JP2002179458A - Low thermal expansion high rigidity ceramic material and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide low thermal expansion and high rigidity ceramics and a method for manufacturing the ceramics having a coefficient of thermal expansion as small as in the range of -0.5 to 1 ppm/K at 20±5 deg.C and a Young's modulus as high as >=150 GPa. SOLUTION: The low thermal expansion and high rigidity ceramics contains SiC and a base material consisting of cordierite expressed by general formula of 2MgO.2Al2O3.5SiO2 with substitution of Ga2O3 for part of Al2O3 and/or substitution of GeO2 for part of SiO2 and having -3 to 0 ppm/K coefficient of thermal expansion at 20±5 deg.C. The ceramics show -5 to 1 ppm/K coefficient of thermal expansion at 20±5 deg.C and >=150 GPa Young's modulus. In the method for manufacturing the ceramics, a base material consisting of cordierite expressed by general formula of 2MgO.2Al2O3.5SiO2 with substitution of Ga2O3 for part of Al2O3 and/or substitution of GeO2 for part of SiO2 and having -3 to 0 ppm/K coefficient of thermal expansion at 20±5 deg.C is mixed with SiC powder, and the mixture is compacted and calcined at 1270 to 1480 deg.C. The obtained ceramics show -0.5 to 1 ppm/K coefficient of thermal expansion at 20±5 deg.C and >=150 GPa Young's modulus.

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 low-thermal-expansion high-rigidity ceramic suitable for a wafer suction chuck and these components, and a method for manufacturing 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, silicon nitride ceramics, and the like have been widely used.

In recent years, however, as electronic circuits have become more highly integrated, these components have been required to have higher positioning accuracy, and a decrease in accuracy has been a problem, especially when the temperature of a manufacturing apparatus changes. 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 ± 5 ° C.) and high rigidity has been required.

In recent years, cordierite-based ceramics as disclosed in Japanese Patent Publication No. 6-97675 have been proposed as low thermal expansion ceramics used for parts of semiconductor manufacturing equipment. 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.

Further, cordierite based ceramics, as shown, such as in JP 55-144468 discloses the addition to the above, a portion of the Al ₂ O ₃ Ga ₂ O ₃ substituted and / or SiO ₂ By substituting part of the part with GeO ₂ ,
It is also known to exhibit a coefficient of thermal expansion of zero or less in an evaluation temperature range of 25 to 800 ° C.

[0006] Lithium aluminosilicate (also represented by the general formula Li ₂ O.
Japanese Patent Application Laid-Open No. 56-164070 discloses that an Al ₂ O ₃ .nSiO ₂ ) -based ceramic, particularly β-spodumene, is produced using a natural material. Japanese Patent Application Laid-Open No. 2000-21 discloses that β-eucryptite can be densified by containing MgO.
No. 9572.

In recent years, higher integration of semiconductor LSIs, VLSIs, etc., typified by storage chips mounted on computers, has been further advanced, and accordingly, formation of ultrafine circuits on the order of submicrons has become essential. . Therefore,
An exposure apparatus for forming an ultrafine circuit on a Si wafer is required to have high precision, for example, 0.05 μm or less in positioning.

[0008] Silicon nitride ceramics and cordierite ceramics, which have higher rigidity than metals and a small thermal expansion coefficient, are used for semiconductor manufacturing equipment and parts thereof. However, in silicon nitride, the rigidity is as high as about 300 GPa (gigapascal, = × 10 ⁹ Pa), but the coefficient of thermal expansion at 20 ± 5 ° C. is 1.31 pp.
m / K (= × 10 ⁻⁶ / K), which means that the length is 1 m
Only when the temperature of the exposure device member changes by 0.05 ° C.
This means that a dimensional change of about 0.6 μm (micron, = × 10 −6 m) occurs, which causes a decrease in quality and yield in forming a precision circuit.

On the other hand, cordierite ceramic has a coefficient of thermal expansion of 0.2 ppm at 20 ± 5 ° C.
/ K, which is small, so that a dimensional change due 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 a dimensional change easily occurs due to external stress.

