Modeling of Subthreshold Characteristics of Recessed Source/Drain Soi Mosfet With Vertical Gaussian Doping Profile

Abstract

Recessed S/D SOI MOSFETs has brought a great revolution in ULSI technology due to its high1current drive capability. In this device structure, 1the source and drain regions are extended into1the buried oxide region so that the high series resistance between source1and drain can be1minimised, resulting high drain current. The electrical parameters viz. surface potential, threshold voltage, subthreshold current and subthreshold swing etc. are obtained by first to analyse the performance and functionality of the device by adjusting the physical parameters like gate oxide thickness, 1 channel1length and channel thickness, thickness of the extended source and drain into the buried oxide etc. A number1of approaches have been done to model the threshold voltage and subthreshold1characteristics of the Fully depleted(FD) SOI MOSFET with uniformly doped channel region. However, the actual doping profile differs from uniform doping after ion implantation and resembles much with Gaussian distribution. Hence, this project work represents a novel model1for the potential based subthreshold characteristics of the recessed source/drain SOI MOSFET with1vertical Gaussian doping profile in the channel by solving 2D1poisson’s equation. The Gaussian profile gives two more parameters i.e. projected range Rp and straggle  p 1which can control the device1 characteristics. An analytical threshold voltage model1 has been derived. The subthreshold swing (S) and subthreshold current (Isub) have been derived using parabolic approximation method. The present model may help to overcome1 degradation in the subthreshold characteristics of the device by improving controllability1of the gate over the channel. The proposed model agrees well with the commercially1 available ATLASTM , a two-dimensional (2D) device simulator1from SILVACO.