JPH11198030A - Molded body for polishing, surface plate for polishing using it and method of polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded body for polishing and a surface plate for polishing, in which the molded body is used, in addition to the method of polishing, which can alleviate the burden of the problem of waste liquid, which allows efficient polishing to a material to be polished in spite of the same degree of finishing in polishing as that attained by the conventional method, and which can increase the efficiency of polishing work owing partly to high durability of the molded body for polishing, in the process of polishing a semiconductor substrate such as a silicone wafer, the material for substrates such as an oxide substrate, and the material for optical instruments requiring precise processing by employing such an abrasive liquid as containing no free, abrasive grains or as containing a little quantity of free, abrasive grains. SOLUTION: A molded body for polishing consists mainly of alumina. Its bulk density is not less than 0.4 g/cm<3> and not more than 2.8 g/cm<3> , its BET ratio surface area is not less than 5 m<2> /g and not more than 250 m<2> /g, and its mean grain size is not less than 0.001 μm and not more than 0.5 μm. This molded body for polishing is used both in the surface plate for polishing and in the method of polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article for use in a method for polishing a substrate material such as a silicon wafer or an oxide substrate, an optical material, and the like, a polishing platen using the same, and a polishing method. Things. For more information,
The present invention relates to a molded body for polishing obtained by subjecting an alumina molded body formed of alumina fine powder to processing such as firing, a polishing platen using the same, and a polishing method.

[0002]

2. Description of the Related Art With the development of industries such as optics and electronics, the demand for processing magnetic disks, semiconductor substrates, single crystal materials, etc. has become extremely strict. It has been polished with a polishing pad of a nonwoven fabric type or a suede type while continuously flowing a polishing liquid containing abrasive grains. In this case, the free abrasive grains used are alumina, silica,
Ceria, zirconia and the like are known, and among them, alumina has been widely used because of its high hardness, excellent polishing performance, and easy availability.

However, according to such a method, since a polishing liquid containing free abrasive grains is used, a polishing waste liquid containing a large amount of free abrasive grains is generated after the polishing treatment. It should be improved in consideration of the impact on wastewater treatment facilities and the environment.
Further, in the polishing process, the polishing cloth needs to be frequently replaced with a new one in order to cause performance deterioration such as clogging, and there has been a problem in terms of efficiency of the polishing process. Further, in a material polished by a conventional polishing method using a polishing cloth (hereinafter, referred to as “material to be polished”), since the surface of the polishing cloth is soft, the corners of the edges of the material to be polished are polished during polishing. As a result, there is a disadvantage that an inefficient finish results in that the entire surface of the material to be polished cannot be uniformly polished.

[0004]

As described above, when the polishing is performed by the conventional method, problems such as a problem of treatment of a polishing waste liquid generated during polishing, an effective use of a material to be polished, and an increase in efficiency of the polishing work arise. Accordingly, the present invention has been made in view of such a problem. The purpose is to use a polishing liquid that does not contain free abrasive grains or contains a small amount of free abrasive grains in the processing process of polishing substrate materials such as semiconductor substrates such as silicon wafers, oxide substrates, and optical materials that require precision processing. By reducing the problem of waste liquid, the material to be polished can be polished efficiently with the same level of polishing finish as the conventional method, and the polishing work is more efficient because the polishing molded body has durability in the polishing process An object of the present invention is to provide a molded article for polishing, a polishing platen and a polishing method using the same.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have found that an alumina molded body molded using alumina fine powder is processed and used as a polishing molded body. Found the following findings.

1) At the time of polishing, the surface of the molded article for polishing is roughened by alumina fine powder as a raw material thereof.
Since this is in direct contact with the material to be polished, it is possible to use a polishing liquid that does not contain free abrasive grains to apply it to the polishing process of substrate materials, etc. And the problem of waste liquid is reduced.

[0007] 2) Since the strength of the molded body for polishing is high, it is durable even in the polishing process, so that the polishing operation can be performed for a long time without replacement.

[0008] 3) The finish of the polished material is almost the same as that of the conventional method, the polishing rate is the same, and the polishing performance does not deteriorate with time.

4) Even when an abrasive containing free abrasive grains is used, the polishing rate is improved at a concentration of the free abrasive grains which is lower than that of the conventional method.

As described above, these excellent points were found by using the molded article for polishing, the polishing platen and the polishing method using the molded article of the present invention, and the present invention was completed.

