INFLUENCE OF W-VIA ON THE MECHANISM OF ELECTROMIGRATION FAILURE IN AL-0.5 CU INTERCONNECTS

This letter reports the effects of via current density on electromigra tion (EM) failure in Al-0.5 Cu conductors. Two-level metallization str uctures, differing in the number of feeding vias (1, 6, and 15), were made with the same pattern of Al lines at two levels to allow simultan eous EM testing of upper- and lower-level lines. It was established th at the lower-level lines were more susceptible to the impact of the vi a, resulting In a failure by the formation of a local void beneath a v ia and a strong dependence of EM lifetime on the via current density. The results led to a phenomenological equation that incorporates via s tructure into failure kinetics. (C) 1998 American Institute of Physics .