Patent ID: 7422979

Claim:
A method of forming a semiconductor device, the method comprising steps of: providing a semiconductor substrate; forming a conductor over the semiconductor substrate, wherein the conductor comprises copper; forming a diffusion barrier stack over the conductor, wherein forming the diffusion barrier stack comprises: forming a layer comprising a metal over the conductor, wherein the layer comprises a first element, a second element, and a third element, wherein: the first element is cobalt (Co) or nickel (Ni) the second element is tungsten (W), rhenium (Re) or molybdenum (Mo), and the third element is boron (B) or phosphorous (P); forming a first dielectric layer substantially devoid of oxygen over the layer, wherein forming the first dielectric layer further comprises forming a first dielectric layer having a thickness less than 20 nanometers, wherein the first dielectric layer has dielectric constant that is less than the dielectric constant of stoichiometric silicon nitride, and wherein: when forming the first dielectric layer, the layer comprising the metal has a substantially uniform thickness between the conductor and the first dielectric layer; and the first dielectric layer is of a thickness that alone it can not serve as a diffusion barrier layer to the conductor; and forming a second dielectric layer over the diffusion barrier stack, wherein the second dielectric layer includes silicon carbide nitride (SiCN).