Modeling CMOS tunneling currents through ultrathin gate oxide due to conduction- and valence-band electron and hole tunneling

A semi-empirical model is proposed to quantify the tunneling currents through ultrathin gate oxides (1-3.6 nn), As a multiplier to a simple analytical model [1], [2], a correction function is introduced to achieve universal applicability to ah different combinations of bias polarities (inversion and accumulation), gate materials (N+, P+,Si, SiGe) and tunneling processes. Each coefficient of the correction function is given a physical meaning and determined by empirical fitting, This new model can accurately predict all the current components that can be observed: electron tunneling from the conduction band (ECB), electron tunneling from the valence band (EVB), and hole tunneling from the valence band (HVB) in dual-gate poly-Si1-xGex-gated (x = 0 or 0.25) CMOS devices for various gate oxide thicknesses. In addition, this model can also be employed to determine the physical oxide thickness from I-V data with high sensitivity, It is particularly sensitive in the very-thin-oxide regime, v;here C-V extraction happens to be difficult or impossible (because of the presence of the large tunneling current).