Two-dimensional PIC-MCC simulations of a capacitively coupled radio frequency discharge in methane

A two-dimensional capacitively coupled radio frequency discharge in methane is simulated by the PIC-MCC method. The results were obtained in the pressure range 50-300 mTorr and the voltage range 40-180 V for a discharge frequency of 13.56 MHz. The electron energy and electron-methane reaction rate spatial distributions show the existence of two regimes of discharge glow: (a) with active sheaths, when electrons are hot in electrode sheaths and cold in the middle of discharge so that the electron-neutral reactions strongly dominate in the sheath regions; (b) with volume domination, when the electron energy is more uniform and the reactions take place over the total discharge volume. The second regime is usually observed for low discharge voltages, and turns to the first one with increasing voltage. In addition, simulation of chemical reactions in the methane plasma was performed to find the gas mixture composition in the discharge volume. The results are in agreement with the known experimental data.