Charge loss behavior of a metal-alumina-nitride-oxide-silicon-type flash memory cell with different levels of charge injection

We found that the charge loss behavior of metal-alumina-nitride-oxide-silicon-type flash memory was highly dependent on the amount of injected charge (Qinj). Beyond the critical level of Qinj, the direction of the dominant charge loss changed from pointing toward SiO2 to pointing toward Al2O3. The highly injected charges could cause the band bending of Al2O3, which reduced the tunneling distance across Al2O3 with the low conduction band offset. These results were verified by experimental results and theoretical device modeling through a comparison of the charge loss rate and the tunneling rate between a SiO2∕Si3N4∕SiO2 stack and a SiO2∕Si3N4∕Al2O3 stack.