JP2012000696A - Polishing slurry and polishing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing process technology capable of realizing a good polishing speed and polishing surface precision, achieving a polishing characteristic similar to that of cerium oxide when manganese oxide is used as abrasive.SOLUTION: A polishing slurry for polishing a base material has such characteristics as an abrasive contains sesquioxide as a main component, the content of the abrasive is less than 10 wt.% with respect to the polishing slurry, and a pH of the polishing slurry is 4 or higher. By using the polishing slurry, the polishing speed and polishing surface precision that are equivalent to cerium oxide or higher can be maintained.

Description

  The present invention relates to a polishing slurry containing dimanganese trioxide as a main component and a polishing method using the slurry, and more particularly to a polishing slurry suitable for polishing glass.

  As polishing particles for polishing a glass substrate such as a hard disk or glass for liquid crystal, cerium oxide that can polish glass at a high polishing rate is widely used. Although cerium oxide is produced only in China and other countries, demand is expected to increase with the expansion of production of hard disks and flat-screen TVs. Yes. For this reason, development of abrasive particles equivalent to cerium oxide is required, and manganese oxide is known as one of the abrasive particles (cited documents 1 to 3).

  In the polishing treatment using these manganese oxides, as in the case of using cerium oxide, a method of polishing the surface of the substrate to be polished with a polishing slurry in which polishing particles are dispersed in an aqueous liquid can be employed. In the polishing slurry, it is considered that the higher the concentration of the abrasive particles, the greater the contact frequency between the substrate and the abrasive particles, so that the polishing rate of the substrate can be improved. From this point of view, when manganese oxide is used as the abrasive particles, the manganese oxide concentration in the polishing slurry tends to be set high in order to improve the polishing rate. For example, in Patent Document 1, the manganese oxide concentration is 10 wt%.

Japanese Patent Laid-Open No. 10-72578 Japanese Patent Laid-Open No. 10-60415 JP 2006-121111 A

  However, when the manganese oxide concentration in the polishing slurry is increased, the polishing rate increases, but the polishing particles tend to stay on the surface of the base material, and the surface accuracy of the polishing surface tends to decrease. From such a background, an object of the present invention is to provide a polishing treatment technique that can maintain both the polishing speed and the high accuracy of the polishing surface even when the polishing particles are made of manganese oxide.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research on an abrasive slurry in which manganese oxide is used as abrasive particles and dispersed in an aqueous liquid. Even when the concentration of the abrasive particles is low, the chemistry of the abrasive particles has been reduced. The inventors have found that the polishing speed can be increased due to the specific characteristics, and have come up with the present invention.

The present invention relates to a polishing slurry for polishing a substrate. The polishing particles are mainly composed of dimanganese trioxide, and the content of the polishing particles is less than 10% by weight with respect to the polishing slurry. Relates to a polishing slurry having a pH of 4 or more. Although it is known that manganese oxide is an excellent abrasive material, manganese manganese oxide (Mn ₂ O ₃ ) is dispersed in the slurry at a low concentration of less than 10% by weight. When the slurry pH is 4 or more, polishing performance comparable to that of conventional abrasives can be realized.

According to the polishing slurry of the present invention, it is possible to maintain a polishing rate comparable to that of cerium oxide even when the content of abrasive particles is as low as less than 10% by weight (wt%), and the polished surface of the substrate is also smooth. Can be polished. In particular, when the substrate to be polished is a substrate containing Si as a component such as soda (lime) glass, quartz glass, or liquid crystal glass, or a substrate having a surface oxide film such as a SiO ₂ film. In some cases, a polishing material comparable to the polishing rate of cerium oxide has not been provided. According to the present invention, a polishing rate higher than that of cerium oxide can also be realized by adjusting the pH of the polishing slurry.

  Hereinafter, the polishing slurry of the present invention will be described in detail. The polishing slurry of the present invention contains dimanganese trioxide as a main component as polishing particles. According to the present invention, while maintaining a polishing speed equivalent to or higher than that when cerium oxide is used, the polished surface accuracy is also good because dimanganese trioxide has a chemical action with the glass substrate. This is considered to be because the surface portion of the glass can be removed at the atomic level. Here, in the present invention, “the abrasive particles are mainly composed of dimanganese trioxide” means that, in the X-ray diffraction measurement of the abrasive particles used in the polishing slurry, other than the maximum X-ray peak of dimanganese trioxide. The oxide has an X-ray peak of 10% or less.

