JP2002321967A - Low thermal expansion ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent ceramic material suitably used as members for a semiconductor manufacturing device, which simultaneously satisfy compactness, high rigidity, low thermal expansion properties, and conductivity. SOLUTION: The ceramic for the material has the following characteristics: the porosity of its pores is <=7%, the pores are closed cell pores, the mean diameter of the pores is <=5 μm, its specific rigidity [Young's modulus (GPa)/ density (g/cm<3> )] is >=30, its thermal expansion coefficient measured on the basis of JIS R1618 is <=3×10<-7> /K, and its specific volume resistance value according to JIS C2141 is 10<5> -10<9> Ω.cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic which can be suitably used as a member for a manufacturing apparatus such as a semiconductor exposure apparatus.

[0002]

2. Description of the Related Art A susceptor, a vacuum chuck, a susceptor used for supporting or holding a wafer, a process for forming a wiring such as a Si wafer, and a member used for a semiconductor device manufacturing apparatus. Ceramics are used as base materials for insulating rings, other jigs, and the like, and members of the XY table of the exposure apparatus because they are relatively inexpensive and chemically stable.

On the other hand, in recent years, the miniaturization and high integration of circuit pattern dimensions of semiconductor devices have been rapidly evolving, and the level of miniaturization required for a so-called photolithography process is becoming increasingly severe.

[0004] Above all, it is the center of photolithography.
In an exposure process for forming a fine pattern of a semiconductor, a positioning accuracy of 0.1 μm or less has been required.

When the conventional ceramics are applied to these semiconductor manufacturing apparatuses, the characteristics are insufficient, such as an exposure alignment error due to a dimensional change of the members, and the quality of the obtained product and the yield are greatly affected. there were.

In order to solve such a problem, recently, as disclosed in Japanese Patent Application Laid-Open No. H11-100275 and the like,
Techniques for applying cordierite ceramics having a small coefficient of thermal expansion to members for semiconductor manufacturing equipment have been developed.

Further, as a technique for solving such a problem,
Japanese Patent Application Laid-Open No. H11-92216 discloses a technology in which a lithium aluminosilicate silicate, which is a material having a high thermal shock resistance and a high heat insulating property and having a low coefficient of thermal expansion, is combined with calcium silicate and applied to a member for a semiconductor manufacturing apparatus. It is disclosed in the gazette, and has excellent heat resistance and specific machinability,
Japanese Patent Application Laid-Open No. H11-60240 discloses a technique in which aluminum titanate, which is easy to machine, is applied to a member for a semiconductor manufacturing apparatus.

However, when these prior art ceramics are used as a base material of a member for a semiconductor manufacturing apparatus, the following problems arise.
In an atmosphere temperature range of ４０40 ° C., a change in the atmosphere temperature of about 0.1 ° C. may cause a dimensional change of several 100 nm (0.1 μm), resulting in a large thermal expansion coefficient.

Further, these ceramics having a large coefficient of thermal expansion generally have a high porosity, that is, a so-called porous structure, so that they are brittle in terms of strength, and there is also a problem that dust and dirt are clogged in the pores.

For this reason, a method has been adopted in which the ceramics are densified by so-called two-stage firing by hot isostatic pressing (HIP).

Further, generally, the above-mentioned ceramic is an insulator, and in a semiconductor manufacturing process, friction is generated due to movement of a stage or the like, and there is a possibility of being charged. Such a charged ceramic member is liable to cause dust to adhere thereto, and has a risk of contaminating a semiconductor wafer.

Such a phenomenon tends to become more remarkable as the width of the wiring formed on the semiconductor by exposure becomes narrower. In particular, when it is necessary to form a wiring with high precision, the above-described conventional technique is used. It has been extremely difficult to apply ceramics.

[0013]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide high-precision material characteristics that simultaneously satisfy denseness, high rigidity, conductivity, and low thermal expansion. An object of the present invention is to provide ceramics suitably used as a base material in a member for a semiconductor manufacturing apparatus.

