Global model and diagnostic of a low-pressure SF6/Ar inductively coupled plasma

Abstract

A global model has been developed for low-pressure (3–20 mTorr), radio-frequency (rf) (13.56 MHz) inductively coupled plasmas (ICPs), produced in SF6/Ar mixtures. The model is based on a set of mass balance equations for all the species considered, coupled to the discharge power balance equation and the charge neutrality condition. Simulations are used to show the impact of operating conditions, such as the rf power, the pressure and the percentage of argon in the mixture, on the evolution of charged and neutral species. Langmuir probe and optical emission spectroscopy measurements are used to determine the electron temperature and the densities of electrons, ions and atomic fluorine in the SF6/Ar ICPs under study. These data are compared with simulation results obtained from the global model. A satisfactory agreement is found between the simulation results and the measured values of the electron density and temperature, for rf powers in the range 900–1700 W, regardless of the percentage of argon in the mixture. Predictions for the atomic fluorine density (∼1014 cm−3) are in good agreement with experiment, for various rf powers.