JP6570382B2 - Polishing silica additive and method using the same - Google Patents

Description

  The present invention relates to a polishing silica additive and a method using the same.

Single crystal sapphire has excellent mechanical properties, chemical stability, and light transmission characteristics, and is used in a wide range of fields such as parts for semiconductor manufacturing equipment, LED substrates, and window materials. In any application, it is necessary to make the sapphire surface highly smooth, but since the hardness is high, processing is difficult, and a more advanced surface polishing technique is required.

Colloidal silica is generally used as the abrasive additive used for polishing the sapphire surface because of cost and polishing characteristics, but when polishing while ensuring low defects and high smoothness on the sapphire surface, There is a problem that the polishing time becomes very long.

As a design of an abrasive additive for increasing the polishing rate of the sapphire surface, for example, Patent Document 1 discloses that the colloidal silica has a first particle size maximum at 2 to 25 nm and a second particle size maximum at 75 to 200 nm. A technique for obtaining a multimodal particle size distribution having a value is disclosed. Patent Document 2 discloses a technique for adjusting the specific surface area (m ² / g) / number average particle diameter (nm) of colloidal silica to 0.5 to 3.0. However, since colloidal silica generally has a low particle density, the effect of improving the polishing rate of the sapphire surface is still insufficient. Since the polishing rate of the sapphire surface greatly affects the productivity of the sapphire substrate, improvement of the polishing rate is the biggest issue, and an abrasive additive that can achieve this is strongly desired.

Japanese Patent Laying-Open No. 2015-51497 JP 2014-187348 A

  An object of the present invention is to provide a polishing silica additive capable of achieving polishing excellent in polishing rate without deteriorating surface roughness and scratch properties, and a polishing slurry containing the same. Is to provide.

The present inventor has intensively studied to achieve the above object, and has found a silica additive for polishing that achieves this. The present invention is based on such knowledge and has the following gist.
(1) The particle density is 2.0 g / cm ³ or more, the specific surface area is 20 m ² / g or more and 100 m ² / g or less, and the average sphericity of particles having a particle diameter of 50 nm or more is 0.80 or more. Polishing silica additive.
(2) The ratio (A) / (B) of the particle diameter (A) having a cumulative volume of 80% and the particle diameter (B) having a cumulative volume of 20% is from 1.5 to 5.0. The polishing silica additive according to (1).
(3) The polishing silica additive as described in (1) or (2) above, wherein the amount of metal Si is 10 ppm or less.
(4) A polishing slurry comprising the polishing silica additive according to any one of (1) to (3).
(5) A method for polishing a material to be polished, including a step of polishing the material to be polished using the polishing slurry according to (4).
(6) A method for polishing a sapphire surface, including a step of polishing the sapphire surface using the polishing slurry according to (4).

  ADVANTAGE OF THE INVENTION According to this invention, the silica additive for grinding | polishing which can achieve the grinding | polishing excellent in grinding | polishing speed, without deteriorating surface roughness and scratch property, and the polishing slurry containing it are provided.

Hereinafter, the present invention will be described in detail.

The polishing silica additive of the present invention needs to have a particle density of 2.0 g / cm ³ or more. When the particle density is less than 2.0 g / cm ³ , the strength of the particles themselves is lowered, and thus the polishing rate cannot be sufficiently improved when used as a polishing slurry. A preferable particle density is 2.1 g / cm ³ or more, and 2.2 g / cm ³ which is a theoretical silica density is more preferable.

  The particle density of the silica additive for polishing of the present invention is measured using a continuous automatic powder true density measuring device “Auto True Denser MAT-7000” manufactured by Seishin Enterprise Co., Ltd. Reagent special grade ethanol was used as a measurement solvent.

The polishing silica additive of the present invention is required to have a specific surface area of 20 m ² / g or more and 100 m ² / g or less. When the specific surface area is less than 20 m ² / g, the number of particles present per unit mass decreases, so that the polishing rate when used as a polishing slurry decreases. On the other hand, when the specific surface area exceeds 100 m ² / g, the number of particles present per unit mass increases, but the influence on the polishing rate per particle is extremely reduced. The polishing rate is reduced. The specific surface area is preferably 30 m ² / g or more and 90 m ² / g or less, more preferably 40 m ² / g or more and 80 m ² / g or less.

