Patent ID: 6091631
Filing Date: 2000-07-18
Classification: G11C

Abstract:
A method of programming a multi-level flash memory cell to one of a plurality of threshold voltage (vt) levels as represented by a plurality of bits, the method comprising the steps of:(a) erasing the cell so that the cell has a threshold set to a lowest one of the vt levels;(b) determining if a state of a most significant one of the bits identifies a first maximum representable threshold value, and if so programming the cell to a first one of the vt levels before preceding to step (c);(c) determining if the state of a next most significant bit identifies a second maximum representable threshold value while a state of the most significant bit identifies less than the first maximum representable threshold value, and if so programming the cell to a second one of the vt levels; and(d) determining if the state of the most significant bit along with a state of the next most significant bit identify both the first and second maximum representable threshold values, and if so programming the cell to a third one of the vt levels.