I guess I was wondering what make a fab open source. I.e. say you did have a 3D chip printer, but you didn’t know how it worked and you couldn’t look inside, would that be open source? If that printer counts as open source then I would argue fabs like MOSIS are the equivalent.

You can get all the tech files for their older stuff, with no NDA, from FreePDK. It works fine with VLSI layout tools like magic, which one can git clone the source of.

That said, there isn’t really a lot of mystery in the larger technology sizes like 0.18um. Plenty of universities will tell you exactly how they do it if you look into it.

The big problem with DIY fab ideas is chemical disposal. This will have to be addressed first. Parts of Mountain View are still a superfund site because of older fabs. HF is no joke.