Evolution of Phase-Change Memory for the Storage-Class Memory and Beyond

In this article, the development history and the technical hurdles of phase-change memory (PCM) are reviewed and recent progress and future directions are discussed. Prospects of PCM for storage-class memory (SCM) are discussed in terms of the technical challenges to satisfy the market requirements, mainly for the performance and cost effectiveness. For a more in-depth discussion, PCM is segmented into the memory part, the access device part, and the sensing scheme part. In the memory part, Set (crystallization)-Reset (amorphization) write characteristics and thermal disturbance (TDB) will be reinterpreted in terms of power consumption and performance of SCM. In the access device part, the application history of various devices, such as the transistor, the diode, and the two-terminal selector, will be reviewed and explained based on the process integration issues and area efficiency. In the next part, various sensing schemes used to make a lower read latency, multilevel cell (MLC), and cross point (X-point) are summarized. Thereafter, future directions and possible evolution pathways of 3-D structures, including X-point and vertical X-point (VXP), will be discussed for the first time. Finally, the feasibility of PCM for neuromorphic application will be followed.