  The specific surface area of the silica additive for polishing of the present invention is a value based on the BET method, and is measured by a BET single point method using a specific surface area measuring machine “Macsorb HM model-1208” manufactured by Mountec. Prior to the measurement, pretreatment was performed by heating at 300 ° C. for 18 minutes in a nitrogen gas atmosphere. The adsorbed gas was a mixed gas of 30% nitrogen and 70% helium, and the flow rate was adjusted so that the indicated value of the main body flow meter was 25 ml / min.

  The polishing silica additive of the present invention requires that the average sphericity of particles having a particle diameter of 50 nm or more is 0.80 or more. When the average sphericity is low, the shape of the particles becomes irritation, and the surface roughness of the polished surface of the material to be polished deteriorates when used as a polishing slurry. In particular, when the sphericity of coarse particles having a particle diameter of 50 nm or more is less than 0.80, the deterioration of the surface roughness becomes remarkable. The average sphericity of particles having a particle diameter of 50 nm or more is preferably 0.83 or more, more preferably 0.86 or more.

The average sphericity of the polishing silica additive of the present invention is measured by the following method. After fixing the silica additive for polishing on the sample stage with carbon paste, osmium coating was performed, and an image taken with a scanning electron microscope “JSM-6301F type” manufactured by JEOL Ltd. with a magnification of 100,000 times and a resolution of 2048 × 1536 pixels I imported it into my computer. Using this image analysis apparatus “MacView Ver. 4” manufactured by Mountec Co., Ltd., particles were recognized using a simple capture tool, and the sphericity was measured from the projected area (A) and the perimeter (PM) of the particles. . If the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle is A / B, so a perfect circle having the same perimeter as the perimeter (PM) of the sample is assumed. Then, since PM = 2πr and B = πr ² , B = π × (PM / 2π) ² , and the sphericity of each particle is sphericity = A / B = A × 4π / (PM) ² . Become. The sphericity of 200 particles having an arbitrary projected area equivalent circle diameter of 50 nm or more thus obtained was determined, and the average value was defined as the average sphericity.

  In the polishing silica additive of the present invention, the ratio (A) / (B) of the particle diameter (A) having a cumulative volume of 80% and the particle diameter (B) having a cumulative volume of 20% is 1.5 to 5.0. Preferably there is. (A) / (B) represents variation in particle size. By giving the particle size a specific variation, when used as a polishing slurry, each particle efficiently enters the gap between the particles, and the number of particles in contact with the polishing surface of the material to be polished increases. As a result, the polishing rate can be further improved. When (A) / (B) is less than 1.5, the particle size is too uniform, so that the number of particles entering the gaps between the particles is small, and the effect of improving the polishing rate is insufficient when used as a polishing slurry. Become. On the other hand, if (A) / (B) exceeds 5.0, the particle size variation is too large, and the abundance ratio of particles capable of improving the polishing rate efficiently decreases. When used as, the effect of improving the polishing rate becomes insufficient. More preferable (A) / (B) is 1.7 or more and 4.5 or less, and further preferably 2.0 or more and 4.0 or less.

The ratio (A) / (B) of the particle size (A) having a cumulative volume of 80% and the particle size (B) having a cumulative volume of 20% of the silica additive for polishing of the present invention is measured by the following method. After fixing the silica additive for polishing on the sample stage with carbon paste, osmium coating was performed, and an image taken with a scanning electron microscope “JSM-6301F type” manufactured by JEOL Ltd. with a magnification of 100,000 times and a resolution of 2048 × 1536 pixels I imported it into my computer. Using this image, an image analysis device “MacView Ver. 4” manufactured by Mountec Co., Ltd. was used to recognize the particles using a simple capture tool, and the projected area equivalent circle diameter of the particles was measured. After measuring the projected area equivalent circle diameter of 2000 particles, the particle size distribution based on the volume standard is automatically analyzed using the above-described image analysis apparatus, and the particle diameter (A) of the cumulative volume 80% and the cumulative volume 20% The particle diameter (B) was determined, and (A) / (B) was calculated.

