Decomposition of SF6 in an RF plasma environment

Sulfur hexafluoride (SFd)-contained gas is a common pollutant emitted during the etching process used in the semiconductor industry. This study demonstrated the application of radio-frequency (RF) plasma in the decomposition of SF6. The decomposition fraction of SF6 [etaSF6 (C(in)-C(out))/C(in) x 100%] and the mole fraction profile of the products were investigated as functions of input power and feed O2/SF6 ratio in an SiO2 reactor. The species detected in both SF6/Ar and SF6/O2/ Ar RF plasmas were SiF4, SO2, Fe2, SO2F2, SOF2, SOF4, S2F10, S2OF10, S2O2F10, and SF4. The results revealed that at 40 W, etaSF6 exceeded 99%, and the reaction products were almost all converted into stable compounds such as SiF4, SO2, and F2 with or without the addition of oxygen. Sulfur oxyfluorides such as SO2F2, SOF2, SOF4, S2OF10, and S2O2F10 were produced only below 40 W. The results of this work can be used to design a plasma/chemical system for online use in a series of a manufacturing process to treat SF6-containing exhaust gases.