JPH0334419A - Quartz glass material for semiconductor heat treatment and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize high heat resistance and effective reduce the diffusion speed of, especially, sodium to be diffused, by using a quartz glass material containing a specified amount of chloride, and practically no OH or metallic impurity. CONSTITUTION:Soot type silica produced by hydrolyzing silicon halogenide in oxygen-hydrogen flame is deposited. By heat-treating the obtained porous quartz glass member material in atmosphere containing chlorinated agent, quartz glass material for semiconductor heat treatment is manufactured, wherein the content of OH is less than or equal to 10ppm, metal impurity is not practically contained, and the content of chloride is adjusted in the range of 500-4000ppm. Said glass material has high heat resistance, and can effectively restrain the contamination of semiconductor caused by metal and the like, and, especially, the contamination caused by sodium whose diffusion speed is large, so that high serviceability suitable also for repetition use is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a quartz glass material useful for forming a furnace tube for heat treatment of semiconductor wafers, and in particular, in a heat treatment process in a heating furnace, The present invention relates to a quartz glass material for semiconductor heat treatment that can highly suppress contamination by metal impurities, and an effective method for manufacturing the same.

[Conventional technology]

Conventionally, furnace tubes and wafer jigs used for heat treatment of semiconductor wafers are required to have heat resistance to prevent deformation in the high temperature range of, for example, 1000 to 1300'C. Furthermore, as the degree of integration of semiconductors increases, trace contamination by metals, especially alkali metals, during the heat treatment process has become a major problem. Contamination in the heat treatment process of semiconductor wafers is caused by metals contained in the quartz glass container and other jigs, and by metals released from the furnace wall and diffused through the quartz glass container. Sodium is attracting attention because of its high speed.

It is known that the diffusion rate of sodium impurities in quartz glass is very small in aqueous synthetic silica glass containing OH'a of 11,000 pp or more, and increases as the OH concentration is small. Such hydrous synthetic quartz glass generally has very little metal impurities in its material, so it is desirable as a furnace tube for semiconductor heat treatment as far as metal contamination resistance is concerned, but it has poor heat resistance and cannot be used in heat treatment above 1000°C. Because it is significantly deformed, it cannot be practically used as a heat treatment member. Furthermore, natural quartz glass is desirable in terms of heat resistance under heat treatment conditions, but it cannot be used because of its high content of various metal impurities.

[Problem to be solved by the invention]

Therefore, one technical object of the present invention is to provide a high-purity quartz glass material that has excellent heat resistance at the heat treatment temperature of semiconductor wafers and contains as few metal components as possible. Another object of the present invention is to provide a quartz glass member that can highly suppress the permeation and diffusion of metal impurities from the furnace.

[Means to solve the problem]

As a result of numerous trial production studies on synthetic silica glass materials that overcome the above-mentioned problems, the present inventors have found that it is desirable to have a glass material that is substantially free of OH and metal impurities and also contains a specific amount of chlorine. It has heat resistance and effectively reduces the diffusion rate especially of sodium diffused from the furnace.
It has been found that this method is extremely effective in improving stain resistance.

That is, the present invention has an OH content of 10 ppm or less, substantially no metal impurities, and a chlorine content of 5 ppm or less.
A quartz glass material for semiconductor heat treatment which is adjusted to a range of 00 to 4,000 ppn+, and an effective method for producing such a material, i.e., produced by hydrolyzing silicon halide in an oxygen/hydrogen flame. The present invention provides a method for producing the above-mentioned quartz glass material for semiconductor heat treatment, which comprises depositing soot-like silica and heat-treating the obtained porous quartz glass member in an atmosphere containing a chlorinating agent.

The quartz glass material for semiconductor heat treatment of the present invention is a novel material in that the synthetic quartz glass substantially free of OH and metal impurities contains chlorine in an amount that can reduce the diffusion rate of sodium. It has the characteristics of

OH contained in the quartz glass material of the present invention is 10pp
If it exceeds m, the heat resistance for semiconductor heat treatment will be insufficient and it will be easily deformed, so that it cannot be put to practical use industrially. Preferably, it is 2 pp+a or less. Furthermore, in the present invention, "substantially free of metal impurities" means such a small amount that contamination of semiconductor wafers during heat treatment can be substantially ignored.
It is important that it is below pm.

