Flash memory wordline decoder with overerase repair

Abstract

The invention provides a flash memory and decoder with overerase repair that can provide three word line voltages to overcome the overerased problems. The wordline decoder includes a wordline latch that provides a high flexibility of erasing size so that single/multiple sub-wordlines, single/multiple wordlines, single/multiple block, and whole array can be erased simultaneously. An exemplary embodiment of a flash memory wordline decoder that can provide three voltages includes a plurality of voltage terminals to receive a plurality of voltages, a plurality of address terminals to receive a plurality of address signals, a procedure terminal to receive a procedure signal, and a plurality of output wordlines adapted to be coupled to a bank of flash transistors. The wordline decoder circuit is configured to decode the address signals and includes a plurality of latches coupled to the wordlines and configured to latch the wordlines and to provide one of a plurality of operational voltages on the wordlines to accomplish a predetermined operation responsive to the procedure signal. The plurality of voltage terminals are configured in a way that the high voltage required for erasure or for programming needs not be discharged in verification. Another exemplary embodiment provides a wordline decoder that provides three wordline voltages for verification and repairing, and also for erasure. Advantages of the invention include available full verifications for erasure, repairing and programming, tight cell threshold distribution, high efficiency repairing, no discharging the high voltage cells in verifications, full range verification voltages.