wafer.space Community - Butting taps

The gf180mcu process allows tap diffusion to abut mosfet source drain. Thinking just about the doped silicon, this is a lateral parasitic diode - not extracted as a device and not connected. However, I think gf180mcu adds a salicide step to the diffusion to reduce resistance. This effectively creates a low resistance layer over all diffusion (not blocked) irregardless of doping. If this is true, then abutting tap and mosfet source/drain are shorted. In the pdk used for chipathon 2026, the magic tech file extracts abutting tap and mosfet source/drain as shorted, but the klayout tech file does not. Does wafer.space use a modified klayout rule that shorts the abutting diffusions? @Leo Moser (mole99) (edited)

cg_amp_tia.gds

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Thanks @bailey for bringing this up. I assume this is the same situation as on ihp, correct? There is definitely salicide being used in the gf180mcu process. There is also a salicide block (SAB) layer. You're refering to this line in the magic tech file regarding butted taps: https://github.com/fossi-foundation/open-pdks/blob/aa3fc215a80d32437b8cca1cb3fdee819d18c4c9/gf180mcu/magic/gf180mcu.tech#L711 As far as I can see, the KLayout connectivity setup for LVS does not consider butted taps: https://github.com/fossi-foundation/globalfoundries-pdk-libs-gf180mcu_fd_pv/blob/035e6d1f4bf0acfb60606b056e7d2159cba30fef/klayout/lvs/rule_decks/general_connections.lvs#L25 Which seems to be an oversight. Do you think it makes sense to add the simple case of a butted tap, without considering SAB for now? By the way, are you planning to use KLayout for LVS?

In magic vss and I_in are shorted, but in klayout they are not.　(old post stuck in queue).

Whether butted taps extract as shorter is a bit inconsistent between magic/klayout and across PDKs. For IHP I think they are now made to be shorted because IHP actually uses that in their standard cells ( i.e. they only connect the butted tap to power/gnd and rely on the salicide to conduct to the source ). On sky130 I think they are not extracted as shorts ( although they actually are ) because the salicide is not great and you should never rely on it for anything. On GF180 I'm pretty sure I've also seen them recommend to always contact both source & tap even for butted taps (although here the salicide is pretty good).

Ignore me -- but my brain completed this as "buttered taps" which kind of sounds tasty