Quantitative Three-Dimensional Characterization of the Morphology of Stressed and Electromigrated Aluminum Lines

The volumes of slit, edge, erosion and erosion/slit voids in stressed and electromigrated aluminum conductor lines were quantitatively determined with low resolution standard and high resolution enhanced tips by atomic force microscopy. These three-dimensional results were compared to semiquantitative determinations of void volumes extrapolated from two-dimensional backscattered scanning electron microscopy area determinations of the passivated aluminum conductor. After the passivation was removed by plasma etching, void volumes were also determined from two-dimensional scanning electron microscopy micrographs. The volumes of the nearest hillocks on the anodic side of the voids were quantitatively determined by atomic force microscopy, and these hillock volumes were determined to be independent of the respective void volumes.