Reactor optimization strategies for remote plasma sources: Numerical insights into argon inductively coupled plasma at Torr pressures

The semiconductor industry increasingly relies on remote plasma sources (RPS) for advanced processing techniques. In this study, we numerically explored the performance optimization of inductively coupled plasma at pressures above 1 Torr, suitable for RPS applications. Using a two-dimensional fluid model, we examined how process parameters affect plasma density and analyzed the contributions of various chemical reactions to plasma density changes in an argon discharge. Our findings show that increasing radio frequency (RF) power, gas pressure, and flow rate elevates electron and ion densities in the downstream region of the RPS. The increase in RF power generates strong inductive heating, which leads to convective transport of thermal energy in the downstream region of the RPS. This transferred thermal energy is expected to efficiently transfer radicals downstream through dissociation reactions with low threshold energy. Increased flow rates boost ion flux and improve axial electron transport, while elevated pressures lower electron temperatures and reduce the ambipolar field. We also observed that ion distribution is influenced by multi-component diffusion downstream. Thus, optimizing power, flow rate, and pressure enhances radical transport efficiency to the lower stage of the RPS. These results were validated experimentally using a Langmuir probe in argon discharge, confirming our numerical predictions.