Electromigration-induced hillock growth in polycrystalline Al segments was extensively investigated. Hillocks composed of columnar grains grew near to the anode via epitaxial Al additions to the bottom Al/TiN interface; which pushed up the original Al film. The hillocks rotated away from their initial (111) out-of-plane orientation in a manner which was consistent with the physical rotation of the hillock surface. Wedge-like and rounded hillocks were observed, and their formation was explained by an interaction between grain extrusion and grain growth. The trends revealed by analyzing both thermal- and electromigration-induced hillock studies could be explained in terms of the mechanisms identified here.

Growth of Electromigration-Induced Hillocks in Al Interconnects. J.A.Nucci, A.Straub, E.Bischoff, E.Arzt, C.A.Volkert: Journal of Materials Research, 2002, 17[10], 2727-35