynitrate, and using zirconium oxynitrate A with N / c of 2.3 as the zirconium oxynitrate, a significantly higher polishing removal rate was achieved compared to Comparative Example 1 using zirconium oxynitrate B with N / c of 1.6. It is considered that the difference in the ratio N / c of the molar concentration c of zirconium measured with respect to the used zirconium oxynitrate and the molar concentration N of the acid brought about the difference in the evaluation results of the polishing removal rate.

[0081] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

Claims

1. An abrasive composition comprising a permanganate and an oxyzirconium salt, wherein the oxyzirconium salt has a ratio N / c of ​​the molar concentration c of zirconium to the molar concentration N of the acid, measured in an aqueous solution of the oxyzirconium salt, which is greater than 1.

8.

2. The polishing composition according to claim 1, wherein the oxyzirconium salt is at least one selected from the group consisting of zirconium oxynitrate, zirconium oxysulfate, and zirconium oxychloride.

3. The polishing composition according to claim 1 or 2, further comprising abrasive grains.

4. The polishing composition according to claim 3, wherein the abrasive grains contain silica.

5. The polishing composition according to claim 1 or 2, used for polishing materials with a Vickers hardness of 1500 Hv or higher.

6. The polishing composition according to claim 1 or 2, used for polishing silicon carbide.

7. A polishing method comprising the step of polishing an object to be polished using the polishing composition described in claim 1 or 2.

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