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 resolve d concentrations were obtained for both tetrafluoroethylene (TFE) and hexaf luoropropylene oxide (HFPO) feed gases. In the TFE plasma, the CF2 producti on 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 obser ved in the plasma on time. Two production regimes exist, one presumably due to HFPO dissociation and the second due to an unknown source, beginning ab out 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 belie ved to be related to surface processes. (C) 2001 American Institute of Phys ics.