Method for polishing silicon carbide substrate and polishing composition

Abstract

The invention relates to a method for polishing a silicon carbide substrate and a polishing composition. Provided is a polishing method capable of reducing line defects on the surface of a substrate during polishing of a silicon carbide substrate. Provided is a method for polishing a silicon carbide substrate. The polishing method includes a step of supplying a polishing composition to a substrate to be polished and polishing the substrate to be polished. The polishing composition contains abrasive grains. The abrasive grains have a zeta potential X [mV] in the polishing composition. The surface of the substrate to be polished has a zeta potential Y [mV]. Here, for the zeta potential Y, the surface of the substrate to be polished in the polishing composition is measured using a solid zeta potential measurement device. The zeta potential X [mV] and the zeta potential Y [mV] satisfy X * Ygt; 250).

Description

Technical Field

[0001] The present invention relates to a polishing method for a silicon carbide substrate and a polishing composition. Background Art

[0002] In the past, the surfaces of materials such as metals, semi-metals, non-metals, and oxides thereof were ground using a grinding composition. For example, a grinding object having a surface composed of a compound semiconductor material such as silicon carbide can be processed by grinding (lapping) performed by supplying diamond abrasive grains between a grinding plate in contact with the surface of the grinding object and the grinding object. However, grinding using diamond abrasive grains is prone to defects and deformation caused by the generation and residue of scratches and notches. Therefore, grinding (polishing) performed by using a grinding pad and supplying a grinding liquid between the grinding pad and the grinding object after or instead of grinding using diamond abrasive grains is being studied.

[0003] It should be noted that Patent Document 1 describes that, when polishing a sapphire substrate, the zeta potential X1 of the abrasive (colloidal silica) in the polishing composition and the zeta potential Y1 of the object to be polished have a relationship of X1×Y1≤0.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-183530 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] Usually, from the viewpoint of manufacturing efficiency and cost, it is desired that the grinding removal rate when supplying the grinding liquid to grind the grinding object is sufficiently large in practicality. For example, in the grinding of the grinding object composed of high hardness materials such as silicon carbide, from the viewpoint of improving the grinding object yield rate, it is desired to further improve the grinding removal rate. However, the grinding composition designed for the purpose of improving the grinding removal rate sometimes causes the generation of line defects, for example, by the abrasive particles in the grinding composition. The required level of the surface quality after grinding of the silicon carbide substrate becomes higher, and it is useful if a high-quality surface without the above-mentioned line defects can be achieved together with the practical grinding removal rate.

[0009] Based on the above background, the inventors have found out the zeta potential of the surface (polishing target surface) of the silicon carbide substrate to be polished by using a solid zeta potential measuring device in the research and development of polishing of silicon carbide substrates. Based on the above insights, in-depth research was conducted, and the present invention was completed as a result. That is, the object of the present invention is to provide a polishing method that can reduce linear defects on the surface of a substrate during polishing of a silicon carbide substrate. Another related object is to provide a polishing composition suitable for the above-mentioned polishing method.

[0010] Solutions for solving problems

[0011] According to the present specification, a method for polishing a silicon carbide substrate is provided. The polishing method includes a step of supplying a polishing composition to a polishing target substrate to polish the polishing target substrate. The polishing composition includes abrasive grains. The abrasive grains have a zeta potential X [mV] in the polishing composition. In addition, the surface of the polishing target substrate has a zeta potential Y [mV]. Here, the zeta potential Y is the zeta potential measured on the surface of the polishing target substrate in the polishing composition using a solid zeta potential measuring device. Moreover, the zeta potential X [mV] and the zeta potential Y [mV] satisfy X·Y>250. If polishing is performed using a polishing composition designed in such a way that the zeta potential X of the abrasive grains in the polishing composition and the zeta potential Y of the surface of the polishing target substrate in the polishing composition satisfy the relationship: X·Y>250, the linear defects of the surface after polishing can be reduced, and a polished surface without linear defects can be appropriately achieved.

[0012] In some preferred embodiments, the product (X·Y) of the zeta potential X [mV] and the zeta potential Y [mV] is in the range of 370 to 2000. By selecting the zeta potential X of the abrasive and the zeta potential Y of the substrate to be polished so that the X·Y is in the range of 370 to 2000, a practical polishing removal rate can be achieved, and preferably, linear defects on the surface after polishing can be reduced.

[0013] In some preferred embodiments, the zeta potential Y is lower than -25 mV and not less than -50 mV. The technology disclosed herein can be preferably implemented when the zeta potential Y of the polishing target substrate surface in the polishing composition measured using a solid zeta potential measuring device is within the above range.

[0014] In some preferred embodiments, the zeta potential X is lower than -10 mV and not less than -70 mV. In the embodiment in which the zeta potential X of the abrasive in the polishing composition is within the above range, the technology disclosed herein can be preferably implemented.

[0015] In some preferred embodiments, the abrasive grains described above include alumina particles. In the embodiments where alumina particles are used as the abrasive grains, the techniques disclosed herein can be preferably implemented by designing in a manner that satisfies the relational expression of the zeta potential described above. In addition, by using a polishing composition containing alumina particles as the abrasive grains, a practical polishing removal rate can be easily obtained.

[0016] In some embodiments, the polishing composition described above further includes an oxidizing agent. In the embodiments where the polishing composition includes an oxidizing agent, the techniques disclosed herein can be preferably implemented by designing in a manner that satisfies the relational expression of the zeta potential described above. In addition, by using a polishing composition containing an oxidizing agent, a practical polishing removal rate can be easily obtained. Among them, in the embodiments where a composite metal oxide (such as permanganic acid) is included as the oxidizing agent described above, the techniques disclosed herein can be better implemented.

[0017] In some embodiments, the pH of the polishing composition described above is 8.0 or more and 12 or less. In the embodiments where the pH of the polishing composition is within the above range, the techniques disclosed herein can be preferably implemented.

