Method to predict length dependency of negative bias temperature instability degradation in p-MOSFETs

Abstract We propose a method to predict the length dependency of the magnitude of degradation caused by negative bias temperature instability (NBTI) stress applied to a p-MOSFET. Threshold voltage degradation Δ V th varied according to the drain bias V d , during the measurement of drain current I d . The depletion length L dep into the channel was calculated based on a particular V d value and the channel doping concentration. L dep was used to extract the channel edge region length L edge , then the center channel region length L cen was obtained by subtracting L edge from the gate length L gate . We proposed an equation that uses L dep , L cen , L edge and degree of Δ V th variation to calculate Δ V th according to L gate while the p-MOSFET is under NBTI stress. Equation estimates of Δ V th at different L gate were similar to measurements.

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