Electromigration-induced damage in near-bamboo lines initiated at polygranular clusters which were longer than a critical length and which acted as fast-diffusion segments. It was proposed that 2 neighboring sub-critical clusters could also lead to damage via the interaction of their stress fields. In order to study such proximity effects, artificial clusters were generated by creating continuous segments of plastic deformation in single-crystal lines by means of nano-indentation. Pairs of segments having different separation distances and lengths were made. The in situ electromigration tests showed that these segments generated damage in the form of voids and hillocks, even when the individual segments were shorter than the critical length. The void growth rate was found to be a function of the separation distance and the segment length. A simple analytical model for the electromigration flux in these structures was shown to be consistent with the measured void growth rates. Electromigration characteristics such as the diffusivity, effective charge and critical stress for void formation could be extracted by comparing experimental results and model predictions.

Electromigration Proximity Effects of Two Neighboring Fast-Diffusion Segments in Single-Crystal Aluminum Lines. Y.C.Joo, C.V.Thompson, S.P.Baker, E.Arzt: Journal of Applied Physics, 1999, 85[4], 2108-13