Method for forming interconnect structures

Methods of fabricating interconnect structures in a semiconductor integrated circuit (IC) are presented. A preferred embodiment comprises forming interconnect lines and vias through a dual-damascenes process. It includes forming a via dielectric layer, an etch stop layer directly over the via dielectric layer, and a trench dielectric layer over the etch stop layer. The etch stop layer is patterned through a first photolithography and etch process to form openings in the etch stop layer, prior to the formation of the trench dielectric layer. A second photolithography and etch process is performed after formation of the trench dielectric layer to create trench openings in the trench dielectric layer and via openings in the via dielectric layer, where the patterned etch stop layer acts as a hard-mask in forming vias in the via dielectric layer.