JPH08175840A - Quartz glass for fixture for heat treatment of silicon semiconductor element and its preparation - Google Patents

Abstract

PURPOSE: To obtain quartz glasses adequate as jig materials for semiconductor treatment of an enlarged silicon wafer or the like which have high heat resistance and little influence of iron element of semiconductor toxicity.

CONSTITUTION: Quartz glasses for heat treatment of silicon semiconductor devices have a viscosity ≥10^12.9 dPa.s at 1200°C, OH group content ≤30 ppm, aluminum element content of 5 to 30 ppm and iron element content less than 0.8 ppm. The glasses are produced by heat melting natural crystal powder, which contains aluminum element in the range of 5 to 30 ppm and iron element less than 0.8 ppm, under 1.3×10^-2 to 1.3×10³ Pa using an electric heating means to vitrify.

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for producing quartz glass for heat treatment jigs for silicon semiconductor devices, particularly for producing quartz glass jigs for wafer boats, furnace core tubes, wafer supports and chambers of single-wafer heat treatment furnaces. Quartz glass and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, quartz glass has been used as a heat treatment jig for silicon semiconductor devices because it has a higher purity than other refractory materials and can be fused by welding. . However, in recent years, due to the increase in the integration of semiconductor elements and the emergence of elements such as flash memory that extremely hate impurities, the purification of jigs has been required, and quartz, which is a typical semiconductor poison, has a low iron content. The development of glass is eagerly awaited. However, in the quartz glass produced by melting natural quartz, it is difficult to set the iron element concentration to 10 ppb or less. Therefore,
Synthetic silica glass with a total purity of less than 0.1 ppm, especially with an iron element content of 1 ppb or less, has been produced in an extremely high purity, but it contains no aluminum element and contains many hydroxyl groups. Since it was included, it was inferior in heat resistance. Therefore, although synthetic quartz glass which does not contain iron element and which is doped with aluminum element is manufactured, it is expensive and it is not at a stage where it can be industrially advantageously used.

On the other hand, it has been found that even if the quartz glass is made of natural quartz, the quartz glass produced by the oxyhydrogen flame melting method is less harmful to the silicon wafer than the quartz glass produced by the electric melting method. There is. However, the quartz glass produced by the oxyhydrogen flame melting method is inferior in heat resistance to the quartz glass produced by the electric melting method, and is 1 × 10 ^12.9 Pa · s at 1200 ° C. required for a single-wafer heat treatment jig.
It did not satisfy (1 × 10 ^13.9 poise).

[0004]

In view of the current situation,
The present inventors, as a result of continuing intensive studies, have come to the conclusion that the production by the electric melting method is optimal for obtaining quartz glass having excellent heat resistance, and further about the production of the quartz glass by the electric melting method. Research has shown that in the conventionally known vacuum electric melting method, the above problems can be solved by setting the degree of vacuum to a specific range and using purified natural quartz powder as a raw material. Headline,
The present invention has been completed. That is,

The present invention has a viscosity of 10 at 1200 ° C.
It is an object of the present invention to provide a quartz glass for a heat treatment jig for a silicon semiconductor device, which has a heat resistance of ^12.9 dPa · s or more and does not substantially harm the silicon wafer.

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

[0007]

Means for Solving the Problems The present invention which achieves the above object has a viscosity at 1200 ° C. of 10 ^12.9 dPa · s or more, an OH group content of 30 ppm or less, an aluminum element content of 5 to 30 ppm, and an iron element content. 0.8 ppm
The present invention relates to a quartz glass for a heat treatment jig for a silicon semiconductor element, which is characterized by being less than, and a method for producing the same.

The above-mentioned quartz glass of the present invention has a low OH group concentration and an appropriate aluminum content, so that it has high heat resistance and is 1 × at 1200 ° C. which is required for quartz glass for single-wafer heat treatment jigs. It is a quartz glass that satisfies the requirement of 10 ^12.9 Pa · s or more and does not adversely affect the silicon wafer by the iron element which is a semiconductor poison. German Patent No. 4234 discloses a method for quantitatively and simply measuring the damage of the semiconductor poison on the heat treatment of a silicon wafer.
No. 715. According to the publication, when quartz glass is placed in contact with or close to a silicon wafer and heated, the diffusion length of minority carriers in the wafer changes. The measuring method described in the above publication utilizes this phenomenon to measure the contamination due to semiconductor poisons.

