Time resolved ultraviolet absorption spectroscopy of pulsed fluorocarbon plasmas

Ultraviolet absorption spectroscopy has been used to quantitatively measure CF2 transients in 1 Torr capacitively coupled pulsed plasmas. Time resolved concentrations were obtained for both tetrafluoroethylene (TFE) and hexafluoropropylene oxide (HFPO) feed gases. In the TFE plasma, the CF2 production kinetics follow a first order rise to concentrations of similar to 10(14)/cm(3). In the plasma afterglow, a net production of CF2 is observed for a few milliseconds before the transient becomes dominated by a second order recombination process. In the HFPO plasma, three distinct regimes are observed in the plasma on time. Two production regimes exist, one presumably due to HFPO dissociation and the second due to an unknown source, beginning about 5 ms into the on time. Finally, the CF2 concentration passes through a maximum and decreases to steady state. The afterglow processes are similar to those observed for TFE. The production observed in the off time is believed to be related to surface processes. (C) 2001 American Institute of Physics.