  The polishing silica additive of the present invention preferably has a metal Si content of 10 ppm or less. If the amount of metal Si exceeds 10 ppm, the scratch property of the polished surface of the material to be polished may be deteriorated when used as a polishing slurry. A more preferable amount of metallic Si is 5 ppm or less, and further preferably 1 ppm or less.

  The polishing silica additive of the present invention is preferably produced by a metal Si oxidation reaction method as described later. The particle size of the metal Si contained in the polishing silica additive obtained by the metal Si oxidation reaction method is often about several μm, and the particle size is very large compared to the polishing silica additive. If metal Si having a large particle size is present, the scratch property may be significantly deteriorated. Therefore, the amount of metal Si contained in the polishing silica additive is preferably reduced as much as possible at the time of production. Further, when the amount of metal Si during production is not sufficient, an operation for further reducing metal Si can be added. The method is not particularly limited, but it is preferable to use a wet classification method such as sedimentation separation or centrifugal separation utilizing the difference in particle diameter between the silica additive for polishing and the metal Si.

  The amount of metallic Si in the polishing silica additive of the present invention is measured using an ICP emission analysis method. Prior to the measurement, the metal Si was concentrated so that the amount of metal Si in the polishing silica additive could be detected even in a very small region. First, 900 g of water was added to 100 g of polishing silica additive to prepare a slurry having a polishing silica additive concentration of 10% by mass, and “SONIFIER450 (crushing horn 3/4 ″ solid type)” manufactured by BRANSON was used. The dispersion process was performed for 2 minutes at an output level of 8. 40 g of the slurry after dispersion treatment is transferred to a centrifuge tube “CT-500B” manufactured by Sampleratech Co., Ltd. and centrifuged at 1000 G for 30 minutes using a multi-frame cooling centrifuge “EX-126” manufactured by Tommy Seiko Co., Ltd. Allowed to settle. After centrifuging the whole slurry, the supernatant liquid was removed and the precipitated silica additive for metal Si concentration polishing was recovered, dried at 120 ° C. for 24 hours, and the weight was measured. Then, 1 g of silica additive for metal Si concentration polishing is precisely weighed on a platinum dish, 20 mL of reagent special grade hydrofluoric acid is added, water is added to the extent that the sample is immersed, and it is heated at 160 ° C. for 2 hours using a hot plate. Heated to dissolve and dry the sample. Next, 0.5 ml of reagent grade nitric acid and 3 mL of hydrofluoric acid were added to the dried product of the platinum dish and redissolved, and then transferred to a 25 mL resin flask and made up to volume with pure water. The amount of Si in the solution was measured for emission intensity at a wavelength of 251.6 nm using an ICP emission spectroscopic analyzer “ICPE-9000” manufactured by Shimadzu Corporation. This measured value was quantified by a calibration curve prepared using an atomic absorption Si standard solution (1000 mg / L) manufactured by Kanto Chemical Co., and the metal Si content contained in the silica additive for metal Si concentration polishing was determined. From the value, the amount of metallic Si contained in the original polishing silica additive was calculated. For example, if the weight of the metal Si concentrated polishing silica additive is 5 g with respect to 100 g of the original polishing silica additive, and the amount of metal Si in the metal Si concentrated polishing silica additive is 40 ppm, the present invention The amount of metallic Si contained in this polishing silica additive is calculated to be 2 ppm.

  The method for producing the polishing silica additive of the present invention is preferably a metal Si oxidation reaction method in order to realize the particle density, sphericity and particle size ratio of the polishing silica additive of the present invention. For example, a method of spheroidizing metal Si by throwing it into a high-temperature field formed by a chemical flame or an electric furnace, etc., and making it spheroidize (for example, Japanese Patent No. 1568168), oxidation reaction by spraying metal Si particle slurry into the flame It can be produced by a spheroidizing method (for example, JP-A-2000-247626).

The polishing slurry of the present invention is a polishing slurry containing the polishing silica additive of the present invention. The content of the silica additive for polishing in the polishing slurry is preferably 3 to 70% by mass, more preferably 5 to 60% by mass.

