The effect of hydrogenation on silicon nitride storage layer: A first-principles investigation

In this paper, based on first-principles calculations, we have carried out a comprehensive study of the hydrogenation effect on hexagonal silicon nitride (β-Si3N4). There are two types of nitrogen in β-Si3N4, we name them as N1 and N2. We choose nitrogen vacancy and silicon substitution as the main defects in Si3N4. For each defect, we first compare the retention characteristics of the modified Bader charge and trap energy before and after hydrogenation. The results show that hydrogenation will weaken the defects to maintain both electrons and holes. Moreover, the defect of silicon substitution at N2 site would only trap holes after hydrogenation. With regard to endurance characteristic, our studies reveal that the defects present differences after hydrogenation. For nitrogen vacancy, hydrogenation has no effect on endurance. However, the endurance of silicon substitution at N1 site degenerates after hydrogenation. Taking full account of retention and endurance, we deem that nitrogen vacancy is the better charge trap in hydrogenated silicon nitride storage layer.