Plastic deformation in sub-micron wide interconnects was studied  in situ  by straining within a transmission electron microscope. It was found that dislocation motion occurred readily in non-passivated lines, but was non-existent in passivated lines due to the presence of stiff oxide side-walls. Heterogeneous void nucleation occurred instead, upon straining to a critical limit. The void morphology was always nearly hemispherical, and nucleation always took place at line edges. Further stretching of the lines led to rupture of the side-walls away from the lines; thus resulting in immediate dislocation motion. Void nucleation, cross-slip and the operation of dislocation sources at line edges were observed. It was noted that dislocations almost parallel to the plane of the lines were rarely observed, and their movement was sluggish. On the basis of the dislocation configurations which were observed in these lines, a generalized geometrical model was developed in order to determine the effect of grain orientation upon the yield stress of passivated lines with columnar bamboo grains. The frequent occurrence of twinning within the grains confirmed that plastic deformation was restricted in confined metal lines.

In Situ Transmission Electron Microscopy Study of Plastic Deformation and Stress-Induced Voiding in Al-Cu Interconnects D.Jawarani, H.Kawasaki, I.S.Yeo, L.Rabenberg, J.P.Stark, P.S.Ho: Journal of Applied Physics, 1997, 82[4], 1563-77