Thermal effects on plasma characteristics in inductively coupled Ar/O2 discharges: a fluid simulation approach

Abstract

This study investigates the impact of neutral gas heating on plasma characteristics in inductively coupled Ar/O2 discharges using a 2D axisymmetric fluid model incorporating thermal flow and heat transfer. Unlike conventional isothermal models, the model incorporates multiple gas heating pathways, such as Franck-Condon heating, ion-neutral charge exchange, and metastable quenching. The analysis was performed across a wide range of operating conditions, including variations in input power, pressure, and O2 mole fraction. Results show that elevated neutral gas temperatures lead to reduced electron, ion, and radical densities due to decreased neutral density and collision frequency, while simultaneously increasing electron temperature through reduced energy loss mechanisms. Additionally, the temperature gradient induces asymmetric radical transport and wall-localized accumulation, particularly for oxygen radicals, driven by the Soret effect and surface recombination dynamics. 300 K and 500 K isothermal models were compared to demonstrate that neglecting thermal effects may result in significant inaccuracies in predicting plasma behavior. The findings emphasize the critical role of incorporating gas heating and thermal transport in plasma modeling to ensure accurate predictions in semiconductor processing applications.