Patent ID: 7965562
Filing Date: 2011-06-21
Classification: G11C

Abstract:
1. In a nonvolatile memory having an array of memory cells, wherein the memory cells are individually programmable to one of a range of threshold voltage levels, a method of programming a memory cell to a target threshold voltage level, comprising: providing a predetermined function for a memory cell under programming, the function yielding programming voltage value as a function of threshold voltage level a memory cell is targeted to be programmed thereto; programming the memory cell to the target threshold voltage level with a programming voltage having increasing amplitude; and stopping programming of the memory cell after the programming voltage has substantially reached a value as determined by the predetermined function evaluated at the target threshold voltage level; said providing a predetermined function that includes: designating a plurality of checkpoints of the function as designated checkpoint threshold voltage levels programmable by corresponding checkpoint programming voltage values; determining the corresponding checkpoint programming voltage values by alternately programming and verifying until individual ones of the checkpoint threshold voltage levels are program-verified; and calibrating the predetermined function to fit the checkpoint programming voltage values when evaluated at the checkpoint threshold voltage levels before being used to determine a programming voltage value for programming the memory cell to the target threshold voltage level.