A novel electrostatic probe method for ion flux measurements

A novel electrostatic probe method is described in which the ion flux is determined from the discharging of an RF-biased capacitance in series with the probe. By using a large-area planar probe, with a guard ring and located in or on other surfaces, edge effects and perturbations to the plasma volume can be kept small. The ion flux to the probe can be determined even when its surface is coated with insulating material from the plasma itself. Results are reported for ion fluxes in RF-excited plasmas in Ar and in CF4 in a RIE reactor. In Ar, ion fluxes to the earthed surfaces increase with pressure and power over the ranges 50-200 mTorr and 30-200 W. In CF4, over the same ranges the ion fluxes to the surfaces decrease with increasing pressure.