Electrical characterization of an rf planar magnetron in inert gases

Electrical aspects of an rf planar magnetron discharge in noble gases at pr essures below 50 mTorr are discussed. The electrical parameters of the expe rimental device are measured by a diagnostic system consisting of two probe s, a capacitive voltage divider and a current loop. The measurements of the rf current and voltage and the fast Fourier transform treatment of recorde d signals are used to verify the validity of the 'subtraction' method in or der to estimate the power deposited into the plasma. This technique shows a better power coupling with a metallic target, up to 90% of the rf delivere d power, than for tin insulating target for which the power efficiency hard ly reaches 50%. In addition, the elementary mechanisms sustaining the rf pl anar magnetron discharge are analysed. A transition from a combination of c r ('wave-riding') and gamma (secondary electron emission) regimes above a c ritical pressure to an ct dominant regime at very low pressure is pointed o ut. This phenomenon is explained by the results of a particle-in-cell Monte Carlo collision simulation.