CHARACTERIZATION AND MODELING OF ELECTROMIGRATION FAILURES IN MULTILAYERED INTERCONNECTS AND BARRIER LAYER MATERIALS

Electromigration failure mechanisms of TiN/Al-alloy/TiN multilayered i nterconnect and TiN, TiW barrier layer materials have been studied, Th e stress induced in Al electromigration instead of severe joule-heatin g 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 multilayer ed structure has been investigated. The experimental results show that the failure observed in TiN and TiW barrier layer materials was not c aused by electromigration, instead it was due to a thermally activated process. The activation energy of this thermal process for TiN was fo und to be 1.5 eV. The 10-year lifetime was projected to be attainable if the hottest spot in TiN film was kept below 408 degrees C. This sug gests that TiN may safely conduct 2.4x10(7) A/cm(2) for the typical th ermal impedance of a hot spot.