Novel Heat Dissipating Cell Scheme for Improving a Reset Distribution in a 512M Phase-change Random Access Memory (PRAM)

Abstract

Programming with larger current than optimized one is often preferable to ensure a good resistance distribution of high-resistive reset state in high-density phase-change random access memories because it is very effective to increase the resistance of cells to a target value. In this paper, we firstly report that this larger current writing may conversely degrade the reset distribution by reducing the resistance of normal cells via the partial crystallization of amorphous Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> Sb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> Te <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> and this degradation can be suppressed by designing a novel cell structure with a heat dissipating layer.