By definition, half of all interconnects fail before the measured mean time to failure (t50) is reached. To predict early failures the basic reactions occurring in the metallization and its environment must be understood. To this end, fatal interconnect failure sites were characterized by Auger electron spectroscopy, atomic force microscopy and backscattered scanning electron microscopy. CVD silicon dioxide passivation layer/fatal void interfaces of typical early failure voids were characterized and compared to a typical late failure void interface. The topographies of these fatal voids were also quantitatively compared to increase our understanding of early failure sites and electromigration.