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qrc parasitic c extraction for reflected caps

stevep2
I'm using a dfII qrc flow with an LVS clean layout in UMC 018u tech. We have a fully differential design with 2 reflected caps, however when extracted with qrc they have paracitics (coupled between the top and bottom plate) that differ by ~5f.  Corresponding track coupling to achieve 5f would be huge and very obvious!!!!

We only have QRC-L license so cannot use field solver for more accurate extraction (?).

in summary, coupled C only extraction, no substrate, all nets , no exclusions.  Anyone got any ideas?

We've tried adding metal to both caps to increase parasitics and sanity check the flow, both caps are being extracted independently, but we cannot justify the difference between the 2.

anyone?

 
Steve

  • Hi Steve

    We can troubleshoot accuracy issues as follows:
    a. Retry using latest version of QRC. If this does not work, go to next step.

    b. Re-simulate process file (ictfile) using latest version of Techgen to generate a new qrcTechFile. Re-simulation can help in creating additional cap models which might aid in resolving the accuracy issue. The simulation will take lots of CPUs (e.g. 20~100) and hence it is better to request for a new qrcTechFile from UMC. If it still does not work, go to next step.

    c. Contact Cadence support. It might be a bug. We will need a testcase to do more troubleshooting. : )

    Best regards
    Quek

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