Electron collisions with the CF3 radical using the R-matrix method

Abstract

Fluorocarbons are the main species used in etching plasmas and their properties are driven by CFx (x = 1-3) radicals. Previous calculations on CF and CF2 show low-lying resonances which may lead to dissociative electron attachment under standard plasma conditions. Here the R-matrix method is used to treat electron collisions with the polyatomic radical CF3 at its equilibrium geometry using a coupled states expansion. These calculations concentrate on obtaining low-energy, sub-10 eV, elastic and excitation crosssections. A CF3- bound state of 1A1 symmetry is detected but no low-lying resonances. These findings suggest that CF3 is unlikely to undergo dissociative electron attachment; the possible consequences of this for etching plasmas are discussed.