Polishing composition

Abstract

Provided is a polishing composition which is capable of suppressing the generation of aggregated powder of abrasive grains, has good dispersibility of the abrasive grains, does not generate polishing scratches on a surface to be polished, and obtains a smooth surface with high smoothness. The polishing composition contains diamond abrasive grains, a polyol, pure water, and a dispersant, and is characterized in that the content of the diamond abrasive grains is 0.01-0.4 mass%, the average particle diameter D50 of the diamond abrasive grains is 10 nm to 1 [mu] m, the content of the polyol is 1-30 mass%, and the average particle diameter D50 of the polyol is 10 nm to 1 [mu] m. The dispersant is at least one of an organic acid salt, an inorganic acid salt, and an octylphenol ethoxylate-based surfactant.

Description

Technical Field

[0001] The present invention relates to a polishing composition, for example, a polishing composition for polishing a polycrystalline SiC substrate. Background Art

[0002] Silicon carbide (SiC) is a wide-bandgap semiconductor having a wide bandgap width of 2.2 to 3.3 eV. Based on its excellent physical and chemical properties, it has been researched and developed as an environmentally resistant semiconductor material. In particular, in recent years, SiC has attracted attention as a material for high-voltage, high-output electronic devices, a material for high-frequency electronic devices, and a material for short-wavelength optical devices from blue to ultraviolet, and research and development have been actively conducted. However, it is difficult to manufacture high-quality large-diameter single crystals of SiC, which has so far hindered the practical application of SiC devices. Therefore, there is a strong expectation for the development of a technology that can provide SiC substrates for semiconductor device applications, particularly for high-voltage, high-output electronic component applications, at low cost.

[0003] Therefore, the following technology has been provided: only the device formation layer portion uses high-quality single-crystalline SiC, and it is fixed to the bonding target surface of a support substrate (a material having strength, heat resistance, and cleanliness capable of withstanding the device manufacturing process: for example, polycrystalline SiC) by a bonding method that does not involve the formation of an oxide film at the bonding interface to form a bonded substrate, thereby manufacturing a semiconductor substrate having both low cost (support substrate portion) and high quality (SiC portion) (for example, refer to Patent Document 1).

[0004] In the bonding process of bonding a single-crystalline SiC substrate and a polycrystalline SiC substrate when manufacturing a bonded substrate, attention is paid to the surface roughness of the bonding target surface of the polycrystalline SiC substrate. The reason is that if the surface roughness of the polycrystalline SiC substrate, that is, the fine irregularities on the surface, becomes large, the polycrystalline SiC substrate and the single-crystalline SiC substrate cannot be sufficiently adhered and cannot be bonded. Or, even if they can be bonded, due to the large surface roughness of the polycrystalline SiC substrate, fine gaps may sometimes be generated at the bonding interface between the polycrystalline SiC substrate and the single-crystalline SiC substrate, resulting in a large number of defects (bonding defects) in the bonded substrate.

[0005] The polycrystalline SiC substrate is formed, for example, by the following method: After growing polycrystalline SiC on a base substrate formed of carbon or the like by chemical vapor deposition (CVD: Chemical Vapor Deposition), the base substrate is removed.

[0006] In the bonding process of bonding a single-crystal SiC substrate and a polycrystalline SiC substrate, the arithmetic surface roughness Ra of the bonding target surface of the polycrystalline SiC substrate is required to be about 0.1 to 0.5 nm. In order to form such a surface roughness, the bonding target surface is subjected to, for example, CMP (chemical mechanical polishing) to obtain a CMP polished surface, and the morphology of this polished surface is different from that of the single-crystal SiC substrate according to the characteristics (crystal structure) of the polycrystalline SiC substrate. In other words, single-crystal SiC is a large grain oriented in the same direction, so the polished surface of the single-crystal SiC substrate can be polished uniformly by CMP, and thus a high-precision polished surface with a smaller surface roughness than the polycrystalline SiC substrate can be easily obtained. On the other hand, polycrystalline SiC is an aggregate of small grains oriented in various directions, so the polishing rate of the polished surface during CMP is different for each grain, and thus the wear amount is different for each grain. As a result, countless irregularities are likely to occur along the grain boundaries on the polished surface. In the case of polycrystalline SiC, it is difficult to obtain a polished surface with a small surface roughness compared to the single-crystal SiC substrate.

