Characterization of an asymmetric parallel plate radio-frequency discharge using a retarding field energy analyzer

A retarding field energy analyzer is used to characterize an asymmetric, 13.56 MHz driven, capacitively coupled, parallel plate discharge operated at low pressure. The characterization is carried out in argon discharges at 10 and 20 mTorr where the sheaths are assumed to be collisionless. The analyzer is set in the powered electrode where the impacting ion and electron energy distributions are measured for a range of discharge powers. A circuit model of the discharge is used to infer important electrical parameters from the measured energy distributions, including electrode excitation voltages, plasma potential and sheath potentials. Analytical models of the ion energy distribution in a radio-frequency sheath are used to determine plasma parameters such as sheath width, ion transit time, electron temperature and ion flux. A radio-frequency compensated Langmuir probe is used for comparison with the retarding field analyzer measurements.