Sulfur Hexafluoride (SF₆): Global Environmental Effects and Toxic Byproduct Formation

Decomposition of SF6in an RF Plasma Environment

“…The discharge plasma can be manipulated at low substrate temperatures without changing its original properties and can replicate submicrometer patterns with anisotropic features. 5 However, in the presence of an RF discharge, SF 6 , acting as an etching/ etching-aid gas, can be decomposed into lower fluorides of sulfur and can generate hazardous byproducts, such as S 2 F 10 , SO 2 F 2 , SOF 2 , SOF 4 , and SF 4 . 4,[6][7][8][9][10] Particularly toxic is S 2 F 10 , which has an LC 50 (concentration needed to kill 50% of a defined experimental animal population) of 0.1 mg/m 3 .…”

“…5 However, in the presence of an RF discharge, SF 6 , acting as an etching/ etching-aid gas, can be decomposed into lower fluorides of sulfur and can generate hazardous byproducts, such as S 2 F 10 , SO 2 F 2 , SOF 2 , SOF 4 , and SF 4 . 4,[6][7][8][9][10] Particularly toxic is S 2 F 10 , which has an LC 50 (concentration needed to kill 50% of a defined experimental animal population) of 0.1 mg/m 3 . 11 Because reducing or eliminating the toxicity of gaseous effluent from the RF discharge process is a serious concern, Breitbarth et al 12 have proposed an oxygen-based RF discharge process in which a glass reactor is connected in series with a commercial RF parallel-plate reactor to decompose fluorocarbon waste gases into CF 4 and C 2 F 6 , which, in the presence of silica walls, are reacted to stable SiF 4 .…”

“…Sulfur hexafluoride (SF 6 ) is commonly used as an etching/ etching-aid gas in fabricating the submicrometer features of modern integrated circuits because it has a higher fluorine content than CF 4 but does not undergo polymerization. [1][2][3] However, the destruction of SF 6 has attracted much interest because of the important environmental issues and the toxicity of sulfur compounds.…”

“…[1][2][3] However, the destruction of SF 6 has attracted much interest because of the important environmental issues and the toxicity of sulfur compounds. 4 Radio-frequency (RF) discharge plasma, which must be manipulated at low pressure, recently has become the most popular plasma technology used in the high-profit semiconductor industry, in both replicating patterns and depositing films. The discharge plasma can be manipulated at low substrate temperatures without changing its original properties and can replicate submicrometer patterns with anisotropic features.…”

“…4,[6][7][8][9][10] Particularly toxic is S 2 F 10 , which has an LC 50 (concentration needed to kill 50% of a defined experimental animal population) of 0.1 mg/m 3 . 11 Because reducing or eliminating the toxicity of gaseous effluent from the RF discharge process is a serious concern, Breitbarth et al 12 have proposed an oxygen-based RF discharge process in which a glass reactor is connected in series with a commercial RF parallel-plate reactor to decompose fluorocarbon waste gases into CF 4 and C 2 F 6 , which, in the presence of silica walls, are reacted to stable SiF 4 . The SiF 4 then can be converted into nontoxic solid products with the aid of a CaO/Ca(OH) 2 absorber.…”