US Patent 7651943 Forming diffusion barriers by annealing copper alloy layers

A method of forming an interconnect structure of an integrated circuit includes providing a semiconductor substrate; forming a dielectric layer over the semiconductor substrate; forming an opening in the dielectric layer; and forming a copper alloy seed layer in the opening. The copper alloy seed layer physically contacts the dielectric layer. The copper alloy seed layer includes copper and an alloying material. The method further includes filling a metallic material in the opening and over the copper alloy seed layer; performing a planarization to remove excess metallic material over the dielectric layer; and performing a thermal anneal to cause the alloying material in the copper alloy seed layer to be segregated from copper.