JP2008290183A - Composition for polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for polishing capable of improving polishing speed and preventing surface polishing scratches. <P>SOLUTION: The composition for polishing a brittle material is constituted of polishing particles and cerium hydroxide as the polishing accelerating agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing composition used for polishing a brittle material such as glass.

  As a process for manufacturing a magnetic recording medium substrate, a semiconductor wafer, an optical lens, a prism, a mirror, and the like, a process of polishing a surface of a material such as glass, carbon, and ceramics is necessary. In the polishing step, an abrasive is used. As the performance of the abrasive, the polishing rate is improved to increase the production efficiency and the surface quality of the workpiece is prevented from being scratched to improve the quality of the product. Is required.

Patent Document 1 discloses a polishing method using abrasive grains. Patent Document 2 discloses a conventional polishing composition used for polishing glass.
JP 2005-205560 A JP 2001-89748 A

  However, in the polishing method described in Patent Document 1, the suppression of polishing scratches due to mechanical polishing of abrasive grains is insufficient, and the polishing composition described in Patent Document 2 is also in terms of polishing rate and polishing scratches. They were not fully satisfied and left room for improvement.

  Then, this invention makes it a subject to provide the polishing composition which can improve a grinding | polishing speed | rate and can prevent surface grinding | polishing scratches.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  The first aspect of the present invention is a polishing composition for polishing a brittle material, containing abrasive grains and cerium hydroxide as a polishing accelerator. The polishing composition according to the first aspect of the present invention contains cerium hydroxide as a polishing accelerator together with abrasive grains. Thereby, the polishing rate can be improved while preventing surface polishing scratches.

  In the first aspect of the present invention, the abrasive is preferably cerium oxide. By using cerium oxide as the abrasive and combining with cerium hydroxide, which is a polishing accelerator, the effect of improving the polishing rate can be exhibited more effectively while preventing surface polishing flaws.

  In the first aspect of the present invention, the abrasive grains are preferably aluminum oxide or diamond. When using aluminum oxide or diamond as abrasive grains, the conventional polishing composition has a problem that the polishing rate is slow, but in the present invention, by combining with cerium hydroxide as a polishing accelerator, The speed can be greatly improved.

  In the first invention, the secondary particle diameter of the abrasive grains is preferably 300 nm or more. By using abrasive grains having such a particle size, the polishing rate can be further improved.

  In the first invention, the primary particle diameter of cerium hydroxide is preferably 50 nm or less. By using cerium hydroxide having such an average particle diameter, the action of promoting the polishing action is more effectively exhibited.

  In 1st this invention, it is preferable that the addition density | concentration of cerium hydroxide shall be 0.4 mass% or more and 60 mass% or less by making an abrasive grain into 100 mass%. By adding a polishing accelerator in such a range, the polishing rate can be greatly improved.

  The polishing composition of the first aspect of the present invention preferably has a pH of 2 or more and 12 or less. By setting the pH to such a range, the degree of acidity and alkalinity can be set to an appropriate range. As a result, wastewater treatment can be facilitated and the production apparatus can be prevented from being corroded.

  Examples of the brittle material to be polished by the polishing composition of the first invention include a workpiece having a silicon-oxygen bond. Specific examples of the workpiece having a silicon-oxygen bond include soda glass, quartz glass, crystal, and aluminosilicate glass.

  The second aspect of the present invention is a method for polishing a workpiece (40) having a silicon-oxygen bond, using the polishing composition (30) of the first aspect of the present invention. According to the second method of the present invention, the workpiece (40) having a silicon-oxygen bond can be subjected to surface polishing at a high polishing rate while preventing surface polishing scratches.

  In the third aspect of the present invention, the polishing composition (30) of the first aspect of the present invention is supplied onto the polishing pad (20), and the workpiece (40) is pressed onto the polishing pad (20) for polishing. A method of polishing a workpiece (40) comprising: a step of sliding a pad (20) and a workpiece (40) to polish the workpiece (40).

  In the third aspect of the present invention, the polishing pad (20) is preferably composed mainly of polyurethane. The main component here means that polyurethane is preferably contained in an amount of 50% by mass or more, more preferably 70% by mass or more, based on the mass of the entire polishing pad (100% by mass). As long as the main component is polyurethane, it may be a composite material blended with other resin components such as acrylic.

