AN IMPROVED TECHNIQUE FOR THE EVALUATION OF SURFACE FERMI ENERGY IN METAL-OXIDE-SEMICONDUCTOR CAPACITORS

The band bending at the Si:SiO2 interface in the metal-oxide-semicondu ctor system is often evaluated using a low-frequency capacitance-volta ge measurement. Here we discuss the effect of commonly used approximat ions for the oxide capacitance and midgap gate voltage on the derived gate voltage dependence of the surface Fermi energy, and show that the y can result in significant systematic errors. Using both high- and lo w-frequency capacitance-voltage data, a simple self-consistent algorit hm is presented that yields a more accurate surface Fermi energy versu s gate voltage characteristic. Hence better estimates of quantities su ch as fixed oxide charge density, interface state capture cross sectio n and density of interface states can be obtained.