An enhanced operating regime for high frequency capacitive discharges

TL;DR

This paper identifies a new operating regime in high-frequency capacitive discharges where plasma density peaks due to electron sheath synchronization with an applied magnetic field, enhancing device performance.

Contribution

It reveals a novel enhanced operating regime in CCP discharges induced by a weak magnetic field, supported by PIC-MCC simulations and theoretical analysis.

Findings

Plasma density peaks when electron cyclotron frequency equals half the RF frequency.

Electron sheath synchronization leads to increased electron energy and ionization.

The regime can be experimentally verified and improves CCP device efficiency.

Abstract

We report the existence of an enhanced operating regime for a high-frequency, low-pressure capacitively coupled plasma (CCP) discharge in the presence of a weak magnetic field applied parallel to the electrodes. Our PIC-MCC simulations show that the plasma density and ion flux values exhibit a sharp peak when the electron cyclotron frequency equals half of the applied RF frequency. The physical mechanism responsible for this behaviour is traced to a synchronization between the oscillatory motion of the electrode sheath edge and the motion of a set of electrons reflected by this sheath. These electrons gain a substantial amount of energy that causes a concomitant higher ionisation leading to a peak in the ion flux. Our theoretical findings should be easy to verify experimentally in present day CCP devices and could provide useful guidelines for enhancing the operational performance of CCP devices in industrial applications.