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Silicon Design

Discussion in 'Electronic Design' started by Tim Williams, Apr 22, 2007.

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  1. Tim Williams

    Tim Williams Guest

    So I was wondering, everyone's clammering to get smaller...but why not just
    build UP? Too hard to epitaxy on top of metal and oxide layers?

  2. how about this?

  3. Tim Williams

    Tim Williams Guest

    Ah, a start!

  4. John Larkin

    John Larkin Guest

    Yup. You get crappy, damaged silicon.

    LCDs and such grow silicon on glass, poly or amorphous, and it makes
    slow, leaky transistors, just good enough to drive pixels. Ditto the
    low-efficiency solar cells used in calculators.

  5. Phil Hobbs

    Phil Hobbs Guest

    3D silicon is an active development area. Stacked memory has been
    available for ages, but afaik it has always done by wire bonding, so it
    isn't really 3D. The silicon through-via technology has been developed
    independently in several places--earliest at IBM, I think. It's useful
    because you can run interconnects through stacked chips like elevator
    shafts in a tall building. The problem has been not so much in drilling
    the holes, as in filling them with a reliable metallization at a very
    dense wiring pitch.

    We (IBM) have a silicon-carrier technology that allows the use of
    IC-type wiring densities in first level packaging. At one point we were
    considering splitting large ASICs up into tiles, and putting them on
    silicon carriers. That's expensive in processing, but you more than
    make it up in yield, due to the smaller area of the individual tiles. I
    don't know if that ever made it into a product offering.

    It's possible to do epitaxy over top of fabricated devices, but I don't
    think that's what will show up in the first real 3D devices, anyway.
    The main problem is yield again--instead of, say, 600 process steps,
    you'll have 1000 process steps, and keeping the yield up through that is
    really, really hard. Wafer bonding improves yields, because you only
    bond good wafers to good wafers.

    Chip-level optical interconnect is intimately involved with 3D issues,
    because the transistor folks won't let us play on their real estate--we
    have to live on a separate silicon level.


    Phil Hobbs
  6. Thanks for that, I just this

    Fun times ahead

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