  In the polishing method according to the third aspect of the present invention, the pressure for pressing the workpiece (40) onto the polishing pad (20) is preferably 3 kPa or more and less than 20 kPa. By setting it as such a pressure, it can prevent that a grinding | polishing damage | wound arises on the surface of a workpiece (40), and can obtain sufficient processing speed. The pressure is more preferably 3 kPa or more and less than 10 kPa.

  4th this invention is a grinding | polishing acceleration | stimulation additive for adding to the polishing composition for grind | polishing a brittle material containing cerium hydroxide, and promoting a grinding | polishing effect | action. By adding the additive, the polishing action of the conventional polishing composition can be promoted.

  The polishing composition according to the first aspect of the present invention contains cerium hydroxide as a polishing accelerator together with abrasive grains. Thereby, the polishing rate can be improved while preventing surface polishing scratches.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
<Polishing composition>
The polishing composition of the present invention contains abrasive grains and cerium hydroxide as a polishing accelerator.
(Use of the polishing composition of the present invention)
The polishing composition of the present invention is used when a brittle material is polished. Examples of the brittle material include soda glass, quartz glass, crystal, aluminosilicate glass, sapphire, silicon carbide, gallium nitride, and gallium arsenide. Specifically, in the process of manufacturing a semiconductor wafer, optical lens, prism, mirror, etc., it is necessary to polish the surface of these brittle materials, and the polishing composition of the present invention is used in this polishing process. .

  An outline of the polishing process is shown in FIG. A polishing pad 20 is attached on the polishing surface plate 10. The workpiece 40 to be polished is affixed to the carrier 50. The polishing composition 30 of the present invention is supplied dropwise from the supply member 35 onto the polishing pad 20. The polishing surface plate 10 and the carrier 50 are rotated in the direction indicated by the arrows with the center as an axis, respectively, and the carrier 50 is pressed downward in the figure, and the surface of the workpiece 40 is pressed against the surface of the polishing pad 20. . Thereby, the surface of the workpiece 40 slides on the surface of the polishing pad 20 onto which the polishing composition of the present invention is dropped, and the surface of the workpiece 40 is polished. The polishing composition 30 of the present invention is preferably supplied so as to always exist on the surface of the polishing pad 20 that slides on the workpiece 40. The supply mechanism of the polishing composition 30 is not particularly limited.

  As the polishing pad 20, a material generally used for polishing a brittle material can be used. For example, polyurethane, acrylic, polyester, acrylic ester copolymer, polytetrafluoroethylene, polypropylene, Examples include polyethylene, cellulose, cellulose ester, and nylon. In addition, it is also possible to apply a circular groove process to the surface of the polishing pad 20 that contacts the workpiece 40 so that the polishing composition remains.

  The number of rotations of the polishing surface plate 10 and the carrier 50 is preferably in the range of 30 to 100 rpm from the viewpoint of the balance between the polishing speed and the surface quality of the workpiece 40. The rotational speeds of the polishing surface plate 10 and the carrier 50 may be different from each other within this range. Further, the pressing pressure of the carrier 50 toward the polishing pad 20 is preferably 3 kPa or more and less than 20 kPa, more preferably 5 kPa or more and less than 10 kPa, and further preferably 6 kPa or more and less than 9 kPa.

(Abrasive grains)
Examples of the abrasive grains contained in the polishing composition of the present invention include cerium oxide, aluminum oxide, diamond, zirconium oxide, silicon carbide, and silicon oxide. Among these, when cerium oxide is used as the abrasive grains, it is known that cerium oxide causes a chemical reaction with the workpiece, resulting in chemical / mechanical polishing and improving the polishing rate. In addition, since the work material is denatured and polished by a chemical reaction, a sufficient polishing rate can be exhibited even if the cerium oxide, which is an abrasive grain, is softer than the work material. For this reason, the grinding | polishing damage | wound of a workpiece can be prevented. In addition, when abrasive grains that do not cause a chemical reaction with the workpiece are used, the solvent has been made acidic or alkaline in order to improve the processing speed. In this case, other than the workpiece There was a problem of corroding the machining apparatus and the like. When cerium oxide is used as the abrasive grains, the abrasive grains themselves can react with the workpiece and the polishing rate can be improved, so that the solvent can be neutral water, and such problems can be prevented.

