JP2001247368A - Silicon carbide sintered compact and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive silicon carbide sintered compact having substantially no pore, suitable for a transportation and a preservation members for a semiconductor wafer, a liquid crystal substrate, etc., a mirror for a stage position measurement in an exposure apparatus, a mirror for a precision optical instrument, etc., and to provide a method for producing a silicon carbide sintered compact, capable of readily producing the inexpensive silicon carbide sintered compact having substantially no pore, suitable for a transportation and a preservation members for a semiconductor wafer, a liquid crystal substrate, etc., a mirror for a stage position measurement in an exposure apparatus, a mirror for a precision optical instrument, etc., in a high yield. SOLUTION: This silicon carbide sintered compact has <=0.1% water absorption and <=10 μm maximum diameter of free carbon contained. This method for producing the silicon carbide sintered compact having <=0.1% water absorption and <=10 μm maximum diameter of free carbon contained is characterized by molding a mixture of boron or its compound, carbon powder or a substance to form carbon in a baking process and silicon carbide powder having <=1 μm average particle diameter, baking the molding to prepare a normal-pressure sintered compact having <=1% water absorption and then subjecting the atmospheric-pressure sintered compact to hot isostatic pressure treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor wafer,
The present invention relates to a silicon carbide sintered body suitable for a member for transporting or holding a liquid crystal substrate or the like, a mirror for measuring a stage position in an exposure apparatus, a mirror for precision optical equipment, and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Metals such as stainless steel have been conventionally used in semiconductor manufacturing processes such as LSIs for transporting semiconductor wafers and holding members. However, with the recent increase in the density and accuracy of circuit patterns, ceramic members have come to be used for transporting and holding devices such as semiconductor wafers and liquid crystal substrates. Ceramics have also been used for mirrors for measuring the stage position and mirrors for precision optical instruments in exposure apparatuses. Above all, silicon carbide has been increasingly used as a material having a high Young's modulus and relatively low contamination of semiconductor wafers.

[0003] In order to prevent dust from adhering to the surface of the ceramic member and having an adverse effect such as exposure failure, the surface of the ceramic member is usually ground and then polished by lapping, polishing or the like, and smoothed. It is used. However, ceramics sintered at normal pressure have pores (hereinafter referred to as pores), and pores remain on the surface even after polishing. If this is used as a member for transporting or holding a semiconductor wafer, a liquid crystal substrate, or the like, dust or the like enters the pores, resulting in exposure failure during circuit formation.

On the other hand, when used in a mirror for measuring the stage position in an exposure apparatus, a mirror for precision optical equipment, etc., the presence of irregularities such as pores causes irregular reflection of laser light.
This was a problem in position measurement. As a countermeasure against these problems, for example, as disclosed in Japanese Patent No. 2777968, chemical vapor deposition (CV) is performed on a ceramic surface.
D) and the like, a vacuum chuck for forming a film of silicon carbide or the like has been proposed, and JP-A-11-14776.
No. 6, as disclosed in Japanese Patent Publication No.
After normal pressure sintering in an inert gas atmosphere at ~ 2050 ° C,
Hot isostatic pressure treatment (hereinafter referred to as H
IP (hot isostatic press) treatment]
A method has been proposed in which the surface of silicon carbide is polished with diamond abrasive grains of 2 μm or less.

However, in the former method, since the formed silicon carbide film does not contain free carbon, a surface substantially free of pores can be obtained by polishing. However, the cost is increased and the thickness of the silicon carbide film is increased. It is difficult to form a film. On the other hand, in the latter method, when the water absorption of the normal pressure sintered body is large, especially when the water absorption exceeds 1%, H
Even if IP processing is performed, it is difficult to obtain a silicon carbide sintered body having substantially no pores. Even if the pores can be substantially eliminated at the time after the HIP treatment, free carbon exists in the sintered body, and when the particle diameter of the free carbon is large, particularly when the maximum diameter exceeds 10 μm, polishing is performed. In this case, there is a problem that free carbon is desorbed and pores are generated in the portion.