[0007] Prior art documents

[0008] Patent documents

[0009] Patent Document 1:

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-15401 Summary of the invention

[0011] Problems to be solved by the invention

[0012] In a polycrystalline SiC substrate, as a method for obtaining a high-precision polished surface, in addition to CMP, for example, mechanical polishing combining diamond particles and a metal stage is known. Since the polycrystalline SiC substrate is an aggregate of grains oriented in various directions, in CMP that includes a chemical action in the polishing mechanism, surface roughness sometimes occurs due to the difference in etching rate generated between each polycrystalline grain. On the other hand, in mechanical polishing that does not include a chemical action, the surface roughness peculiar to the polycrystalline SiC substrate as in the case of CMP is not easily generated. Therefore, compared with CMP, mechanical polishing can finish the polished surface of the polycrystalline SiC substrate with high precision.

[0013] On the other hand, mechanical polishing leaves residual cutting marks and processing strain, so there is a drawback that it is difficult to obtain a smooth surface. In order to obtain a smooth polished surface in mechanical polishing, the particle size of the abrasive grains becomes important. The smaller the particle size is set, the more the smoothness can be improved and the scratches on the polished surface can be suppressed. However, the abrasive grains used in mechanical polishing are used in a state of being slurried by being dispersed in a dispersion medium such as a liquid. When the abrasive grains are dispersed in the liquid, there is a tendency that the smaller the particle size of the abrasive grains, the easier it is for the abrasive grains to agglomerate and precipitate. The agglomerated powder generated therefrom may be the main cause of scratches and other abrasions on the polished surface. Therefore, even when using abrasive grains with a small particle size, scratches with a depth greater than the particle size of the abrasive grains may sometimes be generated on the polished surface.

[0014] In addition, in order to disperse the abrasive grains in the dispersion medium, a dispersant is usually added. However, if the dispersant is insufficient, sometimes the abrasive grains cannot be sufficiently dispersed in the dispersion medium and agglomerated powder is generated. On the other hand, if the dispersant is excessive, sometimes the fine particles of the dispersed abrasive grains easily settle to the bottom of the dispersion medium, and the settled particles become agglomerated powder. That is, in either case of insufficient dispersant and excessive dispersant, there is a risk of generating scratches on the polished surface of the polycrystalline SiC substrate.

[0015] Therefore, in order to solve the above problems, an object of the present invention is to provide a polishing composition, especially for polishing polycrystalline SiC, which can suppress the generation of agglomerated powder of abrasive grains, has good dispersibility of abrasive grains, and does not generate polishing scratches on the surface to be polished and obtains a smooth surface with high smoothness.

[0016] Means for Solving the Problem

[0017] In order to solve the above problems, the polishing composition of the present invention contains diamond abrasive grains, polyhydric alcohol, pure water and a dispersant. Among them, the content of the diamond abrasive grains is 0.01 to 0.4% by mass, and the average particle size D 50 of the diamond abrasive grains is 10 nm to 1 μm, the content of the polyhydric alcohol is 1 to 40% by mass, and the dispersant is at least any one of organic acid salts, inorganic acid salts and octylphenol ethoxylate surfactants.

[0018] Alternatively, the diamond abrasive grains may be any one of single crystal diamond abrasive grains and polycrystalline diamond abrasive grains.

[0019] Alternatively, the polyhydric alcohol may be ethylene glycol.

[0020] Alternatively, the dispersant may be at least any one of sodium hexametaphosphate and octylphenoxy polyethoxyethanol.

[0021] Alternatively, when the dispersant is the organic acid salt and / or the inorganic acid salt, the total content of the organic acid salt and / or the inorganic acid salt is 0.003 to 0.15% by mass.

[0022] Alternatively, when the dispersant is the octylphenol ethoxylate surfactant, the content of the octylphenol ethoxylate surfactant is 0.0025 to 0.07% by mass.

[0023] Alternatively, the polishing composition of the present invention is a polishing composition for polishing a polycrystalline SiC substrate.