Furthermore, the amount of chlorine contained in the glass material of the present invention is 5
If it is less than 00 ppm, the effect of reducing the diffusion rate of sodium is insufficient, and if it exceeds 4,000 ppm, the heat resistance will drop sharply, so it cannot be used. Preferred chlorine content ranges from 800 to 2,500 ppm.

This quartz glass material is a synthetic quartz glass material that is effectively provided by heat-treating a porous quartz glass member obtained by the soot method, which is conventionally known as a method for manufacturing optical fibers, in a chlorinated atmosphere. Oxygen and silicon
It can be easily obtained by depositing soot-like silica produced by hydrolysis in a hydrogen flame and heat-treating the resulting porous quartz glass material in an atmosphere containing a chlorinating agent. The porous synthetic quartz glass material formed in this way is required to have as high a purity as possible, and therefore the raw material silicon tetrachloride used in the soot method must be prepared by commonly known purification methods such as distillation. A highly purified product is used.

Chlorine gas and thionyl chloride are typically used as the chlorinating agent to introduce chlorine into the heat treatment, and these may be used alone or in combination. Further, these chlorinating agents are usually introduced into the furnace atmosphere at a concentration ranging from 3 to 100% by volume, and the adjustment of the concentration yA is mainly performed using an inert gas. Further, in order to efficiently perform chlorination, a temperature of about 700 to 900°C is generally employed.

The chlorination treatment time can be easily determined by a person skilled in the art by simple experiments depending on the type of chlorination agent, its atmospheric concentration, treatment temperature, and in relation to the desired chlorine content. can.

In the glass material of the present invention thus obtained, the porous glass soot undergoes P3 melting under an inert gas atmosphere.

It can be easily turned into transparent glass by heating to a melting temperature of, for example, 1,300 to 1,500°C or higher, and is provided as a glass member suitable for semiconductor heat treatment.

This transparency can be achieved by further increasing the temperature of the furnace in the same atmosphere following the chlorination step described above, but in this case, the chlorination proceeds along with the transparent vitrification, so The chlorination treatment time would be somewhat reduced.

[Effect]

The quartz glass member for semiconductor heat treatment of the present invention has high heat resistance, can effectively suppress contamination of semiconductors with metals, especially contamination with sodium, which has a high diffusion rate, and is suitable for repeated use. To provide members with high practicality.

〔Example〕

Next, the present invention will be explained in more detail using specific examples. In addition, the OH concentration of the sample in the specific example was measured by infrared spectrophotometry, and the chlorine concentration was measured by silver chloride turbidimetry.

Example 1 High-purity silicon tetrachloride was introduced into a gentle oxygen/hydrogen flame and flame-hydrolyzed, and soot-like silica fine particles were deposited in a layered manner to obtain a porous quartz glass base material.

Approximately 700 g of the porous synthetic quartz glass base material thus formed was mixed at a mixing ratio of chlorine:helium of 10:
In a furnace under a mixed gas atmosphere with a volume ratio of 90,
Chlorination treatment was carried out by heating at a temperature of 800° C. for 2 hours.

The chlorine content of the obtained chlorinated glass material is approximately 850p
pm, the OH concentration was below 0.1 ppn+.

This chlorinated glass material (base material) was heated to 1.500°C in a furnace under an atmosphere of helium alone without a chlorinating agent.
A transparent glass member was obtained by heating and melting at the above temperature.

Example 2 A chlorinated quartz glass material was produced in exactly the same manner as in Example 1, except that the chlorination treatment in the furnace at a temperature of 800° C. was performed for 6 hours instead of 2 hours.

The chlorine content of the obtained chlorinated glass material is approximately 2.40
At 0 ppm, the OH concentration is 0. It was less than lppm.

The obtained chlorinated glass base material was heated and melted at a temperature of 1,500° C. or higher in a furnace with a helium gas atmosphere to obtain a transparent glass member.

