A one-dimensional fluid model for an acetylene RF discharge: a study of the plasma chemistry

A one-dimensional (1-D) fluid model is developed for an RF acetylene discharge. In total, 24 species (neutrals, radicals, electrons, and ions) are considered. For every species, a mass balance equation is solved. Further, the electron energy equation and the Poisson equation are also considered. Reactions taken into account include 19 electron-neutral, one ion-neutral, and 17 neutral-neutral reactions. The reaction rate coefficients of the ion-neutral and neutral-neutral reactions are taken from literature. The rate coefficients of the electron-neutral reactions depend strongly on the average electron energy, and are, therefore, obtained from a simplified Boltzmann equation. The 1-D fluid model yields, among others, information about the densities of the different species in the plasma. The most important neutral species in an acetylene plasma are C₂H₂ and H₂. Further, the radicals C₄H₂, C₆H₂, and C₈H₂ (to a minor extent) are also present at high densities. These higher order carbon radicals are mainly formed in neutral-neutral reactions with C₂H. Other radical species present at high densities are H, C₂H₃, CH₂, and C_xH (with x equal to 2, 4, and 6). The most important ionic species are found to be C₄H₂⁺, C₂H₂⁺, and C₆H₂⁺. Finally, a comparison is made between an acetylene and a methane plasma.