Damage and optimization of program/erase operation in MANOS 3D NAND flash memory

Abstract

In this work, the damage caused by program/erase (P/E) operation in 3D NAND memory devices made of Metal-Al2O3-Nitride-Oxide-Semiconductor (MANOS) was examined. The damage caused by program and erase operations independently was intended to be identified and realized using several types of cycling stresses. Physical models were discussed to interpret that the anode hole could be responsible for the damage to the Al2O3-Nitride-Oxide (ANO) gate stacks. The tunnel oxide damage was caused by the erase operation and could be enhanced by a higher cycling temperature. This led to a faster program and a slower erase, and it demonstrated a strong correlation with retention and its active energy (Ea). On the other hand, program operation may merely be contributing to block oxide damage, with an invisible impact on erase efficiency and retention but a reduction in program efficiency. An optimized single pulse erase scheme was discussed. Not only can it reduce ANO damage and improve retention, but it can also decrease erase time. Furthermore, a feasible endurance acceleration method was discussed to save a lot of cycling time.