[0014]

The present invention employs the following means in order to solve the above-mentioned problems. That is, ceramics having independent pores with an average diameter of 5 μm or less, (1) the porosity of the pores is 7% or less, and (2) the specific rigidity (Young's modulus (GPa) / density (g / cm) ³ )) is 3
0 or more, (3) the coefficient of thermal expansion according to JIS R1618 is 3 × 10 ⁻⁷ / K or less, and (4) JIS C2
It is a low-thermal-expansion ceramic having a volume resistivity according to 141 of 10 ⁵ to 10 ⁹ Ω · cm.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied diligently about ceramics which can be suitably used as a base material in a member for a semiconductor manufacturing apparatus, and have so-called independent pores having a specific form of pores. It has been found that such a problem can be solved all at once by using a ceramic in which the porosity and the average pore diameter are in the specified range and the specific stiffness and the thermal expansion coefficient are in the specified range.

The ceramic of the present invention has an average diameter of 5 μm.
A ceramic having the following independent pores,
(1) The porosity of the pore is 7% or less, (2) the specific rigidity (Young's modulus (GPa) / density (g / cm ³ )) is 30 or more, and (3) the coefficient of thermal expansion according to JIS R1618. Is not more than 3 × 10 ⁻⁷ / K, and (4) JIS C214
1 is a low thermal expansion ceramic having a volume resistivity of 10 ⁵ to 10 ⁹ Ω · cm.

The specific rigidity is less than 30, or the coefficient of thermal expansion is 3
^Exceeding × 10 ^-7 / K, when applied to a member for an exposure apparatus, an exposure alignment error occurs due to vibration at the time of positioning or a change in the size of the member, etc., thereby lowering the accuracy and forming a fine wiring circuit. You may not be able to.

If the volume specific resistance exceeds the range, it is charged and dust or dirt adheres. If the volume specific resistance falls below the range, a potential difference is generated between the exposure member and the contacting exposure member, and a spark is easily generated.

The ceramics according to the present invention can be produced by using, for example, spodumene, eucryptite, zirconyl phosphate, or aluminum titanate as a main component.

Here, the "main component" means that the target component is 50
-100% by weight, preferably 55-99% by weight, more preferably 70-99% by weight.

The term "spodumene" used herein means [Li ₂ O.
Al ₂ O ₃ .4SiO ₂ ] and eucryptite are [L
i ₂ O.Al ₂ O ₃ .2SiO ₂ ], zirconyl phosphate is
_{[(ZrO) 2 P 2 O} 7], aluminum titanate, [T
iO ₂ · Al ₂ O ₃ ].
A ceramic mainly composed of a so-called composite oxide.

In these ceramics as main components, spodumene and eucryptite are 55 to 90% by weight, preferably 60% by weight, based on 100% by weight of the ceramics.
To 95% by weight, and zirconyl phosphate and aluminum titanate are 55 to 99% in 100% by weight of ceramics.
%, Preferably 60 to 99% by weight.

These main components are important components that function to lower the thermal expansion of the sintered body. Generally, when each composition exceeds the range, the Young's modulus becomes low, and when the composition falls below the range, the thermal conductivity decreases. The expansion tends to increase.

These spodumene, eucryptite, zirconyl phosphate, and aluminum titanate have insulating properties, low specific gravity, a negative coefficient of thermal expansion at room temperature, and increase with increasing temperature near room temperature. Is a ceramic that has the property of shrinking and has a Young's modulus of 100G
Since it is slightly lower than Pa and is brittle, it is preferable to mix another kind of ceramic having high rigidity in order to improve physical properties.

Specific examples of such another type of ceramics include those selected from the group consisting of silicon nitride, silicon carbide, aluminum nitride, silicon nitride whiskers, tin oxide, carbon, titanium nitride, titanium carbide, titanium boride, and iron titanate. At least one of them.

