Keywords: metal gates, random work function, bulk FinFETs, SOI FinFETs, characteristic fluctuations, device simulation, silicon on insulator, fin–type field effect transistors, simulation, titanium nitride, TiN, electrostatic potential, carrier transportation, nanosized grains, nanotechnology, fluctuation estimation, random effects
Random–work–function–induced characteristic fluctuation in 16–nm–gate bulk and SOI FinFETs
In this paper, we, for the first time, study the metal gate's work–function–fluctuation–induced variability in the 16–nm–gate bulk and silicon on insulator (SOI) fin–type field effect transistor (FinFET) devices using an experimentally calibrated 3D device simulation. According to metal's property, random nanosized grains of titanium nitride (TiN) gate are statistically positioned in the gate region to examine the associated electrostatic potential and carrier transportation characteristics, concurrently capturing fluctuations resulting from nanosized grain's random number, position and size effects. The newly advanced methodology of localised work function fluctuation simulation enables us to estimate characteristic fluctuations and to examine the nanosized grain's random effects for the 16–nm–gate bulk and SOI FinFETs with TiN/HfO2 gate stacks with respect to the aspect ratio (AR = fin height/fin width) of two. The results of this study show that the DC characteristic fluctuation of FinFET devices strongly depends on the high and low work functions of localised nanosized metal grains. The threshold voltage (Vth) varies with the number of grain sizes and the Vth's fluctuation (σVth) is suppressed as the grain size is minimised. σVth of SOI FinFET (about 9.7 mV) is about 1.5 times smaller than that with bulk FinFET (about 14.6 mV). Furthermore, σVth of SOI FinFET with minimal metal grain's size of 2 × 2 nm² can be reduced about 23%, compared with the result of bulk one.