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Well, obviously don't just take my word for it, but:
Photolithography is the use of high-power light, extremely detailed optical masks and precise lenses, and photoresistive chemicals that solidify and become more or less soluble in certain solvents upon exposure to light, to create detailed patterns on top of a substrate material that can block or expose certain portions of the substrate for the chemical modification required to form transistors and other structures necessary to create advanced semiconductors. It's among the most challenging feats of interdisciplinary engineering ever attempted by mankind, requiring continuous novel advances in computational optics, plasma physics, material science, chemistry, precision mechanical fabrication, and more. Without these continuous advances, modern semiconductors devices would struggle to improve without forcing significant complications on their users (much higher power dissipation, lower lifetimes, less reliability, significant cost increases).
The roadmap for photolithographic advances extends for at least 15 years, beyond which there are a LOT of open questions. But depending on the pace of progress, it's possible that 15 years of roadmap will actually last closer to 30; the last major milestone technological advance in photolithography, extreme-ultraviolet light sources, went from "impossible" to "merely unbelievably difficult" around '91, formed a joint research effort between big semiconductor vendors and lithography vendors in '96, collapsed to a single lithography vendors in '01, showed off a prototype that was around 4500x slower than modern machines in '04, and delivered an actual, usable product in '18. No one else has achieved any success with the technology in the ~33 years it's been considered feasible. There's efforts in China to generate the technology within the Chinese supply chain (they are currently sanctioned and cannot access ASML tech); this is a sophisticated guess on my part, but I'm not seeing anything that suggests anyone in China will have a usable EUV machine for at least a decade, because they currently have nothing comparable to even the '04 prototype, and they are still struggling to develop more than single-digit numbers of domestic machines comparable to the last generational milestone.
There are a handful of other lab techniques that have been suggested over the years, like electron beam lithography (etch patterns using highly precise electron beams - accurate, but too slow for realistic use) or nanoimprint lithography (stamp thermoplastic photoresist polymer and bake to harden - fast, cheap, but the stamp can wear and it takes a ludicrously long time to build a new one, and there's very little industry know-how with this tech). They are cool technology, but are unlikely to replace photolithography any time soon, because all major manufacturers have spent decades learning lessons about how to implement photolithography at scale, and no comparable effort has been applied to alternatives.
There's two key photolithographic milestone technologies in the last several decades: deep ultraviolet (DUV) and extreme ultraviolet (EUV), referring to the light source used for the lithography process. DUV machines largely use ArF 193nm ultraviolet excimer lasers, which are a fairly well-understood technology that have now been around for >40 years. The mirrors and optics used with EUV are relatively robust, requiring replacement only occasionally, and usually not due to the light source used. The power efficiency is not amazing (40kW in for maybe 150W out), but there's very little optical loss. The angle of incidence is pretty much dead-on to the wafer. The optical masks are somewhat tricky to produce at smaller feature sizes, since 193nm light is large compared to the desired feature sizes on the wafer; however, you can do some neat math (inverse Fourier transform or something similar, it's been a while) and create some kinda demented shapes that diffract to a much narrower and highly linear geometry. You can also immerse the optics in transparent fluid to further increase the numerical aperture, and this turns out to be somehow less complex than it sounds. Finally, it is possible to realign the wafer precisely with a different mask set for double-patterning, when a single optical mask would be insufficient for the required feature density; this has some negative effect on overall yields, since misalignments can happen, and extra steps are involved which creates opportunities for nanometer-scale dust particles to accumulate on and ruin certain devices. But it's doable, and it's not so insanely complex. SMIC (Chinese semiconductor vendor) in fact has managed quad-patterning to reach comparable feature sizes to 2021 state-of-the-art, though the yields are low and the costs are high (i.e. the technique does not have a competitive long-term outlook).
EUV machines, by contrast, are basically fucking magic: a droplet of molten tin is excited into an ionized plasma by a laser, and some small fraction of the ionization energy is released as 13.5nm photons that must be collected, aligned, and redirected toward the mirrors and optics. The ionization chamber and the collector are regularly replaced to retain some semblance of efficiency, on account of residual ionized tin degrading the surfaces within. The mirrors and optics are to some extent not entirely reflective or transparent as needed, and some of the photons emitted by the process are absorbed, once again reducing the overall efficiency. By the time light arrives at the wafer, only about 2% of the original light remains, and the overall energy efficiency of this process is abysmal. The wafer itself is actually the final mirror in the process, requiring the angle of incidence to be about 6°, which makes it impossible to keep the entire wafer in focus simultaneously, polarizes the light unevenly, and creates shadows in certain directions that distort features. If you were to make horizontal and vertical lines of the same size on the mask, they would produce different size lines on the wafer. Parallel lines on the mask end up asymmetric. I'd be here all day discussing how many more headaches are created by the use of EUV; suffice it to say, we go from maybe hundreds of things going mostly right in DUV to thousands of things going exactly right in EUV; and unlike DUV, the energies involved in EUV tend to be high enough that things can fail catastrophically. A few years back, a friend of mine at Intel described the apparently-regular cases of pellicles (basically transparent organic membranes for lenses to keep them clean) spontaneously combusting under prolonged EUV exposure for (at the time) unknown reasons, which would obviously cause massive production stops; I'm told this has since been resolved, but it's a representative example of the hundreds of different things going wrong several years after the technology has been rolled out. Several individual system elements of an EUV machine are the equivalent of nation-state scientific undertakings, each. TSMC, Intel, Samsung need dozens of these machines, each. They cost about $200M apiece, sticker price, with many millions more per month in operating costs, replacement components, and mostly-unscheduled maintenance. The next generation is set to cost about double that, on the assumption that it will reduce the overall process complexity by at least an equivalent amount (I have my doubts). It is miraculous that these systems work at all, and they're not getting cheaper.
If you're interested in learning more, there's a few high-quality resources out there for non-fab nerds, particularly the Asianometry YouTube channel, but also much of the free half of semianalysis.
From an investment standpoint... Honestly, I dunno. I think you might have the right idea. There's so much to know about in this field (it's the pinnacle of human engineering, after all), and with the geopolitical wedge being driven between China and the rest of the world, a host of heretofore unseen competitor technologies getting increasing focus against a backdrop of increasing costs, and the supposedly looming AI revolution just around the corner, it's tough to say where the tech will be in ten years. My instinct is that, when a gold rush is happening, it's good to sell shovels; AI spending across hyperscalars has already eclipsed inflation-adjusted Manhattan Project spend, and if it's actually going where everyone says it's going, gold rush will be a quaint descriptor for the effect of exponentially increasing artificial labor. So I'm personally invested. But I could imagine a stealthy Chinese competitor carving a path to success for themselves within a few years, using a very different approach to the light source, that undercuts and outperforms ASML...
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