JP2000007428A - Zirconyl phosphate-base composite material and precision apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low thermal expansion and high rigidity ceramic material having low specific gravity and a high Young's modulus and further, free from a change in the lapse of time. SOLUTION: When a ceramic composite material contg. zirconyl phosphate as a principal crystal phase and one or more ceramics having a positive coefft. of thermal expansion at an ordinary temp. and >=150 GPa Young's modulus as a secondary crystal phase is produced, and this zirconyl phosphate-base composite material in which the 2nd crystal phase is added so that the coefft. of thermal expansion at the ordinary temp. becomes <=±0.5×10-6/ deg.C, is used, since the resultant zirconyl phosphate-base composite material is free from a change in the lapse of time, is small in a dimensional change due to a temp. change and the increased size of a member because of the high Young's modulus, it can enhance the precision of a precision apparatus such as a semiconductor and liquid crystal producing apparatus of a stepper or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material of a member for precision equipment, and more particularly to a ceramic material having a low thermal expansion and a high Young's modulus which is suitable as a member of an apparatus for manufacturing semiconductors and liquid crystals.

[0002]

2. Description of the Related Art Conventionally, low thermal expansion glass and invar alloys have been widely used in semiconductor and liquid crystal manufacturing apparatuses, especially in exposure apparatuses, because of their low coefficient of thermal expansion at room temperature. On the other hand, low-thermal-expansion ceramics are often used as materials having excellent heat resistance by utilizing the characteristics of ceramics, as seen in JP-A-54-4914. A material having a low coefficient of thermal expansion was required. Also, as disclosed in JP-A-6-4510 using zirconyl phosphate, a high melting point has been required in order to increase heat resistance.

The details found in JP-A-54-4914 are as follows. Low strength porous low thermal expansion ceramics (for example, lithium aluminum
By adding an oxide of a rare earth element to silicate, cordierite, aluminum titanate), a dense sintered body can be obtained. In this case, the coefficient of thermal expansion at a high temperature (1000 ° C.) is measured.

[0004]

In the case where the conventional low thermal expansion glass is used as a stepper member, for example, when the member becomes large or when a short wavelength KrF excimer laser or the like is used as a light source for exposure, Young. Since the rate is low (100 GPa or less), deformation may occur, and the accuracy of the exposure pattern may be deteriorated. A metal-based low thermal expansion material such as Invar has a Young's modulus of about 150 GPa, which is relatively high, but has a large specific gravity (about 8 g / cc) and has a problem that it changes with time.

In summary, in order to improve the accuracy of a member for a precision device such as a stepper, a material having a low thermal expansion at room temperature, a high Young's modulus and a low specific gravity has been strongly demanded. With low thermal expansion glass and Invar alloy, the level cannot be met.

An object of the present invention is to provide a low thermal expansion and high rigidity ceramic material which has a small specific gravity, a high Young's modulus and does not change with time, and which has an object of the present invention. is there. Further, the non-porous material can be used as a highly rigid mirror material instead of a glass material.

[0007]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and is directed to a ceramic having a main crystal phase of zirconyl phosphate and a second crystal phase having a positive coefficient of thermal expansion at room temperature and a Young's modulus of 150 GPa or more. A ceramic composite material containing at least one of the following, and adding the second crystal phase in such a manner that the coefficient of thermal expansion at room temperature is ± 0.5 × 10 ⁻⁶ / ° C. or less. A zirconyl acid-based composite material was obtained. When the above zirconyl phosphate composite material is used, there is no change with time and the Young's modulus is high, so there is little dimensional change due to temperature changes and large-sized members, so the precision of semiconductors such as steppers and precision equipment such as liquid crystal manufacturing equipment is reduced. Can be enhanced.

Further, when a pressure sintering method such as hot pressing or HIP (hot isostatic pressing) is used, sintering can be performed at a lower temperature, and a fine sintered body having no pores and a high Young's modulus can be obtained. Can be

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a ceramic material mainly composed of zirconyl phosphate, having a small coefficient of thermal expansion at room temperature and a high Young's modulus. It is known that zirconyl phosphate has a low thermal expansion. Conventionally, zirconyl phosphate has been considered only as a heat-resistant material having excellent thermal shock resistance utilizing low thermal expansion. Further, in order to increase the thermal shock resistance, a low Young's modulus is advantageous, and the raw material cost is more expensive than other low thermal expansion ceramics.

In order to obtain a ceramic having a low thermal expansion and a high Young's modulus at room temperature, which is the object of the present patent, a detailed investigation has shown that zirconyl phosphate has relatively high strength among generally-known low thermal expansion ceramics. Because the coefficient of thermal expansion at room temperature is negative, the coefficient of thermal expansion can be made zero by combining with a material having a positive coefficient of thermal expansion, and at the same time, by combining with a material having a high Young's modulus, the coefficient of thermal expansion at room temperature ± Within the range of 0.5 × 10 ⁻⁶ / ° C., a member having a high Young's modulus can be obtained.

