Spatial distributions of the ion flux in a capacitive hydrogen RF discharge using a hollow cathode with double toroidal grooves enclosed by magnets

Abstract

A hydrogen high-density capacitively coupled plasma has been developed using a hollow cathode with double toroidal grooves enclosed by magnets and without an iron yoke disk. It is found that this plasma source allows generating higher plasma densities compared to the conventional RF magnetron plasma sources. Spatial distributions of the ion flux have been measured at various H2 gas pressures, p, of 1–20 Pa. It is found that the hybrid combination of a hollow cathode effect and magnetic confinement of electrons is attained for p ≥ 5 Pa, while for p ≤ 3 Pa, a conventional capacitive discharge is generated. The radial profile of the ion flux becomes uniform with increasing axial distance from the target for the hollow cathode discharge. The characteristic decay length of the roughness of the ion flux profile increases with increasing the gas pressure.