Spatiotemporal evolution of pulsed modulated Ar/O2 plasma in inductively coupled plasmas

Conventional pulsed plasma discharges commonly suffer from slow ignition, limited controllability of plasma density and radial uniformity, and poor discharge stability. In this work, a fluid model is employed to systematically investigate the spatiotemporal evolution of Ar/O2 inductively coupled plasmas (ICPs) under pulsed dual-frequency modulation. The two-dimensional transient evolution of species density and the corresponding plasma chemistry within one pulse cycle are analyzed, and the effects of pulse duty cycle and O2 ratio on plasma discharge characteristics are discussed. Compared with conventional continuous-wave discharges, pulsed dual-frequency modulation can effectively enhance plasma density and radial uniformity and avoid the ignition delay typically observed in conventional single-pulse discharges. Within one pulse cycle, the electron density exhibits an overshoot behavior characterized by a transient rise-drop-rise evolution, and the ion densities show a similar temporal response. The overshoot becomes less pronounced with increasing duty cycle and O2 ratio, owing to the gradual approach to quasi-steady discharge conditions at high duty cycle and the reduction in electron density at high oxygen content. In addition, the ion flux is found to depend on both the pulse duty cycle and the O2 ratio. This research contributes to a better understanding of transient plasma dynamics in pulsed dual-frequency ICP and provides a reference for discharge optimization and process control.