[0006]

The invention according to claim 1 is substantially free of pores, is inexpensive, and has a semiconductor wafer,
An object of the present invention is to provide a silicon carbide sintered body suitable for a member for transporting or holding a liquid crystal substrate or the like, a stage position measuring mirror in an exposure apparatus, a mirror for precision optical equipment, and the like.

The invention according to claims 2 and 3 is substantially free from pores, is inexpensive, and is a member for transporting and holding semiconductor wafers, liquid crystal substrates, etc., a mirror for measuring a stage position in an exposure apparatus, a mirror for precision optical equipment, and the like. It is intended to provide a method for manufacturing a silicon carbide sintered body capable of easily manufacturing a silicon carbide sintered body suitable for a high yield.

[0008]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that the obtained silicon carbide sintered body has a water absorption of 0.1% or less, If the maximum diameter of the free carbon contained in the body is 10 μm or less, it is found that the free carbon does not desorb even if the surface is polished and no pores are generated, and the water absorption of the normal pressure sintered body is 1% or less. Then, it has been found that a silicon carbide sintered body without pores can be obtained by the subsequent HIP treatment, and the present invention has been completed.

The present invention relates to a silicon carbide sintered body having a water absorption of 0.1% or less and containing free carbon having a maximum diameter of 10 μm or less. Further, the present invention, after molding a mixture of boron or a compound thereof and a carbon powder or a substance that forms carbon in the firing process and a silicon carbide powder having an average particle size of 1 μm or less,
Normal pressure firing to produce a normal pressure sintered body with a water absorption of 1% or less,
Next, the normal pressure sintered body is subjected to HIP treatment, wherein the water absorption is 0.1% or less and the maximum diameter of the free carbon contained is 1%.
The present invention relates to a method for producing a silicon carbide sintered body of 0 μm or less. Further, the present invention relates to the method for producing a silicon carbide sintered body, wherein the HIP treatment is a treatment at a pressure of 75 MPa or more and a temperature of 1700 to 2100 ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The silicon carbide sintered body obtained by the present invention has a water absorption of 0.1% or less, preferably 0.08% or less.
%, More preferably 0.05% or less.
% Is most preferable. If it exceeds 0.1%, it is difficult to obtain a pore-free surface. Water absorption rate is JIS
It can be determined according to C 2141.

The maximum diameter of free carbon contained in the silicon carbide sintered body is 10 μm or less, preferably 6 μm or less,
More preferably, it is 4 μm or less, but the lower limit is not particularly limited. If it exceeds 10 μm, there is a problem that free carbon is desorbed during polishing and pores are generated in that portion. The maximum diameter of the free carbon can be determined by measuring the maximum free carbon diameter of an arbitrary 0.1 mm ² with a scanning electron microscope (SEM) at a magnification of 1000 times.

The silicon carbide powder used in the present invention may be either α-type or β-type, but it is preferable to use α-type silicon carbide powder which is inexpensive and has little change in crystal structure during firing. The use of high-purity powder is preferred because it is easy to achieve high purity. However, in the present invention, a normally used GC-grade silicon carbide powder for sintering may be used. The average particle diameter of the silicon carbide powder is 1 μm or less, preferably 0.8 μm or less, and more preferably 0.1 to 0.8 μm. When the average particle diameter exceeds 1 μm, pores are eliminated even when HIP processing is performed. It is difficult. The average particle size of the silicon carbide powder can be determined by measuring with a laser type particle size distribution analyzer (Master Sizer manufactured by MALVERN).

It is preferable to use boron carbide as the boron compound. The amount of boron or its compound added is
It is preferably 0.1 to 1 part by weight, more preferably 0.2 to 0.8 part by weight, based on 100 parts by weight of the silicon carbide powder.