Although it is necessary to bake at a high temperature to increase heat resistance, it is preferable to lower the baking temperature in order to achieve a high Young's modulus and a low coefficient of thermal expansion at room temperature, which are the objects of the present invention. In the case of zirconyl phosphate, when the particle size exceeds 7 μm, microcracks occur, which lowers the Young's modulus and makes the coefficient of thermal expansion unstable. To prevent grain growth, a lower sintering temperature is advantageous. In addition, when the firing temperature increases, the amount of dissolution from the crystal phase to the liquid phase increases, and the decomposition of the crystal phase proceeds, and at the same time, the glass phase at the grain boundaries increases. This results in a decrease in Young's modulus and an increase in coefficient of thermal expansion. Therefore, as long as a dense sintered body can be obtained,
It is necessary to lower the firing temperature.

The conventional sintering condition is 1400 ° C. or higher, but in the present invention, the material can be densely sintered at 1300 ° C. or lower by optimizing the properties and composition of the raw materials and by pressure sintering. It seems to be effective for achieving the purpose. In addition, it is necessary to manufacture a large-sized precision device member which is an application of the present invention, and it is preferable that the firing temperature is low for manufacturing a large-sized product.

[0013]

EXAMPLES <Example 1> Raw materials were obtained by mixing zirconium oxychloride and phosphoric acid in an aqueous solution at a composition ratio of 2ZrO ₂ · P ₂ O ₅ gradually and coprecipitating them, followed by calcining and pulverization. Was. The powder obtained had a purity of 99% or more, 90% or more of α (ZrO) ₂ P ₂ O ₇ and an average particle size of 1.1 μm.
The maximum particle size was about 5μ. As a second crystal phase,
As the oxide, zircon having an average particle diameter of about 1 μm, zirconia having an average particle diameter of 0.3 μm, other alumina, mullite, and the like can be considered. In this case, a large product can be made relatively cheaply because it can be fired in the air. . In addition, as the second crystal phase, carbide ceramic such as SiC / TiC,
It is also considered effective to compound a nitride ceramic such as silicon nitride, sialon, or TiN. However, when carbide or nitride is used as the second crystal phase, it is necessary to devise a firing method such as vacuum firing because firing in the atmosphere cannot be performed due to oxidation. ZnO, MgO, Nb ₂ having a particle size of about 1 μm are used as a sintering aid and a grain growth inhibitor in these main raw materials.
O _{5 and the} like, SiO ₂ powder and the like were added and mixed well by a ball mill. When a silicate such as zirconium silicate is used as the second crystal phase, S
No addition of iO ₂ powder is required. Table 1 shows the second crystal phase.
5 parts by weight of a 10% aqueous PVA solution were added to 100 parts by weight of the mixture of the preparation shown in
After press molding with a 0 mm mold at a pressure of 100 kg / cm ² , rubber pressing was performed at 1 ton / cm ² to form a molded body.

[0014]

[Table 1]

The molded body was heated in an electric furnace at 100 ° C./hr, kept at the firing temperature for 3 hours, and cooled in the furnace to obtain a sintered body. This sintered body was processed and, for a sintered body having microcracks accompanying grain growth, chips and cracks occurred during processing and could not be evaluated, but those without cracks were in each evaluation item. Test pieces were prepared, and the three-point bending strength, specific gravity, Young's modulus, and coefficient of thermal expansion at room temperature were measured. The evaluation results are as shown in Table 1. In addition, NG in Table 1 indicates that the evaluation sample could not be formed due to chipping and cracking during processing, and the evaluation of the characteristic value could not be performed. Show.

The coefficient of thermal expansion of zirconyl phosphate in Table 1 at room temperature is -0.7 × 10 ^-6 / ° C. The Young's modulus of the second crystal phase is 210 GPa or more for ZrSiO ₄ , 80 GPa for SiO ₂ , and 210 GPa for ZrO ₂ .
It is. Zirconyl phosphate itself has a coefficient of thermal expansion at room temperature of less than -0.5 × 10 ⁻⁶ / ° C., but has a positive coefficient of thermal expansion at room temperature and a Young's modulus of 150 GPa or more and is compounded with an appropriate second crystal phase. As a result, an intended coefficient of thermal expansion (± 0.5 × 10 ⁻⁶ / ° C. or less) can be obtained. When compounded with a material having a low Young's modulus, the Young's modulus decreases,
By forming a composite with a material having a high Young's modulus, a composite material having a high Young's modulus can be obtained.