[0024] Advantages of the Invention

[0025] According to the present invention, it is possible to provide a polishing composition that can suppress the generation of agglomerated powder of abrasive grains, has good dispersibility of abrasive grains, and does not generate polishing scratches on the surface to be polished, thereby obtaining a smooth surface with high smoothness. Detailed Embodiments

[0026] Hereinafter, an embodiment of the polishing composition of the present invention will be described in detail.

[0027] The present invention is a polishing composition for mechanical polishing. Especially when the object to be polished is a polycrystalline SiC substrate, it is possible to improve the smoothness of the polished surface and suppress the generation of scratches caused by polishing on the surface to be polished.

[0028] [Polishing Composition]

[0029] The polishing composition of the present invention contains diamond abrasive grains, a polyhydric alcohol and pure water as a dispersion medium, and a dispersant. Hereinafter, each raw material will be described in detail.

[0030] 〈Diamond Abrasive Grains〉

[0031] When polishing a difficult-to-machine material such as a polycrystalline SiC substrate, diamond is likely to maintain its cutting ability in various slurry compositions due to its high hardness, so it is preferably used as an abrasive grain.

[0032] As the diamond abrasive grains, single-crystal diamond abrasive grains or polycrystalline diamond abrasive grains can be used, or they can be used in combination. In addition, as the diamond abrasive grains, abrasive grains composed of synthetic diamond or natural diamond can be used, or they can be used in combination.

[0033] The average particle size of the diamond abrasive grains (D measured by a particle size distribution meter) 50Value, volume basis. The type, method and model of the particle size distribution meter are not specifically specified as long as they are suitable for measuring the particle size) is 10nm~1μm. In order to use diamond abrasives in mechanical grinding and obtain a smooth grinding surface, the particle size of the diamond abrasives becomes important. The smaller the particle size of the diamond abrasives, the more it is possible to improve the smoothness of the grinding surface and suppress the occurrence of scratches on the grinding object surface. However, if the particle size of the diamond abrasive is too small, there is a risk that the smoothness of the grinding surface cannot be improved and the occurrence of scratches on the grinding object surface cannot be suppressed due to agglomeration of the abrasives. Therefore, the average particle size D of the diamond abrasives is set to 400nm. 50 The lower limit of is set to 10 nm.

[0034] In addition, by polishing with the polishing composition of the present invention, it is necessary to adjust the arithmetic surface roughness Ra of the surface of the polycrystalline SiC substrate to 0.5 nm or less. 50 It is 1 μm or less, and more preferably 100 nm or less.

[0035] By using such an average particle size D 50 Diamond abrasive grains with a small particle size of 10 nm to 1 μm can suppress the generation of scratches on the polished surface and improve the smoothness of the polished surface as described above. 50 Diamond abrasive grains with a particle size in the range of 10 nm to 1 μm tend to have extremely poor dispersibility in the dispersion medium compared to particles larger than 1 μm. Therefore, in order to satisfy the dispersibility, the concentration ratio of diamond abrasive grains to polyol, pure water, and dispersant in the polishing composition becomes more important.

[0036] That is, the content of the diamond abrasive grains in the grinding composition is 0.01~0.4 mass %, preferably 0.05~0.25 mass %.The content of the diamond abrasive grains in the grinding composition affects the generation of the grinding speed and scratches on the grinding surface. When this content is less than 0.01, there is a hidden danger of the extreme reduction of the grinding speed of the grinding surface of the grinding composition, which becomes the main cause of the reduction in grinding efficiency. In addition, if this content is greater than 0.4 mass %, there is a hidden danger of the dispersibility variation of the diamond abrasive grains, which becomes the cause of diamond abrasive grains agglomeration and scratches on the grinding surface.

[0037] 〈Dispersion Medium〉

[0038] The dispersion medium is a medium for dispersing diamond abrasive grains, and specifically, polyol and pure water are the dispersion medium.

[0039] (Polyol)

[0040] A polyol is an alcohol having two or more hydroxyl groups in the molecule, and there are no particular limitations on the number of carbon atoms, the number of hydroxyl groups, etc., and alcohols having a valence of divalent or higher can be cited. For example, polyols that are liquid at room temperature such as ethylene glycol, propylene glycol, tripropylene glycol, butanediol, and glycerin can be used. In particular, from the viewpoints of flammability, environmental load, good solubility in water, and low viscosity, ethylene glycol is more preferred.

