JPH107434A - Composite silica glass and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat resistance without contaminating a product to be treated with an impurity metallic element by mixing a specific silica powder with zirconium oxide and aluminum oxide and thermally melting the resultant mixture. SOLUTION: This composite silica glass is produced by uniformly mixing a silica powder having 10-500wt.ppm content of OH groups with 20-10000wt.ppm high-purity zirconium oxide fine particles and 20-5000wt.ppm high-purity aluminum oxide fine particles, thermally melting and transparently vitrifying the resultant mixture. The high-purity zirconium oxide fine particles are uniformly dispersed in a silica glass matrix having 10-500wt.ppm content of OH groups and the composite silica glass has <=0.5wt.ppm content of alkali metallic elements of Li, Na and K, <=1wt.ppm content of alkaline earth metallic elements of Ca and Mg and <=1×10<-10> cm<2> /sec diffusion coefficient of the Na at 1000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite silica glass excellent in shielding metallic impurities, particularly a composite silica glass useful as a furnace material or a jig for heat treatment of semiconductor materials such as silicon wafers, or an optical material. The present invention relates to glass and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, so-called "fused quartz" glass obtained by melting natural quartz or quartz has high purity, high heat resistance, and excellent resistance to rapid heating and rapid cooling. Synthetic silica glass obtained by flame hydrolysis of high purity silicon compounds such as SiCl ₄ for jigs for semiconductor industry, such as cleaning tanks and crucibles, and has excellent light transmittance in the ultraviolet and infrared regions. It has been used as an optical material for optical fibers, optical lithography lenses, prisms and the like. The jig is subjected to an annealing process for removing strain during manufacturing, and then to a heating process for use as a product, and to the optical material, the birefringence is reduced and the refractive index distribution is increased. Generally, an annealing process for homogenization is performed. However, since the heat treatment is performed at a high temperature for a long time, the alkali metal or alkaline earth element present in the furnace material or jig of the heat treatment furnace is sometimes volatilized and diffused to contaminate the product to be treated. Occur. Therefore, the furnace material and the jig are placed under a low oxygen partial pressure (in a stream of N ₂ ) at 1300 to 1
Baking at 500 ° C. for 100 to 120 hours to reduce impurity metal elements, or using a commercially available high-purity Al ₂ O ₃ plate as a hearth plate, placing a semiconductor product thereon and performing heat treatment However, the above-mentioned baking does not sufficiently purify the impurity metal element, and also has the highest purity A in the market.
Even in l ₂ O ₃ plate, the content of alkali metal is several hundred ppm
The above and several ppb of alkali metal content in semiconductor products
It was much higher than several hundred ppb, and the treatment could not prevent the semiconductor product from being contaminated by an impurity metal element, particularly an alkali metal element. Therefore, an attempt was made to make the hearth plate a high-purity silica glass plate synthesized using a silicon compound such as silicon tetrachloride as a raw material. Elements may contaminate semiconductor products through the synthetic silica glass hearth plate. As a quartz glass member for semiconductor production which solves these problems, the total content of alkali metals of Na, K and Li is 2 ppm or less, and Zr is 5 to 10%.
ppm, the total content of other metal impurities is 30 ppm
In the following, a quartz glass member for manufacturing semiconductors having a balance of SiO ₂ has been proposed in Japanese Patent Publication No. 7-102980. Elemental contamination occurred.

[0003]

In view of the current situation,
As a result of intensive studies, the present inventors have found that high-purity zirconium oxide (ZrO ₂ ) fine particles or the above-mentioned ZrO ₂ and aluminum oxide (Al ₂ O ₃ ) are contained in a high-purity silica glass matrix containing a specific amount of OH groups. The present invention has been completed by uniformly dispersing the fine particles of the present invention to obtain a composite silica glass which is less contaminated with an alkali metal element or an alkaline earth element even when a semiconductor product is heat-treated at a high temperature for a long time. It was done. That is,

An object of the present invention is to provide a composite silica glass free from contamination by an impurity metal element, particularly an alkali metal element or an alkaline earth element.

It is another object of the present invention to provide a furnace material and a silica glass for a jig which are free from alkali metal element contamination even in a high-temperature heat treatment at 900 to 1300 ° C.

Another object of the present invention is to provide a method for producing the above silica glass.

