Plasma-relevant fast electron impact study of trifluoromethane

Abstract

Abstract Trifluoromethane is an important etching gas in semiconductor industries as the fluorine source in reactive etching plasma. Electron impact excitations into the dissociation states are essential for plasma modeling. By employing an angle-resolved electron energy loss spectrometer, the generalized oscillator strengths (GOSs) for the valence-shell excited states have been determined at an absolute scale utilizing the crossed-beam based relative flow technique. The measurement was performed with an incident electron energy of 1500 eV at an energy resolution of about 70 meV. The corresponding optical oscillator strengths are also obtained by extrapolating the measured GOSs to the limit of zero momentum transfer. The extrapolated data and fitted linewidths are used to reproduce the photoabsorption spectra and compare with the available experimental and theoretical results. In addition, the integral cross sections from the excitation threshold to 5000 eV of the associated excited states have been derived by using the BE-scaling method. The resulted data can not only be used in plasma models but also serve as a benchmark for further theoretical calculations.