Effect of the presence of trap states in oxides in modeling gate leakage current in advanced MOSFET with multi-oxide stack

Abstract

Abstract A model of trap assisted tunneling due to the presence of trap states distributed over the oxide and at the interface has been introduced to develop a complete analytical model for gate tunneling current in advanced nano-scale MOSFET in addition to the ideal direct tunneling current with double layer silicon oxide-Hafnium Oxide stack used as gate dielectric. Trapping-detrapping of charge carriers is mostly subjected to multiphonon transitions and thus is dependent on temperature, gate bias and the distribution of trap states across oxide. Relative contribution of the direct tunneling and trap-assisted tunneling has been estimated even in the Fowler-Nordheim regime. The assumption of simplified parabolic energy band dispersion with proper boundary conditions in Wentzel-Kramers-Brillouin (WKB) effective mass approximation is employed to determine the probability density of electrons at different materials throughout the MOS structure. It is then modulated by the tunneling probability to estimate the total amount of tunneling current as a function of effective oxide thickness and gate-biasing.