Further, as a substance which forms carbon in the firing step, a substance which is soluble in a solvent at the time of addition and which can uniformly coat the surface of the silicon carbide powder when mixed in a liquid state, for example, becomes carbon after firing It is preferable to use a thermosetting resin having a high carbonization rate such as a phenol resin. The amount of addition is 0.1 to 100 parts by weight of silicon carbide powder.
It is preferably 5 parts by weight, more preferably 0.5 to 3 parts by weight. In the present invention, in addition to the above components, a binder or a dispersant for preparing a slurry or a sheet,
It is preferable to add a plasticizer, and also a material that volatilizes by firing, such as a release agent during molding.

As the binder, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl butyral and the like are used.
The solid content is preferably 0.5 to 3 parts by weight, more preferably 0.7 to 2 parts by weight, based on 0 parts by weight. A surfactant or the like is used as the dispersant, and the amount of the surfactant added is 0.1% in solid content with respect to 100 parts by weight of the silicon carbide powder.
It is preferably from 3 to 1 part by weight, more preferably from 0.4 to 0.7 part by weight.

As the plasticizer, polyethylene glycol, dioctyl phthalate, or the like is used, and the amount of the plasticizer is preferably 0.5 to 3 parts by weight as a solid content with respect to 100 parts by weight of the silicon carbide powder. , 1 to 2 parts by weight. The solvent is preferably water, but the amount added is not particularly limited. As a release agent,
Stearic acid, wax, etc. are used.
0.5 to 3 in solid content with respect to 100 parts by weight of silicon carbide powder
It is preferable to set it as a weight part, and it is more preferable to set it as 0.7-2 weight part.

The mixture of the above components and silicon carbide powder can be formed by a method such as die press molding, cold isostatic pressure (CIP) molding, casting, injection molding, or extrusion molding. The molding pressure is not particularly limited because it differs depending on the molding method.

The atmosphere for firing under normal pressure is preferably firing in an inert gas atmosphere such as argon gas. If the maximum diameter of the free carbon in the normal pressure sintered body exceeds 10 μm, free carbon exceeding 10 μm is also present on the surface of the silicon carbide sintered body after the HIP treatment. The maximum diameter of free carbon in the obtained normal pressure sintered body is also preferably 10 μm or less.

The normal-pressure sintered body has a water absorption of 1% or less, preferably 0.6% or less, more preferably 0.3% or less, and most preferably 0%. If it exceeds 1%, H
It is difficult to eliminate pores even by IP processing.

The HIP treatment is preferably performed in an atmosphere of an inert gas such as nitrogen gas or argon gas. The pressure for HIP processing is 75MP
It is preferably at least a, more preferably at least 98 MPa, even more preferably in the range of 145 to 500 MPa. If the pressure is less than 75 MPa, it tends to be difficult to eliminate pores even by HIP processing.

The HIP processing temperature ranges from 1700 to 21
00 ° C is preferable, 1800 to 2050 ° C is more preferable, and 1900 to 2000 ° C is further preferable. 1700
If the temperature is lower than 0 ° C., the effect of reducing the water absorption rate is small, so that the sintered body has a high water absorption rate, and it tends to be difficult to eliminate pores. If the temperature exceeds 2100 ° C., the maximum diameter of free carbon is 10 μm. And it tends to be difficult to obtain pore-free surfaces. The HIP processing time is preferably from 10 minutes to 3 hours, more preferably from 30 minutes to 2 hours. If the time is less than 10 minutes, it tends to be difficult to eliminate pores.

[0022]

The present invention will be described below with reference to examples. Table 1
And 99 parts by weight of an α-type silicon carbide powder having an average particle diameter shown in Table 2 were mixed with a phenol resin [BRL, trade name, manufactured by Showa Polymer Co.
-219 (non-volatile content 70% by weight)] in solid content of 2 parts by weight (1 part by weight as carbon content), polyvinyl alcohol [Kuraray Co., Ltd., trade name Kuraray Povar 205 aqueous solution (non-volatile content 10% by weight)] 1 part by weight of solid content, 1 part by weight of stearic acid [Cerozol 920 (manufactured by Chukyo Yushi Co., Ltd., trade name: 18% by weight of non-volatile content)], and an average particle diameter of 1.
0.3 parts by weight of 5 μm boron carbide and 100 parts by weight of pure water were added, mixed with a synthetic resin ball mill for 24 hours, and then granulated with a spray drier to obtain a molding powder.

