A 4 Mb NAND EEPROM with tight programmed V/sub t/ distribution

Abstract

Described is a 5-V-only 4-Mb (512K*8 b) NAND EEPROM (electrically erasable programmable ROM) with tight programmed threshold voltage (V/sub t/) distribution, controlled by a novel program-verify technique. A tight programmed V/sub t/ distribution width of 0.8 V for the 4 Mb cell array is achieved. By introducing a compact row-decoder circuit, a die size of 7.28 mm*15.31 mm is achieved using 1.0 mu m design rules. A unique twin p-well structure has made it possible to realize low-power 5 V-only erase/program operation easily and to achieve 100 K-cycle endurance. >