ANALYTICAL MODELING OF DOUBLE GATE MOSFET USING GREEN'S FUNCTION TECHNIQUE

Abstract

Silicon-on-insulator (SOI) technology has been receiving a lot of attention owing to its advantages in reduced second-order effects for VLSI applications. It has been the forerunner of the CMOS technology in the last decade offering superior CMOS devices with higher speed, higher density and excellent radiation hardness. Many novel device structures have been reported in literature to address the challenge of short-channel effects (SCE) and higher performance for deep submicron VLSI integration. Double Gate (DG) MOSFETs using lightly doped ultra thin layers seem to be another very promising option for ultimate scaling of CMOS technology. Excellent short-channel effect immunity, high transconductance and ideal subthreshold factor have been reported by many theoretical and experimental studies on this device. We have proposed a two dimensional analytical model for the modeling of DG-MOSFET's using Green's functions. An analytical model using Poisson's equation also has been presented for the potential distribution and threshold voltage model for the DG-MOSFET. The results are compared with existing model results. In this thesis, an analytical solution for the potential distribution of the two dimensional Poisson's equation with the dirichlet boundary condition has been obtained for the DGMOSFET device by Green's function technique. Based on the calculated potential distribution, the minimum surface potential of the DGMOSFET is determined. From the calculated minimum surface potential, the threshold voltage of the DGMOSFET is determined. It has been verified that the dependence of the calculated threshold voltage, surface potential and potential distribution on device channel length, gate oxide thickness, channel doping concentration, drain and gate biases with previous model results. This general solution of electrostatic potential distribution is uniquely determined by the given dirichlet boundary condition along the rectangular region. It can deal with any arbitrary doping profile.