Electromigration in Cu interconnections, with a selective electroless metal coating (CoWP, CoSnP or Pd) on the top surface of Cu damascene lines, was investigated. The 10 to 20nm-thick metal cap significantly improved the electromigration lifetime by providing protection against the interface diffusion of Cu; which was the main cause of metal line failure via electromigration.

Reduced Electromigration of Cu Wires by Surface Coating. C.K.Hu, L.Gignac, R.Rosenberg, E.Liniger, J.Rubino, C.Sambucetti, A.Domenicucci, X.Chen, A.K.Stamper: Applied Physics Letters, 2002, 81[10], 1782-4