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RTimothyEdwards / magic

Magic VLSI Layout Tool
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implementation of stacked mimcaps #313

Closed marknmartin closed 5 months ago

marknmartin commented 6 months ago

In process there are 2 different mimcaps. You are allowed to stack them and a separate model is provided for the stacked device. I am uncertain what would be the best way to implement these. Currently I draw the layers from the 2 caps, but when I extract I get 2 separate caps which is partially OK but is overestimates the cap to substrate since each cap extracts with a third terminal to the sub. What I really want is to extract a single device that points to the foundry provided model. With minimal investigation on my end I think my options are

  1. Create a new stack cap device. I am unsure how this would work since is needs to live on multiple planes
  2. implement a marker on the comment layer to specify that is the stacked cap. If i go this route would I also need to implement separate markers for the 2 non-stacked caps?
  3. There is a better way I am know privy to in one of the open PDKS that I can use as an example.
marknmartin commented 5 months ago

This issue has been resolved but creating a device from the 2 mimcap layers

device csubcircuit stackedcap *mimcap2 *mimcap w=w l=l

this will also create a second parallel cap from the mimcap to bottom_plate so an additional statement is needed to tell the extractor to ignore this device in the presence mimcap2

device csubcircuit Ignore mimcap bottom_plate +mimcap2

Thanks Tim for your assistance via private communication.