Patent ID: 6198664
Filing Date: 2001-03-06
Classification: G11C

Abstract:
A method of erasing a flash Electrically-Erasable Programmable Read Only Memory (EEPROM) that includes a plurality of memory cells, the method comprising:(a) verifying the erase of the plurality of memory cells to determine if there are undererased memory cells in the plurality of memory cells;(b) applying an erase pulse to the plurality of memory cells if there are undererased memory cells in the plurality of memory cells;(c) repeating steps (a) and (b) until all of the plurality of memory cells verify as erased;(d) setting a flag to NO when all of the plurality of memory cells verify as erased;(e) overerase verifying the plurality of memory cells to determine if there are overerased memory cells in the plurality of memory cells;(f) applying an overerase correction pulse to a bitline to which an overerased memory cell is attached;(g) setting the flag to YES when an overerase correction pulse is applied to a bitline;(h) repeating steps (e) through (g) until all of the plurality of memory cells verify as not being overerased; and(i) determining if the flag is set to YES.