Hereinafter, the present invention will be described in detail. <Characteristics of molded body for polishing> The molded body for polishing of the present invention is mainly composed of alumina, that is, aluminum oxide (Al ₂ O ₃ ).
Having a bulk density of 0.4 g / cm ³ or more and 2.8 g /
cm ³ or less and a BET specific surface area of 5 m ² / g or more and 25 or more.
0 m ² / g or less, and the average particle diameter is 0.00
It is 1 μm or more and 0.5 μm or less.

As the alumina, those having an alumina component of 90% by weight or more based on the total amount of the molded article for polishing are preferably used, and those having an alumina component of 97% by weight or more are preferably used. The alumina component here means the alumina content, and as shown in the examples, is calculated on the basis of the remaining amount excluding water from the total amount of the alumina powder as the raw material, and the burning content, oxide, Etc.

The range of the bulk density of the abrasive compact is as follows.
In order to maintain the shape of the molded body for polishing during polishing and efficiently obtain a smooth surface of the material to be polished, the range is preferably 0.4 g / cm ³ or more and 2.8 g / cm ³ or less.
The range is preferably from 7 g / cm ^{3 to} 1.7 g / cm ³ . If the bulk density is less than 0.4 g / cm ³ , the shape cannot be maintained, and the shape retention will be poor. In addition, 2.8 g / c
When m ³ is exceeded, the strength of the molded article itself becomes too high, and the material to be polished is damaged during polishing, or the surface of the molded article for polishing becomes too smooth due to polishing, and the polishing rate is preferably reduced. Absent.

The range of the BET specific surface area of the molded article for polishing is preferably 5 m ² / g or more to maintain the shape of the molded article for polishing during polishing and obtain a smooth surface of the material to be polished.
m ² / g or less, more preferably 5 m ² / g or more.
The range is preferably 30 m ² / g or less, particularly preferably 5 m ² / g or more and 70 m ² / g. If the BET specific surface area exceeds 250 m ² / g, the shape of the molded article for polishing cannot be maintained. On the other hand, if it is less than 5 m ² / g, on the contrary, the strength of the molded body itself becomes too high, the material to be polished is damaged during polishing, and the surface of the molded body for polishing becomes too smooth by polishing, so that the polishing rate is reduced. It is not preferable because it decreases.

The average particle size of the abrasive compact is preferably in the range of 0.001 μm to 0.5 μm, more preferably 0.01 μm or more in order to facilitate molding into a porous body and obtain a smooth surface of the material to be polished. 0.3 μm or less, especially 0.03 μm
The range is preferably not less than 0.2 μm and not more than 0.2 μm. When the average particle diameter is smaller than 0.001 μm, the primary particle diameter of the raw material powder becomes smaller than 0.001 μm, and it becomes extremely difficult to mold the raw material powder into a porous body. Is also undesired because problems such as defects occurring in the material to be polished may occur. The average particle diameter here means the particle diameter of the alumina fine particles on the surface of the molded article for polishing, and can be measured by, for example, a scanning electron microscope (SEM) as described in Examples.

<Manufacturing Method of Polishing Molded Body> The polishing molded body of the present invention is obtained by processing an alumina molded body formed by using fine alumina powder into a molded body by processing such as firing. There is no particular limitation as long as it has the following characteristics.

The alumina molded body can be produced, for example, by applying pressure to the raw material powder and molding. When molding under pressure, for example, a molding method such as press molding can be exemplified. As the pressure condition, a pressure of usually 5 kg / cm ² or more is preferably used in order to maintain the shape of the obtained molded body. A pressure of 10 kg / cm ² or more is preferably used.

Further, the raw material powder may be subjected to a treatment in order to improve the formability of the raw material powder. As a method of the treatment, for example, a method of preforming by press molding or the like and then classifying using a sieve or the like can be given. The pressure at the time of preforming is not fixed depending on the properties of the powder and the like, but usually 5 kg / cm ² or more and 1000 kg / cm ² or less is sufficient.

Similarly, in order to improve the formability of the raw material powder, the raw material powder may be granulated by a spray-dry method or a rolling method, or a binder may be added. The powder may be mixed with a pore-forming agent so as not to break the powder. Formability is improved by these additives, and furthermore, by using a pore-forming agent, it is possible to obtain an alumina molded body reflecting the particle diameter of the pore-forming agent, and it is easy to control the pore structure in the molded body for polishing. As a result, a molded article for polishing that can improve the polishing rate during polishing is obtained. Before mixing the granulated powder with the pore-forming agent, the granulated powder may be temporarily transferred and stored.