[0018] In addition, by using this specification, a polishing composition used in any polishing method disclosed herein can be provided. The polishing composition contains abrasive grains. The above abrasive grains have a zeta potential X [mV] in the above polishing composition. Moreover, the relational expression between the above zeta potential X [mV] and the zeta potential Y [mV] of the surface of the substrate to be polished in the above polishing composition measured using a solid zeta potential measuring device satisfies X·Y>250. By using the polishing composition satisfying the composition and characteristics for polishing a silicon carbide substrate, linear defects on the surface after polishing can be reduced, and a polishing surface without defects can be appropriately achieved. Detailed Embodiments

[0019] Hereinafter, suitable embodiments of the present invention will be described. It should be noted that matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be grasped as the common means of those skilled in the art based on the prior art in this field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in this field.

[0020] <Zeta Potential Characteristics>

[0021] The polishing composition disclosed herein is characterized by the following: during the polishing of the polishing target substrate, the zeta potential X [mV] of the abrasive in the polishing composition and the zeta potential Y [mV] of the surface of the polishing target substrate in the polishing composition satisfy the relationship: X·Y>250. Here, the zeta potential Y is the zeta potential measured on the surface of the polishing target substrate in the polishing composition using a solid zeta potential measuring device. By using a polishing composition designed in such a way that the zeta potential X of the abrasive in the polishing composition and the zeta potential Y of the surface of the polishing target substrate in the polishing composition satisfy the above relationship, it is possible to reduce linear defects on the surface of the polished silicon carbide substrate and appropriately achieve a polished surface without linear defects. The reason for this is considered to be as follows: when the polishing composition is supplied to the silicon carbide substrate, the zeta potentials of the abrasive in the polishing composition and the polishing target substrate show the same sign, and the product of the zeta potentials of the two (X·Y) shows a value greater than 250, so that the abrasive and the polishing target substrate can be sufficiently repelled without generating linear defects caused by the abrasive. It should be noted that the technology disclosed herein is not limited to the above explanation. In addition, the zeta potential of the grinding object substrate is evaluated using powder of the same material as the substrate in the past, for example, as described in patent document 1, but the influence of the crystal orientation of the substrate to be ground cannot be confirmed in this method, and the correlation with the actual grinding is not clear. The technology disclosed herein can quantitatively evaluate the zeta potential of the surface (grinding object surface, specifically Si surface) of the silicon carbide substrate actually ground by using a solid zeta potential measuring device. By using this method to quantitatively evaluate the zeta potential of the substrate surface in the grinding composition, it is possible to study and derive the composition of the grinding composition that obtains a practical grinding removal rate for the silicon carbide substrate as the grinding object and can achieve a surface with higher quality without line defects based on the zeta potential of the substrate surface. By measuring the zeta potential of the silicon carbide substrate in the grinding composition, the zeta potential of the Si surface that becomes the grinding object surface of the silicon carbide substrate is accurately measured in the manner that the grinding composition includes an oxidant, thereby obtaining the desired effect.

[0022] In some embodiments, the product (X·Y) of the zeta potential X [mV] and the zeta potential Y [mV] may be 300 or more. From the viewpoint of better preventing the occurrence of line defects, it is preferably 370 or more, more preferably 400 or more, further more preferably 500 or more, further preferably 700 or more, and particularly preferably 800 or more. It may be 1000 or more, 1200 or more, 1400 or more, or 1500 or more. In addition, the upper limit of the above X·Y is not particularly limited. From the viewpoint of obtaining a practical polishing removal rate, in some embodiments, the above (X·Y) may be, for example, 5000 or less, 4000 or less, or 3000 or less. In some preferred embodiments, the above (X·Y) is 2000 or less, 1800 or less, 1600 or less, 1400 or less, 1200 or less, 1000 or less, or 900 or less.

[0023] The product (X·Y) of zeta potential X [mV] and zeta potential Y [mV] can be adjusted by the selection of abrasive used in the polishing composition, the selection and amount of additives such as oxidizing agents, the adjustment of pH, the silicon carbide substrate used, and the like.

[0024] The zeta potential X of the abrasive in the polishing composition is appropriately set within the range satisfying the above relationship: X·Y>250, and there is no special limitation beyond that. In some embodiments, the absolute value |X| of the zeta potential X of the abrasive in the polishing composition is preferably greater than 10mV, more preferably greater than 15mV, further preferably greater than 20mV, particularly preferably greater than 25mV, and may be greater than 30mV or greater than 35mV. The larger the above |X|, the better it can prevent the generation of linear defects. In addition, in some embodiments, the above |X| is usually about 100mV or less, and 80mV or less is appropriate. There is a tendency that the smaller the above |X|, the higher the polishing removal rate. From the above viewpoint, in some preferred embodiments, the above |X| is less than 70mV, may be less than 60mV, may be less than 50mV, may be less than 40mV, may be less than 30mV, or may be less than 25mV.

[0025] When the zeta potential Y of the surface of the substrate to be polished is negative, an abrasive having a negative zeta potential X in the polishing composition is used. In this method, the zeta potential X of the abrasive in the polishing composition is preferably less than -10mV, more preferably less than -15mV, further preferably less than -20mV, particularly preferably less than -25mV, and may be less than -30mV or less than -35mV. When the zeta potential Y of the surface of the substrate to be polished is negative, the smaller the zeta potential X, the better the linear defects can be prevented. In addition, in some methods, the zeta potential X is about -100mV or more, and -80mV or more is appropriate. There is a tendency that the smaller the absolute value of the zeta potential X, the higher the polishing removal rate. From this point of view, in some preferred methods, the zeta potential X is greater than -70mV, may be greater than -60mV, may be greater than -50mV, may be greater than -40mV, may be greater than -30mV, or may be greater than -25mV.

[0026] The zeta potential X of the abrasive in the polishing composition is determined by measuring the polishing composition containing the abrasive using a zeta potential meter. Specifically, the zeta potential X is measured by the method described in the examples described below. The zeta potential X can be adjusted by the selection of the type of abrasive, the surface modification of the abrasive, the selection and dosage of additives such as oxidants, the adjustment of pH, etc.

