Study of the electromigration behaviour of Au-Ag thin films deposited on SiO2 substrate using AES, XPS and AFM techniques

The purpose of this work was to study surface diffusion of atoms in Bu-Ag f ilms deposited on SiO2 substrate under the action of a d.c. field, focusing on the effect of chemical reaction at the Au-Ag/SiO2 interface on the elec tromigration behaviour. Atomic force microscopy measurement depicted the ti me evolution of topography of Au-Ag film from uniformly distributed islands to a patch structure upon application of a d.c. current. This was accompan ied by the binding energy shifts of Au 4f and Ag 3d photoelcctrons due to s urface charging during XPS analysis. Auger line scanning showed that the el ectromigration direction of Au atoms in Au-Ag film changed from being prefe rential towards the anode to the cathode when the substrate Si(111) was rep laced by SiO2. However, the electromigration direction of Ag atoms in the s ame Au-Ag film was independent of the substrate. A possible chemical reacti on at the interface between Au-Ag and SiO2 substrate was observed by angle- dependent XPS analysis. The reacted Si product diffused to and segregated a t the patch boundaries of the Au-Ag film, possibly forming the silicide AuS ix. Copyright (C) 1999 John Wiley & Sons, Ltd.