Patent ID: 8194457

Claim:
A soft program method for recovering memory cells, which are over erased in an erase operation, of a memory array including a plurality of memory blocks, the method comprising: (A) soft programming the plurality of memory blocks with a first bias voltage, wherein each of the memory blocks is segmented into a plurality of memory units; (B 1 ) soft programming a selected memory unit within a selected memory block with a second bias voltage; (B 2 ) determining whether a judging criterion corresponding to the selected memory unit is met; if not, repeating from step (B 1 ); (B 3 ) when the judging criterion is met, determining whether the selected unit is a last memory unit within the selected memory block; (B 4 ) when the selected unit is not the last memory unit, assigning other memory unit as the selected memory unit and repeating from step (B 1 ); and (C) when the selected memory unit is the last memory unit, bit-by-bit soft programming the memory array with a third bias voltage.