[0027] The zeta potential Y of the surface of the substrate to be polished in the polishing composition is appropriately set within the range satisfying the above relationship: X·Y>250, and there is no particular limitation thereto. In some embodiments, the absolute value |Y| of the zeta potential Y of the surface of the substrate to be polished in the polishing composition is preferably greater than 25 mV, more preferably greater than 28 mV, further more preferably greater than 30 mV, and further preferably greater than 32 mV. In addition, in some embodiments, the above |Y| is usually about 50 mV or less, and 40 mV or less is appropriate, and can be 35 mV or less, or can be 30 mV or less. There is a tendency that the smaller the above |Y|, the higher the polishing removal rate.

[0028] Although not particularly limited, in some embodiments, the zeta potential Y of the polishing target substrate surface in the polishing composition is preferably lower than -25 mV, more preferably below -28 mV, further more preferably below -30 mV, and further preferably below -32 mV. In addition, in some embodiments, the zeta potential Y is about -50 mV or more, and -40 mV or more is appropriate, and may be -35 mV or more, or -30 mV or more. There is a tendency that the smaller the absolute value of the zeta potential Y, the higher the polishing removal rate.

[0029] Although not particularly limited, in some embodiments, the absolute value |XY| of the difference between the zeta potential X [mV] of the abrasive in the polishing composition and the zeta potential Y [mV] of the surface of the substrate to be polished is preferably 50 or less. By making the difference between the zeta potential X and the zeta potential Y within a specified range, the abrasive and the substrate are appropriately repelled, and the desired effect tends to be easily obtained. From this viewpoint, in some preferred embodiments, the above |XY| is 35 or less, and may be 30 or less, 25 or less, 20 or less, 15 or less, or 10 or less.

[0030] The zeta potential Y of the surface of the substrate to be polished in the polishing composition is the zeta potential measured on the surface of the substrate to be polished in the polishing composition using a solid zeta potential measuring device. Specifically, it is measured by the method described in the examples described later. The zeta potential Y can be adjusted by the selection and amount of additives such as the silicon carbide substrate used, the oxidant, the pH adjustment, etc.

[0031] <Polishing Composition>

[0032] (Abrasive particles)

[0033] The polishing composition disclosed herein contains abrasive grains. The abrasive grains play a role in mechanically polishing the substrate to be polished. The material and properties of the abrasive grains are not particularly limited, and various abrasive grains that can satisfy the above-mentioned zeta potential relationship can be used. For example, the abrasive grains can be any of inorganic particles, organic particles, and organic-inorganic composite particles. For example, 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; etc. Abrasive grains can be used alone or in combination of two or more. Among them, 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 them, silica particles, alumina particles, zirconium oxide particles, chromium oxide particles, and iron oxide particles are more preferred, and alumina particles are particularly preferred.

[0034] Although not particularly limited, the abrasive particles may be surface-modified for purposes such as adjusting the zeta potential X. Although not particularly limited, the abrasive particles (e.g., aluminum oxide particles) may be surface-modified by, for example, chemical modification (e.g., modification based on coupling agents such as alkoxyaluminates, alkoxysilanes, and alkoxytitanates; modification based on adsorption of surface modifiers such as polyacrylates, polyethylene glycol esters, polyethylene glycol ethers, acrylic acid, and methacrylic acid; modification based on immobilized functional groups such as sulfonic acids and carboxylic acids (acetic acid, propionic acid, etc.)), doping, and the like.

[0035] In some preferred embodiments, the polishing composition contains aluminum oxide particles (aluminum oxide abrasive) as abrasive particles. In the embodiment of using aluminum oxide particles as abrasive particles, the effect brought about by satisfying the above-mentioned zeta potential relationship can be preferably exerted. In addition, if a polishing composition containing aluminum oxide particles as abrasive particles is used, a practical polishing removal rate is easily obtained. As aluminum oxide particles, it can be appropriately selected from various known aluminum oxide particles and used. Examples of such known aluminum oxide particles include α-alumina and intermediate aluminum oxide. Here, intermediate aluminum oxide refers to a general term for aluminum oxide particles other than α-alumina, and specifically, γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, χ-alumina, etc. can be illustrated. In addition, aluminum oxide called gas-phase aluminum oxide based on the classification obtained according to the preparation method (typically aluminum oxide particles produced when aluminum oxide salt is calcined at high temperature) can also be used. Furthermore, aluminum oxide called colloidal aluminum oxide or aluminum oxide sol (for example, aluminum oxide hydrates such as boehmite) is also included in the examples of the above-mentioned known aluminum oxide particles. Furthermore, the alumina particles may be surface-modified. From the viewpoint of processability, it is preferred that α-alumina is contained. The alumina particles may be used alone or in combination of two or more.

[0036] When aluminum oxide particles are used as abrasive particles, it is generally advantageous that the proportion of aluminum oxide particles in the total abrasive particles used is high. For example, the proportion of aluminum oxide particles in the total abrasive particles is preferably 70% by weight or more, more preferably 90% by weight or more, further preferably 95% by weight or more, further more preferably 98% by weight or more, and particularly preferably 99% by weight or more. The technology disclosed herein can be preferably implemented in a manner in which substantially 100% by weight of the abrasive particles contained in the polishing composition are aluminum oxide abrasive particles.

[0037] The particle size of the abrasive is not particularly limited, and is selected in a manner that can exert the desired grinding effect. From the viewpoint of grinding removal speed, in some embodiments, it is appropriate that the average secondary particle size of the abrasive (e.g., aluminum oxide particles) is greater than 10 nm, preferably 50 nm or more, more preferably 100 nm or more, further more preferably 200 nm or more, further preferably 300 nm or more, and particularly preferably 400 nm or more. The upper limit of the average secondary particle size of the abrasive (e.g., aluminum oxide particles) is not particularly limited, and in some embodiments, it is appropriate to set it to about 10 μm or less. From the viewpoint of improving surface quality, it is preferably 5 μm or less, more preferably 3 μm or less, further more preferably 1000 nm or less, further preferably 700 nm or less, and particularly preferably 500 nm or less, and can be 400 nm or less, 300 nm or less, or 250 nm or less.

