JPH09208256A - Electrically conductive quartz glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dense large-sized electrically conductive glass not losing its electric conductivity even when used in an oxidizing atmosphere at a high temp. SOLUTION: A sol prepd. by hydrolyzing a partial condensation polymer of silicon alkoxide with a base catalyst in the presence of a solvent, a resin and a salt is made gel and dried. The resultant dry gel is fired at 700-1,300 deg.C to form a porous glass body and a resin soln. is impregnated into the glass body and dried. Vitrification is then carried out by heating in an oxygen-free atmosphere to produce the objective large-sized electrically conductive glass having <=10<11> Ω electric conductivity and withstanding use in an oxidizing atmosphere at a high temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass having conductivity which can be suitably used for a jig for manufacturing a semiconductor.

[0002]

2. Description of the Related Art Quartz glass is widely used as a material for jigs for semiconductor production because it has high purity, low thermal expansion, thermal shock resistance, heat resistance and chemical resistance. However, since it has a low electric conductivity, it is easy to generate static electricity, which causes a problem that the semiconductor element is destroyed by the static electricity charged on the quartz glass. In addition, there is a limitation that it cannot be used for applications requiring conductivity.

For the purpose of imparting conductivity to quartz glass, a porous glass body impregnated with a coating material containing carbon black, or a fine carbon powder dispersed in kerosene, an organic solvent, water or the like is used. Impregnate and heat this,
It has been proposed to dry and carbonize to deposit carbon in the glass to develop conductivity. Also, Takagi et al. Proposes that carbon is contained in glass by heating a wet gel in which the amount of residual organic matter is adjusted in an oxygen-free atmosphere so that the glass exhibits conductivity (JP-A-2- Two
39122 publication).

[0004]

However, the conductive glasses produced by the proposed method are all porous bodies, and when used at a high temperature where the features of quartz glass are utilized, carbon disappears due to oxidation. However, there was a problem that the conductivity was lost. Further, when a wet gel is used, it is difficult to obtain a large conductive glass. The present invention provides a dense and large-sized conductive quartz glass which does not lose its conductivity even when used in a high temperature / oxidizing atmosphere.

[0005]

The present invention was obtained by hydrolyzing a partially condensed polymer of a silicon alkoxide with a base catalyst in the presence of a resin, a solvent and a salt to give a sol, gelling and drying. It is produced by firing a dried gel at a temperature of 700-1300 ° C. to obtain a porous glass, impregnating this porous glass body with a resin solution, drying and then heating in an oxygen-free atmosphere to vitrify 10 ^It is a conductive quartz glass with an electrical conductivity of ¹¹ Ω or less.

The present inventor has studied a method for producing a conductive glass which solves the above problems, and as a result, hydrolyzes a partially condensed polymer of a silicon alkoxide in the presence of a solvent, a resin and a salt using a base catalyst. The prepared sol is gelled, dried to give a dried gel, and fired at a temperature of 700 to 1300 ° C. to give a porous glass body. The porous glass body is impregnated with a resin solution, dried, and then placed in an oxygen-free atmosphere. The present invention has been completed by finding that it is possible to manufacture a large-sized conductive glass that can withstand use in a high temperature and oxidizing atmosphere by heating and vitrifying in the atmosphere.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a partial condensation polymer of a silicon alkoxide used in the present invention, a partial condensation polymer such as silicon tetramethoxide, silicon tetramethoxide and silicon tetrapropoxide can be used. It is preferable to use a partially condensed polymer of silicon tetramethoxide from the viewpoint that the obtained conductive glass can be easily enlarged.

As the solvent used in the present invention, use of a mixed solvent of alcohols such as methanol, ethanol, propanol and the like, high boiling point solvents such as dimethylformamide, dimethylacetamide, tetrahydrofurfuryl alcohol and the like makes the conductive glass large. It is preferable for the purpose.

As the resin used in the present invention, polyvinyl acetate, polyethylene glycol and its derivatives, hydroxypropyl cellulose and the like can be used.

The salts used in the present invention include bases such as ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, trimethylethylammonium hydroxide (choline) and nitric acid, hydrochloric acid and the like. Salts with acids can be used.

As the base catalyst used in the present invention, tetramethylammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, trimethylethylammonium hydroxide (choline) can be used.

The sol prepared by using the above components is poured into a container, allowed to stand, gelated, and dried to prepare a dried gel. For drying the gel, either a method using a known gas permeable film or a method using a pinhole can be used.