[0041] The content of the polyol in the polishing composition is 1 to 40% by mass. It is preferably 5 to 35% by mass, and more preferably 10 to 30% by mass.

[0042] When the content of the polyol in the polishing composition is less than 1% by mass, there is a risk that the diamond abrasive grains are difficult to disperse. For example, when the polishing composition does not contain polyol and the dispersion medium is only pure water, the diamond abrasive grains do not disperse and agglomerate.

[0043] In addition, when the content of the polyol in the polishing composition is greater than 40% by mass, precipitation of diamond fine particles caused by the diamond abrasive grains is confirmed, and sometimes the dispersion stability decreases. The generation of this precipitation is because, under the condition that the amount of the diamond abrasive grains is excessive, the affinity between the diamond fine particles increases, and the fine particles re-agglomerate with each other and precipitate.

[0044] (Pure water)

[0045] In addition, as the dispersion medium, a dispersion medium having high affinity compatible with the polyol is used, and pure water is used in the present invention.

[0046] The content of pure water in the polishing composition is the balance of the contents of the diamond abrasive grains, the polyol, and the dispersant. Although it also depends on the contents of these respective components, the content of pure water in the polishing composition is approximately 59.7 to 99% by mass.

[0047] 〈Dispersant〉

[0048] As an additive, a dispersant having a dispersing effect on the diamond abrasive grains is mainly added. When dispersing the abrasive grains of diamond fine particles in a liquid, there is a tendency that the smaller the diameter of the abrasive grains, the easier it is to generate agglomeration and precipitation in the liquid, and problems such as scratches are generated on the polishing surface due to the agglomerated powder of the abrasive grains. If a polishing composition is composed only of diamond abrasive grains, polyol, and pure water without using a dispersant, agglomeration of the diamond abrasive grains sometimes occurs. Therefore, a dispersant having a dispersing effect on the diamond abrasive grains is added.

[0049] As the dispersant, at least any one of organic acid salts, inorganic acid salts, and octylphenol ethoxylate surfactants can be used.

[0050] Examples of organic acid salts include sodium citrate, sodium tartrate, sodium acetate, etc., and examples of inorganic acid salts include sodium phosphate, sodium sulfate, etc. Among these salts, phosphate salts are preferred, and for example, sodium hexametaphosphate can be added. Sodium hexametaphosphate particularly has the effect of improving the affinity of diamond abrasive grains and polyhydric alcohol with respect to pure water, and is preferably used as a dispersant.

[0051] In addition, as a dispersant, a surfactant having a polyoxyethylene chain in the hydrophilic group and an octylphenol group in the hydrophobic group can be added. Specifically, an octylphenol ethoxylate-based surfactant in which the polyoxyethylene chain and the octylphenol group are bonded by an ether bond is preferred. For example, polyoxyethylene (10) octylphenyl ether (octylphenoxy polyethoxyethanol) known as Triton X-100 can be added. Polyoxyethylene (10) octylphenyl ether particularly has the effect of improving the affinity between diamond abrasive grains and polyhydric alcohol, and is preferably used as a dispersant.

[0052] The organic acid salt, inorganic acid salt, and octylphenol ethoxylate-based surfactant can be used separately alone as a dispersant, or they can be used in combination. The mechanisms of improving the affinity of diamond abrasive grains, polyhydric alcohol, and pure water of the organic acid salt, inorganic acid salt, and octylphenol ethoxylate-based surfactant are different, and a synergistic effect can be expected by adding both, so both the organic acid salt and / or inorganic acid salt and the octylphenol ethoxylate-based surfactant can be used. For example, as a dispersant, at least any one of sodium hexametaphosphate and octylphenoxy polyethoxyethanol can be used alone, and in addition, they can also be used in combination.

