JP2009203113A - Ceramics for plasma treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ceramics for a plasma treatment apparatus capable of being preferably used for a construction member of plasma treatment apparatuses for fabricating a semiconductor-liquid crystal or the like, wherein corrosion resistance against halogen-based gases or their plasma or the like is excellent, a reduction of resistance can be attained, and an impurity metal contamination caused by the component raw material of the ceramics can be suppressed even in a halogen plasma process. <P>SOLUTION: The ceramics are prepared by adding 1-50 mol% of yttria having a purity of 99% or more or a lanthanum oxide having a purity of 99% or more to a cerium oxide having a purity of 99% or more, and by firing them at 1,600-1,900°C, wherein such ceramics are used in which at least a part of the ceramics that is exposed to plasma has a surface roughness Ra of less than 1.6 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ceramic for a plasma processing apparatus that can be suitably used in a plasma processing apparatus for manufacturing semiconductors and liquid crystals.

Among semiconductor manufacturing equipment, the members of equipment in the etching process, the CVD film forming process, and the ashing process that removes resist, which are mainly plasma processes, are exposed to plasmas of halogen-based gases such as highly reactive fluorine and chlorine. .
For this reason, ceramics such as high-purity alumina, aluminum nitride, yttria, and YAG are used as members exposed to the halogen plasma in the above-described process (see, for example, Patent Document 1).
Among these, yttria ceramics is particularly excellent in plasma resistance, and conventionally used as a single sintered body in a plasma processing apparatus.

However, yttria ceramics have a high volume resistivity of 10 ¹³ Ω · cm or higher, and special tuning is required for use as an alternative to silicon members, and plasma generation is hindered and non-uniform. As a result, it may not be usable. Furthermore, it is easy to be charged, and the reaction product is attracted to generate dust.

In response to this, for the purpose of reducing the volume resistivity of yttria ceramics, metals and metal oxides such as titanium oxide and tungsten oxide exhibiting conductivity, metal nitrides such as titanium nitride, titanium carbide, tungsten carbide, carbonized A method of adding a metal carbide such as silicon can be considered.
JP 2000-247726 A

However, when the volume resistivity of yttria ceramics is reduced by adding metal or the like, dielectric loss increases when the ceramics are used as a member of a plasma processing apparatus, and energy is lost during plasma processing. The member generates heat and causes damage.
In addition, the addition of metal or the like not only lowers the plasma resistance, but in some cases may cause contamination of the wafer with an impurity element.

  In recent years, there has been an increasing demand for reduction of impurity metal contamination, particularly yttrium contamination, on wafers to be processed from yttria ceramic members used in plasma processing apparatuses.

Therefore, in order to solve the above technical problem, the present inventors have repeatedly studied a ceramic material that replaces yttria used in a plasma processing apparatus, and in cerium, which is the most abundant and relatively inexpensive among rare earths. Pay attention.
Cerium oxide (hereinafter also referred to as “ceria”) is used for polishing agents in wafer CMP processes, coloring components of glass, etc., and has been used in semiconductor applications, has plasma resistance, and has a volume. It is a material that can also be expected from the point of reducing resistivity.

  That is, the present invention is excellent in corrosion resistance to halogen-based gases or their plasmas, can be reduced in resistance, and can suppress impurity metal contamination caused by constituent materials of the ceramics even in the halogen plasma process. An object of the present invention is to provide a ceramic for a plasma processing apparatus that can be suitably used as a constituent member of a plasma processing apparatus for manufacturing semiconductors and liquid crystals.

The ceramic for a plasma processing apparatus according to the present invention was obtained by adding 1 to 50 mol% of yttria having a purity of 99% or more or lanthanum oxide having a purity of 99% or more to cerium oxide having a purity of 99% or more and firing at 1600 to 1900 ° C. The surface roughness Ra of at least a portion exposed to plasma is a ceramic, and is characterized by being less than 1.6 μm.
In this way, by adding yttria or lanthanum oxide to ceria ceramics, it is possible to reduce resistance while maintaining plasma resistance and to suppress impurity metal contamination caused by constituent materials of the ceramics. it can.

