This article presents experimental evidence of a coupling of power between the rf supply and a collisionless plasma in a capacitively coupled plasma reactor. The reactor is driven in plasma sheath resonance to let high rf currents circulate in the system. These currents allow the formation of strong rf fields inside the nonuniform plasma leading to a double layer with a mechanism similar to the rf plasma sheath at the electrodes. Electrons accelerated by the double layer are very effective in ionizing, because of the increased cross section, and create a dense plasma at low pressures. The power is consequently transferred by the ions accelerated in the electrode sheath to the substrate to be processed with high improvement in both performance and process rate. Diagnostics include a retarding field analyzer on the grounded electrode to measure the energy spectrum of ions hitting the substrate and a capacitive probe to obtain the rf potential variations in the plasma. (C) 2002 American Institute of Physics. References: 19
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