Abstract
Particle generation during stainless steel tube welding and the effect of tube inner surface smoothness for purging tube surface were investigated in order to achieve an ultra-high purity gas supplying system for semiconductor manufacturing processes. It was shown that particles with diameter larger than 0.1 μm were generated at a concentration of about 108 m-3 during full penetration welding of stainless steel tubes at the moisture concentration of 0.15 ppm in back-sealed gas for welding, because of melting, evaporation and recondensation of stainless steel components. The measured particles had a bimodal size distributions whose minimum appeared at particle diameter of 0.2 μm. In order to reduce the particle generation during stainless steel tube welding, the moisture concentration in back-sealed gas for welding was decreased to less than 10 ppb. As a result, generation level of about 107 m-3 for particles with diameter of larger than 0.1 μm was achieved during stainless steel tube welding, which is one order of magnitude smaller than that at the moisture concentration of 0.15 ppm. It was also shown that smoothing the inner surface of tubes is very effective in reducing the particle purging time.
