Impact of oxygen incorporation at the Si3N4∕Al2O3 interface on retention characteristics for nonvolatile memory applications

The correlation between properties of the Si3N4∕Al2O3 interface and retention degradation was investigated for metal-alumina-nitride-oxide-silicon-type flash memory devices. The intermixed region near the Si3N4∕Al2O3 interface showed an oxygen deficiency, which was confirmed by the binding energy of Al and Si peaks from x-ray photoelectron spectroscopy analysis. This oxygen deficiency led to the enhancement of trap-assisted tunneling current. Additional ambient oxygen annealing can eliminate the oxygen deficiency at the intermixed region, which in turn can significantly reduce charge loss through the blocking oxide. With the aim of better memory characteristics, oxygen incorporation shows promise for future nonvolatile memory applications.