Electron collisions with CF radicals using the R-matrix method

Radicals CF (x=1-3) are formed in the upper atmosphere by photolysis of fluorocarbons the bulk of which are generated in the plasma industry. Fluorocarbon plasmas are used in plasma etching technology and surface modification of materials. Many of the processes that occur in these plasmas are poorly characterized and understood, providing a significant roadblock for the construction of reliable models of the etching process. In order to construct/develop models of electron driven processes in such plasma reactors it is necessary to investigate electron interaction with the product radicals (CF ). This has to be done theoretically since it is not currently possible to prepare such radicals with sufficient number densities for electron beam experiments to be performed. The purpose of the work presented in this thesis is to develop a full description of the electron collision processes with the radicals CF at the energies below 10 eV. Particular emphasis is given to determining the formation of resonances in the energy region around 2 eV, as this is the typical energy in industrial etching plasmas. The first ab initio calculations of total elastic and electron impact excitation cross sections have been performed for the CF, CF and CF radicals. The quality of the scattering model depends on a satisfactory representation of the target. Deriving the target parameters is, therefore, a necessary precursor to scattering calculations. The first data on vertical excitation energies for the CF radical are calculated. The first potential energy curves for the CF radical are also obtained. Electron scattering resonances are identified for CF and CF . These are analysed and assigned. Scattering electron – CF system has no low-lying resonances. Low energy electron molecule collisions are often accompanied by negative ionic states, which are important for etching plasmas, as they support possible dissociation processes.