Threshold voltage variation in TG JLFET and cylindrical JLFET due to random dopant fluctuation

Abstract

With advancement in recent VLSI technology, there is an increase in complexity of the circuits. To cope up with this complexity and also to reduce the chip size at the same time, we need to scale the MOSFET devices to deep sub-micron levels. However, traditional MOS transistors comprising of juctions cannot combat the SCEs without degrading the device performance. As a result, to withstand this aggressive scaling without reducing performance, junctionless transistors(JLTs) were developed. In this thesis, different models of JLTs were proposed and their performance especially due to RDF effect were measured especially under short channel length. The variation of threshold voltage (Vth) is used as the parameter for analyzing the effectiveness of these junctionless structures to operate properly when the channel length of thse devices are significantly reduced and all the results were plotted as well as compared using MATLAB simulator. It was quite evident from the plots, that the cylindrical JLFET (GAAFET) performs better TG-JLFET (FinFET) because of its structural advantge over FnFET. It is because in a GAAFET the gate is wrapped around the channel from all the sides and, whereas in a FinFET the gate covers only three sides of the channel. So GAAFET provides better electrostatic over the channel compare to a FinFET thereby improving performance. The effect of quantum confinement of carriers was also considered for both the devices when the channel was reduced to a very small size from all dimensions. It was also shown in the plots that how the Vth variation increases as a result of this effect.