Observation of voids induced by mechanical stress and electromigration in passivated Al lines deposited at different purity levels

Two pure Al passivated line samples were prepared under different metal deposition conditions, and were electromigration tested in a high voltage scanning electron microscope (HVSEM). The sample prepared under ultrahigh purity conditions showed a high resistance to void initiation and a very large grain size, while the more conventionally deposited metal displayed comparatively poor electromigration resistance. The sample prepared at lower purity conditions showed initial stress voids, but these were not the site for electromigration damage.