[0053] When using an organic acid salt and / or an inorganic acid salt as a dispersant, that is, in any case of using only an organic acid salt as a salt, only an inorganic acid salt as a salt, or using both an organic acid salt and an inorganic acid salt as a salt, the total content of the organic acid salt and / or inorganic acid salt in the polishing composition is preferably 0.003 to 0.15% by mass, more preferably 0.005 to 0.1% by mass. When the total content of the organic acid salt and / or inorganic acid salt is less than 0.003% by mass, there is a risk of aggregation of diamond abrasive grains in the polishing composition. For example, when not added at all, aggregation of diamond abrasive grains sometimes occurs. In addition, if the total content of the organic acid salt and / or inorganic acid salt is greater than 0.15% by mass, there is a risk of re-aggregation of diamond abrasive grains dispersed in the polishing composition and precipitation. Here, the total content of the organic acid salt and / or inorganic acid salt is the content of only the organic acid salt when only the organic acid salt is used as a salt, the content of only the inorganic acid salt when only the inorganic acid salt is used as a salt, and the total content of the organic acid salt and the inorganic acid salt when both the organic acid salt and the inorganic acid salt are used.

[0054] In addition, when using an octylphenol ethoxylate surfactant as a dispersant, the content of the octylphenol ethoxylate surfactant in the polishing composition is preferably 0.0025 to 0.07% by mass, more preferably 0.0025 to 0.05% by mass. When the content of the octylphenol ethoxylate surfactant is less than 0.0025% by mass, there is a risk of agglomeration of diamond abrasive grains in the polishing composition. For example, when not added at all, agglomeration of the abrasive grains of diamond abrasive grains sometimes occurs. In addition, if the content of the octylphenol ethoxylate surfactant is greater than 0.07% by mass, there is a risk of re-agglomeration of the diamond abrasive grains dispersed in the polishing composition and precipitation.

[0055] [Method for manufacturing polishing composition]

[0056] The method for manufacturing the polishing composition is not particularly limited as long as it can disperse diamond abrasive grains to the extent that no scratches are formed on the polishing surface. For example, after mixing diamond abrasive grains, polyhydric alcohol, and a dispersant little by little each time to fuse them, pure water is added to adjust the concentration of the diamond abrasive grains to a desired concentration, whereby a polishing composition can be manufactured. Regarding the treatment for dispersing diamond abrasive grains, stirring is sufficient, and a rotation-revolution mixer or the like can also be used for dispersion as needed.

[0057] Examples

[0058] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by any of the following examples.

[0059] As diamond abrasive grains, diamond microparticles having an average particle diameter D 50 of 5 nm to 1 μm were obtained, and diamond microparticles, ethylene glycol, sodium hexametaphosphate, octylphenoxypolyethoxyethanol, and pure water were mixed at the concentration shown in Table 1, and the diamond microparticles were sufficiently stirred to be dispersed to manufacture the polishing compositions of the examples and comparative examples.

[0060] [Evaluation of dispersibility]

[0061] If the content concentration of the dispersant in the polishing composition is insufficient, diamond particles will not be dispersed and will remain at the bottom of the container in the form of agglomerated powder. Therefore, to evaluate the dispersibility of diamond abrasive grains in the polishing composition, after the polishing composition is manufactured and allowed to stand for 1 hour, the supernatant generated in the polishing composition is gradually transferred to another container little by little, and the dispersibility is evaluated based on whether there is any agglomerate remaining at the bottom of the container containing the polishing composition. In Tables 1 to 3, the case where no agglomerate can be visually confirmed is evaluated as ○ (good), the case where particles are observed floating in the liquid is evaluated as △ (fair), and the case where a large amount of agglomerate remains at the bottom of the container is evaluated as × (poor).

[0062] [Evaluation of dispersion stability]

[0063] If the content concentration of the dispersant in the polishing composition is excessive, although the diamond particles are dispersed, their dispersion state is unstable, and a phenomenon occurs in which they gradually settle and precipitate at the bottom of the container from after the polishing composition is manufactured. Therefore, the dispersion stability of diamond abrasive grains in the polishing composition is evaluated. Specifically, for the polishing compositions with ○ or △ dispersibility in the above-mentioned evaluation of dispersibility, the supernatant and the original residue are returned to the original container and remixed to form a polishing agent composition, and then these polishing agent compositions are transferred to a transparent container and allowed to stand for 24 hours. Then, the dispersion stability is evaluated based on the presence or absence of a precipitate of diamond particles after standing for 24 hours. In Tables 1 to 3, the case where no precipitate can be visually confirmed in the polishing composition is evaluated as ○ (good), the case where the depth of particles in the liquid is observed is evaluated as △ (fair), and the case where a precipitate is clearly confirmed is evaluated as × (poor).

