Study of Work-Function Variation in High-kappa/Metal-Gate Gate-All-Around Nanowire MOSFET

Abstract

In this paper, threshold-voltage (VTH) variation caused by work-function variation (WFV) in a high-kappa/metalgate gate-all-around (GAA) nanowire MOSFET is quantitatively estimated through 3-D technology computer-aided design simulations. It is determined that the ratio of average grain size to gate area (RGG) [i.e., RGG = G(size,eff)/(gate area)(0.5)] for the GAA nanowire MOSFET should use the effective grain size (G(size, eff)), instead of using the nominal grain size (G(size)). G(size, eff) is regarded as the effective grain size around the channel region, and it is smaller than the original grain size. In order to compare the WFV-induced VTH variation in GAA nanowire MOSFET against FinFET, the amount of WFV-induced VTH variation is plotted using the RGG concept with G(size, eff). As a result, it was concluded that the cylinder-shaped GAA nanowire MOSFET has better immunity to the WFV-induced V-TH variation by 12.5%, compared with FinFET.