Discharge similarity in capacitive radio frequency carbon tetrafluoride plasmas

Abstract

Although similarity laws for breakdown have been demonstrated for molecular gases (e.g., N2 and NF3), their application to rf plasmas in electronegative gases remains unexplored. In this Letter, we report the discharge similarities in steady-state CF4 rf plasmas via fully kinetic particle-in-cell simulations. The results show that the rf discharges of different dimensional scales obey the similarity law in both the striation mode and drift-ambipolar mode when the similarity conditions are fulfilled with the scaling factor k being relatively small (e.g., k ⩽ 2). As the scaling factor k increases, violations caused by “nonlinear collisions” become important, and deviations from the similarity are observed. The nondimensional parameters, ηω and ηn, for characterizing the formation of the striation mode are evaluated for understanding the mode transitions under similar discharge conditions.