JP2002321969A - Dense cordierite-based ceramic and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide dense cordierite-based ceramic having a higher rigidity than metal, a small thermal expansion coefficient, and the porosity of <=5%, and to provide a method of manufacturing the same. SOLUTION: The method is a manufacturing method for the following ceramics: dense cordierite-based ceramic which contains 93-99.99 wt.% of cordierite expressed by the formula of 2MgO.2Al2 O3 .5SiO2 and 0.01-7 wt.% of silicon nitride and which has the porosity of <=5%; dense cordierite-based ceramic which is made by mixing and molding 93-99.99 wt.% of cordierite powder expressed by the formula of 2MgO.2Al2 O3 .5SiO2 and 0.01-7 wt.% of silicon nitride powder and then sintering the mold at 1,270-1,440 deg.C and which has the porosity of <=5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stage used in a semiconductor manufacturing apparatus represented by an exposure apparatus,
The present invention relates to a dense cordierite ceramic having a relatively high rigidity and a small absolute value of a thermal expansion coefficient suitable for a wafer suction chuck and these components, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, parts of a semiconductor manufacturing apparatus include alumina ceramics and SiC in terms of cost and chemical stability.
Ceramics and the like have been frequently used.

However, in recent years, as the degree of integration of electronic circuits has increased, higher positioning accuracy has been required for these members, and in particular, the accuracy of the manufacturing apparatus with respect to temperature changes has been reduced. That is, in order to improve the processing accuracy and the yield, a material having a small coefficient of thermal expansion near room temperature (20 to 30 ° C.) and a high rigidity has been required.

In a movable member represented by a wafer chuck or a slider, its weight is also important.
In other words, when the specific gravity increases, a large driving force and a long time are required for starting and stopping even if the rigidity is high, so that the production speed and the yield are reduced.

In recent years, silicon nitride ceramics and low thermal expansion ceramics used for parts of semiconductor manufacturing equipment have been used.
Cordierite ceramics, lithium aluminosilicate ceramics, and the like have been proposed.

For example, Japanese Patent Publication No. 6-97675 describes the use of cordierite ceramics as a substrate material for an electrostatic chuck for holding and transporting a Si wafer in a vacuum.

However, cordierite ceramics have very close melting points and sintering start temperatures, and the sintering temperature range is limited to about 10 ° C. If the temperature is lower than this, a dense sintered body cannot be obtained, while if it is higher, there is a problem that deformation due to firing occurs or the material is melted. That is, it was very difficult to obtain dense cordierite ceramics.

In order to solve this problem, Japanese Patent Publication No. Sho 62
The -34205 Publication, by containing 0.3 to 8% by weight of _Y 2 _{O 3} component in the cordierite, can densification without impairing the characteristics of cordierite, 1.6
It is described that a thermal expansion coefficient of 2.8 ppm · K ⁻¹ is obtained.

Japanese Patent Application Laid-Open No. 2001-39764 discloses that the cordierite contains 80 to 92% by weight and the oxide of a rare earth element at 2 to 20% by weight, so that the Young's modulus is 120 GPa or more and Thermal expansion coefficient ±
A cordierite ceramic having 0.25 ppm · K ⁻¹ is described.

A lithium aluminosilicate (also represented by the general formula Li ₂ O.
Japanese Patent Application Laid-Open No. 56-164070 discloses that natural ceramics are used for Al ₂ O ₃ .nSiO ₂ ) -based ceramics, particularly β-spodumene. Japanese Patent Application Laid-Open No. 2000-21 discloses that β-eucryptite can be densified by containing MgO.
No. 9572.

Further, Japanese Patent Application Laid-Open No. 2000-281454
The report includes a low thermal expansion and high rigidity
LiAlS with negative thermal expansion characteristics as Lamix
iO ₄And Si having positive thermal expansion characteristics and high rigidity characteristics
₃N₄Or a sera composed of three components, SiC and MgO
The mix is listed.

