The effect of recovery on NBTI characterization of thick non-nitrided oxides

NBTI degradation and recovery have been investigated for 7 to 50nm oxides and compared to a thin 2.2nm nitrided oxide. A wide regime of stress fields 2.5MV/cm to 8MV/cm has been covered. NBTI effect for the nitrided oxide is larger than for non-nitrided oxides. The percentage of threshold shift DeltaVth which is "lost" during a long measurement delay - which is the quantity leading to curved DeltaVth vs stress-time curves and to errors in extrapolated lifetimes - is about equal for nitrided or thick non-nitrided oxides. The fraction of recovered DeltaVth is strongly dependent on stress time but only weakly dependent on stress field. Recovery in thick oxides leads to exactly the same problems as for non-nitrided oxides and clearly a fast measurement method is needed.