Comparison of Lateral Non-uniformity Phenomena between HfO2 and SiO2 from Magnified C-V Curves in Inversion Region

Abstract

A methodology to evaluate the non-uniformity phenomena in MOS structure from magnified C-V curve is proposed. With considering the effective oxide charge influence on inversion to deep depletion region, the localized injection of avalanche hot carriers from Si-substrate will induce highly leaky areas at Oxide/Silicon interface. These areas can be evaluated quantitatively via local depletion capacitance model in MOS device. Through fitting C-V curves from inversion to deep depletion region with the uniform area ratio K, the index of oxide quality can be obtained. For SiO2, K values increase with EOTs which means the interfacial quality gets better when SiO2 become thicker. For HfO2, K values decrease with EOT which means thicker HfO2 stack gets poor interfacial quality. The uniform area ratio K of HfO2 is lower than SiO2 due to the inherent property of HfO2 film which contains too many traps because they are not as perfect as SiO2.