  When aluminum oxide or diamond is used as the abrasive grains, the abrasive grains themselves do not cause a chemical reaction with the workpiece as described above. Therefore, in general, compared with the case where cerium oxide is used as the abrasive grains. The polishing rate becomes slow. On the other hand, in the present invention, a polishing accelerator described below was added to improve the polishing rate. As a result, even when aluminum oxide or diamond was used as the abrasive grains, the polishing rate was successfully improved to a level comparable to that when cerium oxide was used (see Comparative Example 3 and Example 8).

  The secondary particle diameter of the abrasive grains is preferably 300 nm or more. By using abrasive grains having such a particle size, the polishing rate can be further improved. Secondary particles mean particles formed by agglomeration of primary particles. The particle size of the secondary particles can be measured by a known method, and for example, can be measured by a dynamic light scattering method or a laser diffraction / scattering method.

(Abrasive manufacturing method)
The manufacturing method of an abrasive grain is not specifically limited, The commercial item manufactured by the well-known method is available.

(Polishing accelerator)
The polishing composition of the present invention contains cerium hydroxide as a polishing accelerator. The mechanism by which the polishing rate is accelerated when cerium hydroxide is added is not clear, but the present inventors consider as follows. Cerium hydroxide causes a chemical reaction similar to that of cerium oxide on the workpiece, and the effect is expected to be greater than that of cerium oxide. Therefore, it is considered that the polishing rate is improved and polishing scratches due to mechanical polishing can be suppressed.

  Since cerium hydroxide is a polishing accelerator, it is not necessary to control the particle size in particular. However, in order to exert the accelerating action, the primary particle size is preferably small, and preferably 50 nm or less. The primary particle diameter is taken by transmission electron microscope (TEM), and when the primary particle is sandwiched between two parallel lines, the value of the smallest part is the short diameter, the value of the largest part is the long diameter, The average of the short diameter and long diameter was taken as the primary particle diameter. The primary particle diameter is an arithmetic average value of 100 primary particle diameters.

(Cerium hydroxide manufacturing method)
The production method of cerium hydroxide is not particularly limited, and a commercial product produced by a known method is available.

(solvent)
The polishing composition of the present invention is in the form of a slurry containing the above-described abrasive grains, polishing accelerator and solvent. The solvent is not particularly limited and water is usually used, but other alcohol solvents (ethanol, propanol, butanol, lauryl alcohol, isostearyl alcohol, oleyl alcohol, cyclohexyl alcohol, benzyl alcohol, etc.), polyhydric alcohols Solvents (ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polyoxyethylene polyoxypropylene glycol, glycerin, etc.) and hydrocarbon solvents (n-hexane, n-octane, n-decane, petroleum) Hydrocarbon-based solvents (solvent naphtha, liquid paraffin, mineral spirit, mineral oil, etc.) composed of the components obtained as described above are used.

  As a method for dispersing the abrasive grains and the polishing accelerator in the solvent, for example, a method using a normal stirrer or a method using a ball mill or the like can be employed.

  In the polishing composition of the present invention, the total amount of the abrasive grains and the polishing accelerator is preferably 5% by mass to 50% by mass based on the mass of the entire polishing composition (100% by mass). It is more preferable to set it as mass%-40 mass%. When the total amount is 5% by mass or more, the function as a polishing composition can be effectively exhibited, and when the total amount is 50% by mass or less, the dispersion stability is improved. Manufacturing cost can be reduced.

  The addition amount of the polishing accelerator to the abrasive grains in the polishing composition of the present invention is preferably 0.4% by mass or more and 60% by mass or less, more preferably, based on the mass of the abrasive grains (100% by mass). It is 2 mass% or more and 20 mass% or less, More preferably, it is 4 mass% or more and 10 mass% or less.

  The polishing composition of the present invention has a pH of preferably 2 to 12, more preferably 3 to 11, and further preferably 4 to 8. By setting the pH to such a range, the degree of acidity or alkalinity can be set to an appropriate range. As a result, wastewater treatment can be facilitated and the production apparatus can be prevented from being corroded, which is preferable.

(Other additives)
The polishing composition of the present invention can contain other components in addition to the above-described abrasive grains and polishing accelerator as long as each performance is not affected. For example, a dispersing agent can be added to disperse the abrasive grains. By adding such a dispersant, it is possible to suppress so-called dust from adhering abrasive grains to the surface of the workpiece and to improve dispersibility, which is preferable. As the dispersant, those not containing metal ions can be preferably used. Specifically, water-soluble organic polymers such as ammonium salts of polyacrylic acid, polyvinyl alcohol, water-soluble anionic surfactants such as ammonium lauryl sulfate, and water-soluble nonionic interfaces such as polyethylene glycol monostearate Water-soluble amines such as an activator and monoethanolamine are listed. Further, in order to further improve the stability of the dispersed state and increase the polishing rate, other additives can be blended as necessary.

