Phase-change random access memory: A scalable technology

• Published in: IBM journal of research and development Vol. 52; no. 4.5; pp. 465 - 479
• Main Authors: Raoux, S., Burr, G. W., Breitwisch, M. J., Rettner, C. T., Chen, Y.-C., Shelby, R. M., Salinga, M., Krebs, D., Chen, S.-H., Lung, H.-L., Lam, C. H.
• Format: Journal Article
• Language: English
• Published: Armonk International Business Machines Corporation 01.07.2008
• Subjects: CROSS SECTIONS; DESIGN; DIMENSIONS; GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; Information storage; Information systems; national synchrotron light source; PARTICLE SIZE; PHASE CHANGE MATERIALS; Phase transitions; PROGRAMMING; Random access memory; RELIABILITY; THICKNESS
• ISSN: 0018-8646; 0018-8646; 2151-8556
• DOI: 10.1147/rd.524.0465

Nonvolatile RAM using resistance contrast in phase-change materials [or phase-change RAM (PCRAM)] is a promising technology for future storage-class memory. However, such a technology can succeed only if it can scale smaller in size, given the increasingly tiny memory cells that are projected for future technology nodes (i.e., generations). We first discuss the critical aspects that may affect the scaling of PCRAM, including materials properties, power consumption during programming and read operations, thermal cross-talk between memory cells, and failure mechanisms. We then discuss experiments that directly address the scaling properties of the phase-change materials themselves, including studies of phase transitions in both nanoparticles and ultrathin films as a function of particle size and film thickness. This work in materials directly motivated the successful creation of a series of prototype PCRAM devices, which have been fabricated and tested at phase-change material cross-sections with extremely small dimensions as low as 3 nm × 20 nm. These device measurements provide a clear demonstration of the excellent scaling potential offered by this technology, and they are also consistent with the scaling behavior predicted by extensive device simulations. Finally, we discuss issues of device integration and cell design, manufacturability, and reliability. [PUBLICATION ABSTRACT]