  In the present invention, the abrasive particle content in the polishing slurry is less than 10% by weight. Even if it is 10% by weight or more, the polishing speed is hardly increased, but the surface accuracy of the polished surface tends to be lowered. The content of the abrasive particles is preferably 5% by weight or less, and more preferably 3% by weight or less. This is because the polishing slurry has a good balance between the polishing speed and the polishing surface accuracy. The content is preferably 1% by weight or more, and if it is less than 1% by weight, the polishing rate tends to be low, and it is difficult to maintain a practical polishing rate.

The particle diameter of manganese oxide, which is an abrasive particle, is not particularly limited, but in order to achieve smoother surface accuracy, the 50% diameter D ₅₀ in the volume-based integrated fraction of laser diffraction / scattering particle diameter distribution measurement is It is preferably 1 μm or less, and more preferably 0.5 μm or less.

  The polishing slurry is at a pH of 4 or higher. This is because the higher the pH, the higher the polishing rate, and even if the content of the abrasive particles is low, a polishing rate equal to or higher than that of cerium oxide can be realized. For this reason, the pH is preferably pH 5 or more, more preferably pH 7 or more. A pH exceeding 13 is undesirable because it may adversely affect the polishing machine and the operator during polishing.

  When dimanganese trioxide is dispersed in water as abrasive particles, the pH is usually about 4.7 to 4.9. Therefore, it can be used as an abrasive slurry without adjusting the pH, but in order to have a more preferable pH range. Preparation may be performed. The chemical solution used for pH adjustment is not particularly limited, but it is preferable to use potassium salt such as potassium hydroxide or potassium pyrophosphate, ammonium salt such as ammonium polyacrylate, or ammonia in order to suppress adverse effects on the object to be polished. In particular, potassium salt is preferred.

  In the polishing slurry of the present invention, water or a mixed liquid of water and an organic solvent can be used as the aqueous liquid in which the abrasive particles are dispersed. The mixed solution is a mixture of at least one organic solvent having solubility in water within the range of solubility in water and containing at least 1% of water. Examples of the organic solvent include alcohol and ketone.

  Examples of alcohols that can be used as the organic solvent include methanol (methyl alcohol), ethanol (ethyl alcohol), 1-propanol (n-propyl alcohol), 2-propanol (iso-propyl alcohol, IPA), 2-methyl-1- Examples include propanol (iso-butyl alcohol), 2-methyl-2-propanol (tert-butyl alcohol), 1-butanol (n-butyl alcohol), 2-butanol (sec-butyl alcohol), and the like. Polyhydric alcohols include 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,3-propanediol (trimethylene glycol), 1,2,3-propanetriol. (Glycerin).

  Examples of ketones include propanone (acetone) and 2-butanone (methyl ethyl ketone, MEK). In addition, tetrahydrofuran (THF), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 1,4-dioxane and the like can also be used.

  According to the polishing slurry of the present invention, even when manganese oxide is used as the polishing particles, it is possible to provide a polishing technique that can realize a polishing speed and polishing surface accuracy equal to or higher than those of cerium oxide.

  Embodiments of the present invention will be described with reference to examples and comparative examples. First, the relationship between the polishing performance and the polishing particle concentration in the polishing slurry was tested.

[Examples 1 to 3, Comparative Examples 1 and 2]
Manganese dioxide MnO ₂ (FMH, average particle diameter D ₅₀ 3 μm, manufactured by Tosoh Corporation) was wet-pulverized to an average particle diameter D _{50 of} 0.41 μm. After pulverization, it was calcined at 850 ° C. for 2 hours to obtain dimanganese trioxide Mn ₂ O ₃ . The average particle size _{D 50} after firing was 1.85. Thereafter, wet pulverization was performed again to obtain an average particle diameter D _{50 of} 0.51 μm. This dimanganese trioxide (specific surface area of 32 m ² / g) was dispersed as abrasive particles in water, which is an aqueous liquid, to prepare polishing slurries with various concentrations shown in Table 1. The pH of each slurry was adjusted to the pH shown in Table 1 using potassium hydroxide. The average particle diameter D ₅₀ of Mn ₂ O ₃ was measured with a laser diffraction / scattering particle diameter distribution measuring apparatus (LA920, manufactured by Horiba, Ltd.).

  And soda-lime glass (diameter 50mm) was grind | polished with each grinding | polishing slurry, and the grinding | polishing characteristic was investigated. Before the polishing treatment, the average surface roughness of the glass was measured in the range of 10 μm × 10 μm with an AFM (Atomic Force Microscope: Nanoscope IIIa manufactured by Veeco), and the result was Ra 18 nm.

