LONDON — Micron Technology Inc. (Boise Idaho) has confirmed its support for the phase-change memory product line and R&D inherited when it acquired Numonyx BV in May 2010. But a company executive declined to give further details of its technology roadmap or how it plans to scale the technology below the 45-nm node.
When asked if Micron continued to support phase-change memory Ed Doller, vice president and chief memory systems architect with Micron and formerly chief technology officer with Numonyx, told EE Times: "Absolutely I can confirm that." He added that 80 to 90 percent of the staff that report to him are working on phase-change memory.
Phase-change memory has shown promise as a potential non-volatile replacement for flash memory and DRAM but the technology has been slow to make it out of the laboratory. As the situation stands PCM is behind the rival technologies in terms of both memory capacity in bits and the cost of manufacture. This has given rise to speculation that the technology may be a curiosity that ultimately fails to impact the market. Micron has one phase-change memory product line that customers can buy; the Omneo 128-Mbit device implemented using a 90-nm process technology but Numonyx, and now Micron, have yet to produce a promised follow-on 1-Gbit memory using a 45-nm process technology.
When asked if Micron would respond directly to the technical questions posed within the Internet pages of EE Times, Doller said that Micron has put some technical information in the public domain through the presentation of papers at conferences such as the International Electron Devices Meeting and that other technical material it shares with companies under non-disclosure agreements.
Doller did not disagree with the statement that other memory technologies are already down at 3x-nm and heading for 2x-nm so that for PCM to have a future it must compete at those geometries and beyond.
Doller responded: "There will be challenges but we are on a path to scale the technology further than any of the incumbents, by which I mean NOR, NAND and DRAM." He declined to discuss detailed solutions to the challenges to the scalability of PCM. These could include the non-scaling of current density, electro-migration and thermal cross-talk, amongst others.
When asked about the 1-Gbit device, Doller said: "We will be sampling a 45-nm 1-Gbit to customers this year. Volume production is in 2011. There is no doubt in my mind about this."
Doller said that PCM is targeting mobile phone applications as well computing applications. A different emphasis apparent in Atwood's article was due to the fact that the article was only addressing computing platform applications where Doller said the company does expect design wins in storage applications to come first.
"Is there value in putting expensive PCM in there? When you think about latency, yes," said Doller outlining that magnetic media have delays of the order of milliseconds compared to microseconds for NAND flash solid-state memory, which compares to nanoseconds for PCM. "There is also a case for endurance. NAND endurance is reducing rapidly as we scale," asserted Doller. There continues to be an opportunity in mobile handset memory, said Doller.
When asked about what geometry node Micron would target for the next device after 45-nm and what progress was being made developing a next-generation phase-change memory IC, Doller said: "We are working on what comes next," but declined to comment further.
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Micron, on their website already has 2x nm SLC NAND capable of 300k cycles and the future story continues to look good for NAND.
It looks like due to its large die size and temperature limitations, PCM is destined for niche markets
It doesn't bode well for PCM if even Mr. Doller considers it "expensive," but if we carry the cost per bit argument further, flash won't win out over HDD. But there are other considerations indirectly related to cost, like power consumption.
Having worked in the mass storage division of a computer company I can say: "It is all about the cost per MByte". We had higher performing drive systems we owned/developed, but in the end, the lowest cost off the shelf drives displaced the much higher performing but very expensive drives. Cost rules in most of the consumer applications (cellphones, TVs, games, etc.). If PCM can be cost effective it will be successful, if not, then it will be an interesting curiosity.
History is often a good indicator of the future performance, but not always--particularly when the history is 40 years old. No TV time needed for bubble memory as I was an intern with IBM on Cottle Road in the early 80's when they made the decision to shut down the bubble program.
As far as PCM failing on cost basis, that is pretty much why anything fails. That's why bubble memory failed. A garnet wafer with the Liquid phase epitaxy film was just too expensive... (even though we had demonstrated 0.4 micron resolution using phaseshift masks) Hard drives have fought off nearly every technology in terms of cost for 30 years. A 500gb drive for $50 at fry's in todays paper suggests that it is still doing it. That's good history...
MRAM has no way to compete with NAND flash in terms of storage density or GB/$, though it may find its role as embedded memory to replace eFlash or eDRAM.
A recent very good PCM survey paper from IBM says "if PCM fails, it will be on a cost basis ...", with which I totally agree. Meanwhile, with the help from strong coding and signal processing and other system-level tricks, it should not be a big surprise if NAND flash will be scaled to ~10nm, and we could imagine how difficult it would be for PCM to compete with NAND flash on a cost basis. Lastly, as storage capacity increases, the touted endurance advantage of PCM will become very much irrelevant in most applications.
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