JP2002356345A - Method for producing quarts glass having corrosion resistance and member and apparatus using the quarts glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide quarts glass having both plasma corrosion resistance and good dispersibility of added elements while solving problems of conventional technology, a method for easily producing it, a quarts glass member utilizable for a semiconductor container, jig tools, a bell jar of a plasma etcher or the like, and apparatuses for producing semiconductor and liquid crystal provided with the member. SOLUTION: This method for producing anticorrosive quarts glass comprises the steps of mixing a solution of compounds containing aluminum and/or yttrium with silica powder, and after stirring, holding the mixed solution at 60 to 130 deg.C to gradually evaporate the solvent, raising temperature to 300 to 500 deg.C under oxidative atmosphere to convert the compounds containing aluminum and/or yttrium into oxides, then cooling it to obtain calcined powder, and electrically fusing the obtained powder at a temperature of 1700 deg.C or above under reduced pressure to obtain the quarts glass. The member and the apparatus use the quarts glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing quartz glass having high plasma corrosion resistance. More specifically, since aluminum or yttrium having plasma corrosion resistance can be uniformly dispersed in a quartz glass matrix, plasma resistance can be efficiently improved with a necessary and sufficient amount of addition. Therefore, it can be used as a semiconductor container, a jig, a semiconductor manufacturing apparatus and a liquid crystal manufacturing apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, a plasma reactor has been used in a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus and the like. A bell jar, a focus ring, and the like mainly made of transparent quartz glass are used for a plasma generating portion of these apparatuses. Here, the resistance to fluorine-based plasma, for example, CF ₄ / O ₂ plasma is not sufficient. This is because Si in silica SiO ₂ evaporates in the form of SiF ₄ and is consumed by fluorine radicals.

Therefore, it is conceivable that an oxide of an element having plasma resistance is dry-mixed with silica powder and then melted at a temperature equal to or higher than the melting point (first method). Further, a method of forming a surface modification film on the surface of a quartz glass member by a sol-gel method or the like can be considered (second method).

[0004]

The first method described above has a large segregation of added elements. Since mixing of powders involves generation of static electricity, it is not expected that they are sufficiently mixed in the order of microns. In addition, there is a possibility that contaminants may be mixed in the raw material due to a long-term friction between the container used for mixing and the powder. When the raw material subjected to such dry mixing treatment is fired, cavities (voids) are easily generated in the generated quartz glass. Therefore, the plasma resistance test using this is almost or slightly inferior to the performance of quartz glass itself. This is presumed to be due to the fact that when the segregation of the additional element increases, the probability of generation of oxygen O that is not bonded to any atom increases due to the discrepancy between the valence (tetravalence) of Si and the valence of the additional element. You.

On the other hand, in the film formation by the above-mentioned second sol-gel method, the shrinkage is about 50%, which is very large, and cracks are easily generated. It is not easy to form a film having a thickness of 1 μm. Furthermore, since the linear expansion coefficients of the quartz glass and the surface modification film are different from each other by about 10 times, a strain is applied to the interface, and the surface modification film is easily cracked. In addition, the surface modification film has about 10 times the plasma resistance as compared with the case of pure quartz glass, but has a problem that it is impossible to use for a long time because of its small thickness.

[0006]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies, and as a result, obtained a transparent quartz glass having both good dispersibility of the target additive element and plasma resistance, and developed the present invention. It was completed.

That is, it has been found that aluminum (Al) and / or yttrium (Y) are effective as an additive element in the quartz glass matrix. It is desirable that these additional elements be uniformly interposed in the silica powder, but roughly divided into wet and dry methods. In order to uniformly disperse the target additive substance in the quartz glass matrix, first, the additive element alone or the compound or salt thereof may be mixed by a sufficient time by a dry method. That is, when mixing the silica powder and the additive substance, the dried solid substance containing the additive substance and the silica powder may be put in a container, sealed, and sufficiently mixed on a pot mill rotating table. However, the dry method is affected by static electricity and the particle size distribution of the powder, and the mixing state of the silica powder and the solid powder containing the additive element is limited.

Accordingly, it has been found that a wet method is effective as a means for further improving the dispersibility. That is, when mixing the silica powder and the additive substance, a solution containing the additive substance is prepared, and the solution is added to the silica powder, stirred after immersion, and after the additive substance is substantially uniformly distributed around the silica particles. The inventor has developed a method in which the solution is maintained at a temperature near its boiling point, the solvent is evaporated almost completely, and then calcined to a temperature at which the added substance becomes an oxide to obtain a raw material powder. Here, the solution containing the additive substance may be a “salt” such as a phosphate, a fluoride salt, an oxalate, a hypochlorite, a chloride, a nitrate or a sulfate of the additive substance, and be water-soluble. Is desirable. At this time, nitrates, chlorides or sulfates, whose constituent salts do not remain after firing, are suitable for forming a solution of the added element. These salts have low heat of dissolution and can be safely handled.

