JPH11209171A - Dense low thermal expansion ceramics, its production and member for semiconductor producing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain dense low thermal expansion ceramics almost free from voids. SOLUTION: Powdery starting material having a compsn. contg. 80-99 wt.% cordierite and 1-20 wt.% oxide of a rare earth element is compacted in a prescribed shape, sintered to >=90% relative density and heat-treated at 900-1,400 deg.C in an atmosphere under >=100 atm pressure to obtain the objective dense low thermal expansion ceramic having <=0.1% porosity, <=5 μm max. void diameter and <=1×10<-6> / deg.C coefft. of thermal expansion at 10-40 deg.C. The ceramic is applied to parts for a semiconductor producing device such as a vacuum chuck for an exposure system and a stage position measuring mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a vacuum device structure,
Low thermal expansion ceramics mainly composed of cordierite suitable for susceptors, vacuum chucks, electrostatic chucks, exposure stage mirrors, stage position measurement mirrors, or their supporting members, and various jigs in the semiconductor manufacturing process It relates to the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, cordierite-based sintered bodies have been known as ceramics having low thermal expansion, and have been applied to filters, honeycombs, refractories, and the like. This cordierite-based sintered body is generally made of cordierite powder or MgO, Al ₂ which forms cordierite.
O ₃ and SiO ₂ powders are mixed, and a rare earth element oxide, SiO ₂ , CaO, MgO, etc. are added thereto as a sintering aid, and after forming into a predetermined shape, 1000-1400 ° C.
It is produced by firing at the temperature of
-3629, JP-A-2-229760).

On the other hand, in a process of manufacturing a semiconductor device such as an LSI, in a process of forming wiring on a silicon wafer, a susceptor for supporting or holding the wafer, a vacuum chuck, an electrostatic chuck, an insulating ring, or another jig. For example, alumina and silicon nitride have been widely used because they are relatively inexpensive and chemically stable. Also, ceramics such as alumina and silicon nitride have been conventionally used as an XY table of an exposure apparatus.

Recently, low-thermal-expansion ceramics such as cordierite have been applied to parts for semiconductor manufacturing equipment as disclosed in Japanese Patent Application Laid-Open No. 1-1191422 and Japanese Patent Publication No. 6-976.
No. 75. According to Japanese Patent Application Laid-Open No. 1-1191422, it is proposed that a reinforcing ring to be bonded to a mask substrate in an X-ray mask is formed of cordierite in addition to SiO ₂ , invar and the like to control the stress of the membrane. Japanese Patent Publication No. 6-97675 proposes using an alumina or cordierite-based sintered body as a base for an electrostatic chuck on which a wafer is placed.

[0005]

In recent years, with high integration in LSIs and the like, circuit miniaturization has been rapidly advanced,
The line width is also being refined to a submicron order. High accuracy is required for an exposure apparatus for forming a high-precision circuit on a Si wafer. For example, a stage member of an exposure apparatus requires a 100 nm (0.
At present, a positioning accuracy of 1 μm or less is required, and a positioning error of exposure has a great influence on improvement of product quality and yield.

Ceramics such as alumina and silicon nitride, which are generally used for semiconductor manufacturing equipment, have a smaller coefficient of thermal expansion than metals, but have a coefficient of thermal expansion of 5.2 × 10 ^{-6 at} 10 to 40 ° C. / ° C, 1.5 × 10 ^-6 / ° C
Several hundred nm when the ambient temperature changes by 0.1 ° C.
(0.1 .mu.m), and this change becomes a serious problem in precise steps such as exposure, and the conventional ceramics have low accuracy and lower productivity.

On the other hand, the cordierite-based sintered body has a coefficient of thermal expansion of about 0.2 × 10 ⁻⁶ / ° C., which is lower than that of alumina or silicon nitride. The problem of exposure accuracy is solved to some extent.

However, conventional cordierite is difficult to densify, and only a cordierite having a large number of voids is obtained. Therefore, when surface smoothness is required, such as a mirror for position measurement of an exposure device or a member that requires a surface coating, the presence of irregularities such as voids causes irregular reflection of the laser for distance measurement. Was a fatal problem. Since such voids are caused by the low relative density of the members themselves, these members are required to have a dense material.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a dense low-thermal-expansion ceramic having a low thermal expansion itself and having few voids, and a method for producing the same. Another object of the present invention is to provide a dense semiconductor manufacturing member excellent in surface smoothness of a member requiring a surface coating such as a stage position measuring mirror.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result, have found that a dense body prepared using a composition obtained by adding a rare earth element oxide to cordierite at a predetermined ratio is used. , By further performing high-temperature pressing
The present inventors have found that the relative density can be increased without impairing the low thermal expansion characteristics and the voids in the sintered body can be reduced, and the present invention has been achieved.

