Photoionization cross section of electron traps in thin oxynitride films of metal-oxynitride-oxide-silicon devices

Abstract

The flat-band voltage monitored photodepopulation technique in combination with photoinjection was used to investigate the first-order kinetics of a trap emptying in low-pressure chemical vapor deposited thin films of silicon oxynitride (SiOx Ny ) of metal-oxynitride-oxide-silicon devices. An effective photoionization cross section associated with deep electron traps was determined to be 4.9–18.9×10−19 cm2 over the photon energy range of 2.06–3.1 eV for oxynitride films containing 7–17 at. % of oxygen. At a fixed oxygen concentration, the photoionization cross section decreased from 8.3×10−19 to 4.9×10−19 cm2 as the photon energy was lowered from 2.06 to 2.48 eV. However, the photoionization cross section at a fixed photon energy within this range showed an average decrease of 18% for a 10% increase in the amount of oxygen content in the oxynitride film. The photoionization cross section increased from 4.9×10−19 to 18.9×10−19 cm2 as the photon energy was increased from 2.48 to 3.1 eV. Over this higher photon energy range, a 28% decrease in photoionization cross section was observed for the same 10% increase of oxygen content in the oxynitride films.