Comparison of Tunnel Currents Through SiO_2, HfO_2, Ta_2O_5, ZrO_2 and Dy_2O_3 Dielectrics in MOS Devices for Ultra Large Scale Integration using First Principle Calculations

摘要

The work presented in this paper focuses on the effects of high leakage current in field effect transistors and the possible ways to play down with the leakage currents. This paper combines density functional theory and non equilibrium Green's function formalism to perform atomic scale calculation of tunnel currents through SiO_2i HfO_2, Ta_2O_5, ZrO_2 and Dy_2O_3 dielectrics in MOSFETs. The tunnel currents for different bias voltages applied to Si/Insulator/Si systems have been obtained along with tunnel conductance v/s bias voltage plots for each system and the plots have been analyzed with reference to the presently used bulk Si/SiO_2/Si systems that have SiO_2 as the gate dielectric material. The results justify the use of high dielectric constant materials as gate dielectric in FET devices so as to enable further downscaling of MOSFETs with reduced gate leakage currents thereby enabling ultra large scale integration.