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 extracti on of the increase in the effective electrical oxide thickness (Delta(tox) = t(ox, expt) - t(ox, physical)) in MOS accumulation layers with heavily do ped sudstrates 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 s elf-consistent simulations have been extended to accumulation regions, and the experimental results for the accumulation region have been compared wit h simulations, It has been shown that at moderate to high doping levels, De lta t(ox) is as much as 0.4 to 0.5 nm for both electrons and holes, whereas for very high doping levels (> 1 X 10(19) cm(-3)) Delta t(ox) approaches z ero. Thus, the experimental accumulation cm capacitance is predicted suffic iently well by the classical analysis itself.