The ceramics preferably has a porosity of 2% or less.
When the porosity is in the above range, generation of dust due to etching when the ceramic is used as a member of a plasma processing apparatus can be prevented.

The ceramics preferably has a volume resistivity of 10 to 10 ¹² Ω · cm at 20 to 400 ° C.
With such a low resistance ceramic, the generation of dust can be more effectively suppressed, and the plasma generation in the plasma processing apparatus is not hindered or nonuniform.

  As described above, the ceramic for a plasma processing apparatus according to the present invention is excellent in corrosion resistance to a halogen-based gas or plasma thereof, has a low resistance, and is also attributed to the constituent material of the ceramic in the halogen plasma process. Therefore, it can be suitably used as a component of a plasma processing apparatus in the manufacturing process of semiconductors, liquid crystals, etc., and thus contributes to an improvement in the yield of semiconductor chips manufactured in the subsequent process. Can do.

Hereinafter, the present invention will be described in more detail.
The ceramic for a plasma processing apparatus according to the present invention is a ceramic obtained by adding 1 to 50 mol% of yttria having a purity of 99% or more or lanthanum oxide having a purity of 99% or more to ceria having a purity of 99% or more and firing at 1600 to 1900 ° C. It is. And the surface roughness Ra of the part exposed at least to plasma is less than 1.6 micrometers, It is characterized by the above-mentioned.
That is, the ceramic according to the present invention reduces volume resistivity by adding a predetermined amount of the rare earth metal oxide as described above to ceria having plasma resistance, and also in the halogen plasma process, Impurity metal contamination due to the constituent material of the ceramic can be suppressed.
For this reason, the ceramics can suppress the generation of dust due to charging of the member.

Each material of ceria, yttria, and lanthanum oxide, which are ceramic composition components according to the present invention, uses a high-purity powder having a purity of 99% or more.
When the purity is less than 99%, a sufficiently densified ceramic cannot be obtained, and when used for a member of a plasma processing apparatus, there is a risk of generating dust due to impurities in the raw material.

Moreover, the ceramic according to the present invention is obtained by adding yttria or lanthanum oxide to the ceria powder. Each of these metal oxides is a trivalent rare earth metal oxide, like ceria. These metal oxides may be added alone or in combination.
By adding these metal oxides, the volume resistivity can be reduced without lowering the plasma resistance.

The amount of the yttria or lanthanum oxide powder added is 1 to 50 mol% in total in the ceramic composition.
When the added amount is less than 1 mol%, the effect of lowering the volume resistivity cannot be obtained sufficiently.
On the other hand, when the added amount exceeds 50 mol%, the amount of the added component increases, and conversely, the resistance increases.

The ceramic according to the present invention is fired at 1600 to 1900 ° C.
When the firing temperature is less than 1600 ° C., many pores remain in the ceramic, and a sufficiently densified sintered body cannot be obtained.
On the other hand, when the firing temperature exceeds 1900 ° C., abnormal grain growth of crystal grains is likely to occur, and the strength is reduced.
The firing temperature is more preferably 1700-1850 ° C.

Furthermore, the ceramic preferably has a surface roughness Ra of at least a portion exposed to plasma of less than 1.6 μm.
When the surface roughness Ra of the portion exposed to the plasma is 1.6 μm or more, when the ceramic is used as a member of the plasma processing apparatus, the contact area with the plasma increases, and therefore, etching becomes easy.
Accordingly, at least the surface of the ceramic exposed to the plasma is subjected to a polishing treatment or the like as necessary so as to have the surface roughness.

The ceramics preferably has a porosity of 2% or less.
When the porosity exceeds 2%, dust tends to be generated due to etching caused by residual pores in the ceramic when the ceramic is used for a member of a plasma processing apparatus.
The porosity is more preferably 1% or less.

