Reduction of electron heating in the low-frequency anomalous-skin-effect regime.

It is known that electron thermal motion in the anomalous-skin-effect regime of rf plasma discharges leads to enhancement of rf power absorption by plasma due to the resonant electron-wave interaction, which is a main mechanism of plasma heating in a typical inductively coupled plasma discharge. In this Letter we show, however, that the rf power absorption may be strongly reduced (compared to the Ohmic value) at low frequencies due to the electron thermal motion; an even further reduction occurs due to the nonlinear effects of the rf magnetic field. The absorption reduction occurs for omega<nu<v(th)/delta (omega is a driving frequency of rf wave, nu is the collision frequency, v(th) is the thermal velocity, and delta is characteristic skin depth of the wave) and may be observed in low pressure inductive plasmas driven at low frequency and in a dc plasma with strong field inhomogeneity.