[0010] Lithium aluminosilicate ceramics have a thermal expansion coefficient of about -8 to 2 ppm / K at 20 ± 5 ° C depending on the composition, but also have low rigidity and a Young's modulus of 60 to 5 ppm. It is about 90 GPa, which is disadvantageous in that dimensional changes easily occur with respect to external stress similarly to cordierite ceramics.

[0011]

According to the first, second and third aspects of the present invention, the thermal expansion coefficient at 20 ± 5 ° C. is small.
It is intended to provide a low-thermal-expansion high-rigidity ceramic having a Young's modulus as high as 150 GPa or more in the range of 0.5 to 1 ppm / K. The invention according to Claims 4, 5 and 6 has a small thermal expansion coefficient at 20 ± 5 ° C.
Within 1 ppm / K and Young's modulus is 150G
An object of the present invention is to provide a method for producing a low-thermal-expansion high-rigidity ceramic as high as Pa or more.

[0012]

According to the present invention, there is provided a compound of the general formula 2Mg
A part of Al ₂ O ₃ of cordierite represented by O.2Al ₂ O ₃ .5SiO ₂ is replaced with Ga ₂ O ₃ and / or SiO 2
₂ is partially substituted with GeO ₂ , and contains a base material and SiC having a thermal expansion coefficient of −3 to 0 ppm / K at 20 ± 5 ° C., and further has a thermal expansion coefficient of 20 ± 5 ° C. -0.5 ~
The present invention relates to a low-thermal-expansion high-rigidity ceramic having a Young's modulus of 150 ppm or more at 1 ppm / K. Also, the present invention
The present invention relates to a low-thermal-expansion high-rigidity ceramic in which the content of the base material is 60 to 90% by volume and the content of SiC is 10 to 40% by volume. Further, the present invention is a part of 5 to 20 mol% Al ₂ O ₃ Ga ₂ O ₃ substituted and / or SiO ₂ Ge
The low-thermal-expansion high-rigidity ceramic according to claim 1 or _2, which is substituted by O ₂ .

Further, the present invention relates to a compound of the general formula 2MgO.2Al
Al ₂ O cordierite represented by ₂ O ₃ · 5SiO _2
3 is replaced by Ga ₂ O ₃ and / or SiO ₂ is partially replaced by G
After mixing and molding a base material and SiC powder having a thermal expansion coefficient of −3 to 0 ppm / K at 20 ± 5 ° C. after substituting with eO ₂ , firing at a temperature of 1270 to 1480 ° C. The thermal expansion coefficient at 20 ± 5 ° C
The present invention relates to a method for producing a low-thermal-expansion high-rigidity ceramic having a Young's modulus of 1 ppm / K and a Young's modulus of 150 GPa or more. Further, the present invention relates to the above-mentioned metal alloy, wherein the content of the base material is 60 to 90% by volume and Si
The present invention relates to a method for producing a low-thermal-expansion high-rigidity ceramic having a C content of 10 to 40% by volume. Furthermore, the present invention provides
5 to 20 mol% of l ₂ O ₃ is replaced by Ga ₂ O ₃ and / or
5-20 mol% of iO ₂ relates to a manufacturing method according to claim 4 or 5 low thermal expansion and high rigidity ceramic according formed by substituted with GeO _2.

[0014]

Replacing a part of the general used in matrix type 2MgO · 2Al ₂ O ₃ cordierite represented by · 5SiO ₂ Al ₂ O ₃ of the present invention DETAILED DESCRIPTION OF THE INVENTION In Ga ₂ O ₃ and / Or a substance obtained by substituting a part of SiO ₂ with GeO ₂ , at 20 ± 5 ° C.
, The coefficient of thermal expansion is -3 to 0 ppm / K, preferably -2.5 to -0 ppm / K, and more preferably -2 to 0 ppm / K.
It is necessary to use powders in the ppm / K range,
When a powder out of the range of 3 to 0 ppm / K is used, the thermal expansion coefficient at 20 ± 5 ° C. which is the object of the present invention is −
At 0.5 to 1 ppm / K, a low-thermal-expansion high-rigidity ceramic having a Young's modulus of 150 GPa or more cannot be obtained.