That is, the dense low thermal expansion ceramics of the present invention contains cordierite in an amount of 80% by weight or more, a porosity of 0.1% or less, a maximum void diameter of 5 μm or less, and 10 to 40%.
The coefficient of thermal expansion at 1 ° C. is 1 × 10 ⁻⁶ / ° C. or less. As a method for producing such a ceramic, a raw material powder containing 80% by weight or more of cordierite is molded into a predetermined shape, It is characterized by sintering to a density of 90% or more and heat treatment at a temperature of 900 ° C. to 1400 ° C. in a pressurized atmosphere of 100 atm or more.

Further, according to the present invention, such a dense and low thermal expansion ceramic is used as a member for a semiconductor manufacturing apparatus.

In each of the above-mentioned dense low thermal expansion ceramics, the rare earth element is 1 to 20 in terms of oxide.
Desirably, it is contained by weight.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The low thermal expansion ceramic of the present invention is mainly composed of cordierite composite oxide represented by the general formula 2MgO.2Al ₂ O ₃ .5SiO ₂ . This cordierite crystal has an average particle size of 1 to 10 μm.
exists as crystal grains of m. This cordierite is
It is present in the sintered body in a proportion of 80% by weight or more, especially 85% by weight or more.

The sintered body contains a rare earth element as an auxiliary component in an amount of 1 to 20% by weight, especially 5 to 15% in terms of oxide.
It is desirable to contain it in a proportion of weight%. Even if cordierite is 100% by weight or can be densified to some extent, its firing temperature is high and its firing temperature range is extremely narrow at ± 5 ° C., which is not suitable for mass production.
On the other hand, when the rare earth element is contained at 1% by weight or more,
It reacts with the components of cordierite during firing to produce a liquid phase, which has the effect of enhancing sinterability. It can be fired at low temperatures and the firing temperature range can be expanded to about ± 25 ° C, resulting in mass productivity. Can be increased. Therefore, when the amount of the rare earth element is less than 1% by weight, the sinterability is reduced. When the amount exceeds 20% by weight, the coefficient of thermal expansion increases, and characteristics of 1.0 × 10 ⁻⁶ / ° C. or less cannot be achieved.

The rare earth elements contained in the ceramics include Y, Yb, Lu, Er, Ce, Nd, S
m and the like, and among these, Y and Yb are preferable because they can be obtained at low cost.

In order to produce such ceramics, cordierite powder 80 having an average particle size of 10 μm or less is used.
A rare earth element oxide powder having an average particle diameter of 10 μm or less is added in an amount of 1 to 20% by weight, particularly 5 to 15% by weight, to 99 to 99% by weight, particularly 85 to 95% by weight. After blending the respective components in the above ratio, the components 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, an extrusion or the like. The compact at this time is desirably at a relative density of 55% or more. If the compact density is lower than 55%, it is difficult to produce a dense body having a relative density of 90% or more in the subsequent sintering process. Become.

Next, the molded body produced as described above is fired to a relative density of 90% or more, preferably 95% or more. In order to densify to a relative density of 90% or more, a compact having the above composition is placed in air or an inert gas atmosphere.
It can be manufactured by firing at 300 to 1450 ° C. for about 1 to 10 hours. In this firing, it is desirable that the compact be housed in a silicon carbide or alumina sagger and fired.

In the obtained sintered body, for example, N ₂ , A
Heat treatment is performed with a gas such as r or Air in a pressurized atmosphere of 100 atm or more. Next, the pressure heat treatment is performed at 900 to 1
400 ° C. temperature range, preferably 1100-1200 ° C.
For about 1 to 5 hours, the density can be reduced to a relative density of 99.9% or more, a porosity of 0.1% or less, and a maximum void diameter of 5 μm or less. That is, if the processing temperature is lower than 900 ° C., the void cannot be reduced, and
When the temperature exceeds, a part of the sample melts.

If the relative density of the sintered body before the heat treatment in the high-pressure atmosphere is less than 90%, the high-pressure gas is trapped in the pores in the sintered body, and the high-pressure gas in the high-pressure atmosphere thereafter is trapped. This is because the voids cannot be reduced even if the heat treatment is performed.

According to the manufacturing method as described above, finally,
Dense, low thermal expansion ceramics having a porosity of 0.1% or less, particularly 0.08% or less, and a maximum void diameter of 5 μm or less, particularly 4.5 μm or less can be produced.

It is to be noted that such low thermal expansion ceramics must satisfy the characteristics of a porosity of 0.1% or less, a maximum void diameter of 5 μm or less, and a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less at 10 to 40 ° C. In addition to the cordierite component and the rare-earth element compound described above, the composition may contain unavoidable impurities in production and other components for improving sinterability and characteristics. For example, W, Mo, Ni, Fe, Zr, S
r and the like.

Such a dense low-thermal-expansion ceramic is a stage in a vacuum apparatus structure, a susceptor, a vacuum chuck, an electrostatic chuck, an exposure apparatus, or a stage position measuring mirror, or a stage position measuring mirror used in manufacturing a semiconductor element. It is suitably used as a support member, and various jigs in a semiconductor manufacturing process. In particular, it is most suitably used for a member whose ceramic surface is coated, for example, a vacuum chuck and a stage position measuring mirror.