[0007]

According to the present invention, which achieves the above object, the present invention provides a method of dispersing fine particles of high-purity zirconium oxide uniformly in a silica glass matrix having an OH group content of 10 to 500 wt ppm, In addition, the present invention relates to a composite silica glass in which aluminum oxide fine particles are uniformly dispersed, and a method for producing the same.

As described above, the silica glass of the present invention is OH
The group is 10 to 500 wtppm, preferably 100 to 30
The silica glass contains 0 wtppm, and zirconium oxide (ZrO ₂ ) is contained in the silica glass matrix.
Or the fine particles of ZrO ₂ and aluminum oxide (Al ₂ O ₃ ) are uniformly dispersed. O in the above range
By containing the H group, even if the semiconductor product is heated at a high temperature of 900 to 1300 ° C. for a long time, the alkali metal present in the heat treatment atmosphere exchanges with the OH group or H ⁺ ion in the silica glass, and preferentially. Taken into silica glass,
Less contamination of semiconductor products. When the OH group content is less than 10 wtppm, the above-mentioned effect is not obtained.
If the content is more than wtppm, the heat resistance of the silica glass is reduced, and the silica glass is undesirably fused with a product to be processed or deformed during heat treatment.

In the composite silica glass of the present invention, fine particles of high-purity ZrO ₂ are uniformly dispersed together with the OH group content. The high purity means a purity of 99.99% or more, and the high purity ZrO ₂ fine particles have a dispersion amount of 20 to 1%.
By uniformly dispersing in the range of 000 wtppm,
Zr ^{4+ of the} ZrO ₂ fine particles is incorporated into the Si—O bond, and since the ionic radius is larger than Si ⁴⁺ , it ^blocks the diffusion of alkali metal ions. When the ZrO ₂ fine particles are added and Al ₂ O ₃ particles are further contained, the charge balance around the Al ₂ O ₃ particles or around the Al ³⁺ ions is disrupted, so that a positive charge is required to be compensated. Elements, alkaline earth elements, and other impurity metal elements are trapped to further reduce contamination of semiconductor products and the like. Al ₂
The content of the O ₃ fine particles is preferably 20 to 5,000 wtppm, and if it exceeds 5,000 wtppm, the absorption amount of alkali metal ions, that is, the saturation amount of alkali metal ions in silica glass becomes too large, It promotes crystallization, which is not preferable. In addition, ZrO ₂
Glass containing fine particles has higher recrystallization resistance at high temperatures than glass containing only Al ₂ O ₃ fine particles, and has less strength deterioration even at a high temperature treatment of 900 to 1,300 ° C. This is preferred as silica glass for jigs.

In the production of the composite silica glass of the present invention, the OH group content in the raw material powder after vitrification is 10 to 500 ppm by weight, preferably 100 to 300 wppm.
tppm, high-purity ZrO ₂ powder or a mixture of the ZrO ₂ powder and Al ₂ O _3, and the mixture is subjected to electric heating melting, zone melting (zone melting), arc melting, or oxyhydrogen. It is manufactured by melting and clear vitrification by flame Bernoulli method or the like. By heating the obtained composite silica glass at 1700 to 2200 ° C. for a short time, the composite silica glass can be made into a member having an arbitrary shape.

The concentration of the OH group in the raw material cannot be regulated uniformly because the OH group concentration in the silica glass varies depending on the vitrification conditions. It is good to make adsorption water adhere to the surface. Li in the raw material powder, ZrO ₂ powder and Al ₂ O ₃ powder,
The content of alkali metal elements of Na and K is 0.5 p each.
It is important that the content of alkaline earth metal elements of Ca and Mg be 1 ppm or less, respectively. If the content of the alkali metal element and the alkaline earth metal element exceeds the above range, the element may be volatilized in the heat treatment at 900 to 1300 ° C. to contaminate the semiconductor product.

[0012]

Next, the present invention will be described in detail with reference to specific examples, but the present invention is not limited thereto.

Table 1 shows the impurity concentrations of the raw silica powder, alumina powder and zirconia powder used in Examples 1 to 4 and Comparative Examples 1 to 5.

