Dependence of frequency and pressure on electron energy distribution functions in low pressure plasma

The electron energy distribution functions (EEDF), ionization frequency R-i and mean electron energy <(epsilon)over bar> in a low pressure high frequency (13.56 MHz-1 GHz) discharge in Ar gas have been examined using Monte Carlo method. The dependence of driving frequency on the EEDF, R-i and <(epsilon)over bar> is calculated. As the frequency increases, the lower energy electrons increase significantly because they can not follow the applied high frequency electric field. Then, R-i and <(epsilon)over bar> decrease with increasing frequency. The dependence of pressure on EEDF, R-i and <(epsilon)over bar> under applied frequencies of UHF (500 MHz) and RF (13.56 MHz) is also investigated for actual etching pressures. The EEDF, R-i and <(epsilon)over bar> in the UHF plasma do not depend on the pressure, whereas those in the RF plasma are strongly influenced by the pressure. It is considered that the driving frequency (UHF) is higher than the electron collision frequency in the plasma.