The temperature for evaporating the solvent is 60 to 13
Although the range of 0 ° C. can be applied, it is important to keep the temperature at about 80 to 90 ° C. for a long time and gently drive off the solvent (to prevent bumping). In order to convert the “salt” state into an oxide, calcination may be performed at 500 to 1000 ° C. in an oxidizing atmosphere. Calcination in the atmosphere is sufficient, but calcination in an oxygen atmosphere can shorten the calcination time.

In this manner, an oxide calcined body in which the oxide uniformly surrounds the periphery of the silica particles is obtained.

This is set in an electric furnace which can be evacuated and pressurized, and is fired under reduced pressure at a temperature equal to or higher than the melting point of cristobalite. In this way, a quartz glass having a good dispersion state of the additive element can be obtained. Here, EPMA (X-ray microanalyzer) or the like can be used to check the dispersion state of the additive substance.

As a raw material for forming the silica glass matrix, natural quartz powder, synthetic silica powder, fumed silica, soot or the like can be used. When natural quartz powder or synthetic silica powder is used, its particle size affects the dispersibility of the added element in the composite quartz glass, but the particle size range is 40 to 430 μm, and the mode (mode) is 220 μm.
The degree is common. This is because the filling property is good and the powder is hard to fly. Further, it has very little hygroscopicity. However, by using a powder having a size of 300 μm under and a 200 μm increase (most-needed value of 260 μm) or a 200 μm-under (most-needed value of 180 μm), the dispersibility of the additional element can be further controlled. When the above silica powder is used, the pore size and the particle size distribution of the powder affect the dispersibility of the added element in the quartz glass. That is, a silica powder having a uniform and small pore diameter and a silica powder having a small average particle diameter are advantageous.

The quartz glass of the present invention thus obtained can be formed into a quartz glass member having a desired shape by a known method at the time of manufacture.

The plasma corrosion-resistant quartz glass member of the present invention has excellent plasma resistance, and is suitably used for containers for semiconductor manufacturing equipment and liquid crystal manufacturing equipment, jigs, and bell jars for plasma etchers using halogen compounds and their plasmas. A device for manufacturing semiconductors and a device for manufacturing liquid crystal having such a member as a window material or the like are hardly deteriorated by plasma irradiation or the like, and can be used effectively without replacement for a long period of time.

[0015]

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 thereto.

EXAMPLE 1 Quartz (quartz) powder having a purity shown in Table 1 (particle size range: 40 to 430 μm, most likely value = 219 μm) was used as a raw material (purified with hydrofluoric acid), and 223 g of this was used. Weighed.

[0017]

[Table 1]

On the other hand, aluminum nitrate nonahydrate (purity 9
(8.0%) was weighed 1.79 g. In addition, 4.94 g of yttrium nitrate hexahydrate (purity 99.99%) was weighed. These substances were mixed with 150 ml of ultrapure water (resistivity 17M).
Ω · cm), mixed with quartz powder, and allowed to stand for about 1 hour. This mixture was transferred to a quartz boat and calcined in the atmosphere at 90 ° C. for 8 hours, followed by 500 ° C. for 1 hour. The calcined body XRD aluminum nitrate nonahydrate was subjected to (X-ray diffraction) aluminum oxide Al ₂ O _3, yttrium nitrate hexahydrate was converted to yttrium oxide Y ₂ O _3. The concentration of aluminum in the raw material is 550ppm
(0.04 atomic%), the concentration of yttrium is 5000p
pm. The calcined body was smooth and did not need to be ground.

This was filled in a carbon mold that had been subjected to a high-purity treatment. The preparation shape is diameter 90mm, height 25
mm. This was electromelted under reduced pressure while evacuating. The temperature is raised from room temperature to 1850 ° C. at a rate of 5 ° C./min.
After maintaining the temperature at 0 ° C. for 5 minutes, the furnace was cooled in a nitrogen atmosphere. When the aluminum concentration and the yttrium concentration of the produced composite quartz glass were quantified by EPMA, the coefficient of variation was 10 to 60.

The composite quartz glass is cut to obtain CF ₄ / O ₂
When the etching resistance to system plasma and BCl ₃ / Cl ₂ system plasma was confirmed, it was better than solid quartz glass.

