Abatement of sulfur hexafluoride emissions from the semiconductor manufacturing process by atmospheric pressure plasmas

Sulfur hexafluoride (SF6) is an important gas for plasma etching processes in the semiconductor industry. SF6 intensely absorbs infrared radiation and, consequently, aggravates global warming. This study investigates SF6 abatement by nonthermal plasma technologies under atmospheric pressure. Two kinds of nonthermal plasma processes-dielectric barrier discharge (DBD) and combined plasma catalysis (CPC)-were employed and evaluated. Experimental results indicated that as much as 91% of SF6 was removed with DBDs at 20 kV of applied voltage and 150 Hz of discharge frequency for the gas stream containing 300 ppm SF6, 12% oxygen (O-2), and 40% argon (Ar), with nitrogen (N-2) as the carrier gas. Four additives, including Ar, O-2, ethylene (C2H4,), and H2O(g), are effective in enhancing SF6 abatement in the range of conditions studied. DBD achieves a higher SF6 removal efficiency than does CPC at the same operation condition. But CPC achieves a higher electrical energy utilization compared with DBD. However, poisoning of catalysts by sulfur (S)-containing species needs further investigation. SF6 is mainly converted to SOF2, SO2F4, sulfur dioxide (SO2), oxygen difluoride (OF2), and fluoride (F-2). They do not cause global warming and can be captured by either wet scrubbing or adsorption. This study indicates that DBD and CPC are feasible control technologies for reducing SF6 emissions.