Modelling and simulation based analysis of random dopant fluctuation in dg jlfet under quantum confinement

Abstract

Moore’s Law has been observed in the Microelectronics and Semiconductor Industries since 1970. Trend of downscaling transistors smaller and smaller to make processors work faster than before with implementation of VLSI (Very Large Scale Integration), ULSI (Ultra Large Scale Integration), GLSI (Giga Large Scale Integration) techniques require fabrication of nano-scale transistors. This presents significant challenges in term of developing new device structures and manufacturing processes. Because of the laws of diffusion and the statistical nature of the distribution of the dopant atoms in the semiconductor and rise of other Short Channel Effects, formation of ultra shallow junctions with high doping concentration gradients in Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) has become an increasingly difficult challenge for the semiconductor industry. J.P. Collinge proposed an idea of using Junctionless transistors (also called gated resistor) for fabrication of nanoscale transistors. Junctionless transistors commonly known as JLFET (Junctionless Field Effect Transistor) have no junctions since a homogeneous highly doped substrate is used with Gate Oxide deposition over JLFET to control the current flow. These devices have full CMOS functionality and are made using silicon nanowires. Since inception of JLFET in Semiconductor Industries, numerous researches and simulations on its fabrication techniques, device characteristics, etc. have been performed by Researchers.. But analytical models of JLFET under various short channel effects like Quantum Confinement and Random Dopant Fluctuations (RDF) needs more emphasis. In our project, we have proposed an analytical model regarding impact of Quantum Confinement and RDF in Threshold Voltage and other parameters of an ultra short channel DG (Dual Gate) SMG (Single Material Gate) JLFET. We have incorporated Quantum Confinement effects on 3D JLFET into our model and derived threshold voltage for short channel JLFET. In addition, we have introduced a new approach that would give insights regarding impact of dopant atoms on threshold voltage in terms of their lattice site occupancies, and thus, RDF has been included in our model. The dependence of threshold voltage on different physical parameters of JLFET has also been investigated. We have also simulated ultra short channel DG SMG JLFET using Silvaco TCAD Atlas with inclusion of Quantum Confinement Effects and compared simulation results obtained with the results predicted by our model, providing plausible explanations for any deviation from simulation results. The influence of RDF on the threshold voltage has been investigated through model simulation, where randomization of number has been included to account for the random factor regarding positional occupancy of dopant atoms. Finally we incorporate both RDF and Quantum Confinement effects simultaneously in our model and observe fluctuations in threshold voltage for different channel lengths, and also provide statistical interpretation of its behavior.