Improved memory performance of metal–oxide–nitride–oxide–silicon by annealing the SiO tunnel layer in different nitridation atmospheres

Metal–oxide–nitride–oxide–silicon(MONOS)capacitorswiththermallygrownSiO2asthetunnellayer arefabricated,andtheeffectsofdifferentambientnitridation(NH3,NOandN2O)onthecharacteristicsofthememory 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 10 years).The mechanism involved isthatmuchmorenitrogenisincorporatedintothetunneloxideduringNOannealing,resultinginalowertunneling 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 N2O 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.