Determination of the Fitting Region

5.2.1 Determination of the Fitting Region

It is a challenge to determine the range of measurement data within the FPM pulse, which is further used to extract $VTH$ . This is because on the one hand side the noisy subthreshold region should be avoided, but at the same time a preferably large range of data points is required for the fitting algorithm. This balancing act is illustrated in Fig. 5.9. A good compromise is found by using all data points between $VG = − 0.32V$ , where the signal-to-noise ratio is still reasonable high, and the stress level of NBTI at $VG = − 3.0V$ . This range provides the best possible agreement of the manual fitting and the two proposed extraction schemes, $avg$ and $avg + ITH$ .

Figure 5.9: Changes of the threshold voltage of the SPICE level 1 model fit to FPM after [24, 51]. The $VG$ -range used to extract $VTH$ properly is restricted by the noise in the subthreshold regime on the one hand and by the maximally accessible inversion regime on the other hand. The optimum $VG$ -range goes from $− 0.32V$ to $− 3.0V$ .

[next] [front] [up]