IIRC there are a couple ways to produce the intended design. At the end of the day, fabs often take layouts in the GDSII format, which is documented and open. The Klayout open source visualizer is industry-standard in my experience.
Now, how do you generate these layouts? It depends on what you are doing. If more on the experimental side of things, writing scripts to generate structures is fine, as long as these conform to the fab-provided design rules. Technically, that's still what everyone is doing at the industrial level, except the scripts -- often written in tcl -- are provided by the fab.
Now if you have some FPGA experience, you are probably interested in logic synthesis tools. There are a few ones, I've seen some academic with their own place-and-route stage, for instance. https://open-src-soc.org/program.html#T-CHAPUT does that, I think.
The slides linked above outline one of the possible ways to do this: leverage chisel (
https://www.chisel-lang.org/) and the FIRRTL intermediate representation for RTL description. A few tools can ingest the output and try to come up with a layout. Hammer (https://github.com/ucb-bar/hammer) is such a tool, but I don't think that PDK is available with it just yet.
To be honest, I don't think commercial tools are that advanced, and it would be fairly doable to catch up.
There is some interesting work in this field, but since fabbing is expensive, it tends to be more within the academic community than the free software one. I'd look for papers, not on Github, though that's slowly changing.
The chip design world is a slow beast to turn around: everything in the fabrication process is optimized to maximize yield, hence very little leeway is allowed: "If it ain't broken, don't fix it" is the motto, for good reason: if changing humidity levels 0.2% can make a fab lose millions; they won't try to use new and experimental software.
I'm watching this space, notably with Verilog alternatives such as Migen. The open source community starts to embrace FPGA, wich is already great. I wish more manufacturers opened up their bitstream, so maybe we need an open FPGA? Though this free fabbing offer would be a great fit for Wi-Fi chips, I think. I wonder if People at openwifi (https://github.com/open-sdr/openwifi) are interested?
I hope that gives a few interesting pointers to whoever reads this :)
