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The following Review Article appeared in the March/April 2010 issue of the Journal of Vacuum Science and Technology B , volume 28, issue 2, pages 223–262. The published article can be found at link.aip.org/link/?JVB/28/223 

# Phase change memory technology 

Geoffrey W. Burr 1 $^{,a}$, Matthew J. Breitwisch $^{2}$, Michele Franceschini$^{2}$, Davide Garetto$^{1}$, 

Kailash Gopalakrishnan $^{1}$, Bryan Jackson$^{1}$, B¨ ulent Kurdi $^{1}$, Chung Lam$^{2}$, Luis A. 

Lastras $^{2}$, Alvaro Padilla$^{1}$, Bipin Rajendran$^{2}$, Simone Raoux$^{2}$, and Rohit S. Shenoy1 1 

IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 2 

IBM T.J. Watson Research Center, Yorktown Heights, NY 10598 

(Dated: March 30, 2010) 

We survey the current state of phase change memory (PCM), a non-volatile solid-state memory technology built around the large electrical contrast between the highly-resistive amorphous and highly-conductive crystalline states in so-called phase change materials. PCM technology has made rapid progress in a short time, having passed older technologies in terms of both sophisticated demonstrations of scaling to small device dimensions, as well as integrated large-array demonstrators with impressive retention, endurance, performance and yield characteristics. 

We introduce the physics behind PCM technology, assess how its characteristics match up with various potential applications across the memory-storage hierarchy, and discuss its strengths includ- ing scalability and rapid switching speed. We then address challenges for the technology, including the design of PCM cells for low RESET current, the need to control device-to-device variability, and undesirable changes in the phase change material that can be induced by the fabrication procedure. We then turn to issues related to operation of PCM devices, including retention, device-to-device thermal crosstalk, endurance, and bias-polarity effects. Several factors that can be expected to en- hance PCM in the future are addressed, including Multi-Level Cell technology for PCM (which offers higher density through the use of intermediate resistance states), the role of coding, and possible routes to an ultra-high density PCM technology. 

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