Compact modeling of inversion carrier effective mobility for nanoscale FinFET

Abstract

As the device feature size enters into the nanoscale, the modeling and simulation of carrier transport in FinFETs devices becomes challenging. FinFETs technologies under development have channel lengths well below 100 nm where near-ballistic operation becomes feasible. In this thesis an easy approach to model carrier transports in terms of effective mobility in nanoscale FinFETs is presented. The inversion carrier effective mobility has been analyzed for nanoscale n-channel FinFET. The effective mobility has been simulated by considering the phonon scattering, coulomb scattering and surface roughness scattering mechanisms. Mobility due to each scattering phenomenon has been modeled in terms of effective electric field. In order to determine the effective electric field in the FinFET channel, the inversion layer charge density and the depletion layer charge density have been calculated by using semi-classical expression. By using this effective mobility, current-voltage characteristics have been studied for different operating regions of FinFETs of different channel lengths and also for different oxide thickness. The effect of channel length on mobility in nanoscale devices has been considered and found that the effective mobility decreases with the shrinking of the channel length. To eliminate this discrepancy of mobility the “Mathiessen-like” semi-classical expression has been used with appropriate modification by incorporating a parameter. The range of this parameter has been specified by several simulation works of different FinFET devices for a specific range of channel length. The decrease of threshold voltage with decrease in gate length is a well-known short channel effect called the “threshold voltage roll-off” has been investigated. Channel conductance and output transconductance has also been calculated for nanoscale FinFETs for different operating regions. In order to test the validity of the proposed model the simulation results have been compared with the available experimental and/or simulation data. The analytical expressions derived in the present model can be a useful tool in device design and optimization.