Instabilities in electronegative ICP-type discharges
Abstract
Electronegative ICPs are widely used for plasma processing. The stability of such discharges is a key problem to control the process and its reproducibility. We have studied the stability of an Ar/SF6 inductively coupled discharge originally designed for helicon operation. For most of the usual operating conditions, the discharge is unstable with strong modulation of the plasma parameters. Two different instabilities have been identified: source oscillations (E-H relaxation oscillations) [1] and downstream instabilities due to the opposite flows of negative and positive ions [2]. For the latter, spatial measurements show a narrow region (in the downstream region) of abrupt change in the time-averaged plasma parameters. This region is unsteady and separates a weak electronegative plasma (upstream) and a high electronegative plasma (downstream). The dynamics of the fluctuations are currently investigated using time resolved probe measurements. [1] Lieberman et al. 1999 App. Phys. Lett 75 3617 [2] Tuszewski et al. 2003 Phys. Plasmas 10 539
- Publication:
-
APS Annual Gaseous Electronics Meeting Abstracts
- Pub Date:
- September 2004
- Bibcode:
- 2004APS..GECKM1001P