Analysis of NBTI degradation- and recovery-behavior based on ultra fast VT -measurements

Abstract

We present a new direct VT measurement technique with arbitrary choice of drain voltage and a μs delay (factor of 1000 improvement) after stress. As shown this technique enables a meaningful comparison of data to theory (e.g. △VT measurable as response to stress times from 100μs over 10 decades in time and an analysis of recovery over 11 decades in time) which may lead to a better understanding of NBTI. A fast precursor due to bulk trapping was found to significantly influence degradation slopes for all times. Based on a physical model - standard reaction/diffusion model plus fast bulk trapping - with just 3 fit parameters experimental degradation can be well modelled (see Fig. 4, 10, 11) and degradation slopes <1/4 as well as >1/4 (both reported in literature) can be explained. A lifetime extrapolation based on this physical model is superior to the common straight line fit. There is no satisfying agreement of recovery data with reaction/diffusion theory. Further experimental and theoretical work is going to be needed. © 2006 IEEE.