TID effects on retention of 0.13 μm SONOS memory cell: A device simulation approach

Flash memory cells used in space applications are under continuous impact of Total Ionizing Dose (TID) effects. It causes charge trapping in the oxide and in the oxide/substrate interface. In this work, we investigate the TID radiation response of 0.13μm SONOS flash memory cell with different charge states upto 1 Mrad(Si). It is found that threshold voltage of programmed and virgin states of memory decreases with irradiation due to accumulation of holes. For erased state, accumulation of induced holes and loss of holes in nitride layer tends to cancel each other, causing no significant change. Further, we also proposed a device simulation approach to test data retention at room and high temperature as a function of TID irradiations received. We observed that retention is not much dependent on irradiation dose. TID exposure degrades the device retention and this effect enhances with increase in temperature due to thermally activated electron detrapping. All the analyses are accomplished using physical simulation models of charge trapping in Sentaurus TCAD suite, comparing results with established qualitative models.