Retention Reliability Improvement of Silicon–Oxide–Nitride–Oxide–Silicon Nonvolatile Memory with N2O Oxidation Tunnel Oxide

Abstract

The reliability characteristics of silicon–oxide–nitride–oxide–silicon (SONOS) devices with different thin tunnel oxides are studied. The device with the tunnel oxynitride grown in pure N2O ambient at a high temperature has better performance, including better leakage current, programming speed, read-disturb, and retention characteristics, than that with a tunnel oxide layer grown by dry oxidation with N2 annealing treatment. Moreover, the properties of two-bit operation are also displayed by a reverse read method. Furthermore, the surface roughness and interface states between a tunnel oxide layer and a Si substrate are also observed by atomic force microscopy (AFM) and charge-pumping method to evaluate interfacial nitrogen incorporation. The results show that data retention reliability attained a significant improvement while maintaining good programming/erase performance and two-bit operation. This work can provide a straightforward way of reliability improvement for future flash memory application.