<Example 2> A portion of the sintered body obtained in Example 1 was subjected to HIP. HIP has a pressure of 100
The holding time at 0 atm and the maximum temperature is 1 hr, and the heating rate is 1
The test was performed at 00 ° C./hr. Table 2 shows the composition and evaluation results.
Shown in

[0018]

[Table 2]

The coefficient of thermal expansion of zirconyl phosphate itself in Table 2 at room temperature is -0.7 × 10 ^-6 / ° C. The Young's modulus of the second crystal phase is that ZrSiO ₄ is 210 GPa or more, and ZrO ₂ is 210 GPa. From Table 2, it can be seen that the specific gravity and the Young's modulus are higher than those of Example 1 by performing HIP even with the same composition. I understand. This is HIP
It is considered that pores are eliminated and the density is increased.

Example 3 The same procedure as in Example 1 was carried out for the raw material powders and the mixing thereof. The obtained mixed powder is filled into a 50 × 50 mm carbon mold at a height of 20 mm, and while the temperature is increased at 100 ° C./hr, a pressure of 0.5 kg /
The temperature was kept at the maximum temperature for 1 hour at a temperature of cm ² and hot pressing was performed. The composition is shown in Table 3. Processing and evaluation contents are the same as in Example 1, and the evaluation results are shown in Table 3.

[0021]

[Table 3]

The coefficient of thermal expansion of zirconyl phosphate itself in Table 3 at room temperature is -0.7 × 10 ^-6 / ° C. The Young's modulus of the second crystal phase is 210 GPa or more for ZrSiO ₄ , 44 GPa for SiC, and 210 GPa for ZrO ₂ .
Table 3 shows that a dense sintered body can be obtained at a low temperature by hot pressing.

Example 4 The same procedure as in Example 1 was carried out for the raw material powder and the mixing thereof. The obtained mixed powder is made of an iron container having an inner diameter of 40 mm and a height of 100 mm (thickness of 3 mm).
And sealed HIP was performed. When sealing HIP is performed using ordinary ceramics, the glass is melted and sealed, which is very troublesome. However, some of the materials of the present invention can be sintered at a temperature of 1300 ° C. or lower. In this case, the seal HIP can be easily performed because the material may be packed in an iron container as described above. Processing and evaluation contents,
As in Example 1, the evaluation results are shown in Table 3.

[0024]

[Table 4]

The coefficient of thermal expansion of zirconyl phosphate itself in Table 4 at room temperature is -0.7 × 10 ^-6 / ° C. The Young's modulus of the second crystal phase is 210 GPa or more for ZrSiO ₄ and 310 GPa for Si ₃ N _{4. From} Table 4, it can be seen that a dense sintered body can be obtained at a low temperature by the seal HIP.

[0026]

As described above, according to the present invention, by forming a suitable composite material based on zirconyl phosphate, low thermal expansion and low thermal expansion can be obtained.
A material with a high Young's modulus can be obtained, the Young's modulus is significantly superior for low thermal expansion glass, and for Invar alloy,
It is possible to obtain a member suitable for precision equipment, which is characterized by having no change over time, a low specific gravity, and a high Young's modulus, especially a member for semiconductor and liquid crystal manufacturing equipment.

Claims (6)

[Claims] 1. A zirconyl phosphate as a main crystal phase,
As a second crystal phase, one or more ceramic phases having a positive coefficient of thermal expansion at room temperature and a Young's modulus of 150 GPa or more are included, and the ratio of zirconyl phosphate to the second crystal phase is adjusted. A zirconyl phosphate-based composite material having a temperature of 5 × 10 ⁻⁶ / ° C. or less. 2. Zirconyl phosphate as a main crystal phase,
One or more ceramics having a positive thermal expansion coefficient at room temperature and a Young's modulus of 150 GP or more as the second crystal phase, ZnO and MgO as sintering aids of 0.2% or more, and silica as a grain growth inhibitor of 0.2% or more. %, The ratio of zirconyl phosphate to the second crystal phase is adjusted, and the coefficient of thermal expansion at room temperature is
A zirconyl phosphate-based composite material having a temperature of ± 0.5 × 10 ⁻⁶ / ° C. or less. 3. The zirconyl phosphate composite material according to claim 1, wherein the second crystal phase contains 5 to 60 wt% of zirconium silicate. 4. The method according to claim 1, wherein the zirconyl phosphate composite material is 13
The zirconyl phosphate composite material according to any one of claims 1 to 3, wherein the zirconyl phosphate composite material is sintered at a temperature of 00C or lower. 5. The method according to claim 1, wherein the zirconyl phosphate-based composite material is 13
The zirconyl phosphate composite material according to any one of claims 1 to 3, wherein after sintering at a temperature of 00 ° C or lower, HIP or a seal HIP or a hot press at 1300 ° C or lower is performed. 6. A precision instrument using the zirconyl phosphate composite material according to claim 1 for a precision instrument member.