Barrier layer effect of titanium-tungsten on the electromigration in sputtered copper films on polyimide

Titanium-tungsten is employed as the diffusion barrier in a Cu/barrier/polyimide/Si system. The electromigration damage (EMD) of Cu with a TiW barrier is investigated utilizing an empirical formula. Two activation energies are obtained suggesting a surface electromigration mechanism at low temperature (140-190 degrees C) and a combined migration mechanism at high temperature (190-230 degrees C). The presence of the TiW barrier layer improves the high temperature electromigration resistance. The effects of the TiW barrier on the microstructure and electrical properties of Cu metallization are discussed.