[0038] The average secondary particle size of the abrasive grains can be measured as a volume average particle size (volume-based arithmetic mean diameter; Mv) for particles less than 500 nm by, for example, a dynamic light scattering method using the model "UPA-UT151" manufactured by Nikkiso Co., Ltd. In addition, for particles larger than 500 nm, the volume average particle size can be measured by a pore resistance method using the model "Multisizer 3" manufactured by BECKMAN COULTER, etc.

[0039] The content of abrasive grains in the grinding composition disclosed herein is not particularly limited. In some embodiments, the content of abrasive grains (e.g., aluminum oxide particles) in the grinding composition can be about 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.5% by weight or more, further more preferably 1% by weight or more, further preferably 2% by weight or more, and particularly preferably 3% by weight or more from the viewpoint of improving the grinding removal rate. In addition, from the viewpoints of dispersibility, grinding stability, etc., it is usually appropriate that the content of abrasive grains (e.g., aluminum oxide particles) in the grinding composition is set to 50% by weight or less, preferably 20% by weight or less, more preferably 15% by weight or less, and can be 10% by weight or less, or 8% by weight or less.

[0040] In some ways, the grinding composition preferably does not contain diamond particles as abrasive particles in fact. Diamond particles can become a factor that limits the improvement of smoothness due to its high hardness. In addition, diamond particles are usually expensive, so they cannot be said to be favorable materials in terms of cost performance. From a practical point of view, the dependence on high-priced materials such as diamond particles can be reduced. Here, abrasive particles do not contain diamond particles in fact and refer to that the ratio of diamond particles in the overall abrasive particles is below 1 weight %, more preferably below 0.5 weight %, typically below 0.1 weight %, and the ratio comprising diamond particles is 0 weight %. In such a way, the application effect of the technology disclosed herein can be suitably brought into play.

[0041] (Oxidant)

[0042] In some ways, the grinding composition preferably includes an oxidant. The oxidant can play the effect of reducing the hardness of the grinding object substrate (specifically, a silicon carbide substrate), making the substrate surface fragile, and improving the grinding removal rate. In addition, using the technology disclosed herein, in the mode in which the grinding composition includes an oxidant (such as a composite metal oxide described later), the effect brought by the relationship between the above-mentioned zeta potential can be preferably played. As an oxidant, metal nitrates, ferric acids, permanganates, chromic acids, vanadic acids, ruthenic acids, molybdic acids, perrhenic acids, and tungstic acids can be cited. Among them, ferric acids, permanganates, chromic acids, vanadic acids, molybdic acids, and tungstic acids are more preferred, and permanganates (such as permanganates) and vanadic acids are further preferred. The oxidant can be used alone or in combination of two or more.

[0043] In some preferred embodiments, the polishing composition contains a composite metal oxide as an oxidant. The polishing performance can be easily improved by using a polishing composition containing a composite metal oxide as an oxidant. Specific examples of composite metal oxides include metal nitrates such as iron nitrate and silver nitrate; ferric acids such as potassium ferrate; permanganates such as sodium permanganate and potassium permanganate; chromates such as potassium chromate and potassium dichromate; vanadates such as sodium vanadate and potassium vanadate; ruthenic acids such as salts of perruthenic acid; molybdic acids such as ammonium molybdate and disodium molybdate; rhenic acids such as salts of perrhenic acid; tungstic acids such as disodium tungstate. The composite metal oxides can be used alone or in combination of two or more.

[0044] In the method of using a composite metal oxide as an oxidant, as the above-mentioned composite metal oxide, it is more preferred to use a composite metal oxide having a univalent or divalent metal element (which does not include a transition metal element.) and a 4th period transition metal element of the periodic table. Suitable examples of the above-mentioned univalent or divalent metal elements include Na, K, Mg, and Ca. Among them, Na and K are more preferred. Suitable examples of the 4th period transition metal elements of the periodic table include Fe, Mn, Cr, V, and Ti. Among them, Fe, Mn, Cr are more preferred, and Mn is further preferred. The above-mentioned composite metal oxide can more effectively induce low hardness and brittleness of the surface on the surface of silicon carbide as a high hardness material. Thus, the effect of improving the grinding removal rate can be more appropriately exerted.

[0045] It should be noted that, when the composite metal oxide is a salt (eg, permanganate), the composite metal oxide may be present in the polishing composition in the form of ions.

[0046] In the method of using a composite metal oxide as an oxidant, the polishing composition may also contain an oxidant other than the composite metal oxide, or may not contain an oxidant other than the composite metal oxide. As oxidants other than composite metal oxides, for example, peroxides such as hydrogen peroxide; periodic acid, sodium periodate, potassium periodate and other periodic acids as salts thereof; iodic acid, ammonium iodate and other iodic acids as salts thereof; bromic acid, potassium bromate and other bromic acids as salts thereof; persulfuric acid such as permonosulfuric acid and peroxydisulfuric acid, ammonium persulfate, potassium persulfate and other persulfuric acids as salts thereof; chloric acid or its salts, perchloric acid, potassium perchlorate and other chloric acids and perchloric acids as salts thereof; osmic acids such as perosmic acid and osmic acid; selenic acids such as perselenic acid and selenic acid; ammonium cerium nitrate. Oxidants other than composite metal oxides may be used alone or in combination of two or more.

[0047] When using composite metal oxide as oxidant, it is advantageous that the proportion of composite metal oxide in the overall oxidant used is usually higher. For example, it is appropriate that the proportion of composite metal oxide in the overall oxidant is set to more than 50 wt % (for example, more than 50 wt %) from the viewpoint of effectively exerting the effect of containing composite metal oxide, preferably more than 70 wt %, more preferably more than 90 wt %, further preferably more than 95 wt %, further more preferably more than 98 wt %, particularly preferably more than 99 wt %. The technology disclosed herein can be preferably implemented in a manner that substantially 100 wt % of the oxidant contained in the grinding composition is composite metal oxide.

