The two described extraction schemes of the FPM-method, namely the 
-
and the 
-extraction, have shown that fully automated handling of a
dataset helps to consistently compare experimental results. However, the
performed measurements also underlined the fact that even with proper
fitting/smoothing methods to avoid noise as much as possible, the practicability
of the measurement routine has to be checked first, especially when dealing with
different pulse polarities for NBTI and PBTI.
In the case of PBTI a detailed characterization via FPM is simply not
possible because the pulse settings are not suitable for both PBTI stress and
recovery characterization in a single measurement. The settings are usually a
compromise between maximizing the data range for the 
-characteristics
on the one hand and preventing the device from undesired NBTI stress on the
other hand. The latter case occurs when the device is driven too far into
inversion. Despite these drawbacks the trend of the degradation can be
determined, cf. Fig. 5.5 and Fig. 5.6. It features a negative shift of the threshold
voltage, comparable to NBTI but smaller. So far this refutes the existence of
electron tunneling as stated in [24], but unfortunately the actual type of defects
contributing to BTI still remains unclear. Therefore the measurement technique
proposed at the beginning of this chapter using charge pumping will be
investigated next. Special emphasis is again put on the measurement method
itself.