APDE scheme for flash memory application

摘要

A method for erasing a flash EEPROM device that includes a plurality of memory cells. The plurality of memory cells is erase verified and an erase pulse is applied to the memory cells if there are undererased memory cells and the memory cells are again erase verified. This cycle repeats until all cells verify as erased and a flag is set to NO. The plurality of memory cells is overerase verified and an overerase correction pulse is applied to the bitline to which the overerased memory cell is attached and the flag is set to YES. This cycle repeats until all cells verify as not being overerased. If it is determined after the overerase verification step that the flag is set to YES, the plurality of memory cells is again erase verified and the procedure repeats. If it is determined after the overerase verification step that the flag is set to NO, the erase procedure is considered finished.