[0048] In the mode that the grinding composition includes an oxidant, the content of the oxidant is not particularly limited. In some ways, from the viewpoint of improving the grinding removal rate, it is appropriate that the content of the oxidant is set to about 0.1% by weight or more, preferably 0.3% by weight or more, more preferably 0.5% by weight or more, further more preferably 0.8% by weight or more, further preferably 1.0% by weight or more (for example, more than 1.0% by weight), can be 1.2% by weight or more, can be 1.4% by weight or more, and can also be 1.6% by weight or more. In addition, in some ways, it is appropriate that the content of the oxidant in the grinding composition is set to about 30% by weight or less from the viewpoint of the surface quality after grinding, preferably 10% by weight or less, more preferably 8% by weight or less, further more preferably 6% by weight or less, further preferably 4% by weight or less, and particularly preferably 3% by weight or less.

[0049] In the embodiment in which the polishing composition includes an oxidant, the content of the oxidant can also be limited according to the relative relationship with the content of the abrasive. Although not particularly limited, in some embodiments, the ratio of the content Wx [weight %] of the oxidant to the content Wa [weight %] of the abrasive, i.e., Wx / Wa, is, for example, about 0.01 or more, preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.25 or more. If Wx / Wa changes to a larger value, there is a tendency for the contribution of chemical polishing to become greater relative to the contribution of mechanical polishing. In addition, from the viewpoint of increasing the contribution of mechanical polishing, in some embodiments, Wx / Wa is, for example, less than 100, less than 50 is appropriate, preferably less than 10, more preferably less than 5, further preferably less than 3, and particularly preferably less than 1.

[0050] (water)

[0051] The polishing composition disclosed herein typically contains water. As water, ion exchange water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used. The polishing composition disclosed herein can also contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water as required. Usually, it is appropriate that 90% by volume or more of the solvent contained in the polishing composition is water, preferably 95% by volume or more is water, and more preferably 99 to 100% by volume is water.

[0052] (acid)

[0053] For the purposes of pH adjustment, grinding promotion, etc., the grinding composition can contain acid as needed. As acid, both inorganic acid and organic acid can be used. As examples of inorganic acids, sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, etc. can be cited. As examples of organic acids, aliphatic carboxylic acids such as formic acid, acetic acid, propionic acid, aromatic carboxylic acids such as benzoic acid, phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, etc. can be cited. These can be used alone or in combination of more than two. When using acid, its dosage is not particularly limited and can be set to the dosage that meets the purpose of use (such as pH adjustment). Alternatively, in some ways, the grinding composition can be a composition that does not substantially contain acid.

[0054] (Basic Compounds)

[0055] For the purpose of pH adjustment, grinding promotion, etc., the grinding composition may contain alkaline compounds as needed. Here, the alkaline compound refers to a compound having the function of increasing the pH of the composition by adding it to the grinding composition. Examples of alkaline 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 hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; and amines. Alkaline compounds can be used alone or in combination of two or more. When using alkaline compounds, the amount used is not particularly limited and can be set to an amount that meets the purpose of use (such as pH adjustment). Alternatively, in some embodiments, the grinding composition can be a composition that does not substantially contain alkaline compounds.

[0056] (Dispersant)

[0057] The polishing composition may contain a dispersant as needed for the purpose of preventing sedimentation of the abrasive grains and improving dispersion. By adding a dispersant to the polishing composition, the zeta potential X of the abrasive grains in the polishing composition can be adjusted. Examples of the dispersant include phosphoric acid and its salts, sulfonic acid esters, polyoxyalkylene alkyl ethers, and the like. Examples of phosphoric acid and its salts include inorganic phosphoric acid such as phosphoric acid (orthophosphoric acid), pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, and hexametaphosphoric acid; inorganic phosphates; organic phosphates such as methyl acid phosphate, ethyl acid phosphate, ethylene glycol acid phosphate, and isopropyl acid phosphate; phosphates such as phytic acid (myo-inositol-1,2,3,4,5,6-hexaphosphoric acid); phosphonates such as nitrilotri(methylenephosphonic acid) (NTMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, and methanehydroxyphosphonic acid; and salts of phosphonates. Examples of sulfonic acid esters include alkylbenzene sulfonates and diallylsulfosuccinate. As polyoxyalkylene alkyl ethers, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, etc. can be mentioned. As other examples of dispersants, carboxylic acid polymers and low molecular weight carboxylic acids can be mentioned. Here, the carboxylic acid polymer is a polymer containing carboxylic acid units such as acrylic acid, methacrylic acid, and maleic acid, and various carboxylic acid polymers that can be used as dispersants for abrasive particles can be used. The weight average molecular weight (Mw) of the carboxylic acid polymer is not particularly limited, and is within the range of about 1000 or more and 500000 or less. The above Mw can be the weight average molecular weight (water system, polyethylene glycol conversion) obtained by GPC. In addition, the low molecular weight carboxylic acid is a carboxylic acid with a molecular weight of less than 1000 (for example, 46 or more and less than 1000), and various low molecular weight carboxylic acids that can be used as dispersants for abrasive particles can be used. The dispersant can be used alone or in combination of two or more.

[0058] When a dispersant is used, its amount is not particularly limited and can be set to an amount that meets the purpose of use (e.g., prevention of sedimentation of abrasive particles, improvement of dispersion, adjustment of the zeta potential X of abrasive particles in the polishing composition). Alternatively, in some embodiments, the polishing composition can be a composition that does not substantially contain a dispersant.

[0059] (Other ingredients)

[0060] The polishing composition disclosed herein may also contain known additives such as chelating agents, thickeners, surface protective agents, wetting agents, surfactants, rust inhibitors, preservatives, and mildew inhibitors that can be used in polishing compositions (specifically, polishing compositions used in polishing of silicon carbide substrates) as needed within the scope of not impairing the effects of the present invention. The content of the above additives can be appropriately set according to the purpose of addition, and since it does not give characteristics to the present invention, a detailed description is omitted.

[0061] Although not particularly limited, the effect brought about by the technology disclosed herein (specifically, the effect obtained based on the relationship of zeta potential) can be preferably exerted in a mode in which the polishing composition contains aluminum oxide particles as abrasive particles, an oxidant (suitably a composite metal oxide) and water. From this viewpoint, the total content of aluminum oxide particles, oxidant and water in the polishing composition is preferably 90% by weight or more, more preferably 95% by weight or more, further more preferably 98% by weight or more, further preferably 99% by weight or more, and can be 99.5% by weight or more, or 99.9% by weight or more.