Thereafter, the molding powder is filled in a mold, and the
Press-molding is performed under the pressure of a to produce a disk having a diameter of 30 mm (φ) and a thickness of 5 mm, and then holding for 1 hour at a temperature shown in Tables 1 and 2 in an atmosphere of argon gas and normal pressure firing. Then, a normal pressure sintered body was obtained. About the obtained atmospheric pressure sintered body,
The water absorption was determined according to JIS C 2141. The results are shown in Tables 1 and 2. Thereafter, the obtained normal pressure sintered body was further kept in an argon gas atmosphere at a temperature and a pressure shown in Tables 1 and 2 for 1 hour to perform a HIP treatment to obtain a silicon carbide sintered body.

Next, the surface of the silicon carbide sintered body obtained above was ground and mirror-polished to obtain an evaluation sample. For this evaluation sample, the water absorption was determined according to JIS C 2141. Also, using a scanning electron microscope (SEM),
With respect to mm ² , the maximum free carbon diameter, the presence or absence of desorption of free carbon, and the presence or absence of pores were examined. These results are summarized in Tables 1 and 2.

[0025]

[Table 1]

[0026]

[Table 2]

As shown in Tables 1 and 2, it is clear that the silicon carbide sintered body according to the present invention has substantially no pores even after the surface is ground and mirror-polished. On the other hand, the silicon carbide sintered bodies of Samples Nos. 6, 8, 14 and 20, which are not included in the present invention, have a maximum free carbon diameter of 10 μm.
m, desorption of free carbon was observed, and pores were formed in that portion. Sample No. whose water absorption after HIP treatment exceeded 0.1%. The silicon carbide sintered bodies of Nos. 9, 15, and 21 had pores on the surface. Further, the water absorption of the normal pressure sintered body exceeds 1% and the water absorption after HIP treatment is 0.1%.
The average particle diameter of the silicon carbide sintered bodies and silicon carbide powder of sample Nos. 1 and 2 exceeding 1 μm exceeded 1 μm, the water absorption of the normal pressure sintered body exceeded 1%, and the water absorption after HIP treatment was 0%. In the silicon carbide sintered body of sample No. 25 exceeding 0.1%, pores were generated on the surface in the same manner as described above.

[0028]

According to the first aspect of the present invention, the silicon carbide sintered body has substantially no pores, is inexpensive, and is a member for transporting and holding semiconductor wafers and liquid crystal substrates, a mirror for measuring a stage position in an exposure apparatus, and precision optics. It is a silicon carbide sintered body suitable for a mirror for equipment and the like. The silicon carbide sintered body obtained by the method according to claims 2 and 3 has substantially no pores, is inexpensive, and is a member for transporting and holding semiconductor wafers, liquid crystal substrates, etc., a mirror for measuring a stage position in an exposure apparatus, and a precision mirror. It is a silicon carbide sintered body that can easily produce a silicon carbide sintered body suitable for a mirror for an optical device with a high yield.

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Claims (3)

[Claims] 1. A silicon carbide sintered body having a water absorption of 0.1% or less and containing free carbon having a maximum diameter of 10 μm or less. 2. A mixture of boron or a compound thereof, a carbon powder or a substance that forms carbon in the firing step and a silicon carbide powder having an average particle diameter of 1 μm or less is formed, and then fired under normal pressure to obtain a water absorption of 1%. The following normal pressure sintered body is produced, and then the normal pressure sintered body is subjected to hot isostatic pressure treatment.
% Or less, wherein the maximum diameter of the free carbon contained is 10 μm or less. 3. The method for producing a silicon carbide sintered body according to claim 2, wherein the hot isostatic pressure treatment is a treatment at a pressure of 75 MPa or more and a temperature of 1700 to 2100 ° C.