Abstract: First of all, there is provided a production process of a synthetic quartz glass which has less impurity, has a high-temperature viscosity characteristic equal to or more than that of a natural quartz glass, and hardly deforms even in a high-temperature environment, and especially a production process of a highly heat resistant synthetic quartz glass which is free from the generation of bubbles and is dense. Secondly, there is provided a highly heat resistant synthetic quartz glass body which is easily obtained by the production process of the present invention, and especially a transparent or black quartz glass body which is free from the generation of bubbles, is dense, has high infrared absorption rate and emission rate, and has an extremely high effect for preventing diffusion of alkali metal. The process is a process of producing a highly heat resistant quartz glass body having an absorption coefficient at 245 nm of 0.

Abstract: First of all, there is provided a production process of a synthetic quartz glass which has less impurity, has a high-temperature viscosity characteristic equal to or more than that of a natural quartz glass, and hardly deforms even in a high-temperature environment, and especially a production process of a highly heat resistant synthetic quartz glass which is free from the generation of bubbles and is dense. Secondly, there is provided a highly heat resistant synthetic quartz glass body which is easily obtained by the production process of the present invention, and especially a transparent or black quartz glass body which is free from the generation of bubbles, is dense, has high infrared absorption rate and emission rate, and has an extremely high effect for preventing diffusion of alkali metal. The process is a process of producing a highly heat resistant quartz glass body having an absorption coefficient at 245 nm of 0.

Abstract: An object of the present invention is to provide a quartz glass jig, which, when employed in a processing apparatus using plasma, is less in generation of abnormal etching and particles and low in contamination with impurities. This object is obtained by a quartz glass jig for a processing apparatus using plasma, wherein a surface of the jig is subjected to grinding or a sandblast processing and has a surface roughness Ra in the range of from 2 ?m to 0.05 ?m, and microcracks of grinding marks formed during the grinding or sandblast processing have a depth of 50 ?m or less.

Abstract: A silica glass jig for semiconductor industry, characterized by having, on the surface of the jig, pyramidal projected structures with their cut-off apices and concave portions provided therebetween, and small projections are uniformly distributed thereon; the silica glass jig has a surface with many dimple-form concave portions each having a width of from 20 to 300 &mgr;m exist and there are grooves each having a width of from 0.5 to 50 &mgr;m at an interval of from 20 to 300 &mgr;m, and small projections each having a width of from 1 to 50 &mgr;m and having a height of from 0.1 to 10 &mgr;m are uniformly distributed between the grooves and in the grooves.

Abstract: It is an object of the present invention to provide a quartz glass jig excellent in the plasma etching resistant characteristics, which does not generate an abnormal etching and particles when used for a plasma generating apparatus. The above Object is obtained by a plasma resistant quartz glass jig that is used for an apparatus of generating plasma, wherein the surface roughness Ra of the quartz glass surface is in a range of from 5 &mgr;m to 0.05 &mgr;m, the number of microcracks of the surface is not more than 500 microcracks/cm2, and the hydrogen molecule concentration in the quartz glass is at least 5×1016 molecules/cm3.

Abstract: An object of the present invention is to provide a quartz glass jig, which, when employed in a processing apparatus using plasma, is less in generation of abnormal etching and particles and low in contamination with impurities. This object is obtained by a quartz glass jig for a processing apparatus using plasma, wherein a surface of the jig is subjected to grinding or a sandblast processing and has a surface roughness Ra in the range of from 2 &mgr;m to 0.05 &mgr;m, and microcracks of grinding marks formed during the grinding or sandblast processing have a depth of 50 &mgr;m or less.

Abstract: A silica glass jig for semiconductor industry, which is does not contaminate semiconductor elements, and generates less cracks and a production method thereof are provided.

Abstract: It is an object of the present invention to provide a quartz glass jig excellent in the plasma etching resistant characteristics, which does not generate an abnormal etching and particles when used for a plasma generating apparatus.

Abstract: Cristobalite-containing silica glass is provided wherein .alpha.-cristobalite in the shape of a small sphere or a small, round-edged or sharp-edged, three-dimensional region is dispersed in the silica glass matrix. The diameter of each .alpha.-cristobalite sphere or region is, in the range of 0.1 um to 1000 um, and the content of the .alpha.-cristobalite is at least 10 wt. %. The cristobalite-containing silica glass is produced by heating a mixture of two kinds or more of crystalline silicon dioxide powder with melting points different from each other by 20.degree. C. or more. The mixture contains silicon dioxide having the highest melting point in the range of 10 wt. % to 80 Wt. % and is heated at temperatures ranging from the lowest melting point to a temperature lower than the highest melting point.