By the way, the quartz glass manufactured by the conventional electric melting method is a general-purpose grade iron element manufactured by the oxyhydrogen flame melting method even if the iron element content is 10 ppb of the highest purity that can be reached at present. In comparison with quartz glass, which contains about 100 ppb, the semiconductor wafer is more likely to be infected with semiconductor poisons, and the diffusion length of minority carriers in the wafer is 100.
The diffusion length is more than doubled.

In the production of quartz glass by the electric melting method, the raw material used is ultra-high-purity natural quartz or high-purity natural quartz as described in US Pat. No. 4,983,370. Obtained by performing a purification treatment to remove the iron element as a halide and an aluminum element content of 5 to 30 ppm and an iron element content of 0.8 ppm
Less than 1.3 × 10 ^{-2 to} 1.3 × 10 ³ Pa
When melted and vitrified by heating using an electric heating means under reduced pressure, the viscosity at 1200 ° C. is 10 ^12.9 dPa · s or more, the OH group content is 30 ppm or less, the aluminum element content is 5 to 30 ppm, and the iron element is Content 0.8
Quartz glass of less than ppm is obtained. For example, as described in Japanese Utility Model Publication No. 55-35297, a hollow ingot is made into a quartz glass tube using a stretch forming means in a horizontal electric furnace to form a quartz glass tube, which is glass-worked to form a jig.
It is possible to obtain a jig in which a decrease in the diffusion length of minority carriers in the wafer is suppressed, that is, a quartz glass jig with less contamination by semiconductor poisons.

In the above manufacturing method, for example, in order to manufacture an ingot for a quartz glass tube, Japanese Patent Laid-Open No. 49-90.
The means described in Japanese Patent No. 710, that is, the means for manufacturing the hollow ingot by melting the raw material powder in a vacuum using a rotary mold may be used. Further, in order to produce a quartz glass block, the means described in JP-A-56-169137 is used.
A means for manufacturing a solid ingot by melting raw material powder in a vacuum is used. Rods and plates can be manufactured by these known methods and used for glasswork.

The quartz glass of the present invention is not limited to being used for a single-wafer heat treatment jig as described above, but is also suitably used for ordinary integrated circuit manufacturing.

[0013]

EXAMPLES Natural quartz powder was refined to obtain refined quartz powders A to C having the iron and aluminum element contents shown in Table 1. Also,
Aluminum chloride was mixed with high-purity silicon tetrachloride and hydrolyzed to obtain aluminum-doped synthetic quartz glass powder. Table 1 shows the results of measuring the elemental iron and aluminum element concentrations in the obtained powder by the atomic absorption photometry.

[0014]

[Table 1]

Example 1 60 kg of crystal powder A shown in Table 1 was charged in an electric furnace equipped with a graphite heater and a graphite crucible in a vacuum chamber equipped with a water cooling jacket. A small hole was provided at the bottom of the graphite crucible, and melting was performed with a temperature distribution in which melting started from above the crucible and proceeded downward. The pressure during melting was 100 Pa. With respect to the obtained quartz glass block, the OH group content, the influence on the minority carrier diffusion length, and the viscosity at 1200 ° C. were measured. The results are shown in Table 2.

Using this quartz glass, a set of quartz glass jigs such as a furnace core tube of a vertical furnace and a wafer boat was prototyped, and a step of attaching a thin gate oxide film to an 8-inch wafer was performed. All the oxide films maintained good insulation and had a good yield.

Example 2 A quartz glass block was manufactured in the same manner as in Example 1 using quartz powder B as a raw material. For the obtained quartz glass, the OH group content, the influence on the minority carrier diffusion length and the viscosity at 1200 ° C. were measured in the same manner as in Example 1.
The results are shown in Table 2.

Comparative Example 1 Crystal powder A was made into quartz glass by Bernoulli method using oxyhydrogen flame. Regarding the obtained quartz glass, the OH group content, the influence on the minority carrier diffusion length, and the viscosity at 1200 ° C. were measured. The results are shown in Table 2.

Comparative Example 2 In a molybdenum crucible, which is commonly used as a method for producing quartz glass for the semiconductor industry by an electric melting method, the quartz powder A is electrically melted under a mixed atmosphere of 80% hydrogen and 20% nitrogen at about atmospheric pressure. Then, quartz glass was manufactured. Regarding the obtained quartz glass, the OH group content, the influence on the minority carrier diffusion length, and the viscosity at 1200 ° C. were measured. The results are shown in Table 2.

Comparative Example 3 Quartz glass was manufactured in the same manner as in Example 1 except that the crystal powder C shown in Table 1 was used. Regarding the obtained quartz glass, the OH group content, the influence on the minority carrier diffusion length, and the viscosity at 1200 ° C. were measured. The results are shown in Table 2.

