Point -of -Use ammonium compounds removal - keeping exhaust emission clear
Abstract – Many wafer fabs face the challenge of managing effluent generated from compound semiconductor process-specific and that includes ensuring Point-of-use (POU) abatement devices meets the required or desired performance. For POU abatement systems, we usually focus on the main electric/fuel oxidation abatement mechanism but not on wet scrubbing section. It was found that poor abatement efficiencies of wet scrubbing could lead to environmental issues such as generation of fine particle at the stack and corrosion of exhaust duct. Those fine particles from exhaust duct is made of unabated completely ammonia (NH3) and hydrogen fluoride (HF) combination . We evaluated the NH3 and HF abatement efficiency in two major types of POU abatement systems by comparing fluoride ion concentration and pH in the water supply tank. Based on the study, water quality and pH affect the abatement efficiency of water-soluble gases significantly, especially for tools that are running high nitrite or chamber clean recipes. By introducing fresh water supply method and optimized pH adjustment on the wet scrubber sections, we are able to improve POU abatement efficiency significantly and eliminate the environmental issue of fine particles generation at the stacks.