JP3260340B2 - Composite ceramic and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite ceramic and a method for producing the same, and more particularly, to an air slide, a surface plate,
The present invention relates to a composite ceramic suitable for various industrial equipment parts such as vacuum equipment structures, susceptors, electrostatic chucks, stages, and other semiconductor manufacturing equipment, precision equipment, measuring equipment, and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, ceramics have been widely used as parts for semiconductor manufacturing equipment, precision equipment, measuring equipment, and the like. For example, air slides made of silicon nitride in measurement equipment and semiconductor manufacturing processes,
Further, in the step of forming wiring on a silicon wafer in a semiconductor manufacturing process, a susceptor for supporting or holding the wafer, an electrostatic chuck, an insulating ring tool, and an X
Alumina and silicon nitride are widely used as a Y table and the like.

As described above, the reason why ceramics have been used for the above-mentioned applications is largely attributable to a low coefficient of thermal expansion and high rigidity. That is, in the case of a component made of a metal that has been used so far, the coefficient of thermal expansion is extremely large, so that the expansion and contraction of the component due to a slight temperature difference has a decisive effect on the accuracy of the product, so that it is difficult to use the component. Thus, ceramic parts have been used instead.

In recent years, however, the trend toward higher precision has been further accelerated, and in semiconductor manufacturing processes and the like, circuit miniaturization has been rapidly advanced along with high integration in LSIs and the like, and the line width has also increased. The precision is increasing to the submicron level. For example, in an exposure apparatus for forming a high precision circuit on a silicon wafer,
100nm (0.1μm) for stage member of exposure equipment
At present, the following positioning accuracy is required, and the alignment error of exposure has a great influence on the improvement of the quality of the product and the improvement of the yield at present.

Ceramics such as alumina and silicon nitride which have been generally used as members for semiconductor manufacturing equipment are:
Although certainly has a smaller thermal expansion coefficient than metals, are each 5 × 10 ^-6 /℃,1.5×10 ^-6 / ℃ about the number when the ambient temperature changes 0.1 ° C. 100 nm (0.1 [mu]
m) will occur. This change has become a serious problem in precision processes such as exposure, and the accuracy of conventional ceramics is not sufficient, resulting in a decrease in productivity.

On the other hand, in the case of a material having a low coefficient of thermal expansion, such as a lithium aluminosilicate-based sintered body or a magnesium aluminosilicate-based sintered body,
For example, in the case of a lithium aluminosilicate-based sintered body or the like, which exhibits a low thermal expansion property close to zero expansion, the above-described problem with respect to the exposure accuracy, for example, is solved to some extent as compared with alumina and silicon nitride.

[0007] However, when the support on which the Si wafer is mounted is moved and stopped at a high speed to a position where the exposure processing is performed, such as a stage of an exposure apparatus, the support itself after the movement is moved to a predetermined position. However, there is a problem that the exposure accuracy is reduced when the exposure process is performed in the vibrated state. This is more remarkable as the width of the wiring formed by exposure becomes narrower, and has been a fatal problem in forming a fine wiring circuit.

[0008] Such a problem is also the same in an air slide or the like. Even if the coefficient of thermal expansion is small, if the rigidity is small, the basic structure is a beam structure, and bending due to its own weight deformation occurs. This may cause a decrease in the accuracy of the device. Such vibration and deflection are caused by low rigidity of the members themselves, and high rigidity is required for these members.

In addition, a member having a small ratio of the rigidity of the member to the specific gravity and a small specific rigidity (rigidity / specific gravity) is not preferable because even if the rigidity is high, it may cause vibration or bending. The reason that the metal material is not used is that it has a large coefficient of thermal expansion.
This is because the specific rigidity is small in spite of the large rigidity due to the large front and rear portions, and the specific rigidity is small.

