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Clipping layer in Layout

MichR

The layout cell I am working on has a given P&R boundary. Over the cell area I inserted a set of uniformly distributed metal lines using the Mosaic feature. However, some metal lines go out of the boundary and I need to cut them.
See the following picture as an example of the problem I am facing:

As far as I know there are two solutions:

  • Flatten the metal layer and manually cut the protruding lines
  • Use the Layer Generation feature (explained here).

However, both methods require the Mosaic to be flatten (actually haven't tried the Layer Generation method yet so can't say for sure). Since the metal pattern may not be the definite one, I was wondering if there were a way to keep the Mosaic intact so that I could modify if required. I was thinking about a "clipping" layer that once placed over the P&R boundary automatically "cuts" everything in my cell's scope. Maybe this function is already present in the software but I don't know the name of it.

Kind regards,

Michele

  • Andrew Beckett

    Michele,

    There's no built-in way of doing this; it would require support for the clipping in all flows because stream out, physical verification and so on would have to know how to deal with this clipping layer. Obviously it could be built into some chip-finishing physical verification rule deck, but you'd still be seeing the raw shapes in the layout which would be confusing.

    One idea that comes to mind is to create a fluid PCell (which could have a stretchable area) which has lib/cell/view parameters for the cell to be arrayed and the rows/columns/spacings that you'd use in the mosaic. The PCell could then fill the rectangle with a core mosaic and then around the edges place and flatten overlapping mosaics, and then and them with the area. Or it could just place as a mosaic and flatten. Or you could commit the rows/columns and have that computed by the PCell and just specify the spacings/pitch. This is the kind of thing that would be pretty easy to do with PCell Designer and you'd not need to write any SKILL code.

    Regards,

    Andrew

  • MichR
    in reply to Andrew Beckett

    Thank you, Andrew.

    I think I understand the problem that a clipping layer would cause. A PCell seems to be a reasonable solution to this. However, I am still quite inexperienced in Cadence tools so I think I will just go with the simpler flatten-and-cut solution. I will definitely try working with PCells in the future though!

    Thank you again for taking the time to answer me.

    Kind regards,

    Michele

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