： Metal-oxide-nitride-oxide-silicon （MONOS） capacitors with thermally grown SiO2 as the tunnel layer are fabricated, and the effects of different ambient nitridation （NH3, NO and N20） on the characteristics of the memory capacitors are investigated. The experimental results indicate that the device with tunnel oxide annealed in NO ambient exhibits excellent memory characteristics, i.e. a large memory window, high program/erase speed, and good endurance and retention performance （the charge loss rate is 14.5% after l0 years）. The mechanism involved is that much more nitrogen is incorporated into the tunnel oxide during NO annealing, resulting in a lower tunneling barrier height and smaller interface state density. Thus, there is a higher tunneling rate under a high electric field and a lower probability of trap-assisted tunneling during retention, as compared to N20 annealing. Furthermore, compared with the NH3-annealed device, no weak Si-H bonds and electron traps related to the hydrogen are introduced for the NO-annealed devices, giving a high-quality and high-reliability SiON tunneling layer and SiON/Si interface due to the suitable nitridation and oxidation roles of NO. Key words： MONOS memory; memory characteristics; annealing; nitridation