[0014]

[Table 1]

The measured values of Examples 1 to 4 and Comparative Examples 1 to 5 were measured according to the following methods. (I) OH group concentration measurement: infrared absorption spectroscopy (D.
M. Dodd, D .; B. Fraser, Journal
al of Applied Physics, Vo
l. 37, p. 3911 (1966)) (ii) Measurement of diffusion coefficient of Na: dimensions 20 × 20 × 5 m
m, a mirror-finished sample was prepared, and a saline solution was applied thereon, dried at 100 ° C., and then dried in air at 100 ° C.
After a heat treatment at 0 ° C. for 50 hours, the LMA method (La
a method of measuring the Na diffusion concentration distribution in the depth direction from the glass surface by the Ser Micro Analysis method, and obtaining the diffusion coefficient according to Fick's law. (Iii) Impurity analysis: Atomic absorption spectroscopy

[0016]

【Example】

Examples 1 to 4 and Comparative Examples 1 to 5 are silica powders which have been subjected to a purification treatment to adjust the OH group content,
ZrO ₂ powder having a particle size of 10 to 200 μm, a content of an alkali metal element and an alkaline earth element, and a synthetic cristobalite powder of Table 1 having a particle size of 0.1 to 10 μm and a purity of Table 1;
Alternatively, the ZrO ₂ powder and the Al ₂ O ₃ powder were mixed at the mixing ratio shown in Table 2 and uniformly mixed with a V-type mixer. The mixture was heated and melted to produce a composite silica glass. Table 2 shows the melting conditions of the glass and the OH group content in the glass.
A sample for measurement was cut out from the obtained composite silica glass, and the diffusion coefficient of Na was measured. Table 2 shows the results.

The above transparent silica glass plate (10 mm thick)
Is placed at the bottom of a high-temperature atmosphere furnace, a silica glass sample (Shin-Etsu Quartz Co., Ltd. Heralux-LA) is placed at the center of the plate, and the silica glass bell jar manufactured as described above is put thereon,
Heat treatment was performed at 1100 ° C. for 1000 hours. The transparent silica glass plate, the bell jar and the sample after the heat treatment were collected, a sample for analysis was cut out, and the contamination amount and strength of the silica glass were measured. Table 2 shows the results.

[0018]

[Table 2] 中 in Table 2 above: Indicates that the decrease in bending strength is extremely small. Δ: Bending strength was slightly reduced. X: indicates that the strength is significantly reduced.

As shown in Table 2 above, the composite silica glass of the present invention has a low diffusion coefficient of Na at 1000 ° C., indicating that contamination by Na is unlikely to occur. In addition, it can be seen that the treated sample is an excellent silica glass with little contamination by Na even when the heat treatment is performed at a high temperature of 1100 ° C. for a long time.

[0020]

As described above, the composite silica glass of the present invention is 900 to 900%.
Even in the high-temperature heat treatment at 1300 ° C., the product to be treated is not contaminated with impurity metal elements, particularly alkali metal elements or alkaline earth elements, and has excellent heat resistance. Therefore, the composite silica glass is a furnace material for a semiconductor product heating furnace,
It is useful as a jig and a heating furnace material for optical lens heat treatment.

Claims (8)

[Claims] 1. A composite silica glass characterized in that fine particles of high-purity zirconium oxide are uniformly dispersed in a silica glass matrix having an OH group content of 10 to 500 wt ppm. 2. A composite silica glass, wherein fine particles of high-purity zirconium oxide and high-purity aluminum oxide are uniformly dispersed in a silica glass matrix having an OH group content of 10 to 500 wt ppm. 3. An OH group content of 100 to 300 wt ppm.
The composite silica glass according to claim 1 or 2, wherein 4. The content of the zirconium oxide fine particles is 20 to
2. The composite silica glass according to claim 1, wherein the content is 10,000 wtppm. 5. The content of the zirconium oxide fine particles is 20 to
The composite silica glass according to claim 2, wherein the content of the aluminum oxide fine particles is 10,000 wtppm, and the content of the aluminum oxide fine particles is 20 to 5,000 wtppm. 6. The method according to claim 1, wherein the contents of the alkali metal elements of Li, Na and K are 0.5 wt ppm or less, respectively, and the contents of the alkaline earth metal elements of Ca and Mg are 1 wt ppm or less, respectively. Or the composite silica glass according to 2. 7. The diffusion coefficient of Na at 1,000 ° C. is 1
3. The composite silica glass according to claim 1, wherein the composite silica glass is at most ¹⁰ × 10 ⁻¹⁰ cm ² / sec. 8. A method for producing a composite silica glass, which comprises uniformly mixing silica powder and zirconium oxide fine particles or fine particles of zirconium oxide and aluminum oxide having an adjusted OH group concentration and melting by heating.