Electromigration performance of two-level Al(Cu) interconnects with w-filled and Al-filled vias

摘要

The electromigration (EM) performance of two-level Al-0.5percent Cu interconnects with W-filled and Al-filled vias was compared. Both via types had a Ti/TiN liner. After EM testing, the test structures with W-filled vias had voids at the Al/via interface. In the structures with Al-filled vias, voids formed in M1 or M2 leads. The Ti/TiN liner does not seem to block the Al migration, possibly because the liner is non-continuous. However, there is evidence that the Al via filling process increases the tensile stress in both M1 and M2 lines, which in turn accelerates electromigration. While the t_50 values were significantly larger for two-level test structures with Al-filled vias, the standard deviation of failure times was larger as well.