Oxidation Resistive Cu Films by Room Temperature Surface Passivation with Thin Ag Layer

Abstract

A displacement-deposited Ag layer was investigated as an oxidation barrier in damascene Cu structure for high performance interconnection. A 40 nm thick bright and continuous Ag film was formed at the surface of electrodeposited Cu by immersing the copper film into the silver displacement solution. The Ag film at Cu surface significantly blocked oxygen diffusion into the Cu film and retarded oxidation. More importantly, an elevated barrier performance for oxygen diffusion through elimination and stuffing of grain boundaries of Cu was observed upon annealing in a 400°C N2 atmosphere. Outward Cu diffusion through Ag layer controlled Cu oxidation when the surface was passivated with Ag layer.