Reactive DC magnetron sputtering of elemental targets in Ar/N-2 mixtures: relation between the discharge characteristics and the heat of formation ofthe corresponding nitrides

A systematic study of the discharge characteristics of a series of elementa l targets (aluminium, silicon, titanium, chromium, indium, tin) during reac tive magnetron sputtering in Ar/N-2 mixtures has been carried out. Furtherm ore, the deposition rate and some properties (stoichiometry, resistivity, i ndex of refraction) of the nitrides formed have been investigated as a func tion of the nitrogen-to-argon ratio, which has been varied from 0 to 100%. The nitrides prepared from these targets show metallic (TIN, CrN). semicond ucting (Sn3N4, InN) and insulating (AIN, Si3N4) behaviour. The discharge power of the direct current (100 W) and the total sputtering pressure (0.5 Pa) were kept constant during these experiments. The change o f the discharge voltage, which is mainly due to different secondary-electro n emission coefficients for clean and nitrogen-covered target surfaces, sho ws the same trends as the corresponding targets in Ar/O-2 mixtures. The typ e of nitride or oxide does not influence the change of the discharge voltag e. The deposition rates always decrease with increasing nitrogen partial pr essure. The nitrogen partial pressures where stoichiometric nitrides were d eposited depend on the heat of formation (binding energy) of the nitrides. The more noble a target material, the higher the nitrogen pressure for the preparation of the corresponding nitride. The results of this study complet e earlier investigations in our group concerning the reactive magnetron spu ttering of oxides. These measurements are an experimental contribution towa rds a better theory of reactive sputtering. (C) 1999 Elsevier Science S.A. All rights reserved.