Energy concepts involved in MOS characterization

Abstract

Starting from a quantum statistical reasoning, it is demonstrated that entropy properties of silicon/silicon dioxide interface electron traps may have a strong influence on measured distributions of interface states, depending on measurement method used. For methods, where the Fermi-level is used as a probe to define an energy position, the scale is based on free energy. On the other hand, methods based on thermal activation of electrons give the distribution on an enthalpy scale. It is shown that measured interface state distributions are influenced by the distribution of entropy, and that common features of measured energy distributions may be influenced by entropy variations. These results are used to interpret experimental data on the energy distribution of electron capture cross sections with an exponential increase followed by a more or less constant value as the energy distance of the traps from the conduction band edge increases. Such a relation is shown to be consistent with a situation where the emission and capture processes of electrons obey the Meyer-Neldel rule.