The kind of the binder can be used without any particular limitation as long as it does not hinder the granulation operation. In general, a binder, a plasticizer, a lubricant and the like can be used. Polyolefin resins, waxes, lower fatty acids such as stearic acid, higher alcohols such as stearyl alcohol, and the like,
These can be used alone or in combination of two or more.

Examples of the pore-forming agent include waxes such as paraffin wax and microcrystalline wax, powders of acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, polyethylene, polypropylene, ethylene-vinyl acetate copolymer. ,ethylene·
Powders of olefin resins such as ethyl acrylate copolymer, polystyrene powder, powders of lower fatty acids such as stearic acid, potato starch, corn starch, ethyl cellulose, carbon powder and the like can be exemplified, and these may be used alone or in combination of two or more. it can.

When an organic substance such as a binder or a pore-forming agent is added to the raw material powder before molding in order to improve the formability of the raw material powder into an alumina molded body, the material is degreased during processing into a molded body for polishing. Is preferred. The degreasing method is not particularly limited, and examples thereof include degreasing by heating in an air atmosphere, and degreasing by heating in an inert atmosphere such as nitrogen, argon, and helium. At this time, the pressure of the atmosphere gas may be under pressure or under normal pressure, and may be under reduced pressure in some cases. Similarly, in order to improve the moldability, it is also possible to add moisture and to dry before the subsequent firing operation.

Next, since the molded body from which the binder and the pore-forming agent have been removed is generally weak in strength, it is heated in order to increase the strength and improve the durability as a polishing platen. Is preferably performed. But,
The method for improving the durability is not limited to heating and firing.

As described above, as a method for processing the alumina molded body into a polishing molded body, a method using heat degreasing, heat baking, machining, or the like can be exemplified. There is no particular limitation as long as the processing method can be performed.

<Structure of Polishing Surface Plate> Next, a method of assembling the molded body for polishing as a polishing surface plate and further performing polishing using the platen will be described.

First, a polishing surface plate is formed by using the polishing molded body and the auxiliary components for polishing.

Here, the auxiliary parts are structures of various materials and shapes constituting a polishing platen, and a molded body for polishing is arranged on the auxiliary parts by a method described below.
The polishing platen is formed by fixing. As a method of fixing both, a method of bonding and fixing using an adhesive such as an elastic adhesive, a method of forming irregularities on ancillary parts, embedding in the fixing place, and the like, a method that can achieve the object of the present invention. If there is, it can be used without restriction.

With respect to the number of the molded bodies for polishing when the molded articles for polishing are fixed to the accessory parts for polishing, one or more than two molded bodies may be used, and more preferably two or more are used. This is because 1) the polishing rate is improved by appropriately discharging the polishing liquid used in the polishing process during polishing. Therefore, when the polishing platen is formed by using two or more polishing compacts, the polishing liquid can be discharged from the gap between the polishing compacts. When one is used, it is preferable to provide an appropriate groove structure capable of discharging the polishing liquid on the side of the polishing surface of the molded body. 2) Further, when the polishing platen is formed by using two or more polishing compacts, the contact with the material to be polished is improved, and the polishing speed is improved without unevenness in the polishing rate over the entire surface of the material to be polished. become able to.

The shape of the abrasive compact to be used is not particularly limited, and any shape can be adopted as long as the abrasive compact can be mounted on the accessory part for polishing. For example, columnar pellets, square columnar pellets,
Examples include prismatic pellets such as triangular prism pellets,
Furthermore, any shape in which the contact surface with the material to be polished can be formed by combining a straight line and a curve can be exemplified. The size is not particularly limited as long as it is within a range normally used, and is determined according to the size of an accessory part for incorporating a molded body for polishing in a polishing table.

The mode of the method of arranging the molded article for polishing used in the present invention as a polishing platen is not particularly limited as long as the method has the above-mentioned characteristics of the molded article for polishing. Instead, for example, a method of combining and integrating small pieces of a molded article for polishing, a method of embedding in a large disk, and the like can be mentioned.

When two or more such molded bodies for polishing are arranged on a polishing platen, it is desirable to arrange the polished surface of the arranged molded bodies for polishing so as to match the shape of the material to be polished. In this case, it is possible to select an accessory that matches the shape of the accessory. For example, when the surface of the material to be polished is flat, it is desirable to flatten the contact surface of the molded body for polishing with the material to be polished, and when it is a curved surface, it is desirable to have a curved surface conforming thereto. This ensures that the material to be polished and the molded body for polishing can be in direct contact with each other when polishing is performed using the obtained polishing surface plate, so that a large contact surface can be obtained. That's why. In particular, in the case of flattening, it is preferable to arrange them so that there is no variation in the vertical height from the polishing platen.

