METHOD FOR MULTILEVEL PROGRAMMING OF PHASE CHANGE MEMORY CELLS USING A PERCOLATION ALGORITHM

摘要

A method and apparatus for programming a phase change memory cell (2) is disclosed. A phase change memory cell (2) includes a memory element (10) of a phase change material having a first state ("11"), in which the phase change material is crystalline and has a minimum resistance level, a second state ("00") in which the phase change material is amorphous and has a maximum resistance level, and a plurality of intermediate states with resistance levels there between. The method includes using programming pulses to program the phase change memory cell (2) in either the set, reset, or one of the intermediate states. To program in the intermediate states, a programming pulse creates a crystalline percolation path having an average diameter (D) through amorphous phase change material and a second programming pulse modifies the diameter (D) of the crystalline percolation path to program the phase change memory cell to the proper current level.