Recently, however, semiconductor LSIs such as storage chips mounted on computers and V
Higher integration of LSIs and the like has been further advanced, and accordingly, it has become essential to form ultra-fine circuits on the order of submicrons. Therefore, an exposure apparatus that forms an ultrafine circuit on a Si wafer is required to have high accuracy, for example, an accuracy of 0.05 μm or less in positioning.

However, conventional silicon nitride ceramics have a rigidity of a Young's modulus of about 300 GPa (= × 10 ⁶ P
a) is high, but the coefficient of thermal expansion at 20 to 30 ° C. is 1.
31 ppm · K ⁻¹ (= × 10 ⁻⁶ / K), which is about 0.06 μm (= × 10 ⁻⁶ m) only by changing the temperature of the exposure apparatus member having a length of 1 m by 0.05 ° C. This means that the dimensional change occurs, and the quality and yield in forming a precision circuit are reduced.

On the other hand, cordierite ceramics have a coefficient of thermal expansion of 0.2 pp at 20 to 30 ° C.
As small as about m · K ⁻¹ , a dimensional change with respect to a temperature change can be reduced. However, in terms of rigidity, the Young's modulus is as low as about 100 to 120 GPa, and there is a disadvantage that dimensional changes easily occur due to external stress.

The lithium aluminosilicate ceramics have a thermal expansion coefficient at -20 to 30 ° C. of about −8 to −2 ppm · K ⁻¹ depending on the composition, but still have low rigidity. , Young's modulus is 60-90
GPa, which is disadvantageous in that dimensional changes are likely to occur with respect to external stress as in cordierite ceramics.

[0016]

The first and second aspects of the present invention provide a dense cordierite ceramic having a higher rigidity, a lower coefficient of thermal expansion, and a porosity of 5% or less as compared with metal. It is. The third and fourth aspects of the present invention provide a method for producing a dense cordierite ceramic having a higher rigidity, a lower coefficient of thermal expansion, and a porosity of 5% or less as compared with a metal.

[0017]

According to the present invention, there is provided a compound of the general formula 2Mg
Cordierite 93 to 99.99 wt% and silicon nitride represented by _{O · 2Al 2 O 3 · 5SiO} 2 0.01~7
The present invention relates to dense cordierite-based ceramics containing 5% by weight and having a porosity of 5% or less. In addition, the present invention has a thermal expansion coefficient at −20 to 30 ° C. of −0.5 to +
In 0.5 ppm · ^{K -1,} and Young's modulus of 130GPa
The present invention relates to dense cordierite ceramics.

Further, the present invention relates to a compound of the general formula 2MgO.2Al
₂ O ₃ · 5SiO cordierite powder 9 represented by ₂
3 to 99.99% by weight and 0.01 to 7% by weight of silicon nitride powder are mixed and molded, and then calcined at a temperature of 1270 to 1440 ° C. The present invention relates to a method for producing porous ceramics. Furthermore, the present invention has a coefficient of thermal expansion at 20 to 30 ° C.
0.5 to +0.5 ppm · K ^-1 and a Young's modulus of 1
4. The method for producing a dense cordierite ceramic according to claim 3, which is at least 30 GPa.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Cordiera used in the present invention
The powder is 2MgO.2Al as a general formula. ₂O₃・ 5
SiO₂Is a composite oxide represented by
Al₂O₃And SiO₂Is the range of characteristics in the present invention.
Must be exactly 2: 2: 5 in molar ratio if not removed
There is no. However, without adding sintering aids,
The sintered body obtained by molding and firing
-2.0 to +1.0 ppm · K^-1About
It is preferred to use cordierite powder of different degrees.

For the cordierite powder, for example, powders of MgO, Al ₂ O ₃ and SiO _{2 having} a purity of 99% or more are weighed so as to have a molar ratio of about 2: 2: 5, and are used with a ball mill. After wet mixing, drying and granulation, 1
It can be calcined at a temperature of 000 to 1400 ° C. for about 10 hours and then pulverized to an average particle size of about 0.5 to 30 μm for use. Further, cordierite ore produced naturally can be used after being crushed.

