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Total toxicity equivalents emissions of SF(6), CHF(3), and CCl(2)F(2) decomposed in a RF plasma environment.

Wang YF, Shih M, Tsai CH, Tsai PJ

Department of Bioenvironmental Engineering, Chung Yuan Christian University, No. 200, Chung Pei Road, Chung-Li 320, Taiwan.

Sulfur hexafluorine compound (SF(6)), trifluoromethane (CHF(3)) and diclorodifluoromethane (CCl(2)F(2)) are extensively used in the semiconductor industry. They are global warming gases. Most studies have addressed the effective decomposition of fluorine compounds, rather than the toxicity of decomposed by-products. Hence, the concepts of toxicity equivalents (TEQs) were applied in this work. The results indicated that HF and SiF(4) were the two greatest contributors of TEQ to the SF(6)/H(2)/Ar plasma system, while F(2) and SiF(4) were the two greatest contributors to the SF(6)/O(2)/Ar system. Additionally, SiF(4) and HF were the two greatest contributors of TEQ to both the CHF(3)/H(2)/Ar and CHF(3)/O(2)/Ar plasma systems. HF and HCl were the two greatest contributors of TEQ to the CCl(2)F(2)/H(2)/Ar plasma system, and Cl(2) and COCl(2) were the two greatest contributors to the CCl(2)F(2)/O(2)/Ar system. HCl and HF can be recovered using wet scrubbing, which reduces the toxicity of these emission gases. Consequently, the hydrogen-based plasma system was a better alternative for treating gases that contained SF(6), CHF(3) and CCl(2)F(2) from the TEQs point of view.

Published 1 March 2006 in Chemosphere, 62(10): 1681-8.
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