Characterization and modeling of electromigration failures in multilayered interconnects and barrier layer materials

Electromigration failure mechanisms of TiN/Al-alloy/TiN multilayered interconnect and TiN, TiW barrier layer materials have been studied. The stress induced in Al electromigration instead of severe joule-heating has been attributed to the damage healing or resistance oscillation observed in TiN/Al-alloy/TiN multilayered interconnects. The lifetime dependence on interconnect geometry (length and width) for multilayered structures has been investigated. The experimental results show that the failure observed in TiN and TiW barrier layer materials was not caused by electromigration, instead it was due to a thermally activated process. The activation energy of this thermal process for TiN was found to be 1.5 eV. A 10-year lifetime was projected to be attainable if the hottest spot in TiN film was kept below 408°C. This suggests that TiN may safely conduct 2.4×10⁷ A/cm ² for the typical thermal impedance of a hot spot