Extinction simulation of capacitively coupled plasma under different afterglow voltage

Abstract Extinction is an inevitable process in the discharge of capacitively coupled plasma and frequently occurs many times in some special discharges, such as pulse-driven discharges. However, this indispensable process has rarely been studied in detail. In this study, based on the particle-in-cell/Monte-Carlo collision algorithm, this process is demonstrated and studied. The extinction evolution of electron density, energy under different external circuit, voltage decay time, and different pressure are first given and analyzed. The whole extinction process may take the slow diffusion of electrons, which can take hundreds of microseconds and even milliseconds, and will take much longer time under high pressure. Longer decay time of rf voltage will shorten the extinction. Three-body recombination cannot be ignored at 20 mTorr lower pressure. Furthermore, the effects of the voltage suddenly changes from a high sustaining voltage (pre-voltage) of 200 V to lower extinction voltage (post-voltage) are observed. The plasma will extinguish at a much faster speed under the lower post-voltage of several volt than directly switched off. The extinction process driven by different post-voltages under different background pressures was also examined. There is a minimum sustaining voltage at the middle pressure of about 100 mTorr, and post-voltage (several volts to tens of volts) to minimize the extinction time. These results may provide a reference for optimizing the radio-frequency (rf) power sources of the rf pulse-driven plasma sources to reduce extinction time.