On the other hand, a commercially available powder can be used as the silicon nitride powder (Ni ₃ O ₄ ). The average particle diameter of the silicon nitride powder is preferably 0.1 μm or more, more preferably 0.5 μm or more, and 0.6 to 0.6 μm.
A range of 10 μm is more preferable.

The average particle size of the cordierite powder and the silicon nitride powder can be determined by using a laser type particle size distribution analyzer (MALVER).
(Master Sizer manufactured by N Company).

The silicon nitride powder preferably has a coefficient of thermal expansion at 20 to 30 ° C. of 0.5 to 1.5 ppm · K ⁻¹ and a Young's modulus of 200 GPa or more. The coefficient of thermal expansion at 20 to 30 ° C is 0.8 to 1.3 ppm · K ^{- 1} , and the Young's modulus is 250 to
More preferably, silicon nitride powder in the range of 300 GPa is used.

In the present invention, the mixing ratio of cordierite powder and silicon nitride powder is
Silicon nitride powder is 0.01 to 3 to 99.99% by weight.
To 7% by weight, cordierite powder 9
0.1 to 4 silicon nitride powder for 6 to 99.9% by weight
A range of weight% is more preferred. If the cordierite powder is less than 93% by weight and the silicon nitride powder exceeds 7% by weight, foaming occurs from the inside of the sample during firing, and a dense cordierite ceramic cannot be obtained. On the other hand, when the cordierite powder exceeds 99.99% by weight and the silicon nitride powder is less than 0.01% by volume, a dense cordierite ceramic having a Young's modulus of 130 GPa or more cannot be obtained, and the Dimensional changes are likely to occur.

The porosity of the dense cordierite ceramic obtained by the present invention is 5% or less, preferably 4% or less, more preferably 3% or less, and most preferably 0. If the porosity exceeds 5%, the change with time and the generation of free gas cannot be suppressed, and the Young's modulus decreases as the porosity increases. The porosity is
It can be determined by measuring by the Archimedes method.

The dense cord obtained by the present invention
Thermal expansion of yeritic ceramics at 20-30 ° C
The tension coefficient is -0.5 to +0.5 ppm · K^-1Range of
Preferably, -0.4 to +0.3 ppm · K^-1Range of
More preferably, -0.2 to +0.2 ppm · K^-1Range of
Enclosures are more preferred. -0.5 to +0.5 ppm · K
^-1Out of the range, the dimensional change for a slight temperature change
Tend to occur. The thermal expansion coefficient is the total expansion type thermal expansion
It can be determined by measuring with a meter.

The dense cordierite ceramic obtained by the present invention has a Young's modulus of 130 GP.
a or more is preferable, and 135 GPa or more is more preferable,
It is more preferably 140 GPa or more, and there is no particular upper limit. If it is less than 130 GPa, dimensional change tends to occur due to external stress. The Young's modulus can be determined by measuring using an ultrasonic pulse method.

The method of mixing the cordierite powder with the silicon nitride powder is not particularly limited.
It can be ground and mixed using a mortar or the like. There is no limitation on the molding method, and molding can be performed by a method such as die press molding, injection molding, or isostatic pressing. The molding pressure is not particularly limited because it differs depending on the molding method.

The firing is preferably performed in an atmosphere of an inert gas such as a nitrogen (N2) gas or an argon (Ar) gas or in a vacuum in order to obtain a high Young's modulus. The firing temperature is 1270-1440 ° C., preferably 1280-1.
The temperature is set to 430 ° C, more preferably 1300 to 1400 ° C. If the temperature is lower than 1270 ° C, the obtained ceramics will not be densified.

Hereinafter, the present invention will be described with reference to examples.

Example: Magnesium hydroxide having a purity of 99% or more was
Magnesium oxide raw material obtained by calcining at 00 ° C. for 1 hour, and Al ₂ O ₃ and SiO ₂ each having a purity of 99% or more.
Was mixed in a molar ratio of 2: 2: 5, wet-mixed in a ball mill for 24 hours, dried and granulated, and then calcined at 1400 ° C. for 10 hours in air to obtain a cordier. Light powder was obtained. As a result of measuring the obtained cordierite powder with an X-ray diffractometer, almost single-phase cordierite powder was obtained.

