Properties of highly electronegative plasmas produced in a multipolar magnetic-confined device with a transversal magnetic filter

Mihai Draghici (1) , Eugen Stamate (2)

1 Risø DTU - Risø National Laboratory for Sustainable Energy
2 National Institute of Materials Physics

Highly electronegative plasmas were produced in Ar/SF 6 gas mixtures in a DC discharge with multipolar magnetic confinement and transversal magnetic filter. Langmuir probe and mass spectroscopy were used for plasma diagnostics. Plasma potential drift, the influence of small or large area biased electrodes on plasma parameters, the formation of the negative ion sheath, and etching rates by positive and negative ions have been investigated for different experimental conditions. Reducing the electron temperature below 1 eV the density ratio of negative ion to electron exceeded 100 even for very low amounts of SF 6 gas. The plasma potential drift could be controlled by proper wall conditioning. A large-electrode biased positively had no effect on plasma potential for density ratios of negative ion to electrons larger than 50. For similar electronegativities or higher a negative ion sheath could be formed by applying a positive bias of a few hundred volts.

Mots clés: negative ions; ion-ion plasma; Ar/SF 6 plasma; plasma diagnostics

Mihai Draghici, Eugen Stamate. Properties of highly electronegative plasmas produced in a multipolar magnetic-confined device with a transversal magnetic filter. Journal of Physics D: Applied Physics, 2010, 43 (15), pp.155205. ⟨10.1088/0022-3727/43/15/155205⟩. ⟨hal-00569576⟩