Method to improve flash EEPROM cell write/erase threshold voltage closure
 A method to erase data from a flash EEPROM cell while electrical charges trapped in the tunnel oxide of a flash EEPROM cell are eliminated to maintain proper separation of the programmed threshold voltage and the erased threshold voltage after extended programming and erasing cycles. The method to erase a flash EEPROM cell begins by first applying a first relatively high positive voltage pulse to the source of the flash EEPROM cell. Simultaneously a ground reference voltage is applied to the control gate and to the semiconductor substrate. At this same time the drain is floating. The flash EEPROM cell is then detrapped by floating the source and drain and applying a second relatively high positive voltage pulse to the semiconductor substrate. At the same time a relatively large negative voltage pulse is applied to the control gate. 
Taiwan Semiconductor Manufacturing Company, Ltd.
G
G11C
inventional
Ming-Chou Juang-ker Kuo-Reay Jian-Hsing
Ho Yeh Peng Lee