In the present invention, the general formula 2MgO.2Al
_TwoO_Three・ 5SiO_TwoCordierite represented by_Two
O_ThreePart of Ga_TwoO_ThreeAnd / or SiO_TwoPart of
GeO_TwoTo be used.
Reduce the coefficient of thermal expansion of Lamix at 20 ± 5 ° C
In terms of_TwoO_ThreePart of Ga_TwoO_ThreeTo replace with
Al_TwoO_ThreeFrom 5 to 20 mol% of Ga_TwoO_ThreeCan be replaced by
Preferably, Al_TwoO_Three10 to 20 mol% of Ga_TwoO_ThreePut in
It is more preferable that the replacement is performed. On the other hand, SiO _TwoPart of
GeO_TwoWhen substituting with_Two5 to 20 mol% of
GeO_TwoIt is preferable to substitute_Two10-2
0% by mole of GeO_TwoIt is more preferred to substitute

The cordierite is made of Al ₂ O ₃
Is partially replaced by Ga ₂ O ₃ and SiO ₂ is partially replaced by G
When used in combination with those substituted with eO ₂ , use Al ₂ O
Ge to the substitutions mol% and SiO ₂ of Ga ₂ O ₃ for ₃
The sum of the substitution mole% of O ₂ is 20
In terms of reducing the coefficient of thermal expansion at ± 5 ° C, 5-30
The range of mol% is preferable, the range of 10 to 27 mol% is more preferable, and the range of 15 to 25 mol% is further preferable.

The above-mentioned base material powder has, for example, a purity of 9%.
9% or more MgO, Al_TwoO_Three, Ga _TwoO_Three, SiO_Twoas well as
GeO_TwoIn a molar ratio of 2: 1.6 to 1.9: 0.
1 to 0.4: 4 to 4.75: 0.25 to 1
Weigh, wet mix using a ball mill, dry, granulate
After that, it is calcined in the air, and then the average particle size is 10 to 20 μm.
m can be obtained by granulation.

On the other hand, the SiC powder used in the present invention is:
Although it may be either α-type or β-type, it is preferable to use α-type SiC powder which is inexpensive and has little change in crystal structure during firing. It is preferable to use a high-purity powder for the purity, but in the present invention, a GC-grade SiC powder for sintering which is generally used may be used.

The average particle diameter of the SiC powder is 0.1 μm.
m or more, more preferably 0.5 μm or more,
The range of 0.6 to 10 μm is more preferable. If the average particle size is less than 0.1 μm, the cost of SiC powder is several hundred times or more, which is expensive and uneconomical. The average particle size of the SiC powder can be determined by measuring with a laser type particle size distribution measuring device (master sizer manufactured by MALVERN). In addition, Si
C powder has a coefficient of thermal expansion of 1.5 to 20 ± 5 ° C.
It is preferable to use a powder having a Young's modulus of 200 GPa or more at 2.5 ppm / K.

In the present invention, the mixing ratio of the base material and the SiC powder is preferably in the range of 10 to 40% by volume of the SiC powder with respect to 60 to 90% by volume of the base material. Thus, the SiC powder is more preferably in the range of 15 to 40% by volume, and the base material is more preferably in the range of 20 to 40% by volume with respect to 60 to 80% by volume. Base material is 6
If the SiC powder is less than 0% by volume and the SiC powder exceeds 40% by volume, the resulting ceramic tends not to be densified, and the Young's modulus of the ceramic obtained if the base material exceeds 90% by volume and the SiC powder is less than 10% by volume. Is not more than 150 GPa, and there is a tendency that a dimensional change is easily caused by external stress. The volume% in the present invention is a value calculated by dividing the weight of a component by the density of the component.

