Computational investigations of impedance matching for pulsed capacitively coupled plasmas

Abstract This numerical study investigates impedance matching strategies for pulsed capacitively coupled plasmas to address the challenge of realizing high-quality matching of time-dependent plasma impedances in pulsed discharges. We develop a self-consistent simulation framework that couples a kinetic particle-in-cell/Monte Carlo collisions plasma model with an external radio frequency matching circuit. The model evaluates three approaches: fixed set-point matching, ideal time-dependent capacitance tuning, and realistic rate-limited capacitor adjustment. The results demonstrate that due to the rapid change in plasma impedance during the pulse period, fixed set-point matching produces significant impedance mismatch and power reflection throughout the entire pulse discharge process, especially in the first few µ s when the voltage is switched on. Ideal time-dependent capacitance tuning reduces the reflection coefficient to values below 0.01 throughout the pulse cycle and suppresses reflected power to negligible levels ( < 0.01 % for average) across diverse conditions (duty cycles: 10 % –90 % , pulse frequencies: 2.5–10 kHz, pressures: 100–400 mTorr). For practical implementations, a capacitance change rate greater than 0.5 pF µ s −1 is required to keep the reflection coefficient < 0.04 and the average reflected power < 0.1 % . A linear scaling between the adjustment time ( τ lim ) of the matchbox capacitors and the average reflected power is revealed, with the average reflection coefficient following | Γ | ∝ τ lim . Our results provide design guidelines for time-dependent matching networks, highlighting that optimal performance necessitates capacitance adjustment rates aligned with plasma transition dynamics.