Patent ID: 7440315

Claim:
A method for resetting a phase change memory cell having a memory cell threshold voltage, the memory cell threshold voltage being a voltage at which at least a portion of the amorphous phase change material of the memory cell starts to break down, the memory cell coupled to an access device having an access device threshold voltage, comprising: selecting a voltage V WL , voltage V WL being larger than the access device threshold voltage; reading a resistance of the memory cell by (a) applying a voltage, smaller than the memory cell threshold voltage, to a bit line coupled to the memory cell, and by (b) applying a voltage, larger than the access device threshold voltage, to a word line coupled to the access device; if the resistance is larger than a chosen resistance, end the resetting of the memory cell; if the resistance is not larger than the chosen resistance, then proceed by: applying a voltage, larger than the memory cell threshold voltage, to the bit line; and applying voltage V WL to the word line to reset the memory cell; reading the resistance of the memory cell by (a) applying a voltage, smaller than the memory cell threshold voltage, to the bit line coupled to the memory cell, and by (b) applying a voltage, larger than the access device threshold voltage, to the word line; if the resistance is larger than the chosen resistance, end the resetting of the memory cell; if the resistance is not larger than the chosen resistance, then proceed by: applying a voltage, larger than the memory cell threshold voltage, to the bit line; increasing voltage V WL by a voltage ΔV; and applying increased voltage V WL to the word line to reset the memory cell; and return to the second reading step.