Further, the volume resistivity of the ceramic is preferably 10 to 10 ¹² Ω · cm at 20 to 400 ° C.
When the volume resistivity exceeds 10 ¹² Ω · cm, the ceramic is easily charged, and when used as a member of a plasma processing apparatus, it is difficult to prevent the generation or nonuniformity of plasma generation in the plasma processing apparatus. In addition, the generation of dust is not sufficiently suppressed.
On the other hand, the smaller the volume resistivity, the higher the conductivity. However, in the ceramic composition according to the present invention, it is practically difficult to make the volume resistivity less than 10 Ω · cm.

In the ceramic according to the present invention as described above, 1-50 mol% of yttria powder having a purity of 99% or more or lanthanum oxide powder having a purity of 99% or more is added to a ceria powder having a purity of 99% or more, and after molding, 1600 ° C or more. It can be obtained by firing at 1900 ° C. or lower. Specific production methods are as shown in the following examples.
In addition, you may add sintering aids, such as a binder, to the said raw material powder as needed.
Further, the firing atmosphere may be a reducing atmosphere, an inert gas atmosphere, or an air atmosphere.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
15 mol% of yttria (Y ₂ O ₃ ) powder with a purity of 99.6% was added to ceria (Ce ₂ O ₃ ) powder with a purity of 99.5%, and a binder was added at 1 wt% with respect to the ceria powder. Was granulated.
The obtained granulated powder was pressure-molded at 1500 kgf / cm ² with a cold isostatic press (CIP), and the obtained molded body was fired at 1800 ° C. in a hydrogen atmosphere, did.

[Example 2]
A ceramic sintered body was produced in the same manner as in Example 1 except that lanthanum oxide having a purity of 99.3% (La ₂ O ₃ ) was used instead of the yttria powder.

[Examples 3-8, Comparative Examples 1-6]
Ceramic sintered bodies were produced in the same manner as in Example 1 under the conditions shown in Examples 3 to 8 and Comparative Examples 1 to 6 in Table 1 below.

Various physical properties of the sintered bodies obtained in the above Examples and Comparative Examples were evaluated by the following methods.
The porosity measurement was performed according to JIS R 1634.
The resistivity was measured at room temperature (20 ° C.) according to JIS K 6911 and JIS K 7194.

Furthermore, a focus ring was prepared by subjecting the sintered body to surface polishing so that the surface roughness Ra of the portion exposed to plasma was 1.0 μm (comparative example 6 was 2.0 μm).
Using this, plasma processing is performed on a silicon wafer having a diameter of 200 mm with an RIE etching apparatus (used gas: CF ₄ , O ₂ ), and then dust of 0.15 μm or more on the wafer is detected by a laser particle counter. Number was measured.
These measurement results are summarized in Table 2.

As shown in Table 2, the ceramics according to the present invention (Examples 1 to 8) were found to have a low porosity and a reduced volume resistivity. Furthermore, when used as a member of a plasma processing apparatus, it was confirmed that the plasma resistance was excellent and the generation of dust was suppressed.
In addition, the ceramic sintered body (Comparative Example 3) obtained by firing at 1950 ° C. was a low value for the porosity, volume resistivity, and number of dusts. And damaged.

Claims (3)

  A ceramic exposed to 1 to 50 mol% of yttria with a purity of 99% or more or lanthanum oxide with a purity of 99% or more to cerium oxide with a purity of 99% or more and fired at 1600 to 1900 ° C., at least a portion exposed to plasma The ceramic for plasma processing apparatus characterized by having a surface roughness Ra of less than 1.6 μm.   The ceramic for a plasma processing apparatus according to claim 1, wherein the porosity is 2% or less. The ceramic for plasma processing apparatus according to claim 1, wherein the volume resistivity at 20 to 400 ° C. is 10 to 10 ¹² Ω · cm.