<Polishing additive>
The polishing promoting additive comprising cerium hydroxide of the present invention is used by adding to a polishing composition containing abrasive grains for polishing a brittle material, which has been conventionally used. The polishing composition to be added is not particularly limited, but the polishing composition containing aluminum oxide and / or diamond as abrasive grains is highly effective since the effect of the polishing promoting additive of the present invention is greatly expressed. It is preferable to add to it. In addition, as cerium hydroxide contained in the polishing accelerating additive, those similar to those in the above-described polishing composition of the present invention can be used.

  The amount of the polishing accelerating additive added is preferably 0.4% by mass or more and 60% by mass or less, more preferably based on the mass of the abrasive grains in the polishing composition (100% by mass). The amount is 2% by mass or more and 20% by mass or less, more preferably 4% by mass or more and 10% by mass or less.

  The polishing promoting additive may be a slurry containing cerium hydroxide in a high concentration in a solvent, or may be a powder of cerium hydroxide fine particles. The method for forming the solvent and the slurry is the same as that for the polishing composition described above.

<Polishing method>
The polishing method using the polishing composition of the present invention is performed, for example, using the apparatus shown in FIG. About this apparatus, it is as having demonstrated in the use of polishing composition previously.

<Adjustment of polishing composition>
Example 1
A commercially available product (manufactured in China, secondary particle size 1.8 μm) was used as the cerium oxide as the abrasive grains. A commercially available product (manufactured by Wako Pure Chemical Industries, Ltd., cerium (IV) hydroxide, primary particle size 20 nm) was used as the cerium hydroxide as the polishing accelerator.

  10% by mass of the cerium oxide obtained above, 0.05% by mass of cerium hydroxide and water as a balance were mixed and stirred with a stirrer to obtain a slurry-like polishing composition of the present invention. The resulting polishing composition had a pH of 7.3. Soda glass was used as the workpiece.

(Example 2)
In Example 1, the polishing composition of this invention was obtained like Example 1 except the addition amount of cerium hydroxide having been 0.3 mass%. The polishing composition obtained had a pH of 6.1. Soda glass was used as the workpiece.

(Example 3)
In Example 1, the polishing composition of this invention was obtained like Example 1 except the addition amount of cerium hydroxide having been 0.6 mass%. The resulting polishing composition had a pH of 5.9. Soda glass was used as the workpiece.

Example 4
In Example 1, the polishing composition of this invention was obtained like Example 1 except the addition amount of the cerium hydroxide having been 1.2 mass%. The resulting polishing composition had a pH of 5.8. Soda glass was used as the workpiece.

(Example 5)
In Example 1, the polishing composition of this invention was obtained like Example 1 except the addition amount of cerium hydroxide having been 5 mass%. The resulting polishing composition had a pH of 5.6. Soda glass was used as the workpiece.

(Example 6)
In Example 1, the polishing composition of this invention was obtained like Example 1 except the addition amount of cerium hydroxide having been 10 mass%. The resulting polishing composition had a pH of 5.6. Soda glass was used as the workpiece.

(Example 7)
In Example 1, the polishing composition of this invention was obtained like Example 1 except the addition amount of cerium hydroxide having been 0.6 mass%. The resulting polishing composition had a pH of 5.9. Quartz glass was used as the workpiece.

(Example 8)
In Example 1, aluminum oxide (manufactured by Fujimi Incorporated, white alumina, average particle size 1.2 μm) was used as abrasive grains, the addition amount was 10 mass%, and the addition amount of cerium hydroxide was 1.2 mass. The polishing composition of the present invention was obtained in the same manner as in Example 1 except that the content was%. The resulting polishing composition had a pH of 5.2. Soda glass was used as the workpiece.

Example 9
In Example 1, the polishing composition of this invention was obtained like Example 1 except having added the cerium hydroxide addition amount to 0.6 mass% and adding hydrochloric acid as a pH adjuster. The resulting polishing composition had a pH of 2.5. Soda glass was used as the workpiece.

(Example 10)
In Example 1, the polishing composition of this invention was obtained like Example 1 except having added the addition amount of cerium hydroxide to 0.6 mass%, and adding sodium hydroxide as a pH adjuster. The resulting polishing composition had a pH of 11.1. Soda glass was used as the workpiece.

