Particle simulation of radio-frequency plasma discharges of methane for carbon film deposition

Abstract

Particle-in-cell/Monte Carlo (PIC/MC) simulations of capacitively coupled radio-frequency (RF) glow discharges were carried out for low pressure CH/sub 4/ plasmas. The present computational scheme includes the motions and collisions of both neutral and charged particles. The CH/sub 4/ plasma is modeled by combining a one-dimensional PIC/MC method with a polyatomic particle 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. Space and time dependent results show ionization rate is high at the sheath region. The dissociation rate of CH/sub 4/ is found to be high at the sheath as well as in the plasma bulk. Deposition rate of carbon film is calculated by sampling impinging particles at at the powered electrode. The calculations show that neutral radicals are the major depositing species for the cases studied. Ion energy impinging to the electrode was found to be strongly dependent on the "imposed" dc bias (as opposed to self-bias) voltage for a given RF voltage. Deposition rate was found to be almost independent of the "imposed" dc bias voltage as the RF voltage remained constant.