Characteristics of electron energy distribution function of capacitively coupled plasma excited by 60MHz RF source

Abstract

Capacitively coupled plasma (CCP) source excited by very-high-frequency (VHF) source has attracted much attention in semiconductor industry due to its ability to generate high density plasma with a large area. The electron behavior and discharge properties of capacitively coupled plasma excited by 60MHz RF source were investigated by using current and voltage probe and Langmuir probe techniques. The experimental results show that equivalent resistance or capacitance of capacitively coupled plasma decreases or increases, respectively, with the increment of input RF power. It is also shown that the electron behavior in the plasma is related not only with RF input power but also discharge pressure. Increase in pressure causes the transition of electron energy distribution function from Bi-Maxwellian type to Druyvesteyn type, with its transition pressure much lower than that reported by others, which is due to a great decrease in efficiency of electron bounced resonance heating in CCP driven by 60MHz.