Hey everyone, I have been having an issue with parasitic extraction. I am seeing a lot of "nan" and ...

Derek Hines-Mohrman

04/08/2022, 5:07 PM

Hey everyone, I have been having an issue with parasitic extraction. I am seeing a lot of "nan" and "-inf" capacitance values. When looking at the extraction log, I see some warnings "Missing substrate connection of device at ...". I am pretty sure all the substrates are connected correctly in this design because DRC checks for that (in "complete" mode). Attached is a snipped of the extracted spice model and the extraction log. Also attached is the design (top level is "SSTL.mag") and the extraction script.

nan_cap_example.tar

Derek Hines-Mohrman

04/09/2022, 7:18 PM

I figured out the "missing substrate connection" warning isn't the issue. The warning appears to happen when a n-fet does not have an explicit pwell layer under it. As far as I can tell, this isn't related to any other issue...

Tim Edwards

04/10/2022, 2:16 AM

What version of magic? Also, what version of open_pdks?

Tim Edwards

04/10/2022, 2:18 AM

I can't tell exactly from the screenshot, but are you running "extresist" on a hierarchical layout? Because that's known to have many issues.

Derek Hines-Mohrman

04/10/2022, 2:38 AM

Magic version 8.3.277, open_pdks version 1.0.303 The cell should have been flatted before extraction... I meant to add the extraction script to that tar... but looks like I forgot. Here it is.

pex_netgen.tcl

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