Evaluation of absolute charge density at the bottom of high aspect capillary holes exposed to a pulsed very high frequency plasma

Abstract

Absolute values of the surface charge densities at the top and bottom of a capillary plate (CP) placed on a powered electrode were evaluated under the influence of pulse-modulated very high frequency (40 MHz) plasma. The peak-to-peak voltage at the top and bottom of the CP was measured using a high-voltage probe; this voltage was carefully calibrated, removing the influence of probe impedance. Based on the peak-to-peak voltage, the capacitances of the sheath and the CP were evaluated. Based on the average voltage, the surface charge density was evaluated for the plasma-on and off phases. A charge density of the order of 10−5 C m−2 was obtained at the bottom of the CP. Furthermore, two important observations were made during the plasma-off phase, namely: conservation of the surface charge density at the bottom of the CP and presence of the residual negative surface charge at the top of the CP.