JPH0450263B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention introduces a very small amount of nitrogen into synthetic quartz glass, particularly synthetic quartz glass, to improve its viscosity, hardness, Young's modulus, and electrical resistance at high temperatures.
Synthetic quartz glass has significantly improved chemical durability, making it useful for silicon pulling crucibles, diffusion process tubes, diffusion jigs, and cleaning tanks for the semiconductor industry, as well as as high-temperature insulators and substrate glass for various equipment. It is related to. (Conventional technology) Quartz glass has the highest purity, heat resistance, and mechanical strength among silica-based glasses, but there are still many applications that cannot be satisfied with the current level of silica glass, and improvements in these properties are needed. requested. Therefore, for this silica glass, the oxygen atoms of the ≡Si-0≡ group in this molecule are replaced with nitrogen atoms.

It has been proposed to have the structure [Formula]. For example, a Vycol type porous glass with 96% silicic acid and a specific surface area of about 200 m ² /g is heated with ammonia using nitrogen gas as a carrier gas. treatment to reduce the nitrogen content to 3.
There is a report that a glass with a weight percent of
275] This glass is said to have improved the annealing point by 150°C. There is also a report that an oxynitride film was formed on a silicon wafer by vapor phase synthesis as an example of introducing nitrogen into quartz glass [see J. Electrochem. Soc., 115 (1968) 318]. Another method being considered is to pass ammonia through a porous gel made by the sol-gel method at 400 to 800°C. (Problem to be Solved) However, although the silica glass disclosed in this known method contains a large amount of nitrogen, it is only stated that the annealing point of the glass is improved.
The silicon wafer treatment has an oxynitride film on the surface and is not related to quartz glass blocks.Furthermore, the treatment of porous gel with ammonia using the sol-gel method has the disadvantage that it becomes a foam, making it impractical. There is. (Means for Solving the Problems) The present invention relates to a synthetic quartz glass that solves these disadvantages and a method for producing the same, which has a viscosity of 10 ^{to 10} poise or more at 1400°C and a Vickers hardness of 1000 Kg/mm ² , the Young's modulus is 90 GPa or more, and the electrical resistance at 1200°C is 10 ^-8 Ω・
cm/cm ² or more, and the above-mentioned synthetic quartz glass characterized by producing silica particles by hydrolyzing methyl silicate in the presence of ammonia and using the silica particles as a raw material. The present invention relates to a method for producing synthetic quartz glass. That is, the present inventors have studied various methods of modifying silica glass by introducing nitrogen into quartz glass, and have found that in order to introduce nitrogen into quartz glass, alkoxysilane is hydrolyzed to produce silica particles. In the so-called sol-gel method, in which silica glass is obtained by melting this, methyl silicate is used as the alkoxysilane, and this hydrolysis is carried out in the presence of ammonia, which is then heated to release a very small amount of nitrogen into silica glass. In addition, the physical properties of the quartz glass thus obtained were surprisingly improved, with a viscosity of 10 ¹⁰ at 1400°C.
Poise or more, Bitskers hardness is 1000Kg/ ^mm2 or more,
The present invention was completed by confirming that the Young's modulus was 90 Gpa or more and the electrical resistance at 1200°C was 10 ⁻⁸ Ω·cm/cm ² or more. This will be explained in further detail below. (Function) The physical properties of the synthetic silica glass of the present invention are greatly improved by introducing a small amount of nitrogen into it. Hydrolysis may be carried out in the presence of. The synthetic silica glass of the present invention may be produced by the so-called sol-gel method, which involves hydrolyzing methyl silicate in the presence of ammonia to produce sol-like silica particles, which are then dried to form gel-like silica particles. , heat treatment is sufficient. The amount of ammonia present in the system at the time of hydrolysis may be adjusted depending on the amount of nitrogen to be introduced into the synthetic quartz glass aimed at. Since a very small amount of 10 to 1000 ppm by weight is sufficient, the amount should be 50 to 500 parts by weight per 100 parts by weight of methylisilicate, and this hydrolysis is carried out at room temperature in the presence of this ammonia. You can do it with The sol-like silica particles obtained by this hydrolysis are dehydrated in a centrifugal dehydrator, dried at 150°C in a nitrogen gas stream to form gel-like silica particles, and then heated from room temperature to oxygen gas.
It can be vitrified by heating it to 1200℃ for about 10 hours, but this quartz glass is further heated in a vacuum from room temperature to 1500℃ for 2 hours, then from 1500℃ to 1700℃.
It is preferable to sinter by heating to ℃ for about 10 hours. The synthetic quartz glass obtained in this way is 10~
Since 1000 ppm of nitrogen has been introduced, the physical properties of this product are significantly improved compared to commercially available synthetic silica glass and natural quartz glass, and the viscosity value at 1400°C is 10 to ¹⁰ poise or higher. It exhibits excellent physical properties such as a Bitkers hardness of 1000 Kg/mm ² or more, a Young's modulus of 90 Gpa or more, and an electrical resistance value of 10 ⁸ Ω・cm/cm ² or more at 1200°C. It is useful for silicon pulling crucibles, diffusion process tubes, diffusion jigs, and cleaning tanks, as well as for high-temperature insulators and substrate glass for various devices. (Example) Next, examples of the present invention and comparative examples will be given. Examples, Comparative Examples 1 to 2 130 liters of semiconductor grade ammonia water and 30 liters of ultrapure water were placed in a 500 liter glass-lined reactor and heated to 0°C.
265 kg of methyl silicate (distilled product) was added dropwise to the mixture while stirring with a Teflon-coated stirring rod, and after the addition was completed, it was dehydrated using a centrifugal dehydrator to produce 105 kg of sol-like silica powder. Next, this silica powder was heated to 150% in nitrogen gas.
After drying at ℃ to form gel-like silica powder, this was packed into a quartz furnace tube and heated from room temperature in an oxygen gas stream.
The material was heated to 1200°C, and the 25kg was packed in a high-purity graphite case and sintered in a vacuum from room temperature to 1500°C for 2 hours, and then from 1500°C to 1700°C for 10 hours. Next, this sintered body is crushed to have a particle size of 50 to 80 mesh, washed with HCl and HF, dried, passed through a magnetic separator, and then packed back into a high-purity graphite case.
When the temperature was raised from room temperature to 1800℃ over 20 hours in a vacuum of 10 ^-3 Torr, a transparent synthetic quartz ingot measuring 300mmΦ x 600mmL was obtained, but 500ppm of nitrogen was introduced into this quartz glass. Ori,
When the physical properties were measured, the results shown in Table 1 were obtained. However, for comparison, commercially available synthetic quartz glass
When we investigated the physical properties of Splashil [trade name manufactured by Heraus AG, West Germany] (Comparative Example 1) and commercially available natural quartz glass Heraltux [trade name manufactured by Heraus AG, West Germany] (Comparative Example 2), the results were as shown in Table 1. The following results were obtained, and it was confirmed that the synthetic quartz glass of the present invention has excellent physical properties.

【table】

Claims (1)

[Claims] 1. Viscosity at 1400°C of 10 ¹⁰ poise or more, Vickers hardness of 1000 Kg/mm ² or more, Young's modulus of 90 GPa or more, and electrical resistance at 1200°C of 10 ⁸ Ω・
Synthetic quartz glass characterized by cm/cm ² or more. 2. The method for producing synthetic quartz glass according to claim 1, wherein methyl silicate is hydrolyzed in the presence of ammonia to produce silica particles, and synthetic quartz glass is produced using the particles as a raw material.