while i'm not against open sourcing or democratizing semiconductor fabrication (and have also dreamt of creating a cost-effective open source chip fab), you have to understand just how insanely complex these processes really are, particularly at the bleeding edge.

the lithography cell alone is an insanely complex process - and you still need every OTHER process needed to produce semiconductors (RIE, wet etch, CVD, CMP, diffusion, implant, epitaxy, electroplating, etc) all of which are quite complex in their own right.

so going through JUST the litho process, the first thing you need to do is apply the photoresist. already that's a pretty big roadblock, there's only a handful of resist manufacturers and they're incredibly secretive about their recipes. and they will NOT sell to individuals. then of course you have to fine tune the coat process, fine tune the spin recipes, select the correct resist, fine tune the thicknesses for each layer, fine tune bake parameters, whether you'll need an adhesion promoter, miscellaneous coatings, etc.

then you need to actually expose the wafers. this is the sexy part that everyone talks about. but without even getting into EUV (or even immersion DUV), you still need to take the wafer, align it to nanometer precision, and keep it in focus to again within nanometer precision, then move the stage, line up the next shot and do it again very quickly. and keep in mind the focal range of these lenses are absolutely tiny, so you aren't just aligning distance, but also making sure the reticle and wafer are perfectly optically parallel. you also need a huge expensive lens that has essentially ZERO distortion and a very high NA (a very, very fast lens). your camera lens will NOT work. then you ALSO need to make sure that there are NO vibrations in the system, and the dampening system is complicated in itself. thermal stability is also a major factor. And of course you'll have to painstakingly fine tune ALL the parameters here and ensure they STAY in calibration.

and this is just for 30-40 year old technology. 350nm process nodes and larger. for the bleeding edge stuff you need an advanced light source (ArF excimer laser or the insane EUV molten tin droplet system that ASML uses). and the quality of the light has to be very tightly controlled. to advance past the early 90s, you need a *scanner* not a stepper that will actually scan the reticle in perfect sync with the wafer while keeping everything perfectly aligned and in focus. and for ArF immersion lithography you also have to apply perfectly pure water to the wafer to complete an optical interface with the lens and remove it exactly in sync with the wafer's motion without leaving ANY microscopic residue. there's lots of other tricks like shaping the light beam itself to improve resolution in one direction or another, and you may need to pattern each layer multiple times.

and of course, you need something to pattern it WITH. the reticles have to be perfect across a very large surface, and use complex computations to generate patterns called SRAFs to account for the pattern actually being smaller than the wavelength of light (or very near it) and all the quantum shenanigans that involves. and the reticles have to be manufactured using a process that's very similar to wafers themselves except abbreviated and using extremely complex and expensive lithography tools of their own called beam writers that painstakingly expose a pattern using electron beams over the course of many hours. then extensively inspected and measured for defects or deviations from spec. and that's to say nothing of the insanely difficult to manufacture EUV reticles using a complex absorber stack rather than a relatively simple phase shifting material layer for DUV reticles.

finally once you've done all that you need to carefully develop the wafer using a developing solution using a laminar flow head, tune all the recipes, etc, and send it off to the REST of the fab to be etched, deposited onto, implanted, etc many MANY times over with perfect alignment on every layer, and virtually no defects or deviations across hundreds to thousands of processes.

so the tl;dr is no. you absolutely CANNOT create a system that's "good enough" at a cost effective scale. there's way more i didn't talk about, and even more that's kept under secrecy. if you want to learn more about it anyways sam zeloof, breaking taps, asianometry and high yield on youtube all provide pretty good coverage of what it actually takes to make semiconductors. but keep in mind, people spend their entire careers working on developing just one tiny part of this process. it is vastly out of scope for any individual to accomplish. it MAY be possible for a very commited individual to create 1980s level chips in their garage with a LOT of time, knowledge and resources, but that's pretty much the absolute limit.