[0062] (pH)

[0063] It is appropriate that the pH of the polishing composition is generally set to about 2 to 12. When the pH is in the above range, a practical polishing removal rate is easily achieved in the polishing of the polishing object substrate. In some embodiments, the pH may be above 2.5, above 3.0, above 4.0, above 5.0, above 6.0, or above 7.0. In some preferred embodiments, the pH of the polishing composition is above 8.0, more preferably above 8.5. The upper limit of the pH is not particularly limited. In some embodiments, it is appropriate that the pH is set to below 12.0, below 11.0, below 10.0, or below 9.0 (for example, less than 9.0). By changing the pH of the polishing composition, the zeta potential X and the zeta potential Y can be adjusted.

[0064] (Preparation of Polishing Composition)

[0065] The preparation method of the grinding composition disclosed herein is not particularly limited. For example, the components contained in the grinding composition can be mixed using a known mixing device such as a blade stirrer, an ultrasonic disperser, a homogenizer, etc. The manner of mixing these components is not particularly limited, and for example, all the components can be mixed at once or in a properly set order.

[0066] The polishing composition disclosed herein may be a single-component type or a multi-component type headed by a two-component type. For example, it may be constituted in the following manner: a portion A containing a part of the constituent components (e.g., components other than water) of the polishing composition is mixed with a portion B containing the remaining components and used for polishing the polishing target substrate. For example, they may be stored separately before use and mixed during use to prepare a single-component polishing composition. During mixing, dilution water, etc. may be further mixed.

[0067] <Polishing target substrate>

[0068] In the technology disclosed herein, as a substrate to be polished, a silicon carbide substrate having a zeta potential Y that satisfies the above-mentioned zeta potential relationship can be used. Silicon carbide (SiC) is expected to be a compound semiconductor substrate material with low power loss and excellent heat resistance, and the practical advantage of improving its surface properties is particularly great. The above-mentioned silicon carbide substrate can have a single crystal surface of the above-mentioned material that is mechanically and chemically stable. The technology disclosed herein can be particularly preferably applied to the polishing of a single crystal surface of silicon carbide.

[0069] <Grinding method>

[0070] The polishing composition disclosed herein can be used for polishing a substrate to be polished in a manner including the following operations, for example.

[0071] That is, a polishing liquid (slurry) containing any polishing composition disclosed herein is prepared. The preparation of the above-mentioned polishing liquid may include applying concentration adjustment (e.g., dilution), pH adjustment and other operations to the polishing composition to prepare the polishing liquid. Alternatively, the above-mentioned polishing composition may be directly used as a polishing liquid. In addition, in the case of a multi-component polishing composition, the preparation of the above-mentioned polishing liquid may include mixing these components, diluting one component or multiple components before the mixing, diluting the mixture after the mixing, etc.

[0072] Next, the polishing liquid is supplied to the polishing target substrate, and polishing is performed by a method common to those skilled in the art. For example, the method is as follows: the polishing target substrate is placed in a common polishing device, and the polishing liquid is supplied to the polishing target surface of the polishing target substrate through the polishing pad of the polishing device. Typically, the polishing pad is pressed against the polishing target surface of the polishing target substrate while the polishing liquid is continuously supplied, and the two are relatively moved (for example, rotated). After the polishing process, the polishing of the substrate is completed.

[0073] By using this specification, a polishing method for polishing a polishing target substrate (specifically, a silicon carbide substrate) can be provided. The above-mentioned polishing method includes a step of polishing the polishing target substrate using the polishing composition disclosed herein. The above-mentioned polishing method is characterized by the zeta potential X [mV] of the abrasive in the polishing composition and the zeta potential Y [mV] of the surface of the polishing target substrate in the polishing composition satisfying the relationship: X·Y>250. The technical significance, the numerical range of the above-mentioned relationship, the numerical range of the zeta potential X, Y, etc. are as described above, so they are not repeated.

[0074] In some preferred embodiments, the grinding method includes a process for performing pre-polishing (pre-polishing process) and a process for performing finish polishing (finishing polishing process). In a typical embodiment, the pre-polishing process is a polishing process configured before the finish polishing process is about to be performed. The pre-polishing process can be a polishing process of one stage, or a multi-stage polishing process of more than two stages. In addition, the finish polishing process mentioned here is a process for performing finish polishing on a substrate that has been pre-polished, and refers to a grinding process that is configured at the end (i.e., the most downstream side) in the polishing process performed using a polishing slurry containing abrasive particles. In a grinding method including a pre-polishing process and a finish polishing process like this, the grinding composition disclosed herein can be used in the pre-polishing process, can be used in the finish polishing process, and can also be used in both the pre-polishing process and the finish polishing process.

[0075] In a preferred embodiment, the polishing process using the above-mentioned grinding composition can be a pre-polishing process. In the case where the pre-polishing process includes a multi-stage polishing process of more than 2 sections, any grinding composition disclosed herein can also be used to implement the polishing process of more than 2 sections. The grinding composition disclosed herein can be preferably applied to the pre-polishing of the front section (upstream side). For example, it can also be preferably used in the initial pre-polishing process after the grinding process described later, typically in 1 grinding process.

[0076] In another preferred embodiment, the polishing process using the above-mentioned grinding composition is a finishing polishing process. The grinding composition disclosed herein can reduce the linear defects of the surface after grinding, and is therefore suitable as a grinding composition (finishing polishing composition) used in the finishing polishing process of the surface of the grinding object substrate.

[0077] Pre-polishing and finishing polishing can be applied to any of the grinding using a single-sided grinding device and the grinding using a double-sided grinding device. In the single-sided grinding device, the grinding object substrate is attached to a ceramic plate with wax, or the grinding object substrate is held using a holder called a carrier, and the grinding pad is pressed on a single side of the grinding object substrate while supplying a polishing composition and the two are moved relative to each other, thereby grinding a single side of the grinding object substrate. The above-mentioned movement is, for example, rotational movement. In the double-sided grinding device, the grinding object substrate is held using a holder called a carrier, and the polishing composition is supplied from above, while the grinding pad is pressed on the opposite side of the grinding object substrate and they are rotated in opposite directions, thereby simultaneously grinding both sides of the grinding object substrate.

