Decomposition of SF₆ and H₂S Mixture in Radio Frequency Plasma Environment

Sulfur hexafluoride (SF6) is a gaseous pollutant generated in manufacturing processes in the semiconductor industry. Hydrogen sulfide (H2S), as a reductant, was used to treat SF6 in a radio frequency (RF) plasma system. In the SF6/Ar plasma system, SiF4 and SO2 were the two dominant species detected in the glass reactor; other detected species were SO2F2, SOF2, and SOF4. In the SF6/H2S/Ar plasma system, HF and elemental sulfur were the main produced species. Although the species SiF4, SO2, SO2F2, SOF2, and SOF4 were detected in the SF6/H2S/Ar plasma system, adding H2S clearly inhibited the generation of these byproducts of SiO2 etching. At an input power of 5 W and an H2S/SF6 ratio of 2.9, the mass fraction of fluorine from feed SF6 converted into HF was 95.3%, while the mass fraction of sulfur from feed SF6 and H2S converted into elemental sulfur was 96.1%. Given the advantages of recovering HF and reclaiming elemental sulfur, hydrogen sulfide can be used as an auxiliary gas in treating SF6 in an RF plasma system.