<@U0176NW50TB> I recommend we figure out ways to a...
# sky130t
Tim 'mithro' Ansell
07/18/2020, 9:34 PM
@User I recommend we figure out ways to automate the metal file, antenna violations, etc
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Jeremy Holleman
07/18/2020, 9:42 PMSome commercial PDKs have scripts that can automate the metal fill, and I've had students write skill scripts that mostly automate it in other cases. Antenna is a little harder, in that the checker says "you need to increase the size of this device or add a giant diode to ground" and the designer says. "but I don't want to."
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FatsieFS
07/19/2020, 9:09 AM@Tim 'mithro' Ansell @Jeremy Holleman I used klayout for metal fill for NLNet018TV. See use of .fill_region in https://gitlab.com/Chips4Makers/snowwhite/-/blob/master/designs/NLNet018TV/nlnet018tv/NLNet018TV.py. Unfortunately not all data is public so you need to adapt script before it will work.
FatsieFS
07/19/2020, 9:11 AM@Jeremy Holleman Other possibility for fixing antenna rules is to isolate long metal connection from gate with a short connection on a higher metal layer. But antenna rule is a DRC so if people don't fix it, the design normally won't be taped.
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Tim Edwards
07/22/2020, 5:13 PM@FatsieFS (@Jeremy Holleman, @Tim 'mithro' Ansell): It is also easy to do automatic fill using magic, but I have not spent the time to look at the rules for the fill pattern generation, so I have not yet written automatic fill generation into the magic tech file.
Tim Edwards
07/22/2020, 5:15 PM@Jeremy Holleman: The OpenROAD and openlane tools are antenna-rule aware, and while their methods still have a few bugs to solve (as far as I know right now), they have come a very long way toward automatically fixing all antenna problems automatically without user intervention, at least for all the synthesized digital blocks.
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Jeremy Holleman
07/22/2020, 5:20 PMThanks. That's good to know. I guess my bigger concern is with analog and RF blocks. With the cadence tools we always struggle and occasionally wind up making a judgement call that will accept some antenna violations and hope for the best. At least in the processes I've worked with, the antenna rules were there to protect you from yourself, so you could tape out even with violations.
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Tim Edwards
07/22/2020, 7:33 PM@Jeremy Holleman: That is the case here. Any submission will not be rejected on the basis of antenna violations, and the customer accepts responsibility for any yield loss as a result of such antenna violations.
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