JPH10214819A - Electrode plate for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrode plate for plasma etching with reduced production of particles by using glassy carbon having a lattice constant in a specific range regarding a specific plane of an included crystal. SOLUTION: The glassy carbon has a structure where graphite crystals dispersedly exists in an amorphous matrix. Fluorocarbon polymer is generated by entrance of fluorine between the graphite crystal layers, and the polymer becomes particles. However, the production of particles can be reduced by forming an electrode plate 10 for plasma etching with glassy carbon having the lattice constant in the range of 3.450Å to 4.500Å regarding the (002) plane of the graphite crystal. The electrode plate 10 is formed by processing the glassy carbon into a disk having a diameter of 200mm and a thickness of 300mm, forming 1,700 pieces through holes 12 each having a diameter of 0.8mm in the disk, forming an attachment hole 14, then, mirror-processing the surfaces of the disk, thereafter, performing purification processing by using chlorine gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode plate used for an apparatus (plasma etcher) for performing plasma etching, and more particularly to an electrode plate for plasma etching made of glassy carbon which generates little particles.

[0002]

2. Description of the Related Art In the manufacture of a semiconductor integrated circuit, a dry etching apparatus using a reactive gas plasma for etching a whole surface or a specified place of a wafer or a thin film formed on the surface of the wafer to a required thickness is used. An electrode plate is mounted in a room or the like. The material of the electrode plate used in the plasma etching apparatus includes (1) that a reaction product of an etching gas to be used and the electrode material is volatile; (2) that the electrode material does not become a contamination source of impurities; Characteristics such as 3) uniform etching when the electrode itself is etched, and (4) characteristics that the electrode material does not become a source of particles are required. Especially,
When particles adhere to the wafer, the portion is protected from etching, and the etching becomes non-uniform, resulting in a product defect. Therefore, obtaining an electrode material that does not become a source of particles is an important issue.

Japanese Patent Application Laid-Open No. 62-252942 discloses the use of high-purity glassy carbon as a material for an electrode plate for plasma etching. The publication discloses a liquid furan-based resin, a phenol-based resin or a mixed resin thereof, or a mixture obtained by adding and mixing the same type of hardened resin fine powder to these liquid resins, forming and curing into a flat plate having a uniform thickness,
Next, the resin plate was calcined and carbonized at a temperature of about 800 ° C. in an inert atmosphere, and if necessary, graphitized at a temperature of up to 3000 ° C., and the glassy carbon thus obtained was subjected to a high-purity treatment. Later, it is described that it is used for an electrode plate. The publication discloses that the manufactured electrode for plasma etching made of glassy carbon has a homogeneous dense structure having a three-dimensional network glass structure different from graphite, and has high purity, high accuracy, high chemical stability, etc. Describe that it has compatible physical properties.

Japanese Patent Application Laid-Open No. 3-119723 discloses an electrode plate for plasma etching made of high-purity glassy carbon having a maximum pore diameter of 1 μm or less, an average pore diameter of 0.7 μm or less, and a porosity of 1% or less. Disclose. In the technique disclosed in the publication, the number of generated particles is controlled by setting the average pore diameter to 0.7 μm or less, the maximum pore diameter to 1 μm or less, and the porosity to 1% or less. Japanese Patent Application Laid-Open No. 6-128762 attempts to reduce particles generated by processing the glassy carbon electrode plate to have a surface roughness of Rmax 10 μm or less.

[0005] All of these conventional techniques for reducing particles are based on the premise that particles are generated by detachment of carbon particles from a glassy carbon electrode plate. However, as a result of the study, the present inventor did not achieve a sufficient effect in reducing the generation of particles even if the improvement was made under such a premise.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrode plate for plasma etching which generates less particles.

