A fast test to generate flash memory threshold voltage distribution map

Abstract

This paper describes a method to determine threshold voltage (V/sub th/) distribution as a multi-colored bitmap of the die. That is, a visual indication of relative threshold voltages on different areas of the die is provided. The spatial distribution of threshold voltage is felt to be more informative than conventional techniques which provide results as a bell-curve Gauss distribution plot of threshold voltage versus number of cells. The time required for test execution (including data gathering) is considerably less than the time taken by conventional methods.