Z2 – Lithographically fabricated IC in a garage fab

Awesome! I wouldn't have thought that it is possible to make ICs in a garage. Of course it requires a lot of knowledge, etc. But still, not a multi-billion dollar clean room with specialist equipment.

You could make in a garage some decent analog integrated circuits, e.g. audio amplifiers or operational amplifiers or even radio-frequency circuits for not too high frequency ranges.

However you cannot make useful digital circuits. For digital circuits, the best that you can do is to be content to only design them and buy an FPGA for implementing them, instead of attempting to manufacture a custom IC.

With the kind of digital circuits that you could make in a garage, the most complex thing that you could do would be something like a very big table or wall digital clock, made not with a single IC like today, but with a few dozen ICs.

Anything more complex than that would need far too many ICs.

What are the factors you expect to limit the integration scale in a garage fab?

Variance, data rate/cost, and lithography.

You can do lithography small but slow and expensive. But small means you need a stack, which is even more expensive. At small sizes, defectivity/variation are really difficult.

So if you want a paradigmatic shift, you need low cost patterning, and the best way I can see is to use clever chemistry and a much different design style.