The coefficient of thermal expansion at 20 ± 5 ° C. of the low-thermal-expansion high-rigidity ceramic obtained by the present invention is −0.05 ° C.
5-1 ppm / K, preferably -0.5-0.7 ppm
/ K, more preferably in the range of -0.5 to 0.5 ppm / K. If the temperature is outside the range of -0.5 to 1 ppm / K, a dimensional change occurs due to a slight temperature change. The coefficient of thermal expansion can be determined by measuring with a laser interferometry.

The low thermal expansion high rigidity ceramics obtained by the present invention has a Young's modulus of 150 GPa or more, preferably 160 GPa or more, and more preferably 170 GPa or more.
When it is set to Pa or more, and less than 150 GPa, a dimensional change occurs with respect to external stress. The Young's modulus can be determined by measuring using an ultrasonic pulse method.

The method of mixing the base material and the SiC powder is not particularly limited, and may be pulverized and mixed using, for example, a ball mill. There is no limitation on the molding, and molding can be performed by a method such as die press molding, casting, injection molding, extrusion molding, or the like. 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 gas or in a vacuum in order to obtain a high Young's modulus. The firing temperature is 1
270-1480 ° C, preferably 1300-1450
° C, more preferably in the range of 1350 to 1400 ° C. If the temperature is lower than 1270 ° C, the resulting ceramic will not be densified, and if it exceeds 1480 ° C, there will be a problem that the molded body will melt.

[0025]

The present invention will be described below with reference to examples. Purity of 99% of MgO, the _{Al 2 O 3, Ga 2 O} 3, the SiO ₂ and GeO ₂ powder, were weighed in proportions shown in Table 1 50 ml of ion-exchanged water based on the total amount 200g of these powders In addition, the mixture was wet-mixed in a ball mill for 24 hours, and then, when the obtained slurry was transferred to a drying vessel, another 50 ml of ion-exchanged water was added to rinse the inside of the ball mill, and the mixture containing the ion-exchanged water was placed in a drying vessel. Transferred and dried at 45 ° C. for 24 hours.

Then, the dried product is pulverized in a mortar, and the pulverized product is granulated through a 60-mesh sieve, and then at 1,400 ° C. in air (1300 ° C. for sample No. 9 due to a decrease in melting point) for 5 hours. By calcining, a ceramic base material was obtained. 23 ± 1 ℃ of each ceramic base material obtained
Are 1.2 ppm / K (sample No. 1) and -1.5 ppm / K (samples Nos. 2 to 7), respectively.
And sample no. 14 to 19), -1.2 ppm / K (sample No. 8), 0.5 ppm / K (sample No. 9),-
1.2 ppm / K (Sample Nos. 10 and 11) and-
1.1 (Samples Nos. 12 and 13) were ppm / K. Further, as a result of measuring the obtained ceramic base material by X-ray diffraction, it was found to be a cordierite single phase.

Next, the ceramic base material has a coefficient of thermal expansion of 2.13p at 23 ± 1 ° C. as highly rigid particles.
pm / K, Young's modulus is 410 GPa, and average particle size is 0.1 GP.
6 μm α-type SiC powder was added at the ratio shown in Table 2, ground and mixed in a ball mill for 72 hours, dried at 45 ° C. for 24 hours, dried, granulated through a 60-mesh sieve, and then dried at a pressure of 120 MPa. Uniaxial pressure molding, 2 diameter
A pellet-shaped compact having a thickness of 5 mm and a thickness of 12 mm was obtained. Next, the obtained molded body was fired under the conditions shown in Table 2 to obtain a sintered body (low thermal expansion high rigidity ceramic).

The porosity, Young's modulus and coefficient of thermal expansion of the obtained sintered body were determined. Table 2 shows the results. The porosity was determined by the Archimedes method, the Young's modulus was determined by the ultrasonic pulse method, and the coefficient of thermal expansion was determined by the laser interferometry. The coefficient of thermal expansion is 23 ±
The value at 1 ° C. is shown.

