Distance of layers involved in a parasitic capacitor

Discussion in 'Cadence' started by hamidrezah, Nov 24, 2011.

  1. hamidrezah

    hamidrezah Guest

    Hi all Cadence experts,

    I am wondering if there is a way to get the distance between the two
    layers involved in a parasitic capacitor extracted by QRC? Each
    parasitic capacitor requires two involving plates, I need to find out
    the distance between the two.

    The distance should be calculated at the point where the capacitance
    was sensed by Cadence (I assume that point is also the closest the two
    plates come together).

    Is there a way to do this? I think Cadence extraction tool knows this
    info because it calculates the capacitor value but it does not spit
    out the info. Even a switch to force Cadence extraction tool to spit
    this info out will do the job for me.

    Many thanks in advance for any help/clue in this regard.


    hamidrezah, Nov 24, 2011
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  2. hamidrezah

    Marcel Preda Guest

    Hi there,

    I really think that Cadence Qrc DOESN'T know about the distance
    between layers.
    It only calculates the Caps based on the intersection area (eventually
    involve perimeter too).

    For ditance between layers the best answer, I think, should come from
    the people which are developing the technology you are working with.

    Best Regards,
    Marcel Preda, Nov 28, 2011
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  3. hamidrezah

    hamidrezah Guest

    With all due respect, I disagree. How can QRC report a capacitance
    value without knowing the distance between the two conducting plates
    involved? The distance between plates is designer dependent not
    necessarily technology related. The designer can draw two metal
    polygons far or close from/to each other.

    At least the QRCFS (QRC field solver) should know this distance.


    hamidrezah, Nov 28, 2011
  4. hamidrezah

    Marcel Preda Guest

    Hi there,

    Probable I've misunderstood something.
    I was assuming that you are looking for vertical distance between
    shapes of different layers which are overlapping and create a
    Is this not what you want ?

    Maybe you want just the distance between 2 polygons (in 2D)?!?!

    Best Regards,
    Marcel Preda, Nov 28, 2011
  5. hamidrezah

    hamidrezah Guest

    Hi Marcel,

    My terminology was not quiet right, I should have used "conducting
    plates" instead of "layers".

    So, when you have a layout, there are many polygons, they may run in
    parallel at the same layer, or may overlap at different layers, and
    all different combinations which overall lead to many parasitic
    capacitors. A capacitor's value is determined by the distance between
    the conducting plates, the dielectric material between the plates
    (e.g. SiO2) and its permittivity, and the shared area between the
    conducting plates.

    Now what I want is to find the distance between a parasitic
    capacitor's "conducting plates". If the conducting plates are not
    parallel to each other, then I want the distance at the point
    conducting plates come _closest_ to each other. This is really a 3D
    problem not 2D.

    My gut feeling is QRC or its Field Solver has access to and uses this
    information. I just don't know how to get it out.


    hamidrezah, Nov 29, 2011
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