The amounts of these different types of ceramics (hereinafter referred to as subcomponents) are as follows: silicon nitride, silicon carbide, aluminum nitride, silicon nitride whiskers, tin oxide, carbon, titanium nitride, titanium carbide, titanium boride, and titanic acid. When blending at least one ceramic selected from the group consisting of iron, 1 to 100% by weight of the ceramic
44% by weight, preferably in the range of 10 to 35% by weight, when iron titanate alone is blended, 1.5 to 10% by weight
It is better to be within the range. Such an auxiliary component has a positive coefficient of thermal expansion and has the property of expanding at room temperature. Some have conductivity. For this reason, if each composition falls below the range, the resulting ceramic is usually
If the material has a low Young's modulus or an insulator, and exceeds the range, thermal expansion increases.

By adding such an auxiliary component to the main component, the ceramic according to the present invention has a thermal expansion coefficient of 3 × 10 ^-7 / K or less, preferably 3 × 10 ⁻⁷ / K or less, due to the additive property of thermal expansion. It becomes possible to make it 1 × 10 ⁻⁷ / K or less. Furthermore, by blending an appropriate amount of those having conductivity among the sub-components,
Appropriate conductivity can be imparted to the obtained ceramics.

The ceramics according to the present invention have so-called independent pores in which the pores in the material are separated and independent by setting the blending amounts of the main component and the subcomponent within the above-mentioned ranges. ) Has a porosity of 7%
Or less, preferably 3% or less.

Porosity (%) = [1- (actual density / theoretical density)] × 100 (1) In the present invention, for example, spodumene is used as a main component and silicon nitride is used as a sub-component. And titanium nitride, the Young's modulus according to JIS R1602 is 10
0 GPa or more, since the volume resistivity according to JIS C2141 can be 10 ⁵ to 10 ⁹ Ω · cm, it is preferable.

[0030] Thereby, the conductivity of the obtained ceramics is remarkably increased, dust and dust due to electrification are effectively prevented, and exposure defects due to foreign matter are reduced. Becomes

Hereinafter, an example of the method for producing a ceramic according to the present invention will be described. The ceramics according to the present invention is obtained, for example, by sufficiently pulverizing and mixing the above-mentioned inorganic particles having a particle size of 5 μm or less and composed of the above main components and subcomponents with a ball mill or the like, using a die press, cold static After being molded into an arbitrary shape by molding means such as hydraulic pressing and extrusion molding, 900 to 190 by pressure sintering method or normal pressure sintering method.
It can be manufactured by sintering at a temperature of 0 ° C, preferably 900 to 1860 ° C.

In such a production method, it is preferable to select production conditions that are suitable for each type of inorganic particles as the main component and inorganic particles as the subcomponent to be mixed. For example, when spodumene or zirconyl phosphate is used for the inorganic particles of the main component, sintering is preferably performed in a temperature range of 900 to 1350 ° C. It is good to sinter in the temperature range. When using aluminum titanate,
It is preferable to bake in a temperature range of 1300 to 1860 ° C.

Under these manufacturing conditions, the sintering time is preferably in the range of 1 to 10 hours.

The atmosphere in the sintering may be appropriately selected depending on the composition of the material to be fired, either in the air, under reduced pressure, or in an inert gas atmosphere.

The ceramic according to the present invention can be suitably used as a substrate of a member for a semiconductor manufacturing apparatus such as a sample support.

[0036]

The present invention will be described in more detail with reference to the following examples. (Examples 1 to 6, Comparative Examples 1 to 4) Table 1 shows spodumene powder or eucryptite powder having an average particle size of 5 μm, silicon nitride powder having an average particle size of 4 μm, and titanium nitride powder having an average particle size of 1 μm. The mixture was mixed in a bead mill for 2 hours.

