We are getting errors from GF that indicate MT.2a indicating a top metal spacing of 0.46 however the...

James Stine

03/02/2023, 7:03 PM

We are getting errors from GF that indicate MT.2a indicating a top metal spacing of 0.46 however the gf180mcuC.tech has 0.36 in it - has anyone encountered this?

Tim Edwards

03/02/2023, 7:11 PM

This looks like an error in the open_pdks pre-processor script. The block in the ifdef that is supposed to be active for 0.9um and 1.1um thick metal 5 is being passed over. I had not noticed that. Thank you for pointing it out.

Tim Edwards

03/02/2023, 7:16 PM

Seems like my preprocessor only likes

defined(X) || defined(Y)

and not

defined(X || Y)

. Should be easy to fix.

Tim Edwards

03/02/2023, 7:30 PM

I just pushed a fix for this on open_pdks (opencircuitdesign.com) version 1.0.397. By the way, if you're not aware: GF gave us some push-back on our choice of the 0.9um thick top metal for the 5 metal stack used in GF-MPW-1, asserting that it causes delamination issues on the pads when doing wire bonding, and suggesting that we use the 1.1um thick top metal instead. Although the DRC rules are the same for 0.9um and 1.1um top metal, the parasitics are a bit different, so I elected to designate a new PDK variant called

gf180mcuD

using the 1.1um thick top metal 5, to differentiate it from the one we used for the GF-MPW-1 tapeout.

Landon Burleson

03/02/2023, 7:43 PM

Do you have a github link to pull by chance?

Tim Edwards

03/02/2023, 7:43 PM

Let me just force the mirror copy now.

Tim Edwards

03/02/2023, 7:44 PM

@Landon Burleson: Done. Update is available on github now.

👍 1

James Stine

03/02/2023, 7:44 PM

thx @Tim Edwards

James Stine

03/02/2023, 7:44 PM

is this in the caravel link?

James Stine

03/02/2023, 7:45 PM

https://github.com/efabless/caravel-gf180mcu

Tim Edwards

03/02/2023, 7:45 PM

This is https://github.com/RTimothyEdwards/open_pdks

James Stine

03/02/2023, 7:45 PM

Thank you, thank you!

James Stine

03/02/2023, 7:47 PM

@Tim Edwards is this going to fix the other errors that GF indicated?

James Stine

03/02/2023, 7:47 PM

we don't seem to have any errors on our portion

James Stine

03/02/2023, 7:47 PM

just gave us errors on the Caravel core?

James Stine

03/02/2023, 7:47 PM

sorry if that's vague

Landon Burleson

03/02/2023, 7:53 PM

@Tim Edwards Sorry if this is a odd question but where would your

preproc.py

file fit in the caravel flow?

Tim Edwards

03/02/2023, 7:55 PM

@Landon Burleson: Ideally, all files in open_pdks can be written with preprocessor directives that allow the files to be filtered through the definitions declared in the Makefile. Thus, the file

gf180mcu.tech

is not a magic tech file but is a template for all magic techfiles related to

gf180mcu

. It gets filtered through the preprocessor using definition options like

-DTHICKMET1P1

and produces a tech file that is specific to one set of process options.

Philipp Gühring

03/02/2023, 7:56 PM

Please also check other occurances of the preprocessor branches, I fear some other rules like e.g. antenna rules might be affected of bad preprocessor rules as well.

James Stine

03/02/2023, 7:56 PM

Thanks @Philipp Gühring

Tim Edwards

03/02/2023, 7:57 PM

@Philipp Gühring: I looked; only the DRC rules for top metal and a couple of other very minor things (already forgot what) were affected.

👍 2

James Stine

03/02/2023, 7:59 PM

Thanks again @Tim Edwards

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