An improved technique for the evaluation of surface Fermi energy in metal-oxide-semiconductor capacitors

Abstract

The band bending at the Si:SiO2 interface in the metal-oxide-semiconductor system is often evaluated using a low-frequency capacitance-voltage measurement. Here we discuss the effect of commonly used approximations for the oxide capacitance and midgap gate voltage on the derived gate voltage dependence of the surface Fermi energy, and show that they can result in significant systematic errors. Using both high- and low-frequency capacitance-voltage data, a simple self-consistent algorithm is presented that yields a more accurate surface Fermi energy versus gate voltage characteristic. Hence better estimates of quantities such as fixed oxide charge density, interface state capture cross section and density of interface states can be obtained.