An embodiment includes a metal interconnect structure, comprising: a dielectric layer disposed on a substrate; an opening in the dielectric layer, wherein the opening has sidewalls and exposes a conductive region of at least one of the substrate and an interconnect line; an adhesive layer, comprising manganese, disposed over the conductive region and on the sidewalls; and a fill material, comprising cobalt, within the opening and on a surface of the adhesion layer. Other embodiments are described herein.