The influence of matching network on the discharge uniformity of dual-frequency capacitively coupled Ar plasma

An improved L–π type matching network is proposed to optimize the discharge uniformity of dual-frequency capacitively coupled plasma. A combination of the experimental and numerical simulation methods was employed to analyze the discharge characteristics of dual-frequency capacitively (8/100 MHz) coupled argon plasma. Both the low- and high-frequency powers were fixed at 60 W. The electron density, electron temperature, and voltage waveforms were obtained by an experiment, and these parameters were used as input parameters for the L–π-resistor, capacitor, and inductor (RCL) non-linear global model. By varying the capacitance CD1 in the RCL model (CD1 = 1, 3, 5, 7, and 9 pF), the plasma discharge was simulated. The results indicate that as CD1 increases, the oscillation amplitudes of the sheath thickness and sheath capacitance become stable in the latter half of the discharge cycle, and the oscillation waveforms become more regular. The plasma resistance and inductance decrease, while the power transmission efficiency is significantly improved. The introduction of the RCL element significantly reduces the amplitudes and the number of higher-order harmonics in the plasma discharge current, with only the 1st, 12th, and 13th harmonics dominating. Therefore, selecting medium-to-high capacitance values (5, 7, and 9 pF) in the RCL network significantly enhances the stability of the plasma discharge. The optimized matching network effectively improves the uniformity of the plasma discharge for industrial applications.