The Effect of the Subthreshold Slope Degradation on NBTI Device Characterization

For PMOSFET devices NBTI is a serious reliability concern. Because of recovery effects careful stress and measurement methods must be used to determine threshold voltage degradation. These methods assume that mobility and subthreshold slope degradation are minimal. Recent papers have pointed out that this assumption may not be valid. This paper discusses for the first time a unique fast switching NBTI measurement technique that alternates between two V_GS measurement conditions to determine the subthreshold slope vs. stress time. From these measurements the effect of subthreshold slope degradation on V_T degradation can be accurately determined and results compared to the standard techniques. In, addition, this work also introduces an improved NBTI fast switching test methodology to complement the pending NBTI JEDEC testing standard.