Mixed Schottky/p-n junction behavior in diodes produced by outdiffusion from polycrystalline cobalt disilicide

Abstract

Measurements of junctions outdiffused from polycrystalline cobalt disilicide reveal mixed Schottky barrier/p-n junction behavior. Further analysis finds that thin epitaxial silicide regions form along the silicide/silicon interface. This inhibits dopant outdiffusion in the middle of the silicide structure, while dopant outdiffusion at the edges is almost completely blocked. This results in a silicide Schottky contact to a weakly outdiffused region in the middle of such a structure, and a silicide contact to the background doping at the edges. In large area structures, a p-n junction between the weakly outdiffused region and the background doping is present. In narrow structures, no p-n junction forms, and only a direct silicide contact to the background doping is produced. The junctions produced show very variable leakage characteristics and high edge leakage.