Energy partitioning and its influence on surface scatter coefficients within fluorinated inductively coupled plasmas

Abstract

Energy partitioning for molecules formed from fluorinated plasma systems has been measured using laser-induced fluorescence, optical emission, and broadband absorption spectroscopies. For the two radicals discussed here, SiF in tetrafluorosilane plasmas, and CF in CxFy-type fluorocarbon plasmas, high electronic excited state vibrational temperatures, TV, suggest that vibrational modes are preferentially excited over other degrees of freedom. In CxFy plasma systems, rotational temperatures, TR, for the radicals equilibrate to the plasma gas temperature and remain independent of changing plasma parameters. TR for ground state CF2 molecules are elevated in comparison to the excited state radical. Translational temperatures (TT) and TR for SiF increase concomitantly with increasing vibrational temperatures, suggesting that a vibrational-translational energy exchange mechanism is the preferred pathway for vibrational relaxation in these molecules and rotational degrees of freedom are more easily thermalized compared to vibrational modes. Using the imaging of radicals interacting with surfaces technique, surface scattering coefficients measured for each radical show a strong correlation with the associated TV, with little dependence upon TR or TT. Ultimately, this work provides fundamental, molecular-level understanding of fluorinated plasma systems and helps to reveal the complex interactions between the distribution of energy within the plasma and its influence at a surface.