Patent ID: 7443724
Filing Date: 2008-10-28
Classification: G11C

Abstract:
1. A method of programming a nonvolatile memory cell capable of storing n bits of data (n is a natural number equal to or larger than two), the method comprising: applying a first write voltage to the memory cell so as to alter a threshold voltage of the memory cell, when a first bit of data is a first value; determining whether the threshold voltage of the memory cell has reached a first verify level, after applying the first write voltage; increasing the first write voltage by a first amount if it is determined that the threshold voltage of the memory cell has not reached the first verify level; applying the increased first write voltage to the memory cell so as to alter the threshold voltage of the memory cell; applying a second write voltage to the memory cell so as to alter the threshold voltage of the memory cell after determining the memory cell has reached the first verify level; determining whether the threshold voltage of the memory cell has reached a second verify level, after applying the second write voltage, if a second bit of data is a second value; determining whether the threshold voltage of the memory cell has reached a third verify level, after applying the second write voltage, if the second bit of data is a third value, the third value differing from the second value; increasing the second write voltage by a second amount if it is determined that the threshold voltage of the memory cell has not reached the second verify level; and applying the increased second write voltage to the memory cell so as to alter the threshold voltage of the memory cell.