Study of the electromigration behaviour of Au–Ag thin films deposited on SiO 2 substrate using AES, XPS and AFM techniques

Abstract

The purpose of this work was to study surface diffusion of atoms in Au-Ag films deposited on SiO 2 substrate under the action of a d.c. field, focusing on the effect of chemical reaction at the Au-Ag/SiO 2 interface on the electromigration behaviour. Atomic force microscopy measurement depicted the time evolution of topography of Au-Ag film from uniformly distributed islands to a patch structure upon application of a d.c. current. This was accompanied by the binding energy shifts of Au 4f and Ag 3d photoelectrons due to surface charging during XPS analysis. Auger line scanning showed that the electromigration direction of Au atoms in Au-Ag film changed from being preferential towards the anode to the cathode when the substrate Si(111) was replaced by SiO 2 . However, the electromigration direction of Ag atoms in the same Au-Ag film was independent of the substrate. A possible chemical reaction at the interface between Au-Ag and SiO 2 substrate was observed by angle-dependent XPS analysis. The reacted Si product diffused to and segregated at the patch boundaries of the Au-Ag film, possibly forming the silicide AuSi x .