Geometry-induced electromigration degradations in AlSi/sub 1%/ narrow interconnects

The electromigration resistance of AlSi/sub 1%/ 1.2 mu m-wide lines containing bends and width changes has been tested using the conventional lifetime method. Results show the importance of rupture risks due to structural gradients induced by width changes. Depending on width and length of the broad segments, the rapture may be due to the relative weakness of nonbamboo broader segments, or specifically to material flow increase at the broadening. The mean-time-to-failure and standard-deviation decreases, important for the small width changes, seem to saturate for width changes broader than the mean grain size. Considering the bend effect, degradation localisation and results of two-dimensional electrical and thermal calculations clearly show that it can be neither an electrical nor thermal effect. The bend may rather be considered as a short line broadening.<
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