Electrical conductivity in high frequency plasmas

Summary form only given. The electrical conductivity is an important parameter in understanding the mechanism by which power is coupled to a radio frequency discharge plasma, as well as in determining the external electrical characteristics of the discharge. In this paper, we present the results of computations of the resistive and reactive components of the collisional impedance of an argon plasma at 13.56 MHz. The collisional electrical conductivity /spl sigma//sub e/, expresses the relation between the local current density j in the discharge and the local electric field E through Ohm´s law, j=/spl sigma//sub e/E. We have computed /spl sigma//sub e/ from the two-term solution to the Boltzmann equation, including the velocity dependence of the electron collision frequency, as well as non-Maxwellian EEDFs. Our results show that neither of the classical limiting expressions are adequate for discharge pressures in the range of few mTorr to a few Torr, which includes the region of operation for many rf discharges used in many applications of plasma technology. Further, the classical formula assumes that in the high frequency limit the plasma reactance is due entirely to electron inertia. We demonstrate that the plasma reactance may be strongly influenced, and in some cases dominated, by electron collisions.