Extended-Measurement-Stress-Measurement Setup

2.1.3 Extended-Measurement-Stress-Measurement Setup

To save on time and devices when performing NBTI experiments the extended-MSM (eMSM) measurement routine was established [18]. Choosing each stress sequence $tstr,i+1$ to be significantly longer than the previous stress sequence $tstr,i$ ensures that the amount of degradation lost during the recovery within $t rel,i$ is nearly completely restored within $t str,i+1$ . Consequently, regardless if the stress is interrupted or not, more or less the same amount of degradation is obtained after the total stress time, i.e. $∑ ΔVTH (tstr) ≈ ΔVTH ( itstr,i)$ . This is schematically depicted in Fig. 2.3, where the top dotted black line of the continuous degradation is always met by the individual sub-sequences (red dotted lines) of the eMSM-sequence after sufficiently long stresses. When the stress sequences are recorded via the on-the-fly method, which will be explained in Chapter 2.3, both stress and recovery can be monitored with the eMSM routine.

Figure 2.3: Schematic view of the last three out of $N = 9$ stress/relaxation cycles building up an eMSM-sequence like performed by [17, 11]. The stress (dashed red) is interrupted $N − 1$ times to record $N − 1$ short and one long final relaxation sequence on the relative time scales $trel = t− tstr,i$ . After the measurement delay $tM$ marked by the dashed blue lines the monitorable relaxation (solid blue) sets in. A permanent or slowly relaxing component $P$ is indicated for the last two cycles and will be explained in Chapter 4.

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