As for the method of fixing the molded body for polishing and the metal platen, the molded body for polishing is fixed by fixing with an adhesive or by forming an uneven surface corresponding to the size of the molded body for polishing on the metal platen. You may. The adhesive used when fixing the molded body for polishing and the metal platen using an adhesive can be used without particular limitation as long as the object of the present invention can be achieved, and in particular, such as an elastic adhesive In addition, it is preferable to use an adhesive that does not have cracks, cracks, or the like that may occur when the polishing molded body is fixedly adhered to the surface plate.

<Polishing Method Using Polishing Surface Plate> In this way, the molded body for polishing is incorporated into the polishing surface plate. In the method of polishing using the polishing surface plate of the present invention, The shape, polishing conditions, use of a polishing liquid, and the like are not particularly limited as long as the surface plate is used in the polishing process. For example, when a polishing liquid is used, a conventionally used polishing liquid may be used, and for example, water can be used. Here, the polishing platen is used to polish the molded body for polishing directly in contact with the material to be polished, has sufficient strength in the polishing process, and What is necessary is just to have the ability to polish. Therefore, the shape may have not only the same shape as the material to be polished, but also a non-planar shape if necessary. For example, a flat plate shape, a disk shape, a ring shape, a cylindrical shape, and the like can be given.

Since the polishing method of the present invention does not use a polishing cloth, the interruption of the polishing operation due to the replacement of the polishing cloth due to the performance deterioration of the polishing cloth, which was observed in the conventional method during polishing, is not limited to the present invention. The use of the abrasive compact has the advantage that durability is improved and replacement frequency can be reduced, so that the efficiency of the polishing operation can be increased.
Further, with respect to the polishing waste liquid containing free abrasive grains generated in the conventional method using an abrasive, the use of the free abrasive grains by using the molded article for polishing according to the present invention or the use of a small amount is sufficient. The amount of free abrasive grains and grains generated by polishing is reduced, and the problem of waste liquid treatment is reduced. For example, the transmittance when irradiating the polishing waste liquid is higher than that in the conventional method,
It can be confirmed that the amount of unnecessary particles mixed in the polishing waste liquid is reduced. Considering the problem of the polishing waste liquid, the transmittance of the polishing waste liquid at 600 nm is 10% of water.
As described above, it is particularly preferable to set the polishing liquid to 40% or more, and it is preferable to use a polishing liquid having such a transmittance of the waste liquid.

The polishing platen of the present invention is made of a substrate material such as a silicon wafer, a semiconductor substrate such as gallium phosphide or gallium arsenide, an oxide substrate such as lithium niobate, lithium tantalate or lithium borate, or a quartz glass substrate. It is useful for polishing quartz glass, metal materials, stone materials used in the construction field, and the like. Among them, the polished material can be effectively used because there is no surface sagging as compared with the conventional method using a polishing cloth, so that it is preferably used as a substrate material and further preferably used as a semiconductor substrate and an oxide substrate.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, each evaluation was implemented by the method shown below.

Alumina Content Water content and loss on ignition of alumina powder (Loss on I
gnition, hereinafter referred to as “Ig loss”) and Al ₂
O ₃ , Fe ₂ O ₃ , SiO ₂ and Na ₂ O were measured by the following methods. From the total weight of the alumina powder excluding the water content (water content), Ig loss, F
The weight obtained by subtracting the total weight of e ₂ O ₃ , SiO ₂ and Na ₂ O was defined as the alumina content, and the weight was calculated in terms of% by weight.

The water content was determined from the change in weight before and after the heat treatment of the alumina powder at 110 ° C. for 2 hours.

Ig loss was measured at 110 ° C. for 2 hours at alumina powder.
After heating for a period of time to remove moisture,
Heat treatment was performed at 100 ° C., and the weight change was determined before and after the treatment.

The amounts of Fe ₂ O ₃ , SiO ₂ and Na ₂ O were determined based on a sample obtained by heating alumina powder at 110 ° C. for 2 hours to remove water, dissolving it, and then applying JIS H 19
01 in conformity with, the Fe ₂ O ₃ is O- phenanthroline absorptiometry, SiO ₂ by molybdenum blue absorptiometry, Na ₂ O was determined by flame photometry.

