Split gate JL MOSFET with UTB for sensing doping concentration

Abstract

In the conventional bulk MOSFET, as the size of the MOSFET reduces the Short Channel Effects are introduced. To overcome the issues that are occurring due to scaling of the bulk MOSFET, modification in the bulk MOSFET such as Silicon on insulator, Multi-gate devices that is double gate MOSFET , triple gate MOSFET and Fin Field Effect transistor structure. With the help of the mentioned devices there is a reduction in Short Channel Effects of conventional MOSFET. Devices which are based on the silicon on insulator, reduce the problems of leakage mechanism like GIDL, DIBL and drain to body leakage current etc. In the devices which has the multi-gate structure that device has the better control of the gate voltage on the drain current. To overcome the issues that are occurring in the conventional mutigate devices can be resolved with the help of the Junctionless DG MOSFET. JL DG MOSFET based sensors can be used fir biosensing applications. In this thesis work two different JL DG MOSFET as we studied and compared. Each one can be used to sense the biomoleccules and concentration of the micro nutrients in the water by just sensing the small change in Dielectric constant of the biomolecules. A Junctionless DG MOSFET sensor is designed on SILVACO TCAD Tool. Here, we have four- split gates and the underlap region between two gates has been used for sensing application. The underlap region is coated by the biomolecule (biopolymer) with particular concentration of the micro-nutrients. This gives a finite value of the dielectric constant of this mixture by varying the concentration of the micro nutrient in the mixture. The dielectric constant will change the conductivity of the underlap region two channels, which can be easily sensed by the MOSFET operation of the sensor. A new quadruple split gate JL MOSFET has also been designed and stimulated. The stimulation results show that the new proposed sensor has larger sensitivity than other sensors for the sensing of micro nutrients in the biomolecule. Here the underlap channel region in between the gates has been coated with the biomolecule with the particular concentration of the micro-nutrients. Different concentration (1X1016 to 1X1017 cm-3 ) of the boron has been sensed by the biosensor, in terms of threshold voltage of the quadruple split gate JL MOSFET