Catalytic Decomposition of Ammonia from GaN Processes
Van Gompel, Joe
(BOC Edwards, Austin TX)
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Gallium nitride deposition processes use high flows of both H2 and NH3, sometimes approaching 100 slm each. NH3 cannot be vented to the atmosphere, and rooftop abatement is inefficient, so point of use abatement is often required. Wet scrubbing is effective, but NH3 (or ammonium ions) in the fab wastewater may trigger local regulatory issues. Combustion of NH3 is expensive and can raise NOx emissions. Standard dry-bed abatement, where NH3 is collected on an acidic medium, is economically impractical. However, dry-bed catalytic decomposition of NH3 to N2 and H2 generates an exhaust stream that can be discharged to the atmosphere. The exhaust is free of particulate, moisture, and hazardous air pollutants (HAPs). Facilitization of wastewater and fuel gas to the POU scrubber is eliminated. Poisoning of the catalytic bed is resolved by a reactive inlet bed to decompose the organometallics, extending catalyst life to a year or more. Overall cost of ownership is very low compared to other abatement solutions. This methodology has been developed to decompose up to 100 slm NH3 to > 99.9% conversion.