(Comparative Example 1)
A polishing composition was obtained in the same manner as in Example 1 except that cerium hydroxide was not added. The resulting polishing composition had a pH of 7.4. Soda glass was used as the workpiece.

(Comparative Example 2)
A polishing composition was obtained in the same manner as in Example 1 except that cerium hydroxide was not added. The resulting polishing composition had a pH of 7.4. Quartz glass was used as the workpiece.

(Comparative Example 3)
A polishing composition was obtained in the same manner as in Example 8 except that cerium hydroxide was not added. The polishing composition obtained had a pH of 7.8. Soda glass was used as the workpiece.

(Comparative Example 4)
A polishing composition was obtained in the same manner as in Example 1 except that cerium oxide as abrasive grains was not added and the addition amount of cerium hydroxide was 1.2% by mass. The resulting polishing composition had a pH of 5.1. Soda glass was used as the workpiece.

(Comparative Example 5)
A polishing composition was obtained in the same manner as in Comparative Example 1 except that hydrochloric acid was added as a pH adjuster in Comparative Example 1. The resulting polishing composition had a pH of 5.1. Soda glass was used as the workpiece.

<Evaluation method>
The polishing rate was evaluated using the apparatus shown in FIG. A polishing pad 20 made of suede is affixed on the polishing surface plate 10, the workpieces 40 of the respective examples and comparative examples are installed on the carrier 50, and the polishing surface plate 10 and the carrier 50 are each rotated at 60 rpm. The carrier 40 was rotated and pressed in the direction of the polishing pad 20 (downward in the figure) at 7.9 kPa to polish the workpiece 40. Polishing composition 30 of the present invention was polished while being dropped onto polishing pad 20 at a rate of 10 ml / min. The polishing time was 10 minutes.

  After polishing, the workpiece 40 was washed with pure water and dried. Thereafter, the weight of the workpiece 40 was measured with a precision balance, and the thickness of the workpiece 40 removed by polishing was determined from the weight difference before and after polishing, the density and size of the workpiece 40. Further, the surface of the workpiece after polishing was measured with a three-dimensional surface roughness meter (New View 5010, manufactured by Zygo Corporation), and the presence of surface roughness and polishing scratches were confirmed. The results are shown in Table 1. With respect to the polishing scratches, the scratches on the surface of the workpiece 40 were evaluated as “X”, and the scratches not observed were evaluated as “◯”.

  <Evaluation results>

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, it can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and the polishing composition, the method of polishing a workpiece, and the polishing promoting additive that accompany such changes Should also be understood as being included within the scope of the present invention.

It is a figure which shows the outline | summary of a grinding | polishing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polishing surface plate 20 Polishing pad 30 Polishing composition 40 Workpiece material 50 Carrier

Claims (13)

A polishing composition for polishing a brittle material, comprising abrasive grains and cerium hydroxide as a polishing accelerator. The polishing composition according to claim 1, wherein the abrasive grains are cerium oxide. The polishing composition according to claim 1, wherein the abrasive grains are aluminum oxide or diamond. Polishing composition in any one of Claims 1-3 whose secondary particle diameter of the said abrasive grain is 300 nm or more. Polishing composition in any one of Claims 1-4 whose primary particle diameter of the said cerium hydroxide is 50 nm or less. Polishing composition in any one of Claims 1-5 whose addition density | concentrations of a cerium hydroxide are 0.4 mass% or more and 60 mass% or less by making an abrasive grain into 100 mass%. Polishing composition in any one of Claims 1-6 whose pH is 2-12. The polishing composition according to claim 1, wherein the brittle material to be polished is a workpiece having a silicon-oxygen bond. A method for polishing a workpiece having a silicon-oxygen bond, using the polishing composition according to claim 1. A step of supplying the polishing composition according to any one of claims 1 to 8 onto the polishing pad, pressing the workpiece onto the polishing pad, sliding the polishing pad and the workpiece, and the workpiece A method for polishing a workpiece, comprising a step of polishing the workpiece. The method for polishing a workpiece according to claim 10, wherein the polishing pad is mainly composed of polyurethane. The method for polishing a workpiece according to claim 10, wherein the pressure for pressing the workpiece on the polishing pad is 3 kPa or more and less than 20 kPa. A polishing promoting additive for adding to a polishing composition for polishing a brittle material containing cerium hydroxide to promote a polishing action.

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