Surface production of CF, CF2, and C2 radicals in high-density CF4/H2 plasmas

Abstract

Surface production of CF, CF2, and C2 radicals in high-density CF4/H2 plasmas was examined using laser-induced fluorescence spectroscopy. No significant amount of surface production was observed in pure CF4 plasmas. The addition of H2 into CF4 plasmas enhanced the surface production of CFx and C2 from fluorocarbon film deposited on the chamber wall. The characteristics of the surface production in cw discharges are reported, in comparison with surface production in pulsed discharges. In addition, it has been found that the surface production rates are determined not by the partial pressure but by the flow rate of H2, suggesting the significant consumption of feedstock H2 in discharges. The surface production of CFx and C2 indicates that these radicals are not the precursors for the deposition of fluorocarbon film in the CF4/H2 plasma. The deposition mechanism of fluorocarbon film in the CF4/H2 plasma is discussed, taking into account the surface production of CFx and C2.