Subthreshold Modeling and Simulation of Silicon Nanotube Field Effect Transistors (SiNTFETs)

Abstract

The MOS technologies with low device geometry and new architectures have accelerated the pace of computational technology. In order to uphold the challenges of scaling in sub 20nm regime and meet the aggressive specifications of ITRS, a novel and non-conventional devices have to intervene. So came the ultimate solution- Silicon Nanotube Field Effect Transistor (SiNTFET) with its unique architecture which enhances the electrical characteristics of the device and the performance. In this work, an analytical model of surface potential and threshold voltage for SiNTFETs are developed. The two dimensional poisson’s equation with a cylindrical coordinate system, has been evaluated to find surface potential. The concentration of the inversion charge has been evaluated in the channel in subthreshold regime using the surface potential equation and the Boltzmann equation. The threshold voltage of the device is stated as the gate voltage for which the calculated inversion charge equals the threshold charge. Assuming this definition, the threshold voltage of the device for different channel lengths is mathematically modeled. The effect on threshold voltage by the variation of physical parameters is detailed analysed. The physical parameters include gate oxide thickness, tube thickness and core thickness. The effects of DIBL and voltage roll-off are discussed. The model results are verified with the simulation results obtained by using device simulator, ATLASTM. It is observed that for short channel lengths (<30nm), the model values vary from the simulated data; that is because the quantum mechanical effects are neglected during modeling which are vital in those channel lengths. The objective of the work is to provide a basic model for threshold voltage of the SiNTFET. The electrical characteristics show that device has a potential to set a new technology road map and meet the ULSI applications