[0064] [Evaluation results of dispersibility and dispersion stability]

[0065] In Comparative Example 1, Comparative Example 2, and Examples 1 to 4, the average particle size D of the diamond abrasive grains 50It was constantly set to 50 nm. In addition, the contents of diamond abrasive grains and ethylene glycol were set to be constant, and the dispersibility and dispersion stability were evaluated under the conditions of changing the types and contents of dispersants. As a result, in Comparative Example 1 without a dispersant, the dispersibility of diamond abrasive grains was poor, and a large number of aggregates were confirmed. Next, in Example 1 and Example 2 containing only one dispersant, compared with Comparative Example 1, the dispersibility was improved. Although a small amount of aggregates were confirmed, it was used for the grinding of a polycrystalline SiC substrate. Moreover, in Example 3 containing two dispersants, the dispersibility was further improved, and no aggregates could be confirmed visually at all. Further, the dispersion stability was also good in Example 3, and no precipitate was confirmed after standing for 24 hours. In addition, Example 4 and Comparative Example 2 contained two dispersants. Further, in Example 4 to Comparative Example 2, the content of the dispersant was doubled, but it was confirmed that if the concentration of the dispersant was too high, the diamond particles were likely to settle, and the dispersion stability became poor in Comparative Example 2. Especially in Comparative Example 2 with an excessive concentration of the dispersant, a precipitate was clearly confirmed, and the dispersion stability was poor.

[0066] In Comparative Example 3 and Examples 5 to 9, the concentration of the dispersant was set to be constant, and the dispersibility and dispersion stability were evaluated under the condition of changing the average particle size D of the diamond abrasive grains 50 . As a result, in Comparative Example 3 with a particle size of 5 nm, a large amount of aggregated powder was confirmed, and it was confirmed that sufficient dispersibility could not be obtained even with the addition of a dispersant. Examples 5 to 9 were examples in which the average particle size D of the diamond abrasive grains 50 gradually increased. The dispersibility was evaluated as △ in Example 5, and although the dispersibility was good in Examples 6 to 9, it was confirmed that the dispersion stability tended to deteriorate as the average particle size D of the diamond abrasive grains 50 increased.

[0067] Based on Example 9, in which the dispersion stability was slightly reduced and evaluated as △ due to the increase in the average particle size D of the diamond abrasive grains 50 , the concentrations of the two dispersants were each reduced to 1 / 5 to prepare the grinding composition of Example 10. As a result, by reducing the dispersant, the dispersion stability was improved, and no precipitate was seen in the grinding composition of Example 9 after standing for 24 hours.

[0068] [Table 1]

[0069]

[0070] As shown in Table 2, based on the polishing composition of Example 3, polishing compositions with the diamond abrasive content and ethylene glycol content changed were prepared (Examples 11 to 13, Comparative Examples 4 to 6), and changes in their dispersibility and dispersion stability were confirmed.

[0071] In Example 3, Example 11, Example 12, and Comparative Example 4, changes in dispersibility and dispersion stability caused by changes in the diamond abrasive content in the polishing composition were confirmed. When the diamond abrasive content was decreased relative to that in Example 3 as in Example 11, no problems occurred with dispersibility and dispersion stability. However, when the diamond abrasive content in the polishing composition was increased as in Example 12 and Comparative Example 4, a tendency was confirmed that dispersibility and dispersion stability decreased with an increase in their concentration.

[0072] In Example 3, Example 13, Comparative Example 5, and Comparative Example 6, changes in dispersibility and dispersion stability caused by changes in the ethylene glycol content in the polishing composition were confirmed. Under the condition where the ethylene glycol content was slightly decreased relative to that in Example 3 as in Example 13, although the dispersibility slightly decreased, no significant residual agglomerated powder was confirmed and the dispersion stability was good. However, when ethylene glycol was completely absent as in Comparative Example 5, it was confirmed that the diamond microparticles were hardly dispersed, resulting in a poor dispersibility evaluation. In addition, when the ethylene glycol content was excessive as in Comparative Example 6, although the dispersibility of the diamond abrasive was good, precipitation of the diamond abrasive was confirmed and a decrease in dispersion stability was confirmed.

