Quantitative characterization of dislocation structure coupled with electromigration in a passivated Al(0.5wt% Cu) interconnect

New synchrotron x-ray microbeam methodology is used to analyze and test the reliability of interconnects. The early stage of plastic deformation induced by electromigration before any damages become visible has been recently revealed by white beam scanning X-ray microdiffraction during an accelerated test on Al interconnect lines. In the present paper, we provide a quantitative analysis of the dislocation structure generated in several micron-sized Al grains in both the middle region and ends of the interconnect line during an in-situ electromigration experiment. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of randomly distributed geometrically necessary dislocations as well as geometrically necessary boundaries. The orientation of the activated slip systems and rotation axis depends on the position of the grain in the interconnect line. The origin of the observed plastic deformation is considered in view of constraints for dislocation arrangements under applied electric field during electromigration. The coupling between plastic deformation and precipitation in the Al (0.5% wt. Cu) is observed for the grains close to the anode/cathode end of the line.