Density functional theory study of deep traps in silicon nitride memories

Using density functional theory, the interaction of hydrogen with a nitrogen vacancy in β-Si3N4 is investigated. A single H atom was found to be energetically favorable over non- and doubly protonated vacancies. The traps composed of excess silicon and hydrogen have negative correlation energy which is connected with different distances of Si–H and Si–Si bonds in charged and neutral states. The energy gains after trapping are consistent with trap activation energies in advanced silicon nitride memories. Based on the present results, a model of memory traps is proposed.