Electron interactions with CF4

Carbon tetrafluoride (CF4) is one of the most widely used components of feed gas mixtures employed for a variety of plasma-assisted material-processing applications. It has no stable excited states and, in a plasma environment, is an ideal source of reactive species, especially F atoms. To assess the behavior of CF4 in its use in manufacturing semiconductor devices and other applications, it is necessary to have accurate information about its fundamental properties and reactions, particularly its electronic and ionic interactions and its electron collision processes at low energies (< 100 eV). In this article we assess and synthesize the available information on the cross sections and/or the rate coefficients for collisional interactions of CF4 with electrons. Assessed information is presented on: (i) cross sections for electron scattering (total, momentum, elastic differential, elastic integral, inelastic), electron-impact ionization (total, partial, multiple, dissociative), electron-impact dissociation (total, and for dissociative excitation), and electron attachment (total, and for specific anions); (ii) coefficients for electron transport (electron drift velocity, transverse and longitudinal electron diffusion coefficients), electron attachment, and electron-impact ionization; and (iii) cross section sets derived from analyses of electron transport data. The limited ionization data on CF4 radicals are also presented, and references are made to measurements of electron transport properties of CF4 gas mixtures. Based upon the assessment of published experimental data, recommended values for various cross sections and coefficients are generated which are presented in graphical and tabular form. (C) 1996 American Institute of Physics and American Chemical Society.