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stop layout snapping two close by cells to overlap

DavidLou

hello experts,

in Cadence IC6.1.7, the new feature of automatically snapping two close by cells to be perfectly overlapped to each other. but sometime we don't want that. we'd still want to keep more spacing to allow contacts/vias to be possible. how can we turn that feature off?

thanks,

David

  • Andrew Beckett

    Hi David,

    I'm not (and nor is one of my colleagues that I asked for a second opinion) sure what you mean by this. I'm not aware of any "new feature" that would do this - perhaps  you can illustrate somehow precisely what you're doing (which tool are you using - is it VLS L, XL?, which command are you doing? Do you have any snap grids?). There's really very little to go on in your description...

    Regards,

    Andrew.

  • DavidLou
    in reply to Andrew Beckett

    hi Andrew,

    sorry not too clear at first hand. As I tried in VLS XL, if I put the two devices a little bit closer than the first picture so their diffusion touching each other, then they'll go much more overlapped and removing all the contacts in middle as shown in second picture. 

    as you asked, I tried in VLS L then there's no such automation there. the device will be wherever dropped. so this could be one work around solution then. 

    thanks,

    David

  • Andrew Beckett
    in reply to DavidLou

    Hi David,

    OK. The fact that you said "new in IC617" threw me. This is a feature that has been in layout XL for probably at least 20 years! Auto abutment does depend on having suitable properties on the devices in the PDK library, so maybe you were using a PDK that didn't support auto-abutment before.

    Anyway, if you want to turn it off, you can do so by going to Options->Layout XL, and then on the Generation tab, you could either turn off "Abut transistors", or you could leave that on and turn on the "Preserve terminal contacts" checkbox. That would still abut but leave the contacts present.

    Regards,

    Andrew.

  • DavidLou
    in reply to Andrew Beckett

    yup, that works. thanks Andrew

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