New Analysis Method for Time-Dependent Device-To-Device Variation Accounting for Within-Device Fluctuation

Abstract

Variability of nanometer-size devices is a major challenge for circuit design. Apart from the as-fabricated variability, the postfabrication degradation introduces a timedependent variability, originating from statistical distribution of charge location and number. The existing characterization techniques do not always capture the maximum degradation. Some of them does not separate the device-to-device variation from the charging fluctuation within the same device, either. The objective of this paper is to develop a new analysis method for characterizing time-dependent device-to-device variation, accounting for within-device fluctuation (TVF). The TVF captures the maximum degradation, separate device-to-device variation from withindevice fluctuation, and reduce the data points by three orders of magnitude. It is shown that the popular data acquisition at discrete time points does not capture the fluctuation well and drain current must be measured continuously. The TVF shows that degradation has two components-a fluctuation with time and one whose discharge is not observed under a given bias. Although both of them increase with stress time, the correlation between them is weak, indicating two different origins.

Defects for random telegraph noise and negative bias temperature instability

“…2(a). When there are more than 3 traps in a device, however, the step-like Id switching generally is replaced by a complex within-a-device-fluctuation (WDF) [12], as shown in Fig. 2(b).…”

“…As device sizes are downscaled to the nanometer range, both Random Telegraphy Noise (RTN) and Negative Bias Temperature Instability (NBTI) can adversely affect the pMOSFET and, in turn, circuit performance and they have attracted a lot of attentions [1][2][3][4][5][6][7][8][9][10][11][12]. The relationship between RTN and NBTI is not fully understood, although it was suggested that they are the two facets of the same mechanism [1].…”

NBTI prediction and its induced time dependent variation

“…For nanometer devices, individual-charging/discharging can be observed and Fig.5 shows that NBTI-induced aging at a given stress time is no longer a fixed value [19][20][21][22]. It consists of two components: a winthin-a-device fluctuation (WDF) and a lower-envelop (LE) that does not discharge [19][20][21][22].…”

“…It consists of two components: a winthin-a-device fluctuation (WDF) and a lower-envelop (LE) that does not discharge [19][20][21][22]. The upper panel in Fig.…”

“…Device-to-device variations of the lower-envelope, LE. The thick curves marked by 'A, B, C, D' are the results of boundary devices [21]. …”