Accumulation and flow of charge in MOS structures with Al2O3 and SiO2-Al2O3 films on silicon

Abstract

A experimental study has been carried out on the processes involved in the accumulation and flow of charge in MOS structures with thin films of Al2O3 and SiO2-Al2O3 under various polarization conditions. The activation energy, the frequency factors, the sites of the trapping centers of the polarization charge, and the character of the flow of charge on thermal depolarization have been studied. It is shown that in a structure with a double-layer dielectric, the instability of the charge cannot be explained by the Maxwell-Wagner polarization model in its pure form because of the accumulation of charge in the spatially distributed trapping centers throughout the Al2O3 film. The parameters of the traps at the interface between the dielectrics have been determined and the contribution made to the instability of the charge by the migration of ions in these particular structures has been evaluated.