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SONOS Device With Tapered Bandgap Nitride Layer

2005; Institute of Electrical and Electronics Engineers; Volume: 52; Issue: 5 Linguagem: Inglês

10.1109/ted.2005.846347

1557-9646

K. H. Wu, H.C. Chien, Che‐Man Chan, T.-S. Chen, Chien‐Ting Kao,

Ferroelectric and Negative Capacitance Devices

A unique, band-engineered, configuration of the charge-trapping layer in silicon-oxide-nitride-oxide-silicon (SONOS) devices is proposed for high-density Flash memory applications. In this paper, a varying Si-N ratio in modified silicon nitride is obtained by controlling reaction gas flow-rate during deposition. This generates a graded composition profile from Si-rich at the bottom to N-rich at the top in a nitride film. The nonuniform composition profile of the silicon nitride layer corresponds to a tapered bandgap and results in significant improvement in device performance and reliability characteristics including operation window, cycling endurance and data retention. The dramatic improvement can be attributed to increased charge-trapping efficiency of the nitride layer since a significant number of highly accessible trapping levels are created in the tapered bandgap. In addition, the increased barrier height between the nitride and tunnel oxide layers also reduces back-tunneling probability and assists charge trapping. The SONOS device designed in this paper is suitable for next-generation Flash memory applications.