Every modern processor — from the chip in your phone to the GPUs training large AI models — is built using a process called photolithography. It is essentially printing, except the features are smaller than a virus.
The Printing Problem To make a transistor, you shine light through a patterned mask onto a silicon wafer coated with a light-sensitive chemical. Where the light hits, the chemistry changes, and that region can be etched away. Stack hundreds of these patterning steps on top of each other, and you build a working chip.
The smallest feature you can print is limited by the wavelength of the light you use. For decades, the industry used deep ultraviolet light at 193 nm. To get smaller features than that, engineers had to invent tricks: immersion lithography (printing through a layer of water), multi-patterning (printing the same layer multiple times), and computational mask design. Eventually those tricks ran out of room.
EUV: 13.5 Nanometers The solution was to drop the wavelength dramatically — to extreme ultraviolet light at 13.5 nm, about 14 times shorter than what came before. EUV light enables features as small as 2–3 nm in commercial production today.
Generating EUV is brutally difficult. There is no laser that emits 13.5 nm light directly. Instead, ASML's EUV scanners use a system that vaporises tiny molten tin droplets, 30 micrometers across, by hitting them twice with a powerful CO₂ laser — first to flatten the droplet, then to blast it into a plasma. The plasma glows at exactly 13.5 nm. This happens 50,000 times per second inside the machine.
The Mirror Problem EUV is absorbed by almost everything — including air, glass, and ordinary lenses. So the entire optical path must be inside a vacuum chamber, and lenses are replaced by mirrors with dozens of precisely engineered atomic-thin layers. These mirrors reflect only about 70% of the light at each bounce. After several bounces, more than 95% of the EUV is lost.
The One-Company Problem There is exactly one company in the world that builds EUV scanners: ASML, in the Netherlands. Each High-NA EUV machine costs over $370 million, weighs around 165 tons, and takes 13 weeks of cargo flights to deliver. TSMC, Samsung, and Intel are the only companies operating them in volume production.
Why This Matters Without EUV, Moore's Law would have effectively ended a decade ago. The gap between leading-edge chip nodes and the rest of the industry has widened — and so has the geopolitical importance of who can access this technology. EUV is now one of the most strategically guarded supply chains on Earth.
The entire AI revolution runs on light from vaporised metal.