As described in detail above, ceramics having a small coefficient of thermal expansion such as lithium aluminosilicate and cordierite have a small Young's modulus, while alumina, silicon nitride, silicon carbide and the like have a small Young's modulus. Ceramics with sufficiently low thermal expansion and high rigidity do not exist, such as a sufficiently large coefficient of expansion but a large coefficient of thermal expansion. Therefore, in order to obtain such characteristics, it is conceivable to composite a plurality of ceramics, but such composite ceramics have not yet been obtained.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has both low thermal expansion characteristics and high rigidity, and is suitable for parts such as semiconductor manufacturing equipment, measuring equipment, and precision equipment. An object of the present invention is to provide a composite ceramic and a method for producing the same.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by combining two ceramics according to a predetermined formula to form a dense ceramic, low thermal expansion and low thermal expansion have been achieved. It has been found that a material having both high rigidity can be obtained. Further, it has been found that by using this predetermined formula, low-thermal-expansion and high-rigidity characteristics can be uniformly obtained in various combinations of materials.

Conventionally, attempts have been made to adjust the coefficient of thermal expansion of a material by forming a composite. Techniques such as making the coefficient of thermal expansion the same as silicon by combining mullite and cordierite have been proposed. However, a composite material from the above viewpoints has not been proposed, and further, a unified method for obtaining high rigidity characteristics with low thermal expansion has not been obtained, but based on the above findings, Things like that are now possible.

That is, the present invention provides the following (1) to
( 6 ) is provided. (1) Dense composite ceramics composed of a first material and a second material, wherein the weight ratio of the first material is W ₁ %,
The density is ρ ₁ , the coefficient of thermal expansion is α ₁ , the Young's modulus is E ₁ ,
When the weight ratio of the second material is W ₂ %, the density is ρ ₂ , the thermal expansion coefficient is α ₂ , and the Young's modulus is E ₂ , the thermal expansion coefficient α
And Young's modulus E are represented by the following equations, and the value of the coefficient of thermal expansion α near room temperature is −1.5 × 10 ⁻⁶ to 1.
5 × 10 ⁻⁶ / ° C., and the Young's modulus E is 150 GP
a or more, wherein the first material is a material selected from lithium aluminosilicate, alumina skeite, and aluminum titanate; and the second material is silicon carbide, silicon nitride, sialon, alumina, zirconia,
A composite ceramic characterized by being a material selected from aluminum nitride. α = [(W ₁ E ₁ α ₁ / ρ ₁ ) + (W ₂ E ₂ α ₂ / ρ ₂ )] / [(W ₁ E ₁ / ρ ₁ ) + (W ₂ E ₂ / ρ ₂ )] + A E = B × [(W ₁ E ₁ ρ ₂ ) + (W ₂ E ₂ ρ ₁ )] / [(W ₁ ρ ₂ ) + (W ₂ ρ ₁ )] where A = −0.5 × 10 ^{− 6 to} 1.0 × 10 ⁻⁶ , B = 0.8 to 1.2

(2) In the above (1), the first
The material is lithium aluminosilicate;
Material selected from silicon carbide, silicon nitride, sialon
Composite ceramics characterized in that it is an improved material.

( 3 ) The composite ceramic according to the above (1) or (2) , having a specific rigidity of 50 GPa / g / cm ³ or more.

[0017]

( 4 ) In any one of the above (1) to (3), the value of the thermal expansion coefficient α1 of the _first material near room temperature is 1.5 × 10 ⁻⁶ / ° C. hereinafter, the composite ceramic having a Young's modulus _{E 2} of the second material is characterized in that at least 150 GPa.

[0019]

( 5 ) The composite ceramic according to any one of the above (1) to ( 4 ), wherein the lithium aluminosilicate is eucryptite or spodumene.

(6) A raw material powder selected from lithium aluminosilicate, alumina skeite, and aluminum titanate, silicon carbide, silicon nitride, sialon,
A raw material powder selected from alumina, zirconia, and aluminum nitride is mixed and molded, and the compact is compacted in a vacuum or inert gas atmosphere and / or in air.
By firing at a temperature of 200 to 1500 ° C. (1)
A method for producing a composite ceramic, comprising obtaining the composite ceramic according to any one of (1) to (5) .

