An emissive probe with a rhenium filament for measuring plasma potential in a radio frequency oxygen plasma

Plasma potential measurements in a rf inductively coupled oxygen plasma were carried out using an emissive probe with rhenium filaments. Rhenium was chosen because of the remarkable electrical conductivity of its oxide which is 10(8) times higher than tungsten oxide. Using 75 mum diam filaments hot-wire emissive probe measurements of an oxygen plasma potential were performed in pressures of 3-100 mTorr. Due to surface contaminants, filament conditioning was performed in order to allow electron emission. Analysis of time-averaged current-voltage curves yielded the maximum and minimum of the rf fluctuation in the plasma. Axial profiles of the plasma potential fluctuations at 3.3 mTorr show a nearly linear decrease with the distance from the wall, and demonstrate the feasibility for further investigation of oxygen plasmas using rhenium filaments. (C) 2002 American Institute of Physics.