Particle modeling of radiofrequency discharges of SF$_6$

Abstract

The structure of radiofrequency (rf) discharges of SF₆, which includes electrons, positive ions, negative ions, and gas molecules, is examined using the particle-in-cell/Monte Carlo simulation. Electron–neutral collisions, ion–neutral collisions, and positive–negative ion recombination are taken into consideration. An improved ion–molecule collision model is proposed, the use of which reproduces the measured swarm parameters. Results show the double-layer structure typical of the discharge of electronegative gases. Only a small quantity of electrons are involved in SF₆ rf discharges and the main negative species are the negative ions. The loss of negative ions is solely determined by positive–negative ion recombination. The electron temperature in the plasma bulk takes a relatively high value of 5–6 eV.