[0029]

[Table 1]

[0030]

[Table 2]

As shown in Table 2, the sintered body (low thermal expansion high rigidity ceramic) according to the present invention has a porosity of 3.4.
%, The coefficient of thermal expansion when the Young's modulus is 151 GPa or more and the temperature is 23 ± 1 ° C. is in the range of −0.5 to 0.8 ppm / K. On the other hand, Sample No. which is not included in the present invention. The sintered bodies of Nos. 1 and 9 had a low Young's modulus of 125 GPa or less, and a high coefficient of thermal expansion at 23 ± 1 ° C. of 1.2 ppm / K or more.

The sample No. The sintered body of No. 7 is 23 ± 1
The coefficient of thermal expansion at a temperature of 100 ° C. was as high as 1.2 ppm / K. The sintered bodies of 2, 10, 12, and 19 had Young's modulus as low as 130 GPa or less, and the coefficient of thermal expansion at 23 ± 1 ° C was as low as -1.1 ppm / K or less. Further, the sample No. The sintered body of No. 14 could not measure Young's modulus because of high porosity. The sample No. In No. 18, the molded body was melted and a sintered body could not be obtained.

[0033]

The low-thermal-expansion high-rigidity ceramics according to the first, second and third aspects have a coefficient of thermal expansion at 20 ± 5 ° C.
It is a low-thermal-expansion high-rigidity ceramic in the range of 0.5 to 1 ppm / K and having a high Young's modulus of 150 GPa or more. The low-thermal-expansion high-rigidity ceramic obtained by the method according to claim 4, 5 or 6, has a coefficient of thermal expansion in the range of -0.5 to 1 ppm / K at 20 ± 5 ° C and a Young's modulus of 150 GPa or more. And high rigidity ceramics with low thermal expansion.

Claims (6)

[Claims] 1. The general formula 2MgO.2Al ₂ O ₃ .5SiO ₂
Some of the Al ₂ O ₃ of in represented by cordierite Ga ₂
The part of a substituent and / or SiO ₂ in O ₃ was replaced with GeO _2, and 20 thermal expansion coefficient when the ± 5 ℃ is -3~0pp
A low-thermal-expansion high-rigidity ceramic containing a base material of m / K and SiC, having a thermal expansion coefficient of -0.5 to 1 ppm / K at 20 ± 5 ° C, and a Young's modulus of 150 GPa or more. 2. The low thermal expansion and high rigidity ceramic according to claim 1, wherein the content of the base material is 60 to 90% by volume and the content of SiC is 10 to 40% by volume. 3. A low thermal expansion of the replacement and / or 5 to 20 mol% of SiO ₂ formed by substituted with GeO ₂ according to claim 1 or 2, wherein 5 to 20 mole% Al ₂ O ₃ in Ga ₂ O ₃ High rigidity ceramics. 4. The general formula 2MgO.2Al_TwoO_Three・ 5SiO_Two
Al of cordierite represented by_TwoO _ThreePart of Ga_TwoO_Three
And / or SiO_TwoPart of GeO_TwoReplace with
Thermal expansion coefficient at 20 ± 5 ° C. is -3 to 0 ppm / K
After mixing and molding the base material and SiC powder of 1270-
20 ± 5 characterized by firing at a temperature of 1480 ° C.
The coefficient of thermal expansion at -0.5 ° C is -0.5 to 1 ppm / K.
Thermal expansion high rigidity ceramic with a modulus of at least 150 GPa
Manufacturing method. 5. The method according to claim 4, wherein the content of the base material is 60 to 90% by volume and the content of SiC is 10 to 40% by volume. 6. The low thermal expansion of the replacement and / or 5 to 20 mol% of SiO ₂ formed by substituted with GeO ₂ according to claim 4 or 5, wherein 5 to 20 mole% Al ₂ O ₃ in Ga ₂ O ₃ Manufacturing method of high rigidity ceramics.