A rigorous study of measurement techniques for negative bias temperature instability

The active research conducted in the last couple of years demonstrates that negative bias temperature instability (NBTI) is one of the most serious reliability concerns for highly scaled pMOSFETs. As a fundamental prerequisite for a proper understanding of the phenomenon, accurate measurements are indispensable. Unfortunately, due to the nearly instantaneous relaxation of the degradation once the stressing conditions are removed, an accurate assessment of the real degradation is still extremely challenging. Consequently, rather then interrupting the stress in order to measure the degradation, alternative measurement techniques, such as the on-the-fly methods, have been proposed which avoid stress interruption. However, these methods rely on rather simple compact models to translate the observed change in the linear drain current to a threshold voltage shift. As such, all methods have their own drawbacks which are rigorously assessed using a theoretical description of the problem.