Fixed charge density and inversion layer mobility of thin gate oxides

Thin gate-oxide MOSFET's with different oxide thickness (100-400 Å) are fabricated. Improved measurement techniques are utilized and carefully controlled experiments are planned to minimize the usual errors encountered in thin-oxide measurements. It is found that the fixed charge density increases and inversion layer mobility decreases as the oxide thickness is reduced for the as-grown samples, whereas no similar dependence is observed for the samples with oxides etched down to the same thickness. The mobility degradation for the thin as-grown samples can be explained by the effects of coulomb and surface roughness scattering.