By adopting the composite ceramics of the present invention as various components such as semiconductor manufacturing equipment, measuring equipment, precision equipment, etc., it is possible to improve product accuracy and mass productivity.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Consisting of a first material and a second material
Widely known as an equation that describes the coefficient of thermal expansion α of a composite material
There is a Turner's theoretical formula of the following formula (1) (P.
S. Turner, J. Res. NBS,37, 239 (1946)). α = (α₁K₁W₁/ ρ₁+ Α₂K₂W₂/ ρ₂) / (K₁W₁/ ρ₁+ K₂W₂/ ρ ₂ ) (1) Here, the meanings of the symbols are as follows. K: bulk modulus (= E / 3 (1-2v), where E:
, Ν: Poisson's ratio), W: weight fraction, ρ: density.
Of the second material indicates that of the second material.

In general, the Poisson's ratio ν of ceramics is set to 0.3.
It is about 2 to 0.3, and although there is some difference depending on the material, even if it is regarded as a constant value, the error on α obtained from the above equation (1) is very small.

Therefore, assuming that ν ₁ = ν ₂ , the thermal expansion coefficient α is given by the following equation (2). _{α = [(W 1 E 1} α 1 / ρ 1) + (W 2 E 2 α 2 / ρ 2)] / [(W 1 E 1 / ρ 1) + (W 2 E 2 / ρ 2)] ·・ ・ (2)

On the other hand, the Young's modulus of the composite material is
Is given by the mixing rule of the following equation (3). E = E ₁ V ₁ + E ₂ V ₂ (3) where V ₁ = (W ₁ / ρ ₁ ) / [(W ₁ / ρ ₁ ) + ( W ₂ /
ρ ₂ )] and V ₂ = 1−V ₁ , the following equation (4) holds. E = [(W ₁ E ₁ ρ ₂ ) + (W ₂ E ₂ ρ ₁ )] / [(W ₁ ρ ₂ ) + (W ₂ ρ ₁ )] (4) As described above, (2) ) And (4), the thermal expansion coefficient α and the Young's modulus E of the composite material can be uniquely expressed.

In order to obtain the above relationship, it is essential that the first material and the second material are present in the composite material in a state of being chemically stable to each other. The above relationship does not hold when a reaction product is formed by the reaction and becomes a completely different material.

From the viewpoint of obtaining a composite material having a low thermal expansion and a high Young's modulus, the present invention relates to a combination of materials satisfying the above equation, and to what extent the resulting thermal expansion coefficient and Young's modulus actually match the above equation. As a result of various studies, the weight ratio of the first material is W ₁ %, the density is ρ ₁ , the thermal expansion coefficient is α ₁ ,
The Young's modulus and _{E 1,} the weight ratio of the second material _W 2%,
When the density is ρ ₂ , the thermal expansion coefficient is α ₂ , and the Young's modulus is E ₂ , the inventors have found that the thermal expansion coefficient α and the Young's modulus E may be represented by the following equations, and have been completed. α = [(W ₁ E ₁ α ₁ / ρ ₁ ) + (W ₂ E ₂ α ₂ / ρ ₂ )] / [(W ₁ E ₁ / ρ ₁ ) + (W ₂ E ₂ / ρ ₂ )] + A (5) E = B × [(W ₁ E ₁ ρ ₂ ) + (W ₂ E ₂ ρ ₁ )] / [(W ₁ ρ ₂ ) + (W ₂ ρ ₁₎ )] (6) where A = −0.5 × 10 ^{−6 to} 1.0 × 10 ⁻⁶ ,
B = 0.8-1.2

Here, A and B give margins of the equations (1) and (3) when various material systems are considered. Originally, the above equations (1) and (3) are basic theoretical equations, and it is difficult to cover various materials only with these equations. That is, depending on the material system, even if it is substantially chemically stable, a slight reaction product may be formed, or a glass phase may be formed at the grain boundary. The range of B is derived.

The composite ceramic of the present invention has a coefficient of thermal expansion α near room temperature of −1.5 × 10 ^{−6 to} 1.5.
× 10 ⁻⁶ / ° C. and Young's modulus E are preferably 150 GPa or more. When the value of the coefficient of thermal expansion α near room temperature is out of the above range, it is difficult to apply to a low thermal expansion application. If the Young's modulus E is less than 150 GPa, it is difficult to solve the problem of the vibration. Thermal expansion coefficient α
Is more preferably in the vicinity of room temperature.
⁻⁶ to 1 × 10 ⁻⁶ / ° C.

