DETERMINATION OF THE TRAPPED CHARGE-DISTRIBUTION IN SCALED SILICON-NITRIDE MONO NONVOLATILE MEMORY DEVICES BY TUNNELING SPECTROSCOPY

In this paper an analytical model for extraction of the spatial trapped charge density in silicon nitride has been formulated with amphoteric trap statistics. The model includes the energy distribution of traps in nitride and the time-dispersive tunneling transitions from these nitride traps. We have examined charge loss from sub-100 angstrom nitride films with MONOS memory devices at 110 K at different gate bias conditions. We conclude that by maintaining depletion/weak-inversion at the Si surface, the primary charge loss mechanism is back-tunneling of charge from the nitride traps into the Si bands. The actual charge distribution in the nitride is a function of charge injection and trapping. We have demonstrated that modified Fowler-Nordheim tunneling of electrons into the nitride generates a non-uniform spatial distribution of trapped charge for a spatially uniform trap density in the nitride.