Self-consistent particle simulation of radio frequency CF4 discharge:: Effect of gas pressure

The dependence of structure of rf CF4 discharge on gas pressure is investigated using the Particle-in-Cell/Monte Carlo method. When the pressure is decreased, the discharge suddenly changes from electronegative to electropositive. For instance, the electron density increases in excess of negative ion density, and double layer and oscillation of bulk electric field disappear. Therefore, joule heating in the bulk disappears, resulting in an abnormally low electron temperature. The high ionization rate in the bulk under low electron temperature can be explained based on the electron energy probability function.