Variability of Threshold Voltage Induced by Work-Function Fluctuation and Random Dopant Fluctuation on Gate-All-Around Nanowire nMOSFETs

We advance the localized work-function fluctuation (LWKF) method to examine the variability of threshold voltage (Vth) induced by titanium nitride (TiN) metal-gate work-function fluctuation (WKF) and combined the WKF with the random dopant fluctuation (RDF) for various grain sizes on Si gate-allaround (GAA) nanowire (NW) MOSFETs. Our results show that the WKF-induced variability of Vth will be dominated by bambootype TiN grains and its impact is larger than that induced by the RDF with doped channel (RDF (doped)). Additionally, the variability of Vth induced by the WKF and the RDF (doped) could be treated as independent fluctuation sources because the channel dopants are away from the metal-gate/high-K interface. Consequently, statistical models are further proposed for the σVth induced by the WKF and the combined WKF with RDF (doped) by considering position effect of nanosized TiN grains.