Oxide wearout phenomena of ultrathin SiO/sub 2/ film during high-field stress

The behaviour of 3.5nm-thick thermal SiO2 films under high-field (< 14MV/cm) electrical stress is measured. During the stress, time-dependent oxide wearout, which arises via three step processes, has been observed for small-area MOS tunnel diodes. The results showed that stress-induced anomalous conduction, in which the barrier height drops to 0.7 eV, arises in the final degradation process. This finding indicates that a new current path arises via oxide trap sites spreading into the oxide, triggering the oxide breakdown.