On the Weibull shape factor of intrinsic breakdown of dielectric films and its accurate experimental determination. Part II: experimental results and the effects of stress conditions

For pt. I see ibid., vol. 49, no. 12, p.2131 (2002).The Weibull slope measurement techniques described in Part I are used to determine Weibull slopes as function of thickness, voltage, and temperature. The effect of stress temperature and voltage on Weibull slopes is investigated over a wide range of voltage and temperatures for several different oxide thickness values. It was found that Weibull slopes show a strong thickness dependence while Weibull slopes are essentially independent of stress conditions such as voltages and temperature. The implications of the voltage-independent Weibull slope on voltage-dependent acceleration factors are discussed. In addition, the impact of electron injection polarity on Weibull slopes is studied in detail. To further advance understanding, we compare the measured Weibull slopes with different nitrogen incorporation processes under gate injection mode. It was found that for ultrathin oxides below 3 nm to the first order, the Weibull slopes are relatively insensitive to the nitrogen incorporation process for which we investigated. Finally, we discuss the validity of the stress-induced leakage current measurement as an experimental means to measure the critical defect density.

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