  As polishing conditions, MH-N15A (lattice grooved) manufactured by Nitta Haas Co., Ltd. was used as a polishing pad, the load was 8.2 kPa, the rotation speed was 60 rpm, and the polishing time was 30 minutes. After the polishing treatment, the polished surface was washed with water, and the attached slurry was removed and dried. The surface roughness was measured by AFM at any five points on the dry polished surface. The results of the average surface roughness measurement (range of 10 μm × 10 μm) are shown in Table 1. Further, the weight of the soda lime glass before and after polishing was measured, and the polishing rate was calculated from the surface area of the surface to be polished and the specific gravity of the glass, using the difference in weight as the amount of polishing. Table 1 shows the calculated polishing speed.

[Comparative Examples 3 to 7]
The same manganese dioxide MnO ₂ (Tosoh Corp., FMH, average particle size D ₅₀ 3 μm) as in Example 1 was wet pulverized to an average particle size D _{50 of} 0.41 μm. As a result, the slurry was dispersed in water as an aqueous liquid to prepare polishing slurries having various concentrations shown in Table 1. The pH of each slurry was adjusted to the pH shown in Table 1 using potassium hydroxide. And the grinding | polishing characteristic was investigated on the same conditions as Examples 1-3. The results of each polishing slurry of Comparative Examples 3-7 are shown in Table 1. The average particle diameter D ₅₀ of MnO ₂ was measured by a laser diffraction / scattering particle diameter distribution measuring apparatus (LA920 manufactured by Horiba, Ltd.).

[Reference Examples 1-5]
Under the same conditions as in Examples 1 to 3, using a cerium oxide-based abrasive (mean particle size of 0.5 μm, specific surface area of 8 m ² / g, Milleak M60, manufactured by Mitsui Mining & Smelting Co., Ltd.) mainly containing cerium oxide The same substrate was polished. The results are shown in Table 1. The polishing treatment was performed without adjusting the pH of the polishing slurry.

  From Table 1, the polishing slurry (Examples 1 to 3) in which dimanganese trioxide, which is an abrasive particle, is less than 10 wt% has the same polishing rate as the cerium oxide abrasive slurry (Reference Examples 3 to 5). In addition to being able to be maintained, the surface roughness after polishing was smoother than that of a slurry of the same concentration of cerium oxide abrasive. On the other hand, even when the concentration of dimanganese trioxide was set to a high concentration of 10 wt% or more (Comparative Examples 1 and 2), the polishing rate was not improved so much, but the surface roughness was increased. Further, when the polishing particles of Comparative Examples 3 to 7 were dimanganese dioxide, it was confirmed that the surface roughness after polishing could be finished smoothly but the polishing speed was slow.

[Examples 4 to 8, Comparative Example 8]
Next, the relationship of the polishing performance to the pH of the polishing slurry was tested. A polishing slurry having a slurry concentration of 4 wt% was prepared in the same manner as in Examples 1 to 3, and then adjusted to the pH shown in Table 2 with potassium hydroxide. For each slurry, the same substrate as in Examples 1 to 3 was polished under the same conditions. The results are shown in Table 2.

  From Table 2, it was found that the polishing rate was improved by increasing the pH of the polishing slurry. At a pH of 4 or more (Examples 4 to 8), the polishing rate was comparable to that of the cerium oxide-based abrasive, and at a pH of 7 or more (Examples 5 to 8), the polishing rate was higher than that of the cerium oxide-based abrasive. This is presumably because the hydroxyl groups in the polishing slurry increased by raising the pH, and the chemical reactivity with the glass as the material to be polished increased.

  According to the present invention, it is possible to provide a glass polishing treatment technique equivalent to that when a cerium oxide abrasive is used.

Claims (4)

In a polishing slurry for polishing a substrate,
A polishing slurry characterized in that the abrasive particles are mainly composed of dimanganese trioxide, the content of the abrasive particles is less than 10% by weight with respect to the polishing slurry, and the pH of the polishing slurry is pH 4 or more.   The polishing slurry according to claim 1, wherein the substrate is glass.   Abrasive particles are composed mainly of dimanganese trioxide, and the abrasive particles are less than 10% by weight based on the abrasive slurry, and the substrate is polished while maintaining the pH at pH 4 or higher. A polishing method for a substrate characterized by the above.   The method for polishing a substrate according to claim 3, wherein the substrate is glass.