Performance improvement of SONOS memory by bandgap engineering of charge-trapping layer

A significant improvement in device performance and reliability characteristics of silicon-oxide-nitride-oxide-silicon (SONOS) Flash memory has been achieved. Superior endurance characteristic shows no sign of degradation even after 10⁶ program/erase cycles and an extrapolated ten-year detection window of 1.4 V has been attained from retention measurement. The dramatic improvement results from a bandgap engineering of the SiN charge-trapping layer. With a gradual variation of the Si/N ratio from bottom to top of nitride film rather than uniform standard composition, a large number of highly accessible trapping levels are created in addition to the deepened barrier height between nitride and tunnel oxide that reduces back-tunneling probability. The proposed technique shall be valuable in pushing Flash memory technology into the next generation.