[0007]

The inventors of the present invention have conducted intensive studies on the causes of the generation of particles and found that a fluorine-based gas such as trifluoromethane (CHF ₃ ) used as a reaction gas for etching and a glassy carbon electrode. They found that the fluorocarbon polymer generated by the reaction with the plate greatly contributed to the generation of particles. The present inventor has conducted intensive studies in order to obtain a glassy carbon electrode plate in which a fluorocarbon polymer is unlikely to be generated by reaction with a fluorine-based reaction gas. As a result, the lattice constant of the graphite layered structure in the glassy carbon was determined. d
₀₀₂ is related to the degree of particle generation, and the magnitude of the lattice constant is set to 3.450 ° to 4.500 °.
It has been found out that the generation of particles can be further reduced if the ratio is within the range described above, and the present invention has been completed.

That is, the electrode plate for plasma etching of the present invention is characterized in that the crystal constant is made of glassy carbon having a lattice constant d ₀₀₂ with respect to the (002) plane in the range of 3.450 to 4.500 °. .

The lattice constant d ₀₀₂ can be measured, for example, by a method established by the 117th Committee of the Japan Society for the Promotion of Science. Specifically, a glassy carbon material constituting an electrode plate is ground together with a reference substance (silicon) to a predetermined particle size, and the obtained mixed powder is subjected to an X-ray diffraction method to obtain a diffraction peak relating to the (002) plane. The lattice constant d ₀₀₂ can be obtained by correcting the calculated value from the obtained peak with the calculated value obtained from the reference material.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reason why a carbon material is applied to an electrode plate of a plasma etcher is that a product CF ₄ formed by a reaction between carbon and an element (fluorine) constituting a reactive gas for plasma etching is used. This is because it is volatile. However, the form of the reactant produced by the reaction between carbon and fluorine depends on the crystallinity of the carbon to be reacted. When carbon is a graphite phase (highly crystalline), a reaction between carbon and fluorine also produces a fluorocarbon polymer. Glassy carbon generally contains fine graphite crystallites, and has a structure in which graphite layered crystallites are scattered in an amorphous matrix. It has been found that fluorine penetrates between the layers of the graphite layered crystallites to form a fluorocarbon polymer such as (CF) _n or (CF ₂ ) _n, and that this polymer becomes a particle.

The inventor of the present invention has found that when the lattice constant d ₀₀₂ (interlayer distance or spacing) of the graphite layered crystallites is smaller than 3.450 °, the reaction between the invading fluorine and the carbon of the graphite layered crystallites proceeds easily. While it is found that particles are generated in a relatively large amount, the lattice constant is set to 3.450 ° or more, and the electrode plate for plasma etching is formed by glassy carbon set in the range of 3.450 ° to 4.500 °, We succeeded in reducing the generation of particles. On the other hand, this lattice constant is 4.500 °
When the glassy carbon content exceeds the limit, the electrical resistance becomes excessively large and cannot be used as an electrode plate.

As a raw material resin for producing glassy carbon, a phenol resin, a furan resin or the like can be preferably used. When a phenol resin is used as a starting material, the temperature at which the phenol resin is molded and cured, and then fired to obtain glassy carbon, is set at 150 ° C.
The temperature is preferably from 0 ° C to 2000 ° C. When a furan resin is used as a starting material, it is cast-molded and cured, and then, similarly to the case of a phenol resin, at 1500 ° C. to 20 ° C.
Firing at 00 ° C. is preferred. At a temperature as low as about 800 ° C. as in the prior art, the lattice constant becomes relatively too high, and a material that does not function as an electrode plate is likely to be obtained. When the firing temperature is raised to a temperature close to 3000 ° C., d ₀₀₂ becomes relatively too small, and glassy carbon in which the above-described polymer particles are easily generated can be obtained.

