A study of the influence of inter-metal dielectrics on electromigration performance

The relative electromigration performance of test structures with a common Ti/TiN-Al-1%Cu-TiN metallization scheme and with three different inter-metal-dielectric (IMD) layers above an interconnect test line are compared. Differences in lifetimes are observed which are attributable to the influences of the different IMD layers. The IMD layers in question are (A) Polyimide, (B) a flexible inorganic dielectric layer and (C) a rigid inorganic dielectric layer. A matrix of conventional electromigration tests have been carried out. The possible influence of stress migration is investigated and an explanation for the relative behaviour is proposed.