Embodiments of the present disclosure are related to improved methods for forming an interconnect structure in a substrate. In one implementation, the method includes forming a barrier layer on exposed surfaces of a feature in a dielectric layer, forming a liner layer on the barrier layer, forming a seed layer on the liner layer, forming a metal fill on the seed layer by a metal fill process and overburdening the feature using an electroplating process, performing a planarization process to expose a top surface of the dielectric layer, and selectively forming a cobalt-aluminum alloy cap layer on the barrier layer, the liner layer, the seed layer, and the metal fill by exposing the substrate to a cobalt-containing precursor and an aluminum-containing precursor.