Can you do it, given the right tools, training, and patience? Yes.
Will they be any good? No.
Will they be cost-competitive? No.
Getting chips made on a shuttle run for an old node is very affordable. There's really no need for it.
(According to one MPW supplier, 10mm2 of 340nm, up to 10 dies, costs 6400 euros, and it's unlikely 340nm is achievable in a garage anyway)
I believe the way Sam Zeloof circumvents the enormous amount of capital needed for a chip fab by relying on modern technology to create 1970’s technology. He simply mounts a cheap digital projector onto a cheap microscope - they didn’t have that advantage in the 70s, and thus it cost millions to start a chip fab. My point is that it could conceivably be doable for an individual to create old computing technology with the advantages of living in the modern world. I certainly don’t have the drive to do it, but I wish someone did.
If you did it often and didn't count your own labor costs, then maybe the average cost would be less, but that's an incredibly specific situation.
> I believe the way Sam Zeloof circumvents the enormous amount of capital needed for a chip fab by relying on modern technology to create 1970’s technology
Yes, exactly.
Old lithographic technology is so crude that you can even use modern high resolution laserjets to print masks (10000 dpi is less than 3 microns).
Even so, 1970s-era CVD, PVD, and plasma etch is still quite complicated, and CMP is impossible (it hadn't even been invented yet). So the devices you can create are significantly integration-constrained.
This yes can be priceless in some circumstances.
