Phase Change

Alternative Memory Technologies Patiently Wait For Market to Explode

Cross Section of a PCM Bit CellLane Mason of Objective Analysis recently shared with The Memory Guy an article he wrote for the 4 April 2007 Denali Memory Report covering Phase Change Memory (PCM or PRAM.)  It looked like something big was about to happen with the technology: PCM looked nearly ready to enter production.

The article included an excerpt of an EE Times interview with Micron’s CEO, the late Steve Appleton, in which Appleton stated that PCM advocates threatened to take over the memory market in 2000.

Here it is 2012, and PCM represents little more than a drop in the bucket when it comes to memory sales, although Continue reading

A New Way to Build Phase-Change Memory (PCM)

The University of Pennsylvania CrestAn 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 Continue reading

How Do You Make an ReRAM Work?

I/V Curve for Panasonic's ReRAM Select DiodeDuring this week’s International Solid State Circuits Conference (ISSCC) I learned some very valuable information about memories built using crosspoint matrices.

Since ISSCC is a conference at which you meet the best and brightest minds in the industry it should come as no surprise that I was able to meet with several of the most forward-thinking industry luminaries.  One of them explained to me a very fundamental difficulty with resistive RAMs (ReRAMs): These devices require a forward current to be programmed to a “1” and a reverse current to be set to a zero.  This goes against the ideal crosspoint memory design in which a bit would consist of nothing more than a diode in series with a memory element.  By inserting a diode, the current can only run in one direction, so a bit can be programmed or it can be erased, but not both.

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Jim Handy Objective Analysis Memory Market Research +1 (408) 356-2549 Jim.Handy (at)

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