Impurity Amplification in Ultra High Purity Hydrogen Bromide by Water Catalyzed Reactions from Different Cylinder Materials

Abstract

Anhydrous HBr used in reactive ion etch chemistries for the semiconductor industry requires strict control of impurities over time. Proper selection of cylinder materials strongly influences the purity of the HBr over the shelf life of the stored gas. In this work Ni-lined AISI 4130 Cr-Mo steel cylinders are compared to the gas industry standard AISI 4130 Cr-Mo steel cylinders and 316L SS cylinders regarding the generation of atmospheric impurities over the shelf life of the cylinders. In addition an accelerated aging process of water doping was executed to determine variances between materials. Over the period of 18 months, significant amounts of atmospheric impurities such as CH4, CO2, and H2 were generated in the water doped cylinders. However, the Ni lined cylinders inhibited the atmospheric impurity generation by as much as 20 times, compared to the Cr-Mo steel or 316L SS cylinders in the accelerated study. A similar affect was observed in the standard non-accelerated study. These results demonstrate that Ni lined Cr-Mo steel provides a superior package for anhydrous HBr, due to superior contamination control.