Modeling of Fowler Nordheim Tunneling Current through Gate Dielectric in a Double Gate MOSFET

Abstract

The scaling of physical dimensions of MOSFET is accompanied by the decrease in gate oxide thickness and the doping density in the substrate increase. Due to the scaling, gate oxide thickness become less then 5nm a few amount of current flow through the oxide in conduction band of gate according to FN tunneling. Gate leakage current in MOSFET devices caused by tunneling of carriers through the oxide where the barrier height is greater than the energy of electron. The physical mechanism of tunneling was calculated using the Fermi direct function in previous models but in proposed model the quantum phenomena has been used to calculate the charge carrier distribution on the surface. Gate tunneling current of MOSFETs is an important factor in modeling ultra small devices. In this thesis, gate tunneling in present-generation MOSFETs is studied. In the proposed model, the electron wave function at the semiconductor–oxide interface and inversion charge and thickness of inversion layer, by treating the inversion layer as a potential well, including some simplifying assumptions have been calculated. Then we compute the gate tunneling current using the calculated wave function. The proposed model results have an excellent agreement with experimental results in the literature.