The composite ceramic of the present invention has a specific rigidity of 5
It is preferably 0 GPa / g / cm ³ or more. If the specific rigidity is less than this value, it is difficult to effectively prevent vibration.

When viewed from the viewpoint of low thermal expansion and high Young's modulus
If the first material is composed of a thermal expansion coefficient material, the second material
Is composed of a high Young's modulus material. In this case, the first material
The coefficient of thermal expansion at room temperature is 1.5 × 10^-6/ ℃ or less, No.
It is expected that the Young's modulus of material 2 is 150 GPa or more.
Good. The value of the thermal expansion coefficient of the first material at room temperature is 1.5
× 10^-6/ C is less effective in reducing the coefficient of thermal expansion
The Young's modulus of the second material is less than 150 GPa.
When full, the effect of increasing the Young's modulus is reduced, which is preferable.
I don't. The value of the coefficient of thermal expansion of the first material at room temperature is better.
Preferably 1 × 10 ^-6/ C or lower, more preferably 0.
5 × 10^-6/ ° C or less, and the Young's modulus of the second material is
More preferably 200 GPa or more, even more preferred
Or 250 GPa or more.

As the first material, a material selected from lithium aluminosilicate such as eucryptite, spodumene, petalite, β-quartz solid solution, alumina skeite, and aluminum titanate is used. As the second material, silicon carbide is used. A material selected from silicon nitride, sialon, alumina, zirconia, and aluminum nitride is used.

Of the above materials used as the first material,
From the viewpoint of low thermal expansion, eucryptite and spodumene are preferable among lithium aluminosilicates. Further, a material having a low coefficient of thermal expansion more preferably shows a negative thermal expansion, and examples of such a material include eucryptite. like this
Relatively low thermal expansion.
It is possible to reduce the thermal expansion coefficient of the entire composite ceramics by the amount, and therefore, it is possible to reduce the thermal expansion coefficient without lowering the Young's modulus. In addition, a plurality of first materials can be used in combination if they do not chemically react. For example, eucryptite and cordierite can be used in combination. Cordierite has a larger coefficient of thermal expansion than eucryptite, but has a higher Young's modulus than eucryptite, and thus can be preferably used when Young's modulus is prioritized.

Among the above materials used as the second material,
In particular, silicon carbide and alumina are preferable from the viewpoint of high Young's modulus, and silicon nitride and sialon are preferable from the viewpoint that the Young's modulus is relatively large and the thermal expansion coefficient is small.

The above composite ceramics may contain unavoidable impurities up to about 5% by weight in addition to the first and second materials, but more than 5% by weight. And various properties, particularly the coefficient of thermal expansion, are not preferred.

The above-mentioned composite ceramics are prepared by mixing raw material powders selected from lithium aluminosilicates such as eucryptite and spodium, cordierite, alumina skeite, aluminum titanate, and the like;
Raw material powders selected from silicon carbide, silicon nitride, sialon, alumina, zirconia, aluminum nitride and the like are mixed and molded, and the molded body is dried in a vacuum or an inert gas atmosphere, and / or in an air atmosphere at 1200 to 1200 μm. 1500
It can be obtained by firing at a temperature of ° C.

In order to produce such a sintered body, it is preferable to use a powder having an average particle size of about 10 μm or less. After blending the first material and the second material, they are sufficiently mixed by a ball mill or the like, and formed into a desired shape by a desired forming means, for example, a die press, a cold isostatic press, or extrusion. Then, it is fired.

The firing is performed by using the first material and the second material.
If non-oxide is used, oxidizing atmosphere such as air
Vacuum or A
r, N ₂Yan must be fired in an inert gas atmosphere such as
The effect of increasing the logging rate is not exhibited. The first material and the second
When both materials are oxides, vacuum or Ar,
N₂Oxidizing atmosphere such as air even in inert gas atmosphere such as
It doesn't matter if it's an atmosphere.

