Phase Change

Accelerating New Memory Materials Research

Intermolecular Characterization ChartWith all the new emerging memories that are being developed there must be quite a number of test runs to study exactly how well these new technologies and materials can perform.  If a batch of 300mm wafers must be used for a single test then the cost multiplies, particularly if no other test can be run on that wafer.

Another great difficulty is that most memory manufacturers run their wafers on very high-efficiency and high-volume wafer fabs.  It is perilous and wasteful to interrupt a production process to inject a batch of test wafers.  Most fab managers would rather have a tooth pulled than to change their flow to accept an experimental lot.

What can be done to improve this situation?

Well the folks at Intermolecular, Inc. (IMI) explained to the Memory Guy that they have a solution: They have built a small fab that allows single wafers to be processed with varying parameters across a single wafer.  In this way one wafer can be used to run 36 or more different experiments all at the same time.  This is clearly more economical than having to run the experiment on 36 wafers or, even worse, 36 batches of wafers!  Intermolecular says that, while production fabs are optimized for manufacturing, their fab is optimized for materials understanding.

The firm calls itself an Continue reading

Latest White Paper: New Memories for Efficient Computing

A Potpourri of Emerging MemoriesThere has been a lot of discussion in the trade press lately about new memory technologies.  This is with good reason: Existing memory technologies are approaching a limit after which bits can’t be shrunk any smaller, and that limit would put an end to Moore’s Law.

But there are even more compelling reasons for certain applications to convert from today’s leading technologies (like NAND flash, DRAM, NOR flash, SRAM, and EEPROM) to one of these new technologies, and that is the fact that the newer technologies all provide considerable energy savings in computing environments.

Objective Analysis has just published a white paper that can be downloaded for free which addresses a number of these technologies.  The white paper explains why energy is wasted with today’s technologies and how these new memory types can dramatically reduce energy consumption.

It also provides a Continue reading

Original PCM Article from 1970

For a number of years The Memory Guy has wanted to find a copy of the 1970 article, published in Electronics magazine, in which Intel’s Gordon Moore and two authors from Energy Conversion Devices, Ron Neale and D.L. Nelson, showed that PCM could be used as a memory device.  After all, this is the technology behind Micron & Intel’s 3D XPoint Memory.

The cover of the magazine (this post’s graphic) has been used by Intel to promote its PCM or PRAM chips before those were spun off to Numonyx (now a part of Micron).  Intel, though, didn’t appear to have anything to share but the cover photo.

Electronics magazine went out of business in 1995, and that makes the task of finding archive copies more challenging.

It recently occurred to me that the best person to ask might be the article’s lead author, Ron Neale, who has been a regular contributor to EE Times and who now also contributes blog posts to The Memory Guy.

I was astounded to discover that Continue reading

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.

Continue reading