Stress induced void formation of the vias in the Al-based multi-level interconnection system

Effects of the stress induced void formation to submicron vias with the Al based multilevel interconnection have been investigated. In this study, vias with the conventional Al/Al interface and with the titanium interlayer were compared in terms of stress induced open failures. The investigated via diameter varied between 0.6 μm and 1.8 μm. It was found that conventional vias were opened during high temperature storage. Open failures occurred from the small vias and were caused by the passivation stress. In addition, it was considered that the crystal discontinuity of aluminum grain across the via interface enhanced open failures. The effect of the titanium interlayer at the via interface on the suppression of open failures could be caused by the intermetallic layer of Al₃Ti. This intermetallic layer prevented the stress induced void formation of the aluminum conductor