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Abstract

Perfluorocompounds (PFCs) are highly stable chemical compounds used in two integral steps of semiconductor manufacturing: chemical vapor deposition (CVD) chambers and etch chambers. Unfortunately, PFCs are also greenhouse gases linked to global warming. This, combined with their long atmospheric lifetimes gives them global warming potentials much higher than C02 the principal greenhouse gas. In a series of voluntary agreements with the United States and other national governments, the worldwide semiconductor industry has set a goal of reducing PFC emissions to 90% of their 1995 levels. To reach this goal, researchers have explored four main methods of reduction: substitution of PFCs, recovery and recycling of PFCs, tool optimization, and exhaust abatement. While the first three methods have successfully reduced emissions in the CVD chambers, they have proven too costly for or inapplicable to etch chambers. Therefore, it has become apparent that further reductions must be achieved through the abatement of etch chamber exhaust. Herein, we compare three commercially available abatement systems representative of the three techniques currently used to abate PFCs. All three systems are categorized as either downstream systems, which receive diluted exhaust from multiple etch chambers, or point-of-use (POU) systems, which receive concentrated exhaust from a single etch chamber. Though both downstream and POU configurations are equally effective in destroying PFCs, they differ in cost depending on the number of etch chambers in use and the dilution rate per chamber. Given these numbers, our Microsoft Excel-based cost model computes the total cost of each of the three commercial systems, allowing the user to determine which system is most economical for a specific factory setting.

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