The sintering is performed at a temperature in the range of 1200 to 1500 ° C. for several hours. If the temperature is lower than 1200 ° C., it is difficult to densify it, and if it exceeds 1500 ° C., it is melted, and it is difficult to obtain a sound dense ceramic sintered body.

[0041]

EXAMPLE A commercially available eucryptite powder (round glaze) was used as the first material, molded without mixing the second material, and fired at 1380 ° C. to obtain a diameter of 50 mm and a thickness of 4 mm.
mm ceramic sintered body was obtained.

From this ceramic sintered body, 3 × 4 × 15
mm sample was taken out, and the coefficient of thermal expansion was measured in the range of 0 to 100 ° C (Rigaku TAS100: differential thermal expansion meter). Quartz was used for all measurement jigs in terms of measurement accuracy. As shown in Table 1, the thermal expansion coefficient of this sample at room temperature near 30 ° C. was −2.5 × 10 ⁻⁶ / ° C. The crystal phase was β-eucryptite. further,
When the Young's modulus at room temperature was measured by the ultrasonic pulse method, as shown in Table 1, the Young's modulus was 100 GPa, which was low rigidity (Sample No. 1).

As the second material, silicon carbide (UF-10 manufactured by Starck), silicon nitride (SN-E1 manufactured by Ube Industries)
0) and alumina (AL160-SG1 manufactured by Showa Denko Co., Ltd.), and the respective compacts formed by molding each powder without mixing the first material were fired under the conditions shown in Table 1 to obtain a ceramic sintered body. . As shown in Table 1, each sample had a large Young's modulus, but also had a large coefficient of thermal expansion (Sample Nos. 2 to 4).

The above sample No. 1-4 have a problem in either the coefficient of thermal expansion or the Young's modulus,
It could not be used for applications intended by the present invention, such as a surface plate.

Next, the sample no. Sample No. 1 was added to the eucryptite powder of No. 1. 2 to 4 of silicon carbide, silicon nitride, and alumina powders were added at the ratios shown in Table 1, and 2
After mixing for 4 hours, a mold was formed at a pressure of 1 ton / cm ² . Then, the molded body was fired under the conditions shown in Table 1 to obtain samples (Sample Nos. 5 to 7).

As a result of measuring the thermal expansion coefficient at 100 ° C. and the Young's modulus at room temperature of these samples, as shown in Table 1, the eucryptite sintered body of Sample No. 1 was obtained. In comparison with Sample No. 1, the Young's modulus was significantly increased, and the coefficient of thermal expansion was larger than that of Sample No. 1. It was much smaller than 2-4. Therefore, it could be suitably used for applications such as an air slide and a surface plate intended by the present invention. In this case, the A value and the B value in the expressions (5) and (6) are -0.5 × 10 ^{−6 to} 1.0 × 10 ⁻⁶ , respectively, which are defined in the present invention.
It was in the range of 0.8 to 1.2.

Next, a sample was obtained by using natural α-spodumene as the first material and molding without using the second material, followed by firing (sample No. 8). This sample has a small coefficient of thermal expansion of 0.05 × 10 ⁻⁶ / ° C., but also has a Young's modulus of 11
It was as small as 0 GPa.

Sample No. 9 is this spodumene and 2nd
And calcined by mixing silicon carbide as the material. In addition, the sample No. 10 is a spodumene and a sample N
o. Powder obtained by mixing 50% by weight of each eucryptite is used as a first material, and these are mixed and fired using silicon carbide as a second material.

Sample No. As a result of measuring the coefficient of thermal expansion at 30 ° C. and the Young's modulus at room temperature of Sample Nos. 9 and 10, as shown in Table 1, the sample No. 9 which is an α-spodumene sintered body was obtained.
As compared with No. 8, the Young's modulus was greatly increased, and the coefficient of thermal expansion was maintained at a low value. Therefore, it could be suitably used for applications such as an air slide and a surface plate intended by the present invention. In this case, the A value and the B value in the above equations (5) and (6) are respectively -0.0.
It was in the range of 5 × 10 ^{−6 to} 1.0 × 10 ⁻⁶ , 0.8 to 1.2.

