Ovshinsky's memories

Abstract

Flash has been the dominant process for non-volatile storage for two decades, and remains a healthy business, with versions used in many portable electronic products. However, even its strongest proponents agree it is likely to run out of steam as cell scaling becomes harder with smaller geometries. As flash starts to hit the scaling wall, Stanford Ovshinsky's phase-change memories are staking their claim to be the next-generation non-volatile memory technology. Recent announcements of advances with phase-change materials and memory cell structures suggest that memories based on these materials may be the ones to watch and beat. Phase-change materials change their physical properties depending on whether they are in their amorphous or crystalline phase. In phase-change solid-state memory cells, the phase-change materials are deposited as an ultra-thin film on the the surface of a silicon chip, and an electric current is used to effect the switch between phases and to detect the phase change via an electrical resistance measurement. The materials and memory cells are sometimes referred to as ovonic memories, in recognition of Ovshinsky's pioneering role. The basic phase change material used in ovonic memory is an alloy of germanium, antimony and tellurium (GeSbTe). The article discusses the prospects of ovonic memories.