This cordierite powder was pulverized in a mortar, then subjected to isotropic pressure molding, and fired at a temperature of 1350 ° C. in a nitrogen atmosphere. It is shown in FIG. As a result, the porosity was 3% and the coefficient of thermal expansion at 20 to 30 ° C. was −0.2 ppm · K ^{− 1} , but the Young's modulus was as low as 118 GPa.

Next, the above cordierite powder has a coefficient of thermal expansion of 1.1 ppm · K ^{−1, a} Young's modulus of 350 GPa and an average particle diameter of 0.2 at 20 to 30 ° C. as a sintering aid. 6 μm of silicon nitride powder was added at the ratio shown in Table 1, and the mixture was pulverized and mixed in a ball mill for 24 hours.
Granulated through a 0 mesh sieve. Then 20MPa
And then formed into a pellet having a diameter of 25 mm and a thickness of about 10 mm, and then isostatically pressed at a pressure of 120 MPa to obtain a molded body. Next, the obtained molded body was fired under the conditions shown in Table 1 to obtain a sintered body (a dense cordierite ceramic). The sample No. 18
Only mixing and grinding were performed using a mortar.

The porosity, Young's modulus and coefficient of thermal expansion of the obtained sintered body were determined. Table 1 shows the results. The porosity was determined by Archimedes' method, the Young's modulus was measured by an ultrasonic pulse method, and the coefficient of thermal expansion was measured by a total expansion type thermal dilatometer. The coefficient of thermal expansion is 20
The value at ３０30 ° C. was shown.

[0034]

[Table 1]

As shown in Table 1, the sintered body (dense cordierite ceramics) according to the present invention has a porosity of 5% or less, a Young's modulus of 130 GPa or more and 20 to 3
The coefficient of thermal expansion at 0 ° C. is -0.5 to 0.5 ppm · K
It is clear that all characteristics are excellent in the range of ^-1 .

On the other hand, the sample N not included in the present invention
o. The sintered body of No. 6 has a porosity of 16% due to a low firing temperature.
As a result, a dense sintered body could not be obtained, the Young's modulus did not reach 130 MPa, and the coefficient of thermal expansion was out of the range of the present invention. In addition, the sample No. Since the sintered body of the sintered body of No. 11 had a high firing temperature, the sample was melted. further,
Sample No. In samples 14 and 17, foaming occurred from inside the sample during firing, and a dense sintered body could not be obtained.

[0037]

The dense cordierite ceramic according to the first and second aspects is a dense cordierite ceramic having a higher rigidity, a lower coefficient of thermal expansion and a porosity of 5% or less as compared with metal. The dense cordierite ceramic obtained by the method according to claims 3 and 4 has higher rigidity and a smaller thermal expansion coefficient than metal,
It is a dense cordierite ceramic having a porosity of 5% or less.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA07 AA36 AA37 AA52 BA24 GA24 GA27 HA18 5F046 CC08 CC11 DA05

Claims (4)

[Claims] 1. A compound of the general formula 2MgO.2Al ₂ O ₃ .5SiO
93 to 99.99% by weight of cordierite represented by ₂
And a dense cordierite ceramic containing 0.01 to 7% by weight of silicon nitride and having a porosity of 5% or less. 2. The thermal expansion coefficient at 20 to 30 ° C. is -0.0.
5 to +0.5 ppm · K ^-1 and a Young's modulus of 130
The dense cordierite ceramic according to claim 1, which has a GPa or more. 3. A general formula 2MgO _· 2Al ₂ O 3 _· 5SiO
_3. Porosity characterized by mixing and molding 93 to 99.99% by weight of cordierite powder represented by ₂ and 0.01 to 7% by weight of silicon nitride powder, followed by firing at a temperature of 1270 to 1440C. Of a dense cordierite ceramic having a content of 5% or less. 4. The thermal expansion coefficient at a temperature of 20 to 30.degree.
5 + at 0.5 ppm · ^{K -1,} and Young's modulus of 130
4. The method for producing a dense cordierite ceramic according to claim 3, which has a GPa or more.