A programming method for flash erasable programmable memory devices (flash EPROMs) comprises a first step of erasing the array of cells, then applying a control gate voltage to access a number of control gates. Any number of control gates can be accessed, but accessing four or eight control gates may have advantages. Regardless of the number of control gates accessed, a digit line voltage is applied to access one of the digit lines, which activates a number of cells. The digit line voltage is sensed for a voltage drop, which indicates the presence of at least one over-erased activated cell. If a digit line voltage drop is detected, a sense voltage is applied to each of the activated cells to determine which is over-erased. A heal voltage is applied to the over- erased cell for an interval of time to store electrons on the floating gate of the over-erased cell. The sense voltage is applied to the over- erased cell to determine if the cell remains over-erased, and if the cell remains over- erased the heal voltage is again applied to the over-erased cell. The sense voltage is then applied to the over-erased cell to determine if it remains over-erased.
展开▼
