The
electromigration and
stress migration of Cu interconnects is significantly reduced by forming a composite capping layer comprising a layer of β-Ta on the upper surface of the inlaid Cu, a layer of
tantalum nitride on the β-Ta layer and a layer of α-Ta on the
tantalum nitride layer. Embodiments include forming a recess in an upper surface of Cu inlaid in a
dielectric layer, depositing a layer of β-Ta at a thickness of 25 Å to 40 Å, depositing a layer of
tantalum nitride at a thickness of 20 Å to 100 Å and then depositing a layer of α-Ta at a thickness of 200 Å to 500 Å. Embodiments further include forming an overlying
dielectric layer, forming an opening therein, e.g., a via opening or a dual damascene opening, lining the opening with α-Ta, and filling the opening with Cu in electrical contact with the underlying inlaid Cu.