US Patent 7675177 Forming copper interconnects with Sn coatings

A copper interconnect with a Sn coating is formed in a damascene structure by forming a trench in a dielectric layer. The trench is formed by electroplating copper simultaneously with a metal dopant to form a doped copper layer. The top level of the doped copper layer is reduced to form a planarized surface level with the surface of the first dielectric layer. The doped copper is annealed to drive the metal dopants to form a metal dopant capping coating at the planarized top surface of the doped copper layer.