Control of plasma profile by voltage biasing in large diameter RF producedplasma

Control of plasma profile by voltage biasing to the various inserted electr odes was tried in the large diameter RF produced plasma in a wide range of filling pressure P. With an addition of positive DC biasing voltage V of 30 V on the metal disk (P = 20 mTorr), an increase in the ion saturation curr ent by 20% was obtained near the central plasma region, while for the negat ive biasing case this saturation current changed little. For the case of bi asing the inner one of two concentric cylinders to V = 20 V, a drastic incr ease in the ion saturation current near the central plasma region by 60% wa s observed. Optical measurements on Ar I and Ar II line intensities exhibit ed consistent results with the probe data. In the lower filling pressure re gion (P = 0.09 mTorr) with the use of the ring- and disk-type electrodes, t he voltage biasing showed pronounced effects on changing ion saturation cur rent profiles. (C) 1999 Elsevier Science S.A. All rights reserved.