Comparative Example 1 Approximately 700 g of a porous synthetic quartz glass base material prepared in the same manner as in Example 1 was heated at a temperature of 800°C for 2 hours in a furnace with a mixed gas atmosphere with a volume ratio of chlorine:helium = 5:95. Heat treated.

The chlorine content of the obtained chlorinated glass material was approximately 35
There is 0PPO1, and the OH concentration is 0. It was less than lppm.

This chlorinated glass base material was heated and melted at a temperature of 1,500° C. or higher in a furnace with a helium gas atmosphere to obtain a transparent glass member.

Comparative Example 2 A chlorinated glass base material similar to that obtained in Example 1 by performing 2 hours of chlorination treatment in the furnace was heated to a temperature of 1.500°C or higher in the furnace as it was. The temperature was raised, and as chlorination progressed, the material was heated and melted to create a transparent synthetic quartz glass member.

The chlorine content of the obtained chlorinated transparent quartz glass member was approximately 4,800 ppm, and the OHa degree was 0. It was less than lppm.

Example 3 Using the above sample, the heat resistance required for semiconductor wafer heat treatment and the ability to inhibit diffusion of metal impurities were measured and evaluated using the following methods.

Heat resistance: 1 of each sample by Beam B ending method.
, the viscosity η at 200°C is measured.

It is preferable that the logarithm of the viscosity η; Log η is 12.7 or more.

Diffusion prevention property: After dropping a 1% aqueous sodium nitrate solution onto a sample cut into a flat plate, the sample was heated to a temperature of 1,150°C for 2 hours, and then rapidly cooled to change the diffusion profile to LM.
A (LASERMICROANALYSYS) analysis is used to calculate the diffusion coefficient of sodium (DNa ad/5ee) at 1,150°C from the profile.

It is desirable that this value be as small as possible, and from a practical standpoint, a value on the order of 10-9 can be evaluated extremely highly.

Table 1 shows the measurement results for each sample.

For comparison, those of commercially available hydrous synthetic quartz glass 5UPRASIL-1 (manufactured by Heraeus; reference sample 1) and natural quartz glass Heralux (reference sample 2) are also listed.

Table 1 # is the diffusion coefficient of sodium at 1,150°C.

The tree is the measured value shown in the literature, which was determined by the "Na radioisotope method" for DNA.

Table 2 also shows the metal impurity content in each sample measured by atomic absorption spectrometry together with the 0Hfi degree and chlorine concentration. However, the samples of Examples 1 and 2 and Comparative Examples 1 and 2 are substantially the same as Example 1, with slight variations due to differences in chlorine content, and the measured values for Example 1 are representative. and showed. All numbers are in ppm.

Table 2 Reference sample 1 <0.2 <0.2 <0.2 <0.3
<0.2 <5 <0.2 <0.11200 6
0# 2 0.81.0 1.0 1.0 0.5
20 0.8 < 0.1 From the above, the quartz glass material of the present invention has sufficient heat resistance for semiconductor heat treatment, contains extremely few metal impurities, and has a small sodium diffusion coefficient at 1,150°C. It can be clearly understood that contamination by metals and the like during the wafer heat treatment process can be highly prevented.

〔Effect of the invention〕

When the quartz glass material of the present invention is used as a glass member for semiconductor heat treatment, there is little deformation during the high temperature heat treatment process, and in particular, contamination of the wafer due to diffusion of impurities such as alkali metals is effectively suppressed and prevented. It has high industrial value.

Claims (1)

[Claims] 1. The OH content is 10 ppm or less, substantially free of metal impurities, and the chlorine content is 500 to 4,000.
A quartz glass material for semiconductor heat treatment which is adjusted to a ppm range. 2. It is characterized by depositing soot-like silica produced by hydrolyzing silicon halide in an oxygen/hydrogen flame, and heat-treating the obtained porous quartz glass member in an atmosphere containing a chlorinating agent. A method for producing a quartz glass material for semiconductor heat treatment according to claim 1.