Embodiments described herein relate to depositing a cobalt-containing layer by a cyclical deposition process while forming interconnects on a substrate. In one embodiment, a method for forming an interconnect structure is provided which includes depositing a tungsten-containing barrier layer over an exposed contact metal surface within an aperture formed in an insulating material disposed on a substrate, forming a cobalt-containing layer on the tungsten-containing barrier layer using a cyclical deposition process by sequentially exposing the substrate to a cobalt precursor gas and a silicon reducing gas, wherein the cobalt precursor gas contains a cobalt precursor having a cyclopentadienyl ligand, and depositing a copper material on the cobalt-containing layer.