An experimental study of the effect of quantization on the effective electrical oxide thickness in MOS electron and hole accumulation layers in heavily doped Si

This work presents for the first time experimental results for the extraction of the increase in the effective electrical oxide thickness (Δt_ox=t_ox,expt-t_ox,physical) in MOS accumulation layers with heavily doped substrates due to quantum mechanical (QM) effects, using experimentally measured MOS capacitance-voltage (C-V) characteristics and experimentally verified fullband self-consistent calculations. In addition, the fullband self-consistent simulations have been extended to accumulation regions, and the experimental results for the accumulation region have been compared with simulations. It has been shown that at moderate to high doping levels, Δt_ox is as much as 0.4 to 0.5 nm for both electrons and holes, whereas for very high doping levels (>1×10¹⁹ cm^-3) Δt_ox approaches zero. Thus, the experimental accumulation capacitance is predicted sufficiently well by the classical analysis itself