PFC ABATEMENT IN THE SEMICONDUCTOR INDUSTRY, 2009
Van Gompel, Joe
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Semiconductor manufacturing uses fluorine-based chemistries for both etch processes as well as for many deposition steps because the resulting inorganic fluorides are volatile and readily removed under vacuum. Perfluorinated gases (PFCs; CF4, C2F6, SF6, etc.), decomposed in a plasma, are routinely used as sources of fluorine atoms because they are relatively nontoxic and are available in sufficient purity and bulk at reasonable prices. Consumption of these gases in the process is poor – as low as 15% for CF4 – so much of the gas going into the chamber is exhausted. PFCs are very potent global warming gases and, as they are chemically stable, persist in the atmosphere for thousands of years. This is of great concern for their effects on climate change. The semiconductor industry has long acknowledged this concern, and technologies for abating PFCs have been developed. This is increasingly important as various governmental regulatory agencies are developing legislation to require reporting of PFC usage or even PFC emissions control in some cases. This paper will include a brief overview of PFC usage in semiconductor manufacturing processes, followed by a tour of scrubber technologies that are capable of abating PFC gases. These include fuel-fired combustion, plasma destruction, and PFC-specific catalytic destruction. Attention will also be given to the appropriateness of these technologies for the various semiconductor manufacturing processes.