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Assigning a Net Name to a Layer for LVS/RCX

LanceT

Does anyone know of a way to assign a specific net name to a layer for use in LVS/RCX?  We are using a process where the bottom layer of the design will be electrically connected to a signal "GND_SUB" and I want to be able to assign that label without having to create a physical connection to it.  I can create bogus connectivity for that layer just so that it is a "connected" layer that doesn't really connect to anything in the layout but is there a way to assign a specific net name to that layer?

  • Andrew Beckett

     Which tools are you using for LVS and RCX?

  • LanceT

    Yeah, I realized after I posted this that I probably should have mentioned that.  We are using Assura for both LVS and RCX.  Typically, we run from the GUI in icfb.

  • Andrew Beckett

    If there's no physical connection, what are you expecting to see connected to the node? Is it parasitic capacitances from other layers to this substrate? If so, probably what you want is the Ref Node on the Extraction tab in the Assura RCX form. Any decoupled capacitors (or capacitances to "ground") will be connected to this node.

    It's not that clear to me quite what you're trying to do.

    Otherwise if it's a physical shape in the layout, do you need to just label it? (in which case that sounds like a "physical connection" to me, so I'm not sure that's what you're after).

    Regards,

    Andrew.

  • LanceT

    For RCX, being able to specify the substrate as the Ref Node is certainly part of it and I do have it set up to do that.  What I am looking for is a way to define a label for that node without creating a physical label in the layout.  That is what we are currently doing - we have to add a goofy bogus connection in order to assign the net "GND_SUB" to the substrate.  We would like to be able to have Assura LVS understand that the substrate layer will always be connected to net "GND_SUB" without having to create any sort of physical connection or even a label to it in the layout.

  • Andrew Beckett

    Maybe you could use the ?pinTextFile option in avParameters to text the substrate layer? See the Assura documentation for more details.

    Andrew.

  • LanceT

    Thanks for your help Andrew!  I think I can use this.  The only slight limitation is that I need to specify X,Y coordinates (ideally, I would just like the layer to be labeled regardless of its location), but I think we can probably make an assumption that the origin will probably be contained within the extent of the design (since substrate is defined everywhere).  If you know how to do this (label a layer without specifying coordinates) off the top of your head, please let me know.  Otherwise, no worries - I think this will work.

    Thanks again for all your help!

  • Andrew Beckett
    Not off the top of my head - it might be possible but it might need something in the rule file rather than an RSF option (this is a wild guess without consulting the docs)

    Andrew

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