New scaling guidelines for MNOS nonvolatile memory devices

New phenomena in MNOS retention characteristics that originate from stored charge distribution are described and new scaling guidelines are indicated. The most significant phenomenon is that write-state retentivity is less dependent on the programmed depth, and is improved by reducing silicon nitride thickness. This behavior suggests that write-state charges are distributed rectangularly, while erase-state charges are distributed exponentially. The lower limit of the programming voltage is determined by write-state retentivity and not erase-state retentivity, and the write-state charge distribution depth determines the lower limit of silicon nitride thickness. The upper limit of the programming voltage is determined by erase-state retentivity after erase/write cycles. The scaling guidelines indicate that 16-Mb EEPROMs can be designed using MNOS memory devices