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Comparison table for capacitance per um^2 for IC processes?

Discussion in 'Electronic Design' started by Joerg, Jun 29, 2013.

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  1. Joerg

    Joerg Guest


    Might have an IC design coming up, depends on whether we can squeeze it
    all in, and on other external parameters. Anyhow, is there a table that
    compares capacitance per square micrometer between the various CMOS
    processes out there? Like a top 10 chart?

    I am not an IC guy and only (somewhat) familiar with the XH-035 XFab
    process which clocks in at just under 4fF/um^2 for poly-diffusion. But
    less than 1fF/um^2 for poly-poly :-(

    The electrical stuff won't be very demanding, one microwatt level 405MHz
    TX and the rest all audio and below. But I can't have discrete
    decoupling C's, need two caps >300pF and it looks like one of them has
    to be poly-poly. The whole chebang can't be larger than 0.2mm by 1mm,
    caps, circuitry, contact pads. The smallest one I had to deal with so
    far was 0.4mm by 2.5mm, so this would be even more interesting.
  2. Joerg

    Joerg Guest

    Because that's the process I dealt with last :)

    I meant without the HV extension, we won't need that here.

    Hmm, that's less than the 4fF with the XH-035. Well, only for the
    poly-diff cap, not the other one.

    In this case it'll all be low power. I am hoping to get by with a
    milliwatt or two.
  3. Joerg

    Joerg Guest

    Thanks, Jim. This post came in with a delay here for some reason. Will
    try on the weekend, the missus called. Dinner, and she is a really good
    cook. Then margaritas :)
  4. Robert Baer

    Robert Baer Guest

    Color me stupid concerning CMOS processes; if an area can be isolated
    (think DI), then a substrate-iso-metal-iso-metal config with top metal
    tied to substrate can give a hell of a lot of capacitance per square
  5. miso

    miso Guest

    Field oxide is thick because you DON'T want channels forming. That is
    also why you have field implants.

    I'm not sure if any text book covers channel stop layout techniques that
    you use when you make a chip operate at higher than the specd voltage.
  6. Joerg

    Joerg Guest

    I only have one, and only after signing some papers that were talking
    about some sort of tribunal if I ever ... :)

    One of the caps goes to ground, but not the 2nd one. I could compromise
    some parameters and make that 2nd one a bit smaller, down to 200pF possibly.

    As John Wayne once put it, man's got to do what man's got to do. 2.5fF
    sounds a whole lot better than 1.87fF.

    Low power in this case is required for various reasons but it's ok,
    because the TX can be wimpy and the IC doesn't have a very big job
  7. Joerg

    Joerg Guest

    Multi-layer is really cool. But as Jim said, one is quite restricted
    with such structures on an IC.
  8. Joerg

    Joerg Guest

    Wish they would send some Thuringian sausage with shipments. I love those.
    Can't talk about that yet, but I really need some capacitance. If we
    have to lower it we can but it'll come with some penalties for us. It's
    all at a feasibility stage right now, to see if we can do this with an
    IC at all. The challenge is the space it has to go into, the 0.2mm width
    requirement is a hard limit.

  9. Fred Abse

    Fred Abse Guest

    That would be a wurst case scenario ;-)
  10. Joerg

    Joerg Guest

    COB, and the stated dimensions are for the bare die. Aside from
    passivation it may also have to be protected from the elements but that
    won't add much if it is a coating.

    Eventually yes. I am certainly not getting myself into IC design. It may
    likely be IP blocks to a large extent but still, that ain't my turf.
  11. Joerg

    Joerg Guest

    It's knackwurst, not knockwurst :)

    We are lucky, we've got a German butcher in Sacramento. It's a bit of a
    drive but the air-dried Landjaeger alone is worth it. He said he can't
    even get them completely air-dried because they fly off the shelves. So
    we dry them here. Last time I bought 30, surgeon general's nightmare.
  12. Casually including any kind of meat in a shipment to the US would be a
    good way to make sure it never, ever arrives, so definitely "wurst

    Best regards,
    Spehro Pefhany
  13. Joerg

    Joerg Guest

    Just like they call a cell phone a "Handy" on the other side of the pond.

    Tonight we will have tri-tip and "brats", grilled over charcoal. My wife
    scoped out a sale, 16.6lbs Kingsford charcoal for $5 a bag. So we loaded
    up. For that money I can't even make my own charcoal.

    This is our place:

    Kasseler and Leberkaes are also most excellent there, they make
    everything themselves.
  14. Joerg

    Joerg Guest

  15. Joerg

    Joerg Guest

    Price list -> cold cuts -> 3rd from bottom.

    I wonder what a Kung Fu Bologna is. One that burns twice?
  16. Joerg

    Joerg Guest

    Looks like it won't be this easy. After cleaning up line breaks LTSpice
    didn't like the schematic syntax.
  17. Joerg

    Joerg Guest

    Yes, I know, but LTSpice treats it the same way. Something about the
    syntax it doesn't like. Unfortunately is is not very forthcoming when it
    issues error warning boxes.
  18. Joerg

    Joerg Guest

    You have just described why I posted my question. I'd like to know if
    there is a way out of this pickle.

    Looks like we may need more pads after all, maybe four in total. But
    thou need not fret because it's been done before:

    Tons of pads, 15um*17um smallest pad, 75um pitch.

    No, just another one of those projects. One order of "Can't be done" and
    one order of "Impossible"? Comin' right up, Sir. The other IC at
    Endosonics (see link above, 0.4mm by 2.5mm, each having 13 channels with
    full receive and transmit) was also causing reactions like "You guys
    must be out of your minds". In full production since ninteen-sumpthin.
    We had to build the flip-chip bonder (and later two more) ourselves
    because all except one company chickened out.

    There are multi-layer methods but that gets expensive and you can't
    partcipate in shuttle runs, MPW and all that.
  19. Joerg

    Joerg Guest

    Right now I am at 350pF for the one that goes to GND and 150pF for the
    poly-poly. Looking at ways to reduce that some more but it's already 89F
    in the office. Very possibly I won't turn on the computer after church
    but dive into the pool :)

    Anyhow, reducing the caps comes with other penalties unless I can get
    the whole circuit including the 400MHz TX to live on much less than 1mW.
  20. josephkk

    josephkk Guest

    I haven't had good Landjeager since i brought some back from Alpine
    Village in Torrance. I wish to add my own consumption to production load.
    So where do i go?

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