Modified Fowler–Nordheim tunnelling for modelling charge injection into Si3N4 in an Al/Si3N4/Si structure

Abstract

Charge injection behaviours in silicon nitride of an Al/Si3N4/n-Si metal–insulator–semiconductor (MIS) device are systematically studied before and after applying different high constant DC bias conditions with the aim of controlling charge accumulation in the dielectric when a high actuation voltage is applied. We found that both polarity and magnitude of charge accumulation in silicon nitride depend on the biasing direction. Charge injection from the semiconductor to the silicon nitride always dominates over charge injection from the Al electrode to the silicon nitride. Negative charge accumulation happens in silicon nitride when the Al electrode is positively biased, and positive charge accumulation occurs in silicon nitride when the Al electrode is negatively biased. The positive charge accumulation is much bigger than the negative charge accumulation under the same magnitude of stress voltage. Furthermore, the experimental results also show that the charge injection level exponentially increases with the applied voltage across the silicon nitride. These observed experimental results can be well explained by a modified Fowler–Nordheim tunnelling charge injection model, which takes into account the roles of both electrons and holes in the process of charge injection.