Robust Data Retention and Superior Endurance of Silicon-Oxide-Nitride-Oxide-Silicon-Type Nonvolatile Memory with NH3-Plasma-Treated and Pd-Nanocrystal-Embedded Charge Storage Layer

Abstract

In this study, we investigated an ammonia (NH3) plasma-pretreatment (PT) for suppressing the formation of interface states between metal nanocrystals (NCs) and the surrounding dielectric during the NC forming process with the aim of obtaining a highly reliable Pd NC memory. The discharge-based multipulse (DMP) technique was performed to analyze the distribution of trap energy levels in the Pd NCs/Si3N4-stacked storage layer. Through DMP analysis, it is confirmed that the NH3 PT not only significantly increases the quality of the surrounding dielectric of metal NCs but also effectively passivates shallow trap sites in the Si3N4 trapping layer. As compared with the sample without NH3 PT, the NH3-plasma-treated device exhibits better reliability characteristics such as excellent charge retention (only 5% charge loss for 10(4) s retention time) and very high endurance (no memory window narrowing after 10(5) program/erase cycles). In addition, the robust multilevel cell retention properties of the NH3-plasma-treated memory are also demonstrated. (C) 2012 The Japan Society of Applied Physics