Comparative Example 4 Using the synthetic silica glass powder D in Table 1, vacuum electric melting was performed in the same manner as in Example 1 to obtain quartz glass. Regarding the obtained quartz glass, the OH group content, the influence on the minority carrier diffusion length, and the viscosity at 1200 ° C. were measured. The results are shown in Table 2.

[0022]

[Table 2]

In Table 2, the measured value of each example is based on the following measuring method. -OH group content; measured by infrared absorption spectroscopy by FT-IR. Minority carrier diffusion length; measured by the method described in German Patent No. 4234715. The initial diffusion length and the diffusion length after the test are shown in parentheses. In this case, it is judged that it is practically inconvenient if the particle size is reduced to 150 μm or less.・ Viscosity of 1200 ℃; 12 by beam bending method
Calculated from the amount of deformation when held at 00 ° C for 10 hours.

As is apparent from Table 2 above, Examples 1 and 2
The quartz glass has a small minority carrier diffusion length deterioration and, in addition, has a heat resistance and a viscosity required for a single-wafer heat treatment jig.

On the other hand, when melted with an oxyhydrogen flame, the diffusion length does not deteriorate, but the viscosity is insufficient (Comparative Example 1), and the most widely used production method at present is to produce in an atmosphere of approximately atmospheric pressure.
Even if a high-purity raw material is used, the deterioration of the diffusion length is still large and the problem of semiconductor poisoning occurs (Comparative Example 2). Further, even if the manufacturing method of the present invention is used, if the content of iron element in the raw material is large, the contamination of the wafer with semiconductor poison is high (Comparative Example 3). Further, when synthetic quartz glass powder was used as a raw material, the iron element content was reduced, but the heat resistance was low and it could not be used as a material for a single-wafer heat treatment jig (Comparative Example 4).

[0026]

The quartz glass of the present invention has high heat resistance and is less affected by the iron element of the semiconductor poison, and is suitable as a jig material for semiconductor processing such as a large-sized silicon wafer. In addition, the vacuum electromelting method, which has been conventionally used as a manufacturing method, can be used, and the quartz glass can be manufactured at low cost.

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[Procedure amendment]

[Submission date] February 10, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

On the other hand, it has been found that quartz glass manufactured by the oxyhydrogen flame melting method, even if it is a quartz glass using natural quartz, has less harm on the silicon wafer as compared with the quartz glass manufactured by the electric melting method. There is. However,
Quartz glass manufactured by the oxyhydrogen flame melting method is inferior in heat resistance to quartz glass manufactured by the electric melting method, and is 1 × 10 ^12.9 d at 1200 ° C. required for a single-wafer heat treatment jig.
It did not satisfy Pa · s (1 × 10 ^13.9 poise).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

The above-mentioned quartz glass of the present invention has a low OH group concentration and an appropriate aluminum content, so that it has high heat resistance and is 1 × at 1200 ° C. which is required for quartz glass for single-wafer heat treatment jigs. It is a quartz glass that satisfies the requirement of 10 ^12.9 dPa · s or more and does not adversely affect the silicon wafer by the iron element which is a semiconductor poison. German Patent No. 4 discloses a method for quantitatively and simply measuring the damage of the semiconductor poison on the heat treatment of a silicon wafer.
No. 234,715. According to the publication, when quartz glass is placed in contact with or close to a silicon wafer and heated, the diffusion length of minority carriers in the wafer changes. The measuring method described in the above publication utilizes this phenomenon to measure the contamination due to semiconductor poisons.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 21/68 N T (72) Inventor Katsuhiko Kenmochi 88 Kawakubo Kanaya, Tamura-cho, Koriyama, Fukushima Prefecture Shinetsu Quartz Quartz Institute of Technology Ltd. (72) Inventor Dietma Hermann, Federal Republic of Germany 63801 Klein Ostheim Rheinhard Herlaus Ring 29 Herlaus Kralzgrass Geembehr Berreich Halpriter

Claims (2)

[Claims] 1. The viscosity at 1200 ° C. is 10 ^12.9 dPa.
Quartz glass for a heat treatment jig of a silicon semiconductor element, characterized in that it is s or more, the OH group content is 30 ppm or less, the aluminum element content is 5 to 30 ppm, and the iron element content is less than 0.8 ppm. . 2. Natural quartz powder containing aluminum element in the range of 5 to 30 ppm and less than 0.8 ppm of iron element under reduced pressure of 1.3 × 10 ^{−2 to} 1.3 × 10 ³ Pa. A method for producing a quartz glass for a heat treatment jig for a silicon semiconductor element, which comprises melting and vitrifying by heating using an electric heating means.