3D TCAD Modeling And Structural Studies Of Nanoscale MOSFETs

As the feature size of traditional CMOS structure continues to shrink, deep sub micron or even nanometer level has reached the limitation of reduced size, resulting in the performance of the CMOS device face the problem of short channel effects and process constraints. In order to maintain the pace of development of Moore’s law, double-gate MOSFETs and FinFETs as the representative of new device structure with excellent performance in suppressing short-channel effects and improving circuit integration. However, with the feature sizes shrink further, the physical model of traditional planar devices will no longer be applicable,new physical model such as quantum effects should be added;while the problem of centralized heat in non-planar and thin film MOSFET are increasingly serious.This paper mainly relates to the small size effect of nanometer MOSFETs, as well as the physical model of the small size effect. We will study the decrease of effect mobility and drive current relating to the different channel surface crystal orientation, and design new device structure to reduce the impact of differences in crystal and improve heat dissipation issues of non-planar devices, the main research work is as follows:1.according to the device scaling law, analyzed two order effect caused by the mandatory role of short channel condition about the source and drain electric field on the channel,including drain-induced barrier lowering and punch-through effect.Multi-gate MOSFETs can effectively reduce short-channel effects and improve circuit integration as well,but constantly thinner silicon body bring about the reducing mobility and centralized heat.We explore deeply the mobility scattering mechanism of thin film,and discuss the lower thermal conductivity by the impact of size and doping etc.2. Effective physical modeling and TCAD simulation of quantum effects and short-channel effects in Multi-gate MOSFETs will be researched.While for 3D TCAD simulation of small size MOS devices, We discuss how to set up the best 3D grid and numerical math method to match the application of models, achieving the accuracy and speed of three-dimensional device simulation.Aiming at mobility of different channel crystal orientations, effective 2D and 3D modeling and simulation will be studied.3. Investigation about the surface and side channel crystal difference to reduce the effective mobility and drive current will be considered.Aiming at the crystal and heat problem, We design a T-shaped gate structure 3D MOS device to reduce their impact, overcoming the reducing mobility’s issue caused by the interaction of inversion layers and increasing the radiating path,finally achieve the high swithing ratio.