Effects of oxygen content and oxide layer thickness on interface state densities for metal-oxynitride-oxide-silicon devices

Abstract

The interface state density of metal-oxynitride-oxide-silicon (MNOS) devices was investigated as a function of the tunnel oxide thickness and the amount of oxygen in the oxynitride films. Nitrous oxide gas was used to introduce oxygen into the oxynitride film during the deposition process. As 17 at. % oxygen was introduced into the oxynitride film, the lowest oxide-silicon interface state density increased from 3.0 to 3.5×1011 cm−2 eV−1 for 90-Å oxide MNOS devices, and decreased from 5.1 to 3.65×1011 cm−2 eV−1 for 20 Å oxide devices. The increase in interface state density with increasing oxygen for 90-Å oxide devices may be due to an increase in the loss of hydrogen passivation at the interfacial regions as more oxygen is introduced into the film. The higher interface state density for the 20 vs 90 Å oxide samples, for a given oxygen content of the oxynitride films, may be due to additional contributions from the trapping states near or at the oxide-oxynitride interface. However, the decrease in the interface state density for increasing oxygen concentration for 20-Å oxide MNOS devices may be due to passivation of trapping states at the oxide-oxynitride interface by oxygen. The silicon dangling bonds responsible for these trapping states may be compensated by oxygen introduced during the deposition process.