Effect of gas and cathode material on the r.f. hollow cathode reactive PVD

The process of generation of the radio frequency (r.f.) hollow cathode discharge was examined for different gases and different materials of the r.f. electrode. The delivered r.f. power range used in the experiments enabled analysis of the hollow cathode discharge development together with the transition into the hollow cathode are for selected combinations of cathode materials and gases. The results for combinations of argon, nitrogen and Al and Ti electrodes are shown as examples. The threshold r.f power for generation of the hollow cathode discharge, i.e. for the gap-sheath boundary breakdown, depends on the type of gas. With increasing r.f. power, the power dependence of the discharge characteristics exhibits different features for different gases and gas mixtures, which also affects the transition into the are regime. The physical parameters of the target material, e.g. the work function and the melting point, strongly affect the performance of the discharge, too. Reactive deposition, investigated simultaneously with the performance of the discharge, is illustrated by the AIN and Al2O3 film growth. The properties of the r.f. hollow cathode enable the reactive process to be designed with more degrees of freedom with respect to conventional sources. The AIN films with a preferential orientation of (002) were grown without substrate heating. Crystalline phases of transparent stoichiometric alumina films with a typical microhardness of 3300 PN were obtained at a substrate temperature as low as 300 degrees C. (C) 1999 Elsevier Science S.A. All rights reserved.