single-event upset in 3-D charge-trap NAND flash memories

Abstract

The effects of single-event upset (SEU) on the threshold voltage ( VT ) of a programmed cell in 3-D charge-trap (CT) NAND flash memory have been investigated using 3-D technology-computer-aided design (TCAD) simulations. After ion strikes, the surrounding electric field ( E -field) accelerates the generated holes into the CT layer (CTL), which lowers VT of the programmed cell. The tunneling oxide (TOX) strike causes a more severe VT shift than the blocking oxide (BOX) strike due to the higher E -field in the TOX layer. As the strike angle increases from 0° (lateral) to 90° (vertical), the effective irradiation volume is reduced, resulting in the mitigation of the SEU influence. Scaling of cell dimensions becomes more vulnerable to SEU except for the thinner TOX.