Charge Trapping Properties of Thin Plasma Nitrided Oxides Induced by Nitrogen and Hydrogen Incorporation

ABSTRACTIn this work, we report the effects of an ammonia plasma nitridation on the charge trapping properties of thin SiO2 films in correlation with their nitrogen and hydrogen contents. Electron traps characteristics were determined by die avalanche injection technique. Hydrogen contents were measured by Elastic Recoil Detection analysis (ERDA). Nitrogen depth profiles were obtained with Auger spectroscopy. It is shown that the bulk electron trapping properties are essentially controlled by the specificity of hydrogen and nitrogen incorporation in the SiO2 films during the ammonia plasma process. For short nitridation times, an increase of hydrogen related electron trap densities is observed in good agreement with hydrogen ERDA measurements. However hydrogen concentration never exceeds 3 at% and can be scaled down by a short time post-nitridation anneal in oxygen, to a level comparable indeed inferior to that of a non-nitrided oxide. For heavy nitridation, an additional electron trap is detected which could be associated to the presence of nitrogen in the bulk of SiO2.