Effect of substrate doping profile on C-V curves for thin MOS capacitors

We use a full quantum model of MOS (metal oxide semiconductor) structure to study the influence of a non-uniform doping profile of the substrate on th e capacitance-voltage (C-V) behavior of the structure. For different "reali stic" doping profiles, simulations are performed and compared to simulation s with an uniform doping and to C-V measurements for samples with oxide thi ckness in the range [2-5 nm] [1]. In each case, we have extracted the oxide thickness that is found to be independent of the doping and the at-band vo ltage which can be shifted up to 200 mV regarding the different profiles te sted here. Moreover, below about 3 nm, the shape of the C-V simulation is m ore affected, which shows that the doping profile of the substrate has a gr eat importance for an accurate C-V modeling of ultra-thin MOS structures.