Low-temperature diffusion doping of copper interconnects independent of seed layer composition

A method of forming doped Cu interconnects, the method comprising the steps of:

• patterning at least one trench in a dielectric material;
• forming a barrier layer lining the trench and covering a top surface of the dielectric material;
• forming a metal liner on the barrier layer;
• depositing a Cu-containing seed layer on the metal liner;
• plating a Cu fill into and overfilling the trench to form Cu interconnects;
• fully removing a Cu overburden above the trench;
• fully removing the barrier layer and metal liner from a top surface of the dielectric material to access an interface between the metal liner and the Cu fill;
• selectively depositing a dopant layer on only a top surface of the Cu fill without depositing on the dielectric material;
• and
• diffusing at least one dopant from the dopant layer along the interface between the metal liner and the Cu fill to form a Cu interconnect doping layer between the metal liner and the Cu fill, wherein the Cu interconnect doping layer formed by the diffusing fully lines a bottom and sidewalls of the Cu fill.