EUV stands for extreme ultraviolet, a type of light with wavelengths between 10 and 120 nanometers. In practice, when most people encounter the term, it refers to EUV lithography: the technology used to print the tiniest features on modern computer chips. EUV lithography uses light at a specific wavelength of 13.5 nanometers, more than 14 times shorter than the deep ultraviolet (DUV) light it replaced, allowing chipmakers to etch circuit patterns small enough for today’s most advanced processors.
Where EUV Sits on the Light Spectrum
Ultraviolet radiation covers wavelengths from 10 to 400 nanometers, filling the gap between visible light and X-rays. Scientists divide UV into several bands: UVA (320–400 nm), UVB (280–320 nm), UVC (200–280 nm), far UV (120–200 nm), and extreme UV (10–120 nm). EUV occupies the shortest, highest-energy end of the ultraviolet range, bordering on soft X-rays. At these wavelengths, light behaves very differently from ordinary sunlight. It gets absorbed by air, glass, and most other materials, which is why working with it requires an entirely different set of engineering solutions than previous chip-printing methods.
Why Chipmakers Needed Shorter Wavelengths
Printing circuits on a silicon chip works a bit like projecting a photograph onto paper: the finer the light source, the sharper the image. For decades, the semiconductor industry relied on DUV lasers. Krypton-fluoride lasers at 248 nm could print features down to about 80 nm. Argon-fluoride lasers at 193 nm pushed that to roughly 38 nm. Engineers stretched 193 nm light even further using clever tricks like immersion lithography and multiple patterning, reaching the so-called 10 nm node. But physics eventually set a hard floor. To keep shrinking transistors, the industry needed fundamentally shorter light.
EUV lithography, operating at 13.5 nm, broke through that floor. It has enabled chip manufacturers to reach the 7 nm, 5 nm, 3 nm, and 2 nm process nodes. These are the generations of chips powering the latest smartphones, data center processors, and AI accelerators.
How EUV Light Is Generated
You can’t produce 13.5 nm light the way you produce DUV light (by exciting a gas with electricity inside a laser tube). Instead, EUV systems create a plasma. Tiny droplets of molten tin are fired into a vacuum chamber at high speed. A powerful CO2 laser strikes each droplet, heating it so intensely that the tin atoms lose several electrons and form a plasma. That plasma radiates light at 13.5 nm. The process happens tens of thousands of times per second to produce a usable, steady stream of EUV photons.
Mirrors Instead of Lenses
Glass lenses, the backbone of older lithography systems, are useless at EUV wavelengths because the light gets absorbed rather than transmitted. EUV systems rely entirely on mirrors. But even mirrors pose a challenge: at normal angles, most surfaces absorb EUV light instead of reflecting it.
The solution is multilayer mirrors, built from alternating ultra-thin layers of molybdenum and silicon. Each layer is only a few nanometers thick. When EUV light hits these stacked layers, small reflections from each interface add up constructively, producing a usable reflected beam. Even so, each mirror reflects only about 70% of the incoming light, and a typical EUV system uses multiple mirrors in series. By the time the light reaches the silicon wafer, only a small fraction of the original energy remains, which is one reason these machines need such a powerful light source to begin with.
Protecting the Mask
Every lithography system projects light through (or, in EUV’s case, off of) a patterned mask called a reticle. A single particle of dust landing on that mask can ruin thousands of chips. In older systems, a thin transparent film called a pellicle covers the mask to keep contaminants away. EUV pellicles face a unique problem: the membrane must transmit more than 90% of 13.5 nm light while remaining mechanically strong enough to survive inside the machine. Materials like silicon nitride are used as a base because they combine reasonable EUV transparency with durability, sometimes coated with an ultra-thin layer of ruthenium just a few nanometers thick. Even small amounts of oxidation over time can reduce transmittance by a few percentage points, making pellicle longevity an ongoing engineering challenge.
Cost and Scale of EUV Machines
EUV lithography systems are among the most complex and expensive machines ever built. Only one company in the world, the Dutch firm ASML, manufactures them. A standard EUV scanner costs roughly $150 to $200 million. Each machine weighs over 100 tons, contains more than 100,000 parts, and must be shipped in multiple truckloads before being reassembled inside a semiconductor fab.
The newest generation, called High-NA EUV, costs more than $400 million per unit. ASML began developing these machines around 2016, and they are now entering production at leading chipmakers. Despite the staggering price, demand is strong because EUV is the only path to manufacturing the most advanced chips at commercial volumes.
High-NA EUV and What Comes Next
Standard EUV systems have a numerical aperture (NA) of 0.33, a measure of how tightly the optics can focus light. High-NA EUV bumps that to 0.55, a 67% increase. Higher numerical aperture means finer resolution, the same way a better camera lens captures sharper detail.
The practical impact is significant. For the most demanding chip layers at future nodes (with line spacings below 20 nm), a standard 0.33 NA system would need three or four separate mask exposures layered on top of one another to define the pattern. A 0.55 NA system can do it in a single exposure. Fewer exposures means faster production, lower cost per chip, and fewer opportunities for alignment errors. High-NA EUV also enables about a 20% reduction in the area of basic circuit building blocks, allowing more transistors to fit in the same chip footprint. This technology is targeted at nodes beyond 2 nm, sometimes labeled A14 and A10 in industry roadmaps.
EUV Compared to DUV
The simplest way to understand the leap from DUV to EUV is through wavelength. DUV’s most advanced lasers operate at 193 nm. EUV operates at 13.5 nm. That 14x reduction in wavelength translates directly into the ability to print much smaller features without the elaborate multi-patterning workarounds that DUV required at its limits. Multi-patