Embodiments of the present invention relate to a copper interconnect structure and a formation method thereof. A structure with improved electromigration resistance and a method for making the same are provided. The structure having improved electromigration resistance includes a bulk interconnect having a dual layer cap and a dielectric capping layer. The dual layer cap includes a bottom metallic portion and a top metal oxide portion. Preferably the metal oxide portion is MnO or MnSiO and the metallic portion is Mn or CuMn. The structure is created by doping the interconnect with an impurity (Mn in the preferred embodiment), and then creating lattice defects at a top portion of the interconnect. The defects drive increased impurity migration to the top surface of the interconnect. When the dielectric capping layer is formed, a portion reacts with the segregated impurities, thus forming the dual layer cap on the interconnect. Lattice defects at the Cu surface can be created by plasma treatment, ion implantation, a compressive film, or other means.