wafer.space Community - Hmm, _might_ have found a bug in the LVS

5:32 p.m.

Thanks for the report! Yes, it really seems diode_connections.lvs is the only place where nwell is used for the connection to the devices. Everywhere else, i.e. moscap_extraction.lvs/mos_extraction.lvs/mos_sab_extraction.lvs/res_extraction.lvs, nwell_con is used. If you take a look at general_derivations.lvs you can see that nwell_con is defined as: nwell_con = nwell.not(res_mk) I think this is so that nwell resistors are correctly extracted. They are extracted as:

# NWELL
logger.info('Extracting NWELL device')
extract_devices(resistor_with_bulk('nwell', 1000, BResistor), { 'R' => nwell_res, 'C' => nwell_con, 'W' => sub })

You can find a description about the extractor here: https://www.klayout.de/doc/manual/lvs_device_extractors.html Taking a look at the connectivity setup in general_connections.lvs, only nwell_con is connected to ntap:

# Inter-layer
connect(lvpwell_con, ptap)
connect(lvpwell_con, ptap_dw)
connect(dnwell, ntap_dw)
connect(nwell_con, ntap)
connect(ptap, contact)
...

That's the reason why you get anonymous pins with just nwell. Long story short, I agree that nwell_con should be used :)

5:32 p.m.

If you would like to be credited, you can open a PR in the upstream repo: https://github.com/fossi-foundation/globalfoundries-pdk-libs-gf180mcu_fd_pv Otherwise, I will do it for you.

5:32 p.m.

You might want to use the LVS setup in this directory anyway, as @Clyde Laforge has made some important improvements around substrate cuts recently. We are working on creating a new open_pdks PDK, which will allow us to switch from the current wafer.space PDK fork. However, this probably won't happen until next week, as I'll be at Hackaday Europe this weekend :)

Awesome, thanks for taking a look @Leo Moser (mole99)! No credit needed, probably easier/faster for you to make the fix than for me to cobble together a PR

Will take a look at that LVS setup for my own experiments! and goodluck/have fun at hackaday conf

PR is up: https://github.com/fossi-foundation/globalfoundries-pdk-libs-gf180mcu_fd_pv/pull/20 Great, and thank you!

fix: diodenw2ps* connect to nwell_con by mole99 · Pull Request #...

Discovered thanks to a report by Zachary. diodenw2ps* used the wrong layer for the bulk connection. general_connections.lvs uses nwell_con to connect to ntap.

woo!