Chapter 3 - Phase-change memory

Abstract

Phase-change memory (PCM) is a key enabling technology for nonvolatile electrical data storage at the nanometer scale. A PCM device consists of a small active volume of phase-change material sandwiched between two electrodes. In PCM, data are stored using the electrical resistance contrast between a high-conductive crystalline phase and a low-conductive amorphous phase of the phase-change material. An appealing attribute of PCM is that the stored data are retained for a very long time (typically 10 years at room temperature), but is written in only a few nanoseconds. This property could enable PCM to be used for nonvolatile storage such as Flash and hard disk drives, while operating almost as fast as high-performance volatile memory such as dynamic random access memory (DRAM). Another particularly interesting emerging application for PCM is brain-inspired computing, where the memory devices are not only used to store data but also to perform some computational tasks. This chapter first explains the read and write operation principles of PCM and describes the physical mechanisms involved. Then key enablers of PCM for brain-inspired computing are presented along with experimental results on PCM arrays which highlight various opportunities and challenges involved in using PCM for this application.