Effects of electron inertia in capacitively coupled radio frequency discharges

Abstract

The effects of the electron inertia on the plasma and sheath dynamics in capacitively coupled rf discharges with frequency ωωpi are investigated (here, ω and ωpi are the rf frequency and bulk ion plasma frequency, respectively). It is found that the effects of the electron inertia on the plasma density and ion velocity in the quasi-neutral region depend on the ratio of the amplitudes of the discharge current Irf and ion current IB=en0Cs (here, e is the unit charge, n0 is the plasma density at center, and Cs is the ion sound speed). If the ratio is small so that Irf/IBmi/me (here, mi and me are ion and electron masses, respectively), the ion and time-averaged electron densities, ion velocity, and electric fields are little affected by the electron inertia. Otherwise, the effects of the electron inertia are significant. It is also shown that the assumption that the electrons obey the Boltzmann distribution in the sheath is invalid when the electron flux flowing to the electrode is significant.