Comparative Example 1 Quartz powder having a purity shown in Table 1 (particle size range 4
0-430 [mu] m, most likely value = 219 [mu] m). 223 g of this was weighed.

On the other hand, aluminum oxide (purity 99.9)
%) 0.23 g of powder was weighed. In addition, 1.43 g of yttrium oxide (99.9% purity) powder was weighed. The concentration of aluminum in the charged raw material was 550 ppm (0.0
4 atomic%), and the concentration of yttrium was 5000 ppm.

These powders were placed in a polypropylene pot and mixed on a pot mill rotary table for 4 days. this,
It was filled into a highly purified carbon mold. The charging shape was φ90 mm in diameter and 25 mm in height. this,
It was electromelted under reduced pressure while evacuating. Room temperature to 1850
The temperature was raised at a rate of 5 ° C./min to 1 ° C., the temperature was maintained at 1850 ° C. for 5 minutes, and the furnace was cooled in a nitrogen atmosphere. When the aluminum concentration and the yttrium concentration of the produced composite quartz glass were quantified by EPMA, the coefficient of variation was 110 to 150.

The composite quartz glass is cut to obtain CF ₄ / O ₂
When the etching resistance to system plasma and BCl ₃ / Cl ₂ system plasma was confirmed, it was better than solid quartz glass.

Comparative Example 2 Quartz powder having a purity shown in Table 1 (particle size range 4
0-430 [mu] m, most likely value = 219 [mu] m). 223 g of this was weighed. On the other hand, 0.23 g of aluminum oxide (purity 99.9%) was weighed. In addition, 1.43 g of yttrium oxide (purity 99.9%) was weighed.

These powders were placed in a polypropylene pot and mixed on a pot mill rotary table for 2 hours. this,
It was filled into a highly purified carbon mold. The charging shape was φ90 mm in diameter and 25 mm in height. this,
It was electromelted under reduced pressure while evacuating. Room temperature to 1850
The temperature was raised at a rate of 5 ° C./min to 1 ° C., the temperature was maintained at 1850 ° C. for 5 minutes, and the furnace was cooled in a nitrogen atmosphere. When the concentration of aluminum Al and the concentration of yttrium Y in the produced composite quartz glass were determined by EPMA, the coefficient of variation was 160 to 20.
It was 0.

The composite quartz glass is cut to obtain CF ₄ / O ₂
When the etching resistance to the system plasma and the BCl ₃ / Cl ₂ system plasma was confirmed, it was as good as pure quartz glass. In addition, it was worse than in the case of Comparative Example 1.

From the above, it has been found that when the additive elements are uniformly mixed in the quartz glass, the wet method improves the dispersibility and the plasma resistance as well as the dry method.

[0029]

According to the production method of the present invention, a composite quartz glass having a uniform dispersion state of the added element can be obtained. Further, the composite quartz glass according to the present invention has improved plasma resistance. Therefore, it is used, for example, for jigs and tools for manufacturing semiconductors, particularly for reaction tube flanges and bell jars. It is also useful as a component of a semiconductor manufacturing device or a liquid crystal manufacturing device requiring heat resistance.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4G062 AA18 BB02 CC04 DA08 DB02 DC01 DD01 DE01 DF01 EA02 EB02 EC02 ED01 EE02 EF01 EG01 FA01 FB01 FC01 FD01 FE01 FF01 FG01 FH01 FJ02 FK01 FL01 GA01 GA01 GB01 H01 GD01 H01 GD01 HH07 HH09 HH11 HH12 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM04 MM12 MM23 MM31 NN34

Claims (7)

[Claims] 1. A compound solution containing aluminum and / or yttrium is mixed with silica powder and stirred. The mixed solution is maintained at 60 to 130 ° C., and the solvent is gradually evaporated to 300 to 500 ° C. in an oxidizing atmosphere. After raising the temperature to convert the compound containing aluminum and / or yttrium into an oxide, the resultant is cooled to obtain a calcined powder, and the obtained powder is electromelted at a temperature of 1700 ° C. or more under reduced pressure. A method for producing corrosion-resistant quartz glass, characterized by obtaining quartz glass. 2. The method for producing quartz glass according to claim 1, wherein the compound is a salt. 3. The method according to claim 1, wherein the compound is chloride, nitrate or sulfate. 4. A quartz glass member comprising quartz glass obtained by the method according to claim 1. 5. The quartz glass member according to claim 4, which is used for a container for semiconductor production, a jig for semiconductor production, or a bell jar for a plasma etcher. 6. A semiconductor manufacturing apparatus comprising the quartz glass member according to claim 4. 7. A liquid crystal manufacturing apparatus comprising the quartz glass member according to claim 4.