[0073] [Table 2]

[0074]

[0075] Polishing experiments were conducted using the polishing compositions of Comparative Example 1, Comparative Example 2, and Examples 1 to 4. Specifically, when a polycrystalline SiC substrate's polishing target surface was mechanically polished using a metal platform with the polishing composition, the polished surface was evaluated for scratches. The conditions for mechanical polishing were the same for all examples except for the polishing composition. A case without scratches was evaluated as ○ (good), a case with a few scratches was evaluated as △ (fair), and a case with numerous scratches was evaluated as × (poor). The experimental results are shown in Table 3.

[0076] When a polishing experiment was conducted using the polishing composition of Comparative Example 1 with poor dispersibility, numerous scratches were generated on the polished surface. Since there were numerous agglomerated particles in the polishing composition of Comparative Example 1, these agglomerated particles were the cause of the scratches on the polished surface.

[0077] In the case of using the polishing compositions of Example 1 and Example 2, in which the dispersibility is improved as compared with Comparative Example 1, although polishing surface scratches are generated, the number of generated scratches is small and at the level of mechanical polishing for the surface of a polycrystalline SiC substrate in the production of a bonding substrate. The polishing characteristics are improved in this way because the number of aggregated particles is reduced as compared with the polishing composition of Comparative Example 1, and thus the polishing surface scratches are also reduced.

[0078] Then, in the case of using the polishing compositions of Example 3 and Example 4, in which the dispersibility is good, no polishing surface scratches are generated.

[0079] In addition, Comparative Example 2 is a polishing composition in which there are precipitated particles of diamond abrasive grains due to an excessive content of a dispersant. In the case of using this polishing composition, several polishing surface scratches are generated. This is because the particles precipitated on the bottom of the container caused by the diamond abrasive grains are re-aggregated, and they impart polishing surface scratches.

[0080] From the tendency derived from the results shown in Table 3, in either case of the reduction in the dispersibility of diamond abrasive grains due to a shortage of the dispersant and the reduction in the dispersion stability of diamond abrasive grains due to an excess of the dispersant, it becomes a cause of generating polishing surface scratches. Therefore, it is necessary to provide a polishing composition having good dispersibility and dispersion stability.

[0081] [Table 3]

[0082]

[0083] As described above, according to the present invention, it is possible to provide a polishing composition that can suppress the generation of aggregated powder of abrasive grains, has good dispersibility of abrasive grains, and does not generate polishing scratches on the surface to be polished, and can obtain a smooth surface with high smoothness, and thus is industrially useful.

Claims

1. A grinding composition, wherein, the grinding composition contains diamond abrasive grains, polyol, pure water and a dispersant, the content of the diamond abrasive grains is 0.01 to 0.4% by mass, The average particle size D of the diamond abrasive grains 50 is 10 nm to 1 μm, the content of the polyol is 1 to 40% by mass, the dispersant is at least any one of organic acid salts, inorganic acid salts and octylphenol ethoxylate surfactants.

2. The abrasive composition according to claim 1, wherein The diamond abrasive grains are any one of single crystal diamond abrasive grains and polycrystalline diamond abrasive grains.

3. The abrasive composition according to claim 1 or 2, wherein The polyol is ethylene glycol.

4. The abrasive composition according to claim 1 or 2, wherein The dispersant is at least any one of sodium hexametaphosphate and octylphenoxy polyethoxyethanol.

5. The abrasive composition according to claim 1, wherein, When the dispersant is the organic acid salt and / or the inorganic acid salt, the total content of the organic acid salt and / or the inorganic acid salt is 0.003 to 0.15% by mass.

6. The abrasive composition according to claim 1, wherein, When the dispersant is the octylphenol ethoxylate surfactant, the content of the octylphenol ethoxylate surfactant is 0.0025 to 0.07% by mass.

7. The abrasive composition according to claim 1 or 2, wherein The grinding composition is a grinding composition for grinding a polycrystalline SiC substrate.

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