Next, 0.3 MPa using a hot press
While applying the pressure, pressure was applied under the conditions shown in Tables 1 and 2 to prepare a sintered sample, and the sintered sample was mirror-polished and processed into a flat plate shape. JIS for the above flat ceramics
The thermal expansion coefficient in the temperature range of 0 to 50 ° C. by R1618 was measured. Further, Young's modulus at room temperature was measured by an ultrasonic pulse method according to JIS R1602. Further, the volume resistivity at room temperature was measured according to JIS C2141.

Further, the average diameter of the pores was quantified by observation with a scanning electron microscope. Tables 1 and 2 show these measurement results.
It is summarized and shown.

[0039]

[Table 1]

[0040]

[Table 2]

Table 1 shows that the sintering temperature was constant,
The mixing ratio of silicon, silicon nitride and titanium nitride was changed.
The results are shown. Here, in Comparative Example 1, a sintered body can be obtained.
I didn't come. In addition, the plate-shaped ceramic obtained in Comparative Example 2 was used.
Box has a volume resistivity of 10 ¹²Ω · cm or more
It was just an insulator.

On the other hand, in Examples 1 to 3 in which silicon nitride and titanium nitride were blended at a predetermined ratio, the porosity of the closed pores was 3%.
%, An average diameter of 1 μm or less, and a specific rigidity of 42 or more.

In Examples 1 to 3, the Young's modulus was 11
The value was as high as 0 GPa or more, and the volume resistivity was 10 ⁶ to 10 ⁹ Ω · cm.

Table 2 shows the results obtained by changing the mixing ratio of eucryptite, silicon nitride and titanium nitride while keeping the sintering temperature constant. In Comparative Example 3, a sintered body could not be obtained. The plate-shaped ceramic obtained in Comparative Example 4 had a volume resistivity of 10 ¹² Ω · cm or more, and was a so-called insulator.

On the other hand, in Examples 4 to 6 in which silicon nitride and titanium nitride were blended at a predetermined ratio, the porosity of the closed pores was 3
% Or less, an average diameter of 1 μm or less, and a specific rigidity of 41 or more, showing excellent values.

In Examples 1 to 3, the Young's modulus is 11
The value was as high as 0 GPa or more, and the volume resistivity was 10 ⁶ to 10 ⁹ Ω · cm.

As described above, the ceramics shown in each of the examples were able to effectively impart the conductive properties required for use as a member for semiconductor production.

[0048]

According to the present invention, it is possible to provide a ceramic having excellent characteristics with a small dimensional change with respect to a change in the ambient temperature.

Further, the ceramic according to the present invention can be suitably provided to a part for a semiconductor manufacturing apparatus for performing a wafer exposure process for forming a fine circuit, for example, a stage for an exposure apparatus.

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Claims (5)

[Claims] 1. A ceramic having independent pores having an average diameter of 5 μm or less, wherein (1) the porosity of the pores is 7%.
(2) Specific rigidity (Young's modulus (GPa) / density (g / cm ³ )) is 30 or more, and (3) JIS R
(4) Low thermal expansion ceramics having a coefficient of thermal expansion of 3 × 10 ⁻⁷ / K or less according to 1618 and (4) a volume resistivity of 10 ⁵ to 10 ⁹ Ω · cm according to JIS C2141. 2. Young's modulus according to JIS R1602 is 10
The ceramic according to claim 1, which has a GPa of 0 GPa or more. 3. The ceramic according to claim 1, which comprises spodumene, eucryptite, zirconyl phosphate, or aluminum titanate as a main component. 4. The method according to claim 1, wherein the material contains at least one selected from the group consisting of silicon nitride, silicon carbide, aluminum nitride, silicon nitride whiskers, tin oxide, carbon, titanium nitride, titanium carbide, titanium boride, and iron titanate. The ceramic according to any one of 1 to 3, above. 5. A member for a semiconductor manufacturing apparatus using the ceramic according to claim 1 as a substrate.