A physically-based model for quantization effects in hole inversion layers

As MOS devices have been successfully scaled to smaller feature sizes, thinner gate oxides and higher levels of channel doping have been used in order to simultaneously satisfy the need for high drive currents and minimal short-channel effects. With the onset and development of deep submicron (⩽0.25 μm gate length) technology, the combination of the extremely thin gate oxides (t_ox⩽10 nm) and high channel doping levels (⩾10¹⁷ cm^-3) results in transverse electric fields at the Si/SiO₂ interface that are sufficiently large, even near threshold, to quantize the motion of inversion layer carriers near the interface. The effects of quantization are well known and begin to impact the electrical characteristics of the deep submicron devices at room temperature when compared to the traditional classical predictions which do not take into account these quantum mechanical (QM) effects. For accurate device simulations, quantization effects must be properly accounted for in today´s widely used moment-based device simulators. This paper describes a new computationally efficient three-subband model that predicts the effects of quantization on the terminal characteristics in addition to the spatial distribution of holes within the inversion layer. The predictions of this newly developed model agree very well with both the predictions of a self-consistent Schrodinger-Poisson solver and experimental measurements of QM effects in MOS devices