Abatement of perfluorocompounds and chlorofluorocarbons using surface wave plasma technology

Application of surface wave plasma technology for effective abatement of environmentally harmful gases such as perfluorocompounds and chlorofluorocarbons is investigated. Perfluorocompounds (PFCs) are gases that contribute to forced global warming and have been favored for wafer etch and chamber clean applications in the semiconductor industry. Chlorofluorocarbons (CFCs) are ozone depleting gases that were used as refrigerants for commercial and domestic condensers and air conditioners, but current reserves still pose threats to environmental sustainability. Increased average global temperatures and further destruction of the ozone layer have prompted proposal of international initiatives such as the Montreal Protocols and the Kyoto Agreement to curtail emissions of such fugitive gases into the environment. These have increased the need for effective abatement technologies to control such emissions and include surface wave plasma abatement, the subject of this dissertation. Surface wave plasmas are considered high frequency non-equilibrium traveling wave discharges in contrast to the more frequently used standing wave discharges. The use of surface wave plasmas have the advantages of a variety of discharge vessel shapes, reproducibility of application, numerous operating conditions and large plasma volumes which ultimately produce low, molecular weight byproducts that are associated with high effective electron temperatures but low heavy particle temperatures. For these reasons, surface wave plasma abatement technology was developed for the destruction and removal of PFCs and CFCs. Results include final destruction and removal efficiencies (DREs) for octafluorocyclobutane greater than 99.8%, dichlorodifluoromethane greater than 99.995% and trichlorofluoromethane greater than 99.999% using moderate applied microwave powers of less than 2000 watts with the production of low molecular weight byproducts, such as CO2, CO, HF and HCl, that prevent environmentally harmful process emissions from entering the atmosphere. Characterizations of the initial and final products were accomplished by the use of Fourier transform infrared spectroscopy and quadrupole mass spectrometry to provide independent quantitative analyses of plasma processes. In addition to these analytical methods, Global_Kin a kinetic model, of plasma reactions were conducted and compared to all the experimental data determined in order to facilitate understanding of the chemistry involved in the surface wave plasma abatement applications studied. Basic plasma reaction mechanisms were determined for the abatement of octafluorocyclobutane and dichlorodifluoromethane.