An acquaintance recently brought to my attention an article in R&D Magazine about some pioneering research on phase-change memories or PCM. The researchers’ findings hold a lot of promise. (R&D Magazine’s article is based upon an original paper in the journal Science.)
A team led by Ritesh Agarwal, associate professor at the University of Pennsylvania, was trying to develop a better understanding of the mechanism behind the phase changes in PCM. The team found that existing programming algorithms that involve melting the material could be replaced with pulses of electrical current that not only would program the cell without heat, but provided an “On” to “Off” resistance ratio of 2-3 orders of magnitude, which renders the cell significantly easier to read, especially in the presence of noise. This effectively makes memory chip design easier than with current methods.
Furthermore the means of programming the cell and the researchers’ understanding of it indicates that current phase change materials may not be the best to use for PCM, and that new classes of materials may produce better devices.
The Memory Guy hasn’t yet heard back from Dr. Agarwal in response to an e-mail I sent him a week ago, but I hope to establish contact to hear more details of this finding. When I do I will update this post and let readers know whether the team has found a similar way of re-crystallizing the bit to return it t o a high-conductance state, or if that must be done through existing methods. I will also report back on anything I learn about the programming speed of the new approach.
When people ask me which technology is likely to replace NAND flash once it reaches its scaling limit I always say that it’s too early to tell. Research like this really underscores that fact – PCM may gain a significant advantage due to the University of Pennsylvania’s research.
There is a free downloadable white paper about Phase Change Memory on the Objective Analysis website.