Degradation of very thin gate oxide MOS devices under dynamic high field/Current stress

The effects of dynamic high field/current stressing on the thin oxide wear-out mechanism were studied. Less degradation was found under dynamic stress compared to static stress. Significant positive oxide charge detrapping was observed during dynamic field operation. The amount of positive charge detrapping follows a first order rate equation. Positive trapped charges at the anode induce oxide leakage current at low bias voltage and this leakage current can be suppressed by alternately reversing the stress polarity. Generation of interface states was only slightly reduced under dynamic stress. However, oxide time-to-breakdown and charge-to-breakdown were greatly improved under dynamic stressing. The experimental data support the model that oxide breakdown results from the build up of bulk charges instead of interface states generation.