Self-consistent global model for inductively coupled argon plasmas used in ion beam processing

Abstract

Ion beam processing applications require adjustments to the process parameters, in order to operate efficiently and with the optimal precision. Global plasma models offer a fast and reliable approach, to characterize and optimize such ion beam sources. In the scope of this work, a self-consistent global plasma model for inductively coupled plasmas (ICPs) using argon as process gas was developed. Targeting surface modification applications in particular, two novel features are implemented and investigated, describing the ion beam extraction process. The plasma boundary above extraction apertures is calculated in an iterative scheme, solving the balance between extracted ions and charge carriers inside the plasma volume self-consistently. Combined with consideration of spatial varying plasma densities, the model is able to predict plasma properties and extracted ion currents for arbitrary ICP systems, extraction geometries and operating conditions. Thereby, multiple ion beam source configurations validate the model, by comparing simulation results with experimentally investigated plasma and ion beam properties, obtained by electrical measurements and Langmuir probe diagnostics in the low pressure environment (pch = 0.06 −0.12 Pa) of multiple vacuum chambers.