Optical Emission Spectroscopy of Argon-Fluorocarbon-Oxygen Fed Atmospheric Pressure Dielectric Barrier Discharges

Atmospheric pressure filamentary dielectric barrier discharges (FDBDs) fed with argon, a fluorocarbon compound (i.e. CF4, C3F8, C3F6 and c-C4F8) and O-2 were investigated by optical emission spectroscopy (OES). The UV-Vis spectra of the plasma in argon-fluorocarbon mixtures are characterized by narrow signals from Ar atoms, CF2 and CF fragments and by two continua due to CF2+ and CF3. O-2 addition to the feed gas reduces the emissions of fluorocarbon fragments and results in the appearance of an intense narrow emission at 193 nm and of a broad continuum centred at 290 nm ascribed to ArF and Ar2F excimers, respectively. Any signal from F atoms was not detected under the experimental conditions investigated even though the plasma contains F atoms since the dry etching of silicon substrates, a typical process driven by F atoms, was observed. Some possible explanations of this phenomenon are presented.