Analytical Modeling of Subthreshold Current in Graded-Channel Dual-Material Double-Gate MOSFET

Abstract

SOI technology because of its advantages in minimizing second-order effects, has been receiving a lot of attention and offering superior CMOS devices with larger speed, greater density and excellent radiation hardness. To address the SCEs and higher performance in deep submicron regime, a lot of novel device structure has been reported but most of them don’t offer simultaneously reduced SCEs and improved device performance. In this dissertation, a 2-D analytical model of DG MOSFET and graded-channel dual-material double gate (GCDMDG) MOSFET has been proposed. In this model, modeling of MOSFET’s parameter such as surface potential, threshold voltage, subthreshold swing and subthreshold current has been done. The parabolic approximation method has been used for calculating the potential distribution function of this model by resolving 2-D Poisson’s equation with proper boundary conditions. The model of GCDMDG MOSFET has basically developed by intermixing the concepts of graded-doping in the channel region and dual-material in gate engineering. By a careful control of the graded-doping channel length ratios in channel and work function of gate metal, optimum performance can be achieved in a GCDMDG structure. The results obtained by DG MOSFET and GCDMDG MOSFET has been compared and observed that this unique structure (i.e. GCDMDG) gives an improved electron transport efficiency which in turn increases the current drive of device. The proposed analytical model has been compared with the simulated results (for same device parameters) obtained by the numerical analysis using SILVACO ATLAS simulator and they are found to be in good agreement.