Cylinder Materials of Construction for Ultra-High Purity HBr in Advanced Semiconductor Etch Processes

Abstract

Anhydrous HBr used in etch processing for the semiconductor industry requires strict impurity control. However, the gas cylinder material of construction plays a critical role in controlling and maintaining purity levels of the delivered HBr process gas and must be carefully selected. In this work Ni-lined AISI 4130 Cr-Mo steel cylinders are compared against the gas industry standard AISI 4130 Cr-Mo steel cylinders with regard to (a) surface roughness/area and oxide layer thickness after exposure to HBr and (b) the concentration of moisture in delivered HBr gas. Over the period of a year, the surface roughness increase of the polished Cr-Mo steel package doubles that of the Ni-lined package and the penetration of the oxide layer into the metal for the Cr-Mo steel is over 10 times that for the Ni surface. Finally the more inert surface of the Ni lining is shown to lower the moisture concentration in the HBr gas by ~4 times. These findings demonstrate that Ni-lined AISI 4130 Cr-Mo steel provides a superior package for Ultra High Purity HBr storage and delivery.