SiOx memory: how it works

SiOx memory: how it works

Summary: The new memory is non-volatile, offers fast sub-100 ns switching times, can be written 10,000 times and is fully compatible with current CMOS manufacturing processes. A 1,000 bit proof-of-concept chip has been built by a private company. But those aren't the good parts.

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The recent announcement that Rice University grad student Jun Yao has demonstrated a new memory device has created a stir. As well it should.

The new device is non-volatile, offers fast sub-100 ns switching times, can be written 10,000 times and is fully compatible with current CMOS manufacturing processes. A 1,000 bit proof-of-concept chip has been built by a private company.

Those specs are better than or equal to current MLC NAND flash, but there are 3 other important advantages:

  1. Size: devices are only 5 nm wide - 1/5th the feature size of the latest flash devices - which means much higher storage capacity.
  2. Capacity: the architecture lends itself to stacking multiple dies - so-called 3D chips - to create even higher capacity devices.
  3. Simplicity: it is a 2 terminal memory, not 3 as in most memories. This reduces device size and complexity.

The device The device uses silicon oxide (SiOx), a universal component of semiconductor devices for decades, in a novel way. The SiOx is used to create a conductor - not an insulator.

From the Rice press release:

Applying a charge to the electrodes created a conductive pathway by stripping oxygen atoms from the silicon oxide and forming a chain of nano-sized silicon crystals. Once formed, the chain can be repeatedly broken and reconnected by applying a pulse of varying voltage.

I did not find a mention of the voltage needed to form the chain, but given the feature size and mechanism I'd expect it to be much less than the 20 volts required to pump NAND flash. If correct that should also reduce the chance of catastrophic die failure when the insulation shorts out.

Here's a graphic that starts at the chip level and goes down to the nanocrystal level:

Why the limited write/erase lifespan? Presumably the local region runs out of nearby oxygen atoms, stopping the process, accounting for the ?10,000 write limit. Clever materials or manufacturing process engineering might increase that limit.

The Storage Bits take It's great to see something novel found in such a common material as SiOx. Professor James Tour, in whose lab Jun Yao works, says SiOx is one of the most studied materials on earth.

Flash designers have been sounding alarms because they aren't sure they can go below 20nm feature sizes - a fast approaching limit. Of course, storage and semiconductor engineers have been sounding alarms for decades: that's how you keep the suits funding research.

But this development has great promise not only for its theoretical capabilities, but because it creates technological competition. We'll all benefit from that.

Comments welcome, of course.

Topics: Networking, Hardware, Mobility, Processors

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15 comments
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  • RE: SiOx memory: how it works

    Sounds good..... BUT I am a little.... concerned about those 'write limits'. My one USB flash drive here at home has those write limitations (though not as low) as well so I am always looking at the blue light flashing on it thinking "Is that a read..... or a write! If it's the latter, why is it writing!?"
    Lerianis10
    • Write limit may not matter so much

      @Lerianis10: While a 10,000 write limit sounds bad, it's no worse than the first flash memories 20 years ago. Today the techniques for spreading the wear around and managing failures are very well-known and effective. Given that each storage element is smaller than traditional flash, at least initially you can make up for the greater wear with a lot more spare cells and probably still be competitive in price.
      zackers
  • RE: SiOx memory: how it works

    Yeah... the write limits are low for now, but what a great beginning. Good article, Robin. Thanks.
    ITOdeed
  • 20 Volts?

    I have to admit I do not know much about flash, but 20 volts sounds awfully high. Is that correct?
    Economister
    • RE: SiOx memory: how it works

      @Economister<br>Yes. That's why a fault in the insulator layer can fry the whole die pronto. <br><br>Robin
      R Harris
      • Do more research. Lot's of flash show's 5V or less for reprogramming.

        @R Harris

        Look at flash datasheets. It didn't take long to find writeable flash at 1.8V(Intel & AMD), 5V (ATMEL)for ATA, 12V. I didn't find one yet that was 20V.
        MeMyselfAndI_z
    • RE: SiOx memory: how it works

      @Economister
      Based on the datasheets I've seen, it is high. Most of the datasheets for flash that I've found were 5V or less. And there are quite a few that are less generally around 3 Volts. See Atmel, Intel, Micronyx
      MeMyselfAndI_z
      • RE: SiOx memory: how it works

        @MeMyselfAndI_z
        I confess to not being entirely clear on the mechanism, but the flash supply voltages don't tell the whole story. The voltage is pumped up to ?20 volts for a write.

        Several large users of flash chips have confirmed that shorts in flash insulation layers will fry the entire chip. That is why the higher quality flash drives use a form of RAID to protect data against total loss.

        Robin
        R Harris
  • Sounds like an excellent EPROM replacement...

    ...I suspect that the trade off, 1/5th the space, would negate any power concerns. Besides, that is a 20v pulse of extremely short duration and an undefined (By this article) amperage. The full article from Jun Yao can be obtained at http://www.ruf.rice.edu/~mobile/publications/yao09small.pdf
    ReadWryt (error)
    • RE: SiOx memory: how it works

      @readwryt@... <br>Thanks for the link! I looked for the paper and couldn't find it - and I know most of the tricks.<br><br>Robin

      Update: I had not trouble getting the paper from your link - I just couldn't find it before finishing the post. Again, thanks!
      R Harris
      • RE: SiOx memory: how it works

        @R Harris
        Try right click -> save as
        fgendel
      • Oooof!

        @R Harris I linked straight to the PDF of the paper. You can right click and copy the URL and save it to your desktop, then open it with Acrobat Reader if you don't have the Acrobat plugin for your browser...Sorry about that.
        ReadWryt (error)
    • RE: SiOx memory: how it works

      The correct online paper link is as follows:
      http://pubs.acs.org/doi/abs/10.1021/nl102255r

      The link you provided is an old one before finding the mechanism.
      yugi321
  • RE: SiOx memory

    Stanford Ovshinsky put a great deal of time and effort (and money) into something that looked very similar. So far (unlike some of his other ventures) this hasn't been a great success.
    Maybe shrinking geometries and nano-tubes will provide the final piece of the jigsaw. Maybe
    shtromer
  • Is this true crossbar addressing?

    From what I can glean from this article and the paper, it looks at though each bit cell can be addressed separately, rather than in big blocks such as conventional flash. If so, does this eliminate all the huge write issues of traditional flash that make writes take so long?

    Also, I note from the Wikipedia article on resistive switching, apparently SiO2 resistive switching has been studied since 1967 ( https://secure.wikimedia.org/wikipedia/en/wiki/Resistive_random-access_memory#cite_note-7 )

    Also, is this a form of the memristor? These are currently based on titanium dioxide, but at least superficially have much in common with the SiOx approach discussed here.
    zackers