[0078] The polishing pad used in each polishing step disclosed herein is not particularly limited. For example, any of a non-woven type, a suede type, a hard foamed polyurethane type, a polishing pad containing abrasive particles, a polishing pad containing no abrasive particles, etc. can be used. In some embodiments, a suede type polishing pad containing no abrasive particles can be preferably used.

[0079] The abrasive material ground by the method disclosed herein is typically cleaned after polishing. The cleaning can be carried out using an appropriate cleaning solution. The cleaning solution used is not particularly limited, and a known, commonly used cleaning solution can be appropriately selected and used.

[0080] It should be noted that the grinding method disclosed herein may include any other process in addition to the above-mentioned pre-polishing process and the finishing polishing process. As such a process, a grinding process performed before the pre-polishing process may be cited. The above-mentioned grinding process is a process for grinding the grinding object substrate by pressing the surface of a grinding plate, such as a cast iron plate, onto the grinding object substrate. Therefore, a grinding pad is not used in the grinding process. The grinding process is typically carried out by supplying abrasive grains between the grinding plate and the grinding object substrate. The above-mentioned abrasive grains are typically diamond abrasive grains. In addition, the grinding method disclosed herein may include an additional process before the pre-polishing process and between the pre-polishing process and the finishing polishing process. The additional process is, for example, a cleaning process and a polishing process.

[0081] <Method for producing ground material>

[0082] The technology disclosed herein may include providing: a method for manufacturing an abrasive including a polishing process performed using any of the above-mentioned grinding methods, and an abrasive manufactured by the method. The above-mentioned method for manufacturing an abrasive is specifically a method for manufacturing a silicon carbide substrate. That is, using the technology disclosed herein, it is possible to provide: a method for manufacturing an abrasive, including grinding a grinding target substrate (specifically a silicon carbide substrate) using any of the grinding methods disclosed herein; and an abrasive manufactured by the method. According to the above-mentioned manufacturing method, an abrasive having an improved surface quality, specifically a silicon carbide substrate, can be efficiently provided.

[0083] Matters disclosed by this specification include the following.

[0084] [1] A polishing method for a silicon carbide substrate,

[0085] The polishing method comprises the steps of supplying a polishing composition to a polishing target substrate to polish the polishing target substrate.

[0086] The polishing composition comprises abrasive particles.

[0087] The abrasive grains have a zeta potential of X [mV] in the polishing composition,

[0088] The surface of the substrate to be polished has a zeta potential Y [mV] measured using a solid zeta potential measuring device in the polishing composition.

[0089] The zeta potential X [mV] and the zeta potential Y [mV] satisfy X·Y>250.

[0090] [2] The polishing method according to [1] above, wherein the product (X·Y) of the zeta potential X [mV] and the zeta potential Y [mV] is in the range of 370 to 2000.

[0091] [3] The polishing method according to [1] or [2] above, wherein the zeta potential Y is lower than -25 mV and greater than -50 mV.

[0092] [4] The polishing method according to any one of [1] to [3] above, wherein the zeta potential X is lower than -10 mV and not less than -70 mV.

[0093] [5] The polishing method according to any one of [1] to [4] above, wherein the abrasive grains include aluminum oxide grains.

[0094] [6] The polishing method according to any one of [1] to [5] above, wherein the polishing composition further contains an oxidizing agent.

[0095] [7] The polishing method according to [6] above, wherein the oxidizing agent comprises a composite metal oxide.

[0096] [8] The polishing method according to any one of [1] to [7] above, wherein the pH of the polishing composition is 8.0 or more and 12 or less.

[0097]

[11] A polishing composition comprising abrasive particles,

[0098] The abrasive grains have a zeta potential of X [mV] in the polishing composition,

[0099] The relationship between the zeta potential X [mV] and the zeta potential Y [mV] of the surface of the substrate to be polished in the polishing composition measured using a solid zeta potential measuring apparatus satisfies X·Y>250.

[0100]

[12] The polishing composition according to

[11] above, wherein the product (X·Y) of the zeta potential X [mV] and the zeta potential Y [mV] is in the range of 370 to 2000.

[0101]

[13] The polishing composition according to

[11] or

[12] above, wherein the zeta potential Y is lower than -25 mV and not less than -50 mV.

[0102]

[14] The polishing composition according to any one of

[11] to

[13] above, wherein the zeta potential X is lower than -10 mV and not less than -70 mV.

[0103]

[15] The polishing composition according to any one of

[11] to

[14] above, wherein the abrasive grains contain aluminum oxide grains.

[0104]

[16] The polishing composition according to any one of

[11] to

[15] above, further comprising an oxidizing agent.

[0105]

[17] The polishing composition according to

[16] above, wherein the oxidizing agent comprises a composite metal oxide.

[0106]

[18] The polishing composition according to any one of

[11] to

[17] above, wherein the pH thereof is 8.0 or more and 12 or less.

[0107]

[19] The polishing composition according to any one of

[11] to

[18] , which is used in the polishing method according to any one of [1] to [8].

[0108] [Example]

[0109] Hereinafter, some embodiments of the present invention will be described, but the present invention is not intended to be limited to the content shown in the embodiments. It should be noted that in the following description, "%" is based on weight unless otherwise specified.

[0110] <Preparation of polishing composition>

[0111] (Examples 1 to 16)

[0112] Aluminum oxide abrasive grains, potassium permanganate (KMnO4) as an oxidizing agent, and deionized water were mixed, and the pH was adjusted to prepare the polishing compositions for each example. The content of the aluminum oxide abrasive grains was set to 3%, and the content of potassium permanganate was set to 3%. For the pH of the polishing composition, potassium hydroxide (KOH) was used as a pH adjuster and adjusted to the values shown in Table 1. As the aluminum oxide abrasive grains, five types of aluminum oxides (aluminum oxides A to E) shown in Table 1 were prepared and used. As aluminum oxides B and C, aluminum oxides modified with different functional groups were used. In addition, in Examples 1 to 3, a carboxylic acid-based polymer (polyacrylic acid, molecular weight 10,000, 1 wt%) as a dispersant was further added, and in Examples 10 to 12, a low molecular weight carboxylic acid (acetic acid, 1 wt%) as a dispersant was further added.

