Modeling of the I-V characteristics of high-field stressed MOS structures using a Fowler-Nordheim-type tunneling expression

The gate current-voltage characteristic of a high-field stressed metal-oxide-semiconductor structure with trapped charge within the insulator barrier is consistent with a Fowler-Nordheim-type tunneling expression. Instead of considering a correction for the cathode electric field as usual, we use an effective local electric field that takes into account the distortion of the oxide conduction band profile caused by the trapped charge. An energy level at the injecting interface, introduced as an optimization parameter of the model, controls the tunneling distance used for calculating the effective field. Trap generation in the oxide is induced by high-field constant current stress and subsequent electron trapping at different injection levels is monitored by measuring the associated flat band voltage shift. The model applies for positive gate injection regardless the stress polarity and the involved parameters are obtained by fitting the experimental data without invoking any particular theoretical model for the trapping dynamics. In addition, it is shown how the presented model accounts for consistently both the current-voltage and voltage-current characteristics as a function of the injected charge through the oxide.