Then, the dried gel thus prepared was subjected to 700-13.
It is baked at a temperature of 00 ° C. to obtain a porous glass body, which is impregnated with a resin solution, dried, and then dried in an oxygen-free atmosphere.
By heating at a temperature of 00-1500 ° C, a dense composite of silica and carbon can be obtained. If the temperature at which the dried gel is made into a porous glass body is lower than 700 ° C., the strength of the porous glass body is low and the porous body is destroyed during the impregnation with the resin solution, which is not preferable. On the other hand, if the temperature exceeds 1300 ° C., the porous body is densified and the resin impregnation becomes difficult, which is not preferable. As the resin, basically any resin can be used as long as it has a large carbon content remaining after thermal decomposition, but phenol-based, furan-based, epoxy-based, cellulose-based, polyacrylonitrile-based, polyvinyl alcohol Resins and the like can be used. As a solvent for dissolving these resins, basically any solvent can be used as long as it can dissolve the resin. A known method such as vacuum or pressure can be used for the impregnation, and the impregnation operation may be repeated a plurality of times in order to achieve an appropriate carbon content and, as a result, complete silicon carbide formation. The temperature at which the porous glass body impregnated with the resin is heated and densified is 13
It is preferably from 00 to 1500 ° C. At a temperature lower than 1300 ° C., the resulting conductive silica / carbon composite is insufficiently densified, and when the conductive silica / carbon composite is used in a high temperature / oxidizing atmosphere, oxidation of carbon is likely to occur, resulting in conductivity. Is likely to decrease. As the oxygen-free atmosphere used when firing the porous glass body impregnated with resin, nitrogen, argon, helium, vacuum or the like can be used.

[0014]

【Example】

Example 1 100 parts by weight of a partially condensed polymer of silicon tetramethoxide, 500 parts by weight of methanol, dimethylformamide 3
60 parts by weight, tetrahydrofurfuryl alcohol 266
By weight, 2.5 parts by weight of polyvinyl acetate (degree of polymerization: 1800) were mixed. An aqueous solution of 1 M choline nitrate was added to this, and 5x per 100 g of the partially condensed polymer of silicon tetramethoxide.
10 ^-4 mol was added, further 1M choline methanol solution was added portion polycondensate 100g per 1.2x10 ^-4 mol of silicon tetramethoxide, then the solution was added dropwise to water 390 parts by weight with stirring, a further agitation Done to prepare a sol. 4.5 kg of the obtained sol was poured into a 480 mm square stainless steel container coated with Teflon, and a lid having two pinholes with a diameter of 1 mm was opened. After leaving the container to stand and gelling the sol, 50 ℃ to 180 ℃
The gel was dried by gradually heating to the temperature of. The drying time was about 10 days. The obtained dried gel was heated to 1000 ° C. in a nitrogen atmosphere and kept for 1 hour to obtain a porous glass body. Put the porous glass body in a pallet (500 mm square), evacuate in a vacuum desiccator, then pour a methanol solution of novolac-type phenol resin into the pallet,
The porous glass body was impregnated with a resin, and then the solvent in the porous body was dried. The obtained resin-impregnated porous glass body was heated to 1000 ° C. in a nitrogen atmosphere, then the atmosphere was changed to helium, the temperature was raised to 1450 ° C., and the temperature was maintained for 2 hours for densification. In this way about 220 mm square, thickness 8 mm
A dense silica-carbon composite glass without cracks was obtained. The electrical resistance of the selected silica / carbon composite glass was measured and found to be 10 ⁸ Ω.

Example 2 A porous glass body produced in the same manner as in Example 1 was placed in a pallet (500 mm square), and after being evacuated in a vacuum desiccator, a methanol solution of furan resin was poured into the pallet to obtain a porous glass. The body was impregnated with resin and then the solvent in the porous body was dried. When the obtained resin-impregnated porous glass body was fired and densified in the same manner as in Example 1, a dense silica-carbon composite glass without cracks was obtained. The electrical resistance of the obtained silica / carbon composite glass was measured and found to be 10 ⁸ Ω.

Comparative Example A dry gel prepared in the same manner as in Example 1 was heated to 1000 ° C. in a nitrogen atmosphere, then changed to helium and heated to 1450 ° C., and held for 2 hours for densification. It was The obtained glass was a black quartz glass containing carbon, and its electric resistance was measured to be 10 ¹³ Ω.
It was an insulator.

[000]

According to the present invention, a dense and large-sized silica / carbon composite conductive glass which can withstand use in a high temperature oxidizing atmosphere can be easily obtained. The obtained conductive glass has the excellent features of quartz glass such as high purity, low thermal expansion, high thermal shock resistance, and chemical resistance, and since it has conductivity, it is It can be suitably used as a material for products that dislike static electricity, and according to the present invention, the conductivity can be controlled by controlling the carbon content in glass. It can also be applied to applications such as electrostatic chucks, etching electrodes, and heating elements.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroki Terasaki 48 Wadai, Tsukuba City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Tsukuba Development Laboratory

Claims (1)

[Claims] 1. A dry gel obtained by hydrolyzing a partially polycondensed product of a silicon alkoxide with a base catalyst in the presence of a resin, a solvent and a salt to give a sol, gelling and drying.
10 ¹¹ Ω or less produced by firing at a temperature of 0 to 1300 ° C. to obtain porous glass, impregnating this porous glass body with a resin solution, drying, and then heating and vitrifying in an oxygen-free atmosphere. Conductive quartz glass having the electric conductivity of.