Analysis of Subthreshold Behavior of FinFET Using Taurus

This paper investigates the subthreshold behavior of Fin Field Effect Transistor (FinFET). The FinFET is considered to be an alternate MOSFET structure for the deep sub-micron regime, having excellent device characteristics. As the channel length decreases, the study of subthreshold behavior of the device becomes critically important for successful design and implementation of digital circuits. An accurate analysis of subthreshold behavior of FinFET was done by simulating the device in a 3D process and device simulator, Taurus. The subthreshold behavior of FinFET, was measured using a parameter called S-factor which was obtained from the ln(IDS) - VGS characteristics. The value of Sfactor of devices of various fin dimensions with channel length Lg in the range of 20 nm - 50 nm and with the fin width Tfin in the range of 10 nm - 40 nm was calculated. It was observed that for devices with longer channel lengths, the value of S-factor was close to the ideal value of 60 mV/dec. The S-factor increases exponentially for channel lengths, Lg \u3c 1.5 Tfin. Further, for a constant Lg, the S factor was observed to increase with Tfin. An empirical relationship between S, Lg and Tfin was developed based on the simulation results, which could be used as a rule of thumb for determining the S-factor of devices