Patent ID: 8488369

Claim:
A method of altering distribution of a chosen characteristic of a plurality of memory cells forming a memory device, comprising: identifying a subset of said plurality of memory cells whose value of said chosen characteristic is within a predetermined end region of said distribution; performing a burn-in process during which one or more operating parameters of the memory device are set to induce ageing of said memory cells; during the burn-in process, for each memory cell in said subset, fixing the value stored in that memory cell to a selected value which exposes that memory cell to a stress condition; and during the burn-in process, for each memory cell not in said subset, alternating the value stored in that memory cell in order to alleviate exposure of that memory cell to said stress condition, wherein: said chosen characteristic is a read speed with which a read of a data value stored in a memory cell takes place; and the predetermined end region comprises read speed values exceeding a desired read speed, such that said subset determined in said identifying step comprises those memory cells that can be read more quickly than the desired speed.