Detachment-induced electron production in the early afterglow of pulsed cc-rf oxygen plasmas

作者：Kuellig C^*; Dittmann K; Meichsner J

来源：Physics of Plasmas, 2012, 19(7): 073517.

DOI：10.1063/1.4737196

Line integrated electron densities are measured by 160.28 GHz Gaussian beam microwave interferometry in a 10 Hz pulsed (50% duty cycle) cc-rf oxygen discharge, operating at 13.56 MHz. Depending on the processing parameters, the oxygen rf discharge displays two different operation modes regarding its electronegativity. For higher rf power with negative self-bias voltage above -220V, the oxygen discharge acts as electropositive plasma (n_/n(e) %26lt;%26lt; 1), whereas at lower rf power and self-bias voltage the plasma becomes strongly electronegative (n_/n(e) %26gt; 2). In the latter mode, a significant electron density increase is measured in the early afterglow (%26lt;100 mu s) within a pressure range from 20 to 100 Pa. By use of a simple rate equation model, the temporal behavior of the electron density could be reproduced for both modes of electronegativity. The electron production in the early afterglow is mainly caused due to the detachment of negative atomic oxygen ions by metastable oxygen molecules.

• 出版日期2012-7