Compatibility of gas filters with HBr gas

Maintaining specialty gas purity at point-of-use (POU) is involved; clean delivery of corrosive specialty gases is even more difficult. Even a brief exposure of the corrosive gas delivery system to ambient air can result in onset of corrosion and eventually particles. Fortunately, POU gas filters are available to prevent particles from entering the wafer environment, but not all filters have the same degree of corrosion resistance. The 1998 update to the International Technology Roadmap for Semiconductors (ITRS) recommends that the critical-sized particle level in specialty gases should not exceed two particles per liter, i.e. for projected device production with feature sizes of 130 nm in 2002, only two particles >65 nm in size should be present in 1 l of gas. While such contamination control may be easily achievable in many bulk inert and specialty gases, particle control in corrosive gases is problematic. Of the corrosive gases used in semiconductor manufacturing, hydrogen bromide (HBr) is one of the more corrosive gases. This paper details the evaluation of gas filters of various materials with HBr gas. The experiments exposed the filters to HBr gas followed by a purified N₂ purge and compressed air challenge. The compressed air challenge simulated exposure of the filters to ambient air. The filters were then purged with N₂ and evaluated. The corrosion resistance of the filters was determined by particle shed testing and SEM/EDS analyses. Of the filters examined, a next generation filter constructed from chromium had the best performance. The importance of purge time and conditions for corrosion prevention is demonstrated