Investigation of dual-frequency effect on the ion energy and flux in Torr-regime plasma by a two-dimensional GPU-PIC simulation

Abstract

Dual frequency (DF) capacitively coupled plasma (CCP) equipment has been widely used in semiconductor processing and requires particle-in-cell (PIC) simulations to investigate the nonlinear particle dynamics. It is believed that DF driving controls the electron density and ion energy separately, but a strong coupling exists between the two frequencies in reality. The two-dimensional (2D) PIC simulation of DF CCPs under deposition process conditions has not yet been reported due to the heavy computational load that can be resolved with a graphics processing unit (GPU) computation. This study quantitatively investigates the Torr-regime DF CCP using a 2D GPU-PIC simulation. The increase of the low-frequency (LF) power enhances ion transport, which results in the rise of plasma potential, the increase of sheath thickness, and the reduction of the electron density. The ions exhibit the Maxwellian distribution due to the frequent charge-exchange collisions. The ion flux keeps uniformity while electron density becomes abruptly nonuniform with the increase of the LF power, which is suitable to maintain the quality of deposited films.