Modeling of RF plasma discharges of CH/sub 4/ for carbon film deposition

Abstract

Summary form only given. Low pressure radio-frequency (RF) discharges are used for a wide variety of thin film fabrication processes. Particle-in-cell/Monte Carlo simulations of one dimensional capacitively coupled RF (radio-frequency) glow discharges were carried out for low pressure CH/sub 4/ plasmas. The present scheme includes the motions and collisions of both neutrals and charged particles. CH/sub 4/ plasma is modeled combining PIC/MC method with a polyatomic gas collision scheme. The model considers the motions of CH/sub 4/, CH/sub 4//sup +/, CH/sub 3/, C/sub 2/H/sub 5/, H/sub 2/, H and electrons. The model comprises of binary collisions of neutrals, ions, and electrons with neutrals. Electron-electron, electron-ion, and ion-ion collisions were neglected in the present study as the probability of such collisions are small in a weakly ionized plasma. For neutral-electron collisions, elastic scattering, excitation, and ionizing collisions are considered. Charge exchange and ionization collision for ion-neutral collision, and elastic scattering for neutral-neutral collisions are considered. In each collision process total momentum is conserved. Total energy of collision pairs in elastic collisions is conserved, while energy is lost in excitation and ionization processes. Ionization and excitation process are assumed to take place when total energy of the collision pair exceeds a threshold energy. Thus this model accounts for the collision effects of electrons and ions on neutral motion. Anisotropic angular scattering is incorporated with the relative differential cross section for all electron and neutral collisions. Space and time dependent results show ionization rate is high at sheath edge while dissociation rate is also high in the plasma bulk.