A metallic liner stack including at least a Group VIIIB element layer and a CuMn alloy layer is deposited within a trench in a dielectric layer. Copper is deposited on the metallic liner stack and planarized to form a conductive interconnect structure, which can be a metal line, a metal via, or a combination thereof. The deposited copper and the metallic liner stack are annealed before or after planarization. The Mn atoms are gettered by the Group VIIIB element layer to form a metallic alloy liner including Mn and at least one of Group VIIIB elements. Mn within the metallic alloy liner combines with oxygen during the anneal to form MnO, which acts as a strong barrier to oxygen diffusion, thereby enhancing the reliability of the conductive interconnect structure.