they both have the same connections on the outside (they both have the same "netlist") and you can use the exact same SPICE model (a transistor-level simulation) but usually they're entirely empty inside.
so the VLSI tool can still Place-and-Route them, you can still creaate GDS-II Files, but if you send them to the Foundry, the Foundry will look at you like you have two heads or something and won't talk to you again.
that said: some Foundries have their own Symbolic ("ghost") Cell Libraries, which they send you. you run the VLSI tools with those, then when they get the GDS-II files they SUBSTITUTE the REAL cells for the ghost Cells... and then put that into the Fab.
they do this because they're so paranoid they don't even want you to know what's inside their "Symbolic" (ghost) Cells.
Foundry Symbolic Cells are invariably available only under NDA.
sigh.
which begs the question, how the hell is any information is going to leak out from a completely empty Cell, and unfortunately the answer is: quite a lot. number of layers, what the "stack" is of those layers, distance between tracks, width of tracks, and so on, and the PDK also has to include via sizes and so on anyway.
this starts to give you some idea of the levels of insanity we had to workaround, to meet our Audit and Transparency objectives.
bottom line is until we can bust through these final layers of NDAs, customers who really want to verify the complete GDS-II Files are also going to have to sign a Foundry NDA.
so the VLSI tool can still Place-and-Route them, you can still creaate GDS-II Files, but if you send them to the Foundry, the Foundry will look at you like you have two heads or something and won't talk to you again.
that said: some Foundries have their own Symbolic ("ghost") Cell Libraries, which they send you. you run the VLSI tools with those, then when they get the GDS-II files they SUBSTITUTE the REAL cells for the ghost Cells... and then put that into the Fab.
they do this because they're so paranoid they don't even want you to know what's inside their "Symbolic" (ghost) Cells.
Foundry Symbolic Cells are invariably available only under NDA.
sigh.
which begs the question, how the hell is any information is going to leak out from a completely empty Cell, and unfortunately the answer is: quite a lot. number of layers, what the "stack" is of those layers, distance between tracks, width of tracks, and so on, and the PDK also has to include via sizes and so on anyway.
this starts to give you some idea of the levels of insanity we had to workaround, to meet our Audit and Transparency objectives.
bottom line is until we can bust through these final layers of NDAs, customers who really want to verify the complete GDS-II Files are also going to have to sign a Foundry NDA.