Systems and methods to retard copper diffusion and improve film adhesion for a dielectric barrier on copper

Two sequential treatments within a chemical vapor deposition chamber, or within sequential chambers without a vacuum break, are performed on a copper layer to clean and passivate the copper surface prior to deposition of a copper diffusion barrier layer or a dielectric layer. The first treatment includes an ammonia, a hydrogen, or a hydrocarbon plasma cleaning of the copper surface followed by a short initiation of an organosilane precursor or a thin silicon nitride layer. A copper diffusion barrier layer may then be formed over the pretreated copper surface using an organosilane plasma, with or without a carbon dioxide or a carbon monoxide, or a silane with a nitrogen gas and an ammonia gas. Copper diffusion is retarded and film adhesion is improved for a dielectric layer or a copper diffusion barrier layer on the copper surface.