Mechanisms of voltage controlled, reactive, planar magnetron sputtering of Al in Ar/N2 and Ar/O2 atmospheres

Abstract

The relationships between processes occurring on the target surface, substrate surface, and in the glow discharge of a dc planar magnetron are studied for the purpose of controlling film stoichiometry. The positive feedback mechanisms which lead to the well-known transitions between bare and covered target surfaces are correlated with glow discharge characteristics. These data are found in agreement with a model we have developed which allows for two distinct mechanisms of target coverage: chemisorption, and ion plating of reactive gas species to the target surface. This model allows estimation of the stability of the glow discharge against these positive feedback mechanisms, which indicates under what circumstances voltage control of the glow discharge will permit operation at all degrees of target coverage without abrupt transitions between the extreme states of target coverage. It is shown that with this method of voltage control there is a one-to-one relationship between cathode voltage and film stoichiometry. Futhermore, a method is presented for calculating the film composition from the glow discharge characteristics alone and, related to this, a single target technique for producing thin film cermets is presented.