Characterization of pulsed plasma in unbalanced magnetron argon discharge

Abstract

Time-resolved probe measurements have been conducted in a unipolar pulsed dc magnetron system to investigate the temporal evolution of plasma parameters, such as the electron density and the electron temperature, and to determine how the driving frequency and the duty cycle of the dc pulse affect these parameters. A new probe measurement system was employed to perform the time-resolved measurements of I-V characteristic curves and their second derivatives with a maximum time resolution of 100 ns. The measurements were performed in a constant voltage mode, constant current mode, and constant power mode, with various pulse frequencies ranging from 5 kHz to 50 kHz and duty cycles ranging from 10% to 90%, to investigate the detailed temporal evolutions of the electron energy distribution function and the plasma parameters. The results show that as the pulse frequency increases, the electron density and the electron temperature exhibit insignificant changes. However, the reduction of the duty cycles results in a significant increase of the electron temperature, irrespective of the operating mode. A comparison of the measured electron energy distribution functions shows that the increase in the electron temperature is caused by a decrease in the population of trapped low-energy electrons and∕or by an increase in the population of drifting high-energy electrons. This result can be explained by considering the electron heating due to the deep-penetrating cathode sheath.