Effect of field oxide structure on endurance characteristics of NAND flash memory

As NAND flash cell sizes have been scaled down, endurance characteristics have suffered severe limitations in the NAND flash memory. Two NAND flash cell structures, the wing spacer structure and the no wing spacer structure, have been constructed to compare their endurance characteristics. The wing spacer structure has more trap sites at the active edge area due to program/erase (P/E) cycle stress because of the short distance from the active edge to the control poly. Thus, the endurance characteristics are degraded by traps generated at the active edge area. In addition, it has been confirmed that the threshold voltage (V_T) shift of the wing spacer structure was about 15.2% higher in erased cells and 10.9 % higher in programmed cells than those of the no wing spacer structure after the stress of 10⁴ P/E cycles.