The electromigration-induced resistance of via-terminated metal lines was studied. A strong correlation was found between void morphology and a step-like resistance

behavior. In the case of lines which exhibited pronounced resistance steps, voids formed at the top or bottom Al/TiN interfaces. In the case of lines which exhibited gradual resistance increases, only complete void formation - which severed the line entirely - occurred. The step-like resistance behavior was more marked when the current density was close to the critical current density.

Direct Observation of Void Morphology in Step-Like Electromigration Resistance Behavior and its Correlation with Critical Current Density. J.S.Huang, T.L.Shofner, J.Zhao: Journal of Applied Physics, 2001, 89[4], 2130-3