In such a case, as the coating applied to the surface of the ceramic, TiN, Al ₂ O ₃ , diamond, diamond-like carbon (DLC) or the like is coated in a thickness of 0.1 to 10 μm.

The member to which such a coating is applied has a porosity of 0.1% or less and a maximum void diameter of 5 μm.
When the porosity exceeds 0.1% or when the maximum void diameter exceeds 5 μm, a homogeneous coating is not formed and is not suitable for a member for a semiconductor manufacturing apparatus.

[0026]

EXAMPLE A cordierite powder having a purity of 99% or more and an average particle size of 3 μm was prepared by using Y ₂ O ₃ having an average particle size of 1 μm
Yb ₂ O ₃ , Er ₂ O ₃ , and CeO ₂ rare earth element oxide powders were mixed at the ratios shown in Tables 1 and 2, and then mixed in a ball mill for 24 hours. Then, the mixed powder was added to 1 t /
Molding was performed at a pressure of cm ² to produce a molded article having a relative density of 58%.

The compact was placed in a silicon carbide or alumina sagger and fired in an air atmosphere at the temperatures shown in Tables 1 and 2 for 5 hours. The relative density of the obtained sintered body was measured by the Archimedes method, and the results were shown in Table 1,
The results are shown in Table 2.

After the above firing, a heat treatment in a high-pressure atmosphere was further performed for one hour under the conditions shown in Tables 1 and 2. Various ceramics were produced by changing the pressure treatment conditions as shown in Tables 1 and 2.

The obtained ceramic is polished and 3 × 4 ×
Grinding to a size of 15mm, this ceramic 1
The coefficient of thermal expansion from 0 to 40 ° C was measured. The void ratio at room temperature was measured. The results are shown in Tables 1 and 2.

[0030]

[Table 1]

[0031]

[Table 2]

As shown in Tables 1 and 2, according to the present invention, cordierite is contained in an amount of 80% by weight or more and the relative density is 9%.
0% or more of the sintered body is 900 to 140 atm.
By performing the pressure treatment at 0 ° C., the relative density was improved and the porosity was reduced, the porosity was 0.1% or less, and the relative density tended to increase.

However, the processing temperature during high pressure processing is 1400
In Sample No. 22 exceeding 100 ° C., part of the sample was melted, and in Sample No. 1 in which the pressure treatment temperature was lower than 900 ° C.,
The porosity exceeded 0.1%. Sample No. 36 in which the amount of rare earth element oxide added was more than 20% by weight.
In Sample No. 30, which has a large coefficient of thermal expansion and cannot achieve a characteristic of 1.0 × 10 ⁻⁶ / ° C. or less, and has a rare earth oxide content of less than 1% by weight, there is no problem in the characteristics. The possible temperature range was very narrow, ± 5 ° C.

Further, in Sample No. 23 in which the pressure during the high-pressure heat treatment was lower than 100 atm, the void ratio did not decrease, and a porosity of 0.1% or less was not achieved. When the samples Nos. 37 and 38 having a relative density of less than 90% before pressurization were used, the porosity after high-temperature pressurization did not become 0.1% or less, and the maximum void diameter did not become 5 μm or less.

[0035]

As described in detail above, the low thermal expansion ceramic of the present invention can increase the void fraction, that is, the relative density, while maintaining the excellent low thermal expansion characteristics of cordierite. As a result, by using this low thermal expansion ceramic as a part for semiconductor manufacturing equipment such as performing exposure processing on a wafer for forming a fine circuit, for example, a vacuum chuck for an exposure apparatus, a mirror for a stage, etc. There is no dimensional change with respect to temperature change, the smoothness of the component surface can be improved, excellent accuracy can be obtained, and the quality and mass productivity of semiconductor device manufacturing can be improved.

Claims (6)

[Claims] Claims: 1. A cordierite comprising at least 80% by weight,
Porosity of 0.1% or less, maximum void diameter of 5 μm or less, 10
A dense, low-thermal-expansion ceramic having a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less at 40 ° C. 2. A rare earth element in an amount of 1 to 20% by weight in terms of oxide.
The dense low thermal expansion ceramic according to claim 1, which is contained. 3. A raw material powder containing cordierite of 80% by weight or more is molded into a predetermined shape, sintered to a relative density of 90% or more, and further heated at 900 ° C. to 1400 ° C. in a pressurized atmosphere of 100 atm or more. A method for producing a dense low-thermal-expansion ceramic, characterized by performing a heat treatment. 4. The method according to claim 3, wherein said raw material powder contains 1 to 20% by weight of a rare earth element in terms of oxide. 5. It contains cordierite in an amount of 80% by weight or more,
A member for a semiconductor manufacturing apparatus comprising a dense low-thermal-expansion ceramic having a porosity of 0.1% or less and a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less. 6. A rare earth element in an amount of 1 to 20% by weight in terms of oxide.
The member for a semiconductor manufacturing apparatus according to claim 5, which contains.