Further, as a result of experiments, the present inventor has found that in order to suppress the generation of particles, rather than reducing the pore diameter and porosity of the glassy carbon as conventionally proposed, the glassy carbon is contained in the glassy carbon. It has been found that it is more important to keep the lattice constant d _{002 of the} crystal to be obtained within a predetermined range. That is, the lattice constant d ₀₀₂ is 3.450 ° -4.
It has been found that when the temperature is in the range of 500 °, an electrode plate with less generation of particles can be provided even if the pore diameter and porosity are relatively high. According to the present invention, the glassy carbon constituting the electrode plate for plasma etching is 1 μm
May be larger than the maximum pore diameter. For example, even if the maximum pore diameter is up to about 20 μm, the lattice constant d
_{When 002} is in the range of 3.450 to 4.500 °, the generation of particles is small. Further, according to the present invention, the porosity of the glassy carbon constituting the electrode plate may be more than 1%. For example, even if it has a porosity of about 15%, the lattice constant d ₀₀₂ is 3. 450Å-4.500Å
Within the range, the generation of particles is small.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited to these Examples. The value of ₀₀₂ is 3.450Å4.50
It is possible to obtain the electrode plate of the present invention by producing 0 ° glassy carbon.

Examples 1 to 4 A phenol resin was used as a starting material, which was pulverized to an average particle size of 15 μm, and hot-pressed and cured at 200 ° C. The obtained molded body was fired at each temperature shown in Table 1 to obtain a glassy carbon material. The porosity of the glassy carbon material is 0.020.
cc / g (about 3%) or less. Each of the obtained raw materials was processed into a disk shape having a diameter of 200 mm and a thickness of 3 mm. A through hole having a diameter of 0.8 mm was formed in the obtained disc by 1700.
An electrode plate was formed by forming individual pieces, further forming a mounting hole, and mirror-finishing the outer surface by lapping, and then purifying with a chlorine gas. The resulting electrode plate is shown in FIG. The electrode plate 10 for plasma etching has a disk shape, and a large number of through holes 12 are formed in a circular region excluding a peripheral portion. In the periphery, four mounting holes 14 are provided on the circumference.

Example 5 A furan-based resin was used as a starting material, cast-molded and cured, and then calcined at 2000 ° C. to obtain a glassy carbon material having a porosity of 0.095 cc / g (about 14%). Obtained. For glassy carbon material, up to about 20μ
Pores having a diameter of m were observed. The obtained glassy carbon material was processed in the same manner as in Examples 1 to 4, to produce an electrode plate for plasma etching.

Comparative Examples 1 to 3 Electrode plates were prepared in the same manner as in Examples 1 to 4, except that the compacts were fired at the temperatures shown in Table 1, respectively.

A sample piece was cut from the electrode plate obtained as described above, and the lattice constant d _{002 of} glassy carbon was measured.
Was measured according to the method established by the 117th Committee of the Japan Society for the Promotion of Science. Table 1 shows the results. Also, each of the obtained electrode plates was mounted on a plasma etching apparatus, and CH
1 using a reaction gas obtained by mixing F ₃ , CF ₄ and Ar
An etching test was performed for 0 minutes. A 6-inch silicon wafer was used for etching. After the etching operation for 10 minutes, the number of particles existing on the wafer was measured by a particle counter. Table 1 shows the results.

[0019]

[Table 1]

As shown in Table 1, the lattice constant d _{002 of the} crystal
However, the number of generated particles in Examples 1 to 5 falling within the scope of the present invention is significantly reduced as compared with Comparative Examples 1 and 2. In Comparative Example 3 in which the lattice constant d _{002 of the} crystal was larger than 4.5 °, the test could not be performed because the electric resistance of the electrode plate was large.

[0021]

As described above, according to the present invention, it is possible to provide an electrode plate for plasma etching with less generation of particles. The electrode plate of the present invention,
This can provide stable and uniform etching in the manufacture of semiconductor devices, and can contribute to suppressing product defects.

[Brief description of the drawings]

FIG. 1 is a plan view showing a shape of a specific example of an electrode plate for plasma etching according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 electrode plate for plasma etching 12 through hole 14 mounting hole

Claims (1)

[Claims] 1. An electrode plate for plasma etching, comprising a glassy carbon having a lattice constant d ₀₀₂ with respect to a (002) plane of a contained crystal in a range of 3.450 ° to 4.500 °.