[0050]

[0051]

[0052]

Sample No. Nos . 11 and 12 are cases where the firing temperatures are 1150 ° C. and 1550 ° C., respectively, which are outside the range of the present invention. Sample No. lower than 1200 ° C. Sample No. 11 could not be densified, and sample No.
In No. 12 , the molded product was melted, and the thermal expansion coefficient and the Young's modulus could not be measured.

As described above, No. 1 within the scope of the present invention.
5, 6, 7, 9, and 10 were confirmed to have both low thermal expansion characteristics and high rigidity. In addition, it was confirmed that the specific stiffness was 50 GPa / g / cm ³ or more, and the specific stiffness was high.

[0055]

[Table 1]

[0056]

As described above, according to the present invention,
By compounding the two ceramics according to the above specific formula to form a dense ceramic, a composite ceramic having both low thermal expansion and high rigidity can be obtained. Further, by using the above specific formula, it is possible to uniformly obtain low thermal expansion and high rigidity characteristics in various combinations of materials. For this reason, the composite ceramics of the present invention has a small dimensional change with respect to a temperature change of the atmosphere, and has a small bending and vibration.
When applied to precision equipment parts, measurement equipment parts, etc., a product with excellent accuracy can be obtained, and quality and mass productivity can be improved.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-13-58867 (JP, A) JP-A-60-27648 (JP, A) JP-A-59-174572 (JP, A) JP-A-11-588 130523 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/00-35/84

Claims (6)

(57) [Claims] 1. A dense composite ceramic comprising a first material and a second material, wherein the weight ratio of the first material is W ₁ %, the density is ρ ₁ , the thermal expansion coefficient is α ₁ , and the Young is Rate E
₁ , the weight ratio of the second material is W ₂ %, the density is ρ ₂ ,
Assuming that the thermal expansion coefficient is α ₂ and the Young's modulus is E ₂ , the thermal expansion coefficient α and the Young's modulus E are represented by the following equations, and the value of the thermal expansion coefficient α near room temperature is −1.5 × 10
^{−6 to} 1.5 × 10 ⁻⁶ / ° C., the Young's modulus E is 150 GPa or more, and the first material is a material selected from lithium aluminosilicate, alumina skeite, and aluminum titanate; A composite ceramic, wherein the second material is a material selected from silicon carbide, silicon nitride, sialon, alumina, zirconia, and aluminum nitride. α = [(W ₁ E ₁ α ₁ / ρ ₁ ) + (W ₂ E ₂ α ₂ / ρ ₂ )] / [(W ₁ E ₁ / ρ ₁ ) + (W ₂ E ₂ / ρ ₂ )] + A E = B × [(W ₁ E ₁ ρ ₂ ) + (W ₂ E ₂ ρ ₁ )] / [(W ₁ ρ ₂ ) + (W ₂ ρ ₁ )] where A = −0.5 × 10 ^{− 6 to} 1.0 × 10 ⁻⁶ , B = 0.8 to 1.2 2. The composite ceramic according to claim 1, wherein said first material is lithium aluminosilicate, and said second material is a material selected from silicon carbide, silicon nitride, and sialon. . 3. The composite ceramic according to claim 1, wherein the specific rigidity is 50 GPa / g / cm ³ or more. 4. The method according to claim 1, wherein the value of the thermal expansion coefficient α ₁ of the first material near room temperature is 1.5 × 10 ⁻⁶ / ° C. or less, and the Young's modulus E ₂ of the second material is 150 GPa or more. The composite ceramic according to any one of claims 1 to 3, characterized in that: 5. The composite ceramic according to claim 1, wherein the lithium aluminosilicate is eucryptite or spodumene. 6. A raw material powder selected from lithium aluminosilicate, alumina skeite, and aluminum titanate and a raw material powder selected from silicon carbide, silicon nitride, sialon, alumina, zirconia, and aluminum nitride are mixed and molded. The compact is then placed in a vacuum or inert gas atmosphere and / or
Claim 1 by firing at a temperature of 0 to 1500 ° C.
To obtain the composite ceramics according to claim 5.
A method for producing a composite ceramic, comprising: