Optimization of discharge antenna turn and modulation of EEPFs and plasma parameters in dual-frequency cylindrical ICP source at different gas pressures

Abstract

This paper deals with the optimization of the number of discharge antenna turns N, mainly including the effect of N on the plasma parameters [plasma density ne, effective electron temperature Teff, plasma potential Vp, power transfer efficiency η, and electron energy probability function (EEPF)] in cylindrical inductively coupled plasma (ICP) source, and compares axial and radial distribution of ne with different antenna arrangement topologies, mainly referring to the non-interleaved and interleaved antenna arrangement in cylindrical dual-frequency (DF) ICPs. It is found that the cylindrical DF-ICPs with interleaved antenna arrangement can produce a higher ne due to the superposition effect of the high-frequency (HF) and low-frequency (LF) discharge region. Furthermore, based on the above optimized parameters, an optimized cylindrical DF-ICP with an interleaved antenna arrangement is employed, and the modulations of EEPFs and plasma parameters (ne, Teff, and Vp) in the case of (1) fixed HF power and varying additional LF power and (2) fixed LF power and varying additional HF power correspondingly are investigated and compared at different gas pressures of 1, 15, and 60 mTorr systematically. With the wide gas pressure range from 1 to 60 mTorr considered in a combination with two discharge frequencies of 2 and 13.56 MHz, the DF discharge covers discharge maintenance under different conditions with respect to electron heating mechanisms, e.g., collision-less and collision heating. This is a relatively comprehensive work about cylindrical DF-ICPs, which will provide some insights into the design and plasma parameters modulation of cylindrical DF-ICPs.