Yoshiyuki Nakahara

Low outgassing and anticorrosive metal surface treatment for ultrahigh vacuum equipment

We report on a stainless steel passivation technology useful for the future We report on a stainless steel passivation technology useful for the future submicron ultralarge‐scale integration (ULSI) manufacturing. In the near future, low pressure processing will become more important. With presently available equipment, outgassing from the inner surface of metal chambers is one of the factors that can hinder ultrahigh vacuum processing. Therefore, absorbed molecular contaminations must be eliminated. We report the development of low outgassing metal surface that is derived from an O2 or F2 passivation process. This process requires an initial metal surface to have mirror finish without Beilby layer. Specifically, by using a 316L stainless surface, under clean conditions, outgas volume of moisture are shown to be reduced by a factor of 102, compared with conventional finished steel surfaces. In addition O2/F2 passivation, though inherently different, give stainless steel surfaces that show excellent corrosi...

The effect of dry passivation treatments on the corrosion resistance, moisture release and structure of the surface oxide film on electropolished stainless steel

Abstract The objective of the present study is to investigate the effect of dry passivation treatments on corrosion resistance, moisture release behavior and structure of oxide film on electro-polished Type 316L stainless steel. The corrosion resistance was evaluated by measuring the incubation time until H 2 evolution occurred in HCl solution and the linear polarization resistance in boiling 0.005M-Na 2 SO 4 solution. The moisture release behavior was investigated by measuring the volume of H 2 O desorption with ultra pure N 2 gas purging. The structure of surface oxide film was analyzed using AES, XPS, LRS etc. The corrosion resistance and the moisture release resistance were remarkably improved by the oxidation treatments in oxygen atmospheres controlled with a dew point of below −100°C at temperatures from 400°C to 450°C, compared with as-electropolished surface film. At the treatment temperature over 500°C, those properties changed for the worse. From the results of surface analyses, it was clarified that a fine and amorphous oxide film containing enriched Fe and Cr was formed at the oxidation temperature of 400∼450°C, whereas oxide films crystallized and became coarse at oxidation temperature over 500°C.