Synthesis and characterization of electroless deposited Co–W–P thin films as diffusion barrier layer

Selective barriers against copper diffusion deposited by electroless reaction are interesting in term of electromigration. In this article, the barrier layer of cobalt–tungsten–phosphorus (Co–W–P) alloy was electroless deposited onto copper substrates for ultra large scale integration (ULSI) applications. The Co–W–P thin film was formed directly on copper, without a palladium catalyst, from citrate plating baths with sodium hypophosphite as reducing agents. The influence of tungsten addition on the barrier properties has been studied and the optimum conditions to obtain films with the highest oxidation protection have been determined. Co–W–P layer properties such as chemical composition, surface morphology, and phase structure and corrosion behavior have been investigated. The deposited CoWP layer showed higher oxidation and corrosion resistance and soft magnetic behavior.