-Bulk Density-A flat sample of 100 mm x 100 mm x 15 mm (thickness) was prepared and used as a sample of a molded body. This sample was calculated from the weight measured with an electronic balance and the shape and dimensions measured with a micrometer.

[Average Particle Diameter] A part of the surface of the molded article for polishing is adjusted to be flat, and the surface is observed with a scanning electron microscope ISIDS-130 (manufactured by Akashi Seisakusho). It was determined by the intercept method.

-BET specific surface area-The raw material powder was used as it is, and the molded body for polishing was used for measurement after crushing it. The measurement was carried out after drying at 200 ° C. for 15 minutes using MONOSORB (QUANTAC, USA).
(HROME Co., Ltd.) using the BET one-point method.

~ Average Particle Diameter of Powder ~ Alumina powder was used as a sample, and COULTER LS1
It measured with the liquid module using 30 (made by COULTERELECTRONICS). Measurements are on a volume basis.

Polishing Test A cylindrical test piece of a molded body having a diameter of 25 mm and a thickness of 5 mm was prepared, and was rotated on a rotating platen (360 m in diameter) of a high-speed lens polishing apparatus.
m), and the surface of the molded article was flattened. Under the conditions of a platen rotation speed of 100 rpm and a processing pressure of the platen material on the platen of 150 g / cm ² , six 3 inch diameter lithium tantalate substrates were simultaneously used as the platen material, and distilled water was used as the polishing liquid. (Liquid temperature: 25 ° C.), the polishing liquid was dropped at a rate of 1 liter / min and polished while being circulated. After polishing, the surface of lithium tantalate was observed with a microscope (manufactured by OLYMPUS, model: BH-2).
In the evaluation, ○ indicates that the surface was extremely smooth and had no scratches, etc., and X indicates that the surface could not be polished without being smooth.

-Durability of the molded body-The polishing test was continuously performed, the molded body was taken out every hour, and the surface condition was visually observed, and the presence or absence of breakage such as cracks, cracks, chips, etc. was observed. . At the time of evaluation, the time until the molded article was damaged was examined.

<Manufacture and evaluation of molded body for polishing> Example 1 An acrylic binder (manufactured by Chuo Rika Kogyo Co., Ltd., Ricabond SA) was added to an alumina raw material powder having the characteristics shown in Table 1 as an additive.
-200) and stearic acid emulsion (Cellosol 920, manufactured by Chukyo Yushi Co., Ltd.) as raw material powder: acrylic binder (solid content conversion): stearic acid emulsion (solid content conversion): water = 100: 40: 2: 518 by weight ratio. Mix to form a slurry. A granulated powder was prepared from this slurry using a spray drier (manufactured by Okawara Kakoki Co., Ltd., model: LT-8) and press-molded (pressure: 100 kg / cm ² ) using a hydraulic press to obtain an alumina molded body. This was fired in a firing furnace (Koyo Lindberg, Model: 5166)
8) Hold at 400 ° C for 2 hours to degrease,
The temperature was raised to 50 ° C. and baked for 2 hours to obtain a molded body for polishing. This was evaluated by the evaluation method described above. Table 2 shows the obtained results as the bulk density of the abrasive compact, BE
The T specific surface area, the average particle size, the polishing test result and the durability test result of the obtained molded article for polishing are shown.

[0048]

[Table 1]

[0049]

[Table 2]

Example 2 An acrylic binder (manufactured by Chuo Rika Kogyo Co., Ltd., Ricabond SA) was added to an alumina raw material powder having the characteristics shown in Table 1 as an additive.
-200) and stearic acid emulsion (Cellosol 920, manufactured by Chukyo Yushi Co., Ltd.) as raw material powder: acrylic binder (solid content conversion): stearic acid emulsion (solid content conversion): water = 100: 40: 2: 382 by weight ratio. Mix to form a slurry. A granulated powder was prepared from this slurry using a spray dryer (manufactured by Okawara Kakoki Co., Ltd., model: LT-8), and water was sufficiently removed in a desiccator. Potato starch (manufactured by Kishida Chemical Co., Ltd.) was mixed with the dried granulated powder in a volume ratio of dried granulated powder: potato starch = 2: 1 to obtain a raw material powder for molding. This molding raw material powder is press-molded using a hydraulic press (pressure:
100 kg / cm ² ) to obtain an alumina molded body. This was degreased by holding it at 400 ° C. for 2 hours in a firing furnace, heated to 1200 ° C. as it was, and fired for 2 hours to obtain a molded body for polishing. This was evaluated in the same manner as in Example 1 and Table 2
It was shown to.

