Influence of Matching Network on the Discharge Characteristic of Dual—Frequency Capacitively Coupled Ar Plasma

Abstract

This paper examines the impact of different type external matching networks on the discharge characteristics of dual‐frequency capacitively coupled plasma. A nonlinear global model is employed to analyze the discharge of dual‐frequency capacitively coupled argon plasma, with a low frequency of 8 MHz and 60 W and a high frequency of 100 MHz at 10–80 W. Discharge voltage waveforms, current waveforms, and emission spectra of the plasma were measured, while electron density and electron temperature were determined using the Boltzmann method. The electron density and electron temperature are utilized as input parameters for the nonlinear global model, while the plasma discharge is simulated with a fixed low‐frequency radio frequency (RF) source power (60 W) and a varied high‐frequency RF source power ranging from 10 to 80 W. The results indicate that the plasma discharge current, sheath capacitance, plasma resistance, plasma inductance, and the ratio of stochastic heating to Ohmic heating increase, while the sheath thickness decreases with increasing power. It is also found that the fundamental frequency current as well as 12th and 13th harmonic currents in the plasma are caused by the matching network and the nonlinear interaction between the sheath and the plasma. An optimal matching network can be designed to eliminate the effects of the harmonics and to meet industrial requirements for discharge uniformity.