Electromigration lifetimes of multilayered metallizations of Al alloy (Al-0.5%Cu-l.0%Si) sandwiched with refractory metal films have been correlated to the interconnect microstructure and interactions with the underlying layer. In this study, Median Time to Failure (t50%, MTTF) data was obtained for multilayered Al alloy films by varying the Al deposition temperature from 200°C to 400° and the composition of the underlying substrate films. The Al alloys examined in this study were deposited over substrate films of sputtered Ti, reactively sputtered TiN and CVD TEOS deposited SiO2. All Al alloys were capped with a reactively sputtered TiN layer and covered with passivation.
Physical characterization using TEM, XRD, SIMS, and AFM, was performed to determine the microstructural and chemical properties of the films and correlate them to the MTTF of the packaged interconnects. The role of material properties such as the grain size and interactions of the metallization with the underlying layers were found to substantially impact the electromigration lifetime.
Based on data obtained from these studies, a number of interconnect metallization options will be discussed with respect to reliability and associated integration issues.