[0113] <Measurement of zeta potential X>

[0114] For the polishing compositions of each example, the zeta potential [mV] was measured using a high-concentration zeta potential meter "ZetaProbe" manufactured by Colloidal Dynamics Corporation at a liquid temperature of 20 to 25°C. The obtained values are shown in the corresponding columns of Table 1 in the form of the zeta potential X of the abrasive grains in the polishing composition.

[0115] <Measurement of zeta potential Y>

[0116] An SiC wafer (conductive type: n-type, crystalline type 4H-SiC, deviation angle of the main plane (0001) from the C axis: 4°, 2 inches) was immersed in the polishing composition of each example for 24 hours, and the zeta potential Y [mV] of the Si surface of the SiC wafer in a 1 mM KCl aqueous solution was measured using a solid zeta potential measuring device (zeta potential analyzer "Surpass3" for solid surface analysis manufactured by Anton Paar GmbH). The obtained values are shown in the corresponding columns of Table 1. The measurement was carried out in an environment of 25°C ± 2.5°C.

[0117] <Polishing of SiC wafer>

[0118] The surface of the SiC wafer that had been pre-polished with diamond abrasive grains having an average particle size of 5 μm was polished under the following polishing conditions using the polishing composition of each example as a polishing liquid.

[0119] [Polishing conditions]

[0120] Polishing device: Single-side polishing device manufactured by ENGIS JAPAN Corporation, model number "EJ-380IN"

[0121] Grinding pad: "SUBA800" manufactured by Nitta Haas Incorporated.

[0122] Grinding pressure: 300g / cm 2

[0123] Plate speed: 80 rpm

[0124] Grinding time: 1 hour

[0125] Grinding head speed: 40 rpm

[0126] Polishing liquid supply rate: 20mL / min (sagging)

[0127] Grinding fluid temperature: 25°C

[0128] Polishing target substrate: SiC wafer Si surface (conductivity type: n-type, crystal type 4H-SiC, main surface (0001) offset angle relative to C axis: 4°), 2 inches

[0129] <Evaluation of polishing removal rate>

[0130] The polishing removal rate was calculated using the following calculation formulas (1) and (2).

[0131] (1) Polishing amount [cm] = Difference in weight of SiC wafer before and after polishing [g] / Density of SiC [g / cm 3 ](=3.21g / cm 3 ) / grinding object area [cm 2 ](=19.62cm 2 )

[0132] (2) Grinding removal rate [nm / h] = Grinding volume [cm] × 10 7 / Grinding time (= 1 hour)

[0133] The obtained values ​​are shown in the corresponding columns of Table 1.

[0134] <Evaluation of Line Defects>

[0135] The SiC wafer after grinding was evaluated for the presence or absence of line defects of 2 cm or more on the entire surface of the wafer using the SiC wafer defect inspection / review device "SICA-88" manufactured by Lasertec. The absence of line defects was judged as "0", and the presence of line defects was judged as "×", which is shown in the corresponding column of Table 1.

[0136] [Table 1]

[0137]

[0138] As shown in Table 1, in Examples 2 to 3, 5 to 6, 8 to 9, 12, 15 to 16 where the zeta potential X [mV] of the abrasive in the polishing composition and the zeta potential Y [mV] of the polishing target substrate in the polishing composition satisfied X·Y>250, no linear defects were observed on the surface after polishing. In addition, in the polishing using the polishing compositions of Examples 2 to 3, 5 to 6, 8 to 9, 12, 15 to 16, a practical polishing removal rate was obtained. On the other hand, in Examples 1, 4, 7, 10 to 11, 13 to 14 where X·Y>250 was not satisfied, linear defects were observed on the surface after polishing. It should be noted that, in this embodiment, the effect of the present invention was confirmed in the polishing of the Si surface. In the polishing of the SiC substrate, it is believed that if the zeta potential of the substrate and the abrasive have the same sign, a repulsive force will act between the substrate and the abrasive, and as a result, the generation of line defects can be suppressed. Therefore, in the polishing of the C surface, if X·Y>250 is satisfied, the effect of the present invention can also be obtained.

[0139] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the claims. The technology described in the claims includes various modifications and changes to the specific examples described above.

Claims

1. A polishing method, which is a polishing method for a silicon carbide substrate, The polishing method comprises the steps of supplying a polishing composition to a polishing target substrate to polish the polishing target substrate. The polishing composition comprises abrasive particles, The abrasive grains have a zeta potential of X [mV] in the polishing composition, The surface of the polishing target substrate has a zeta potential Y [mV] measured in the polishing composition using a solid zeta potential measuring device, The zeta potential X [mV] and the zeta potential Y [mV] satisfy X·Y>250.

2. The grinding method according to claim 1, wherein: The product (X·Y) of the zeta potential X [mV] and the zeta potential Y [mV] is in the range of 370 to 2000.

3. The grinding method according to claim 1 or 2, wherein: The zeta potential Y is lower than -25 mV and greater than -50 mV.

4. The grinding method according to claim 1 or 2, wherein: The zeta potential X is lower than -10 mV and greater than -70 mV.

5. The grinding method according to claim 1 or 2, wherein: The abrasive grains include aluminum oxide particles.

6. The grinding method according to claim 1 or 2, wherein: The polishing composition further comprises an oxidizing agent.

7. The grinding method according to claim 6, wherein: The oxidant includes a composite metal oxide.

8. The grinding method according to claim 1 or 2, wherein: The polishing composition has a pH of 8.0 or more and 12 or less.

9. A polishing composition for use in the polishing method according to claim 1 or 2, The polishing composition comprises abrasive particles, The abrasive grains have a zeta potential of X [mV] in the polishing composition, The relationship between the zeta potential X [mV] and the zeta potential Y [mV] of the surface of the polishing target substrate in the polishing composition measured using a solid zeta potential measuring apparatus satisfies X·Y>250.

Images