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Extra pins are extracted at dummy poly data.

Hi Matthias,

By using following sample data, I confirmed LVS normal operation.
https://github.com/KLayout/klayout/tree/master/samples/lvs.

Then, I added dummy poly data at both virtical side of INVX1 cell.
This data insertion is common in advanced processes.

As a result, extra pins are generated and the circuit verification
of ringo circuit cannot be completed.

  • Extracted circuit by KLayout

.SUBCKT INVX1 VDD OUT VSS \$4 nc_1 nc_2 IN SUB
M$1 VDD IN OUT \$4 PMOS L=0.25U W=1.5U AS=0.6375P AD=0.6375P PS=3.85U PD=3.85U
M$2 VSS IN OUT SUB NMOS L=0.25U W=0.95U AS=0.40375P AD=0.40375P PS=2.75U PD=2.75U
.ENDS INVX1

How can I suppress this pin generation?

Thanks,

Comments

  • Hi haru_f,

    these floating nodes should be eliminated from the netlist if you use "netlist.simplify" before the compare step.

    Such dummy pins are very common not only in dummy gates but also in filler cells or dummy pattern for uniform density.

    Have you included this step?

    Matthias

  • Hi Matthias,
    Thank you for your comment.
    Yes, "netlist.simply" is used. I use the template script which Klayout provided.
    I think that since dummly poly data of the INVX1 cell is completely overlapped with that of the adjacent cell in this case, the terminal is generated to connect
    each terminal by poly.

  • edited November 19

    Sorry for typo.

    *Netlist normalization
    netlist.simplify

    Thanks,
    haru_f

  • This is the result of LVS.
    "$4", "$5" pins are remain in "layout" netlist.
    Thanks,

  • Another trial result:
    Dummy poly data is added at both side of ND2X1.
    Since the right side dummy poly is connected to the adjacent INVX1's dummy poly, "$4" pin is generated in ND2X1
    while the left side data has been removed as a floating node.

    Thanks,
    haru_f

  • I think I see the issue. I need to look into this. I'd say it's a bug related to "simplify". The case of floating nets connected together apparently isn't captured yet.

    I have created an issue for this: https://github.com/KLayout/klayout/issues/425

    Kind regards,

    Matthias

  • Hi Matthias,
    I hope it will be improved.

    Best regards,
    haru_f

  • There is a fix for this issue. It's a deep modification however and I hope it does not break anything else. See the GitHub link for details.

    Matthias

  • Thank you!
    haru_f

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