A Study of NBTI and Short-Term Threshold Hysteresis of Thin Nitrided and Thick Non-Nitrided Oxides

IEEE Transactions on Device and Materials Reliability (Impact Factor: 1.89). 06/2009; 9(2). DOI: 10.1109/TDMR.2009.2021389
Source: IEEE Xplore

ABSTRACT Negative bias temperature instability (NBTI) degra-dation and recovery have been investigated for 7–50-nm non-nitrided oxides and compared to thin 1.8-and 2.2-nm nitrided oxides from a dual work function technology. A wide regime of stress fields from 2.5 to 10 MV/cm has been covered. Thermal activation has been studied for temperatures from 25 • C to 200 • C. The NBTI effect for the nitrided oxide is larger than for non-nitrided oxides. The percentage of threshold shift ΔV th which is "lost" during a long measurement delay—which is the quantity leading to curved ΔV th versus stress-time curves and to errors in extrapolated lifetimes—is about equal for nitrided or thick non-nitrided oxides. The fraction of recovered ΔV th 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. The effect of short-term threshold shifts has been studied for extremely short stress times down to 200 ns. Index Terms—MOSFET, negative bias temperature instability (NBTI), recovery, relaxation.

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Available from: H. Reisinger, Sep 29, 2015
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    • "The measured ΔVT (which is a function of the thickness) has been converted to an effective density of charged near-interface states using the relation ΔVT= e*N it / C ox . The stress field in the oxide has been calculated from the corresponding CVcurve and Gauss' law [8] for our samples. For the literature data in Fig. 3 we used the equivalent oxide thicknesses given and estimated substrate and gate surface charge layer thicknesses. "
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