Theoretical and experimental studies of the bell-jar-top inductively coupled plasma

The present paper describes a systematic study of argon plasmas in a bell-jar inductively coupled plasma (ICP) source over the range of pressure 5-20 mtorr and power input 0.20.5 kW. Experimental measurements as well as results of numerical simulations are presented. The models used in the study include the well-known global balance model (or the global model) as well as a detailed two-dimensional (2-D) fluid model of the system. The global model is able to provide reasonably accurate values for the global electron temperature and plasma density. The 2-D model provides spatial distributions of various plasma parameters that make it possible to compare with data measured in the experiments. The experimental measurements were obtained using a tuned Langmuir double-probe technique to reduce the RF interference and obtain the light versus current (I-V) characteristics of the probe. Time-averaged electron temperature and plasma density were measured for various combinations of pressure and applied RF power. The predictions of the 2-D model were found to be in good qualitative agreement with measured data. It was found that the electron temperature distribution T_e was more or less uniform in the chamber. It was also seen that the electron temperature depends primarily on pressure, but is almost independent of the power input, except in the very low-pressure regime. The plasma density goes up almost linearly with the power input