What about the tools and processes to manufacture this? Are those open source or broadly available? For instance, is it possible to have a small scale "community" fab for 1999-era chip technology?
Staf will also "protect" you from the Foundry NDAs. you develop with a "symbolic" version of the Cell Library, he runs the "Real" one and sends it to IMEC on your behalf. here's Staf's "symbolic" Cell Library, it's based on FreePDK45 https://gitlab.com/Chips4Makers/c4m-pdk-freepdk45/-/releases
Coriolis2 - http://coriolis.lip6.fr/ - is entirely Libre-Licensed. it's fully automated, you don't have to do any "hand-editing", it has unit tests (so you have demos you can look at and also check you installed everything right). we have some automated setup scripts for it if you're interested: https://git.libre-soc.org/?p=dev-env-setup.git;a=blob;f=cori...
LIP6 have a Silicon-proven ENTIRELY Libre Cell Library called nsxlib, if you really want to go that route. it's Silicon-proven in 360nm and 180nm.
Also, LIP6 have a relationship with a small town in Japan, they have 2 micron fab which is used for "training" of employees of the town. submission for that is entirely free. i know this exists but have not used it, and don't know more details, but i can probably put you in touch with Sorbonne University if you're serious.
and if you really really want to do "at home" stuff, Libre-Silicon is developing a 2in wafer fab, using Ultra-Violet DLPs and high-accuracy stepper motors, that you'll be able to buy and operate from your garage or lab. think "3D printing", i think they're aiming for 2000 nm or something (20 micron)? really big, but proves the concept.
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.
Neither one has published an easily-replicable process, meaning I can't really repeat what they've done. IMO what this space needs is an open source build plan/BoM, with a cottage industry of people selling DiY and pre-assembled kits. Once the 3d printing community got there, that's when things took off -- before kits or at least build guides with proper BoMs, it was just disparate individuals doing their own thing.
Connect me with anyone who's got a good approach to building some sort of replicable open-source fab though, and I'll quit my job and join the project full-time (that's not a joke: I'm serious).
[1] http://sam.zeloof.xyz/category/semiconductor/ [2] https://libresilicon.com/
However, one thing to keep in mind is that below 500nm a lot of the chemicals are extremely toxic and not the kind of thing that garage hackers are qualified to handle in an environmentally safe manner.
Arsenic, phosphene gas, hydrogen fluoride, nasty solvents. I build a lot of crazy stuff in my shop, but I don't even trust myself to dispose of these correctly. If makers like myself get involved in this we're going to end up with a lot of new superfund sites. In residential neighborhoods.
And then of course there's the ion implanter, which none of the fab employees want to spend much time around...
Or maybe we adopt a 500 nm node and stop there :-)