Comparative Example 1 An acrylic binder (manufactured by Chuo Rika Kogyo Co., Ltd., Ricabond SA) was added to an alumina raw material powder having the characteristics shown in Table 1 as an additive.
-200) and stearic acid emulsion (Cellosol 920, manufactured by Chukyo Yushi Co., Ltd.) as raw material powder: acrylic binder (solid content conversion): stearic acid emulsion (solid content conversion): water = 100: 40: 2: 382 by weight ratio. Mix to form a slurry. A granulated powder was prepared from this slurry using a spray drier (manufactured by Okawara Kakoki Co., Ltd., model: LT-8) and press-molded (pressure: 100 kg / cm ² ) using a hydraulic press to obtain an alumina molded body. This was held in a firing furnace at 400 ° C. for 2 hours to degrease it, heated to 1500 ° C. as it was, and fired for 2 hours to obtain a molded body for polishing. This was evaluated by the evaluation method described above.
Table 2 shows, as the obtained results, the bulk density, the BET specific surface area, the average particle size, the polishing test result and the durability test result of the obtained polishing molded body.

Comparative Example 2 A suede-type polishing pad (SURFIN 018-3, manufactured by Fujimi Incorporated) was attached to a metal surface plate of a high-speed lens polishing apparatus, and the rotation speed of the surface plate was 100 rpm.
m, under the conditions of a pressing force of 150 g / cm ² of the material to be polished on the platen, lithium tantalate was used as the material to be polished, and a commercially available alumina abrasive (Fujimi Incorporated, F .M. No. 5) was dropped at a rate of 1 liter / minute using a polishing liquid (liquid temperature: 25 ° C., pH = 10) prepared by adding distilled water to an alumina content of 20% by weight. And polished. Table 2 shows surface accuracy measurement results as the obtained results.

When the results of Examples 1 and 2 and Comparative Example 1 were compared, it was found that if the polishing was performed using a molded article for polishing having the characteristics as in Comparative Example 1, the polishing could not be performed well.

On the other hand, when the results of Examples 1 and 2 and Comparative Example 2 are compared, a polishing molded body applicable to polishing can be obtained by performing polishing using the polishing molded body of the present invention. Moreover, it was found that the surface accuracy of the material to be polished was about the same as that obtained by the conventional polishing method.

<Evaluation of Polishing Waste Liquid> Example 3 The polishing molded body obtained in Example 1 was polished by the method described in the polishing test. For polishing waste liquid,
The turbidity of the generated waste liquid is measured with a spectrophotometer (manufactured by JASCO, model: U
best-55) and a wavelength of 60 with respect to purified water.
It was evaluated by the transmittance at 0 nm. Table 3 shows the results.
It was shown to. When the transmittance is high, it indicates that the amount of free abrasive grains in the polishing waste liquid is small, and when it is low, it indicates that the amount is large.

[0056]

[Table 3]

Example 4 A polishing waste liquid was evaluated in the same manner as in Example 3 except that the molded article for polishing obtained in Example 2 was used.

Comparative Example 3 The polishing waste liquid obtained in the polishing test performed in Comparative Example 2 was evaluated in the same manner as in Example 3, and the results are shown in Table 3.

When the above Examples 3 and 4 are compared with Comparative Example 3, polishing using the polishing table of the present invention results in a higher polishing waste liquid transmittance than the conventional method. It is understood that the amount of free abrasive grains in the waste liquid is extremely small.

[0060]

According to the present invention, almost no polishing waste liquid containing a large amount of free abrasive grains is generated during the polishing process, and the silicon wafer can be as good as the conventional method.
It is possible to polish a substrate material such as an oxide substrate,
Further, since the molded body for polishing in the polishing treatment has durability, it is useful for the polishing process.

Claims (4)

[Claims] 1. A material mainly composed of alumina, having a bulk density of 0.4 g / cm ^{3 to} 2.8 g / cm ³ ,
A T specific surface area of 5 m ² / g or more and 250 m ² / g or less;
A shaped article for polishing characterized by having an average particle diameter of 0.001 μm or more and 0.5 μm or less. 2. A polishing platen comprising the molded article for polishing according to claim 1 and auxiliary components. 3. A polishing method characterized in that a material to be polished is pressed against the polishing platen according to claim 2 and is rubbed. 4. A polishing waste liquid which is polished without using free abrasive grains.
4. The polishing method according to claim 3, wherein the transmittance at 00 nm is 10% or more of water.