The adhesion of a diffusion barrier or capping layer to Cu and/or Cu alloy interconnect members is significantly enhanced by treating the exposed surface of the Cu and/or Cu alloy interconnect members with a silane or dichlorosilane plasma to form a layer of copper silicide thereon prior to depositing the capping layer. Embodiments include electroplating or electroless plating Cu or a Cu alloy to fill a damascene opening in a dielectric interlayer, chemical mechanical polishing, treating the exposed surface of the Cu or Cu alloy interconnect member in a silane or dichlorosilane plasma to form the copper silicide layer and depositing a capping layer of silicon nitride thereon.