Improvement of the dielectric film characteristics of Inter-poly Oxide-Nitride-Oxide (ONO) in Flash memory devices

This Inter-poly Oxide-Nitride-Oxide (ONO) dielectric film has been widely used as dielectric films in stacked gate Flash memory devices. The ONO dielectric film plays an important role in ensuring good reliability in flash memory devices. In this paper, the characteristics of ONO dielectric films have been analyzed. These ONO films were fabricated using different methods, including conventional furnace deposition and an In-Situ Steam Generated (ISSG) process. The quality of the dielectric film has been evaluated electrically on silicon. Electrical characterization of the above-fabricated wafers were first carried out using the constant current stressing method, followed by an additional verification carried out on actual memory cells, to investigate the Flash memory write/erase endurance. Better reliability performance of ISSG deposited film over the conventional furnace deposited film has been demonstrated. The results also suggest that the bottom oxide layer could be the cause of the overall ONO dielectric film degradation. The possibility of further reliability improvement over furnace deposited dielectric film is also described in this paper.