The future of phase-change semiconductor memory devices

Phase-change memory (PCM) has recently been under active development by a number of semiconductor manufacturing companies and research laboratories. This development has been accelerated both by the rapidly growing market for nonvolatile memory in cellular phones and other types of portable electronic equipment and by the realization that Flash memory, the currently dominant nonvolatile memory technology, will face serious challenges as it scales in the future to smaller and smaller dimensions. PCM nonvolatile memory technology has shown scaling, speed, and endurance characteristics which could allow it to replace Flash memory in future applications and, perhaps in time, DRAM memory as well. Commercial introduction of PCM memory chips which can replace NOR Flash is anticipated to begin this year. The performance and scaling advantages of PCM are a direct consequence of the memory cell device physics and fundamental properties of the phase-change alloys and these will be reviewed in light of future memory requirements and competition from other emerging memory technologies.