The polishing slurry of the present invention is preferably used for polishing after adjusting to a desired pH. As the pH adjusting agent, known acids, bases, or salts thereof can be used. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, and propionic acid. Examples of the base include organic bases such as aliphatic amines, alkali metal hydroxides such as potassium hydroxide, and ammonia. The pH value is preferably 4.5-12, more preferably 5-11.

  The polishing slurry of the present invention can contain components such as a solvent, an etching agent, an oxidizing agent, a surface modifier, an antiseptic, an antifungal agent, an antirust agent, a chelating agent, and a rheological agent as necessary.

The method for polishing the material to be polished, particularly the step of polishing the surface of sapphire using the polishing slurry of the present invention, is not particularly limited, and a general method can be adopted. For example, while supplying the polishing slurry onto the polishing cloth of the polishing surface plate, the polishing surface plate and the polishing material are moved relatively while the polishing surface of the material to be polished is pressed against the polishing cloth such as nonwoven fabric or foamed polyurethane. The method of grind | polishing a grinding | polishing surface by this is mentioned.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.
Examples 1-10, Comparative Examples 1-6
The silica additive for polishing uses a device in which a double-pipe LPG-oxygen mixed burner capable of forming an inner flame and an outer flame is installed in the center of the top of the combustion furnace, and a collection system line is directly connected to the lower part. Manufactured. A two-fluid nozzle for slurry spraying was further installed at the center of the burner, and a slurry made of metal Si powder (average particle size 5 μm) and water was sprayed from the center. Oxygen was supplied from the surroundings. The formation of the flame was performed by providing several tens of pores at the outlet of the double tube burner and injecting a mixed gas of LPG and oxygen therefrom. Further, in order to reduce the amount of metal Si contained in the polishing silica additive, a burner was further installed at eight locations around the burner to form a flame, thereby promoting the oxidation reactivity of metal Si. The silica additive for polishing produced from the two-fluid nozzle and passing through the flame was pneumatically transported through a collection line by a blower and collected by a bag filter. In addition, adjustment of the particle density of the silica additive for polishing was performed by adding 0 to 10% by mass of polyvinyl alcohol having an average polymerization degree of 500 in the metal Si powder / water slurry container when jetting the metal Si powder / water slurry, Furthermore, stirring was carried out while sending fine air bubbles into the slurry using a microbubble generator, and the particle density was adjusted by jetting the slurry. Specifically, the amount of polyvinyl alcohol added was increased as the particle density was decreased, and the particle density was adjusted. The sphericity of the silica additive for polishing was adjusted by adjusting the metal Si concentration of the metal Si powder / water slurry in the range of 30 to 70% by mass. Specifically, when the sphericity is increased, the metal Si concentration of the metal Si powder / water slurry is increased, and when the sphericity is decreased, the metal Si concentration of the metal Si powder / water slurry is decreased. It was adjusted. The specific surface area of the silica additive for polishing was adjusted by adjusting the feed amount of the metal Si powder / water slurry in the range of 5 to 30 kg / Hr. Specifically, when the specific surface area was increased, the feed amount of the metal Si powder / water slurry was decreased, and when the specific surface area was decreased, the feed amount of the metal Si powder / water slurry was increased.

In order to further reduce the amount of metallic Si contained in the polishing silica additive collected by the bag filter, the following operation was performed. Add water to the polishing silica additive to make a slurry with a polishing silica additive concentration of 10% by mass and use “SONIFIER450 (crushing horn 3/4 ″ solid type)” manufactured by BRANSON at an output level of 8 Dispersion treatment was performed for 2 minutes. The slurry after the dispersion treatment was centrifuged at 1000 G for 1 to 60 minutes using a multi-frame cooling centrifuge “EX-126” manufactured by Tommy Seiko Co., to precipitate the metal Si, and the supernatant was recovered, and then 120 ° C. The amount of metallic Si was adjusted by drying for 24 hours. Specifically, the amount of metal Si was reduced by increasing the time of centrifugation as the amount of metal Si was decreased.

  The particle density, specific surface area, average particle diameter of particles having a particle diameter of 50 nm or more, particle diameter (A) of cumulative volume 80% and cumulative volume 20% of the silica additive for polishing produced by adjusting the amount of metal Si described above. Tables 1 and 2 show the particle diameter (B) ratio (A) / (B) and the amount of metal Si.

In order to evaluate the characteristics of the manufactured polishing silica additive as a polishing slurry, a sapphire polishing test was conducted. Using ion-exchanged water as the silica additive dispersion medium for polishing and ammonia as the pH adjuster, the concentration of the silica additive for polishing in the slurry was adjusted to 12% by mass and the pH was adjusted to 9.5. A non-woven pad (FPK770 manufactured by Fujibow Atago Co., Ltd.) was used for polishing, the lower surface plate was set at 300 mmφ and the rotation speed was 150 rpm, and the upper surface plate on which a 2-inch φ sapphire a-side substrate (made by Saito Optical Co., Ltd.) was set was rotated at 150 mmφ. The upper surface plate and the lower surface plate were rotated in the same direction at 150 rpm. Polishing was performed at a polishing pressure of 314 g / cm ² and a slurry supply rate of 10 mL / min for 30 minutes. The slurry was poured. About the board | substrate after grinding | polishing, grinding | polishing speed, surface roughness, and scratch property were evaluated according to the following. The results are shown in Tables 1 and 2.

(1) Polishing rate From the change in weight of the sapphire substrate before and after polishing, the amount of change in substrate thickness per hour (μm / hr) was calculated. The polishing test was carried out three times, and the average value of the three measurements was determined as the polishing rate. The larger the polishing rate value, the better the polishing rate.

(2) The surface property of the sapphire substrate after polishing the surface roughness was evaluated using a Nikon optical interference microscope “BW-D507”. The measurement range of the observation image was 50 μm × 50 μm, the height was measured, and the arithmetic average roughness was obtained. Nine measurements were performed on the surface of the polished sapphire substrate. The polishing test was performed three times, and the average value of the arithmetic average roughness of a total of 27 measurements was obtained. It shows that the surface is smooth, so that the value of this arithmetic mean roughness is small.

(3) The surface of the sapphire substrate after scratching polishing was quantitatively evaluated for scratches using an optical surface analyzer “Candela CS10” manufactured by KLA-Tencor. The polishing test was performed three times, and each substrate was irradiated with a laser to measure the number of scratches. The average value of three measurements was obtained to calculate the number of scratches per substrate. The smaller the number of scratches, the better the scratch properties.

  As is clear from the comparison between the example and the comparative example, the polishing rate was 1.03 to 1.21 μm / hr in the example, which could not be achieved by the conventional silica additive having a low particle density. A polishing rate of 1.00 μm / hr or more could be stably obtained. Therefore, according to the present invention, a polishing slurry having an excellent polishing rate is provided without deteriorating the surface roughness of the material to be polished, particularly the sapphire surface, and the scratch property. In addition, a polishing silica additive suitable for the polishing slurry is provided.

  As described above, by using the polishing silica additive of the present invention and the polishing slurry containing the same, polishing with excellent polishing speed is achieved without deteriorating the surface roughness and scratch properties. I can do it. Therefore, by using the polishing silica additive of the present invention and the polishing slurry containing the same, it becomes possible to efficiently polish various materials to be polished, particularly the surface of the sapphire, such as a sapphire substrate. It can contribute to productivity improvement.

Claims (6)

A polishing silica characterized by having a particle density of 2.0 g / cm ³ or more, a specific surface area of 20 m ² / g to 100 m ² / g, and an average sphericity of particles having a particle diameter of 50 nm or more of 0.80 or more. Additive. The ratio (A) / (B) of the particle diameter (A) having a cumulative volume of 80% and the particle diameter (B) having a cumulative volume of 20% is 1.5 or more and 5.0 or less. The silica additive for polishing as described. 3. The polishing silica additive according to claim 1, wherein the amount of metal Si is 10 ppm or less.   A polishing slurry comprising the polishing silica additive according to claim 1.   A method for polishing a material to be polished, comprising a step of polishing the material to be polished using the polishing slurry according to claim 4. The polishing method of the sapphire surface including the process of grind | polishing the sapphire surface using the polishing slurry of Claim 4.