US Patent 9379007 Electromigration-resistant lead-free solder interconnect structures

Embodiments of the invention include a lead-free solder interconnect structure and methods for making a lead-free interconnect structure. The structure includes a semiconductor substrate having a last metal layer, a copper pedestal attached to the last metal layer, a barrier layer attached to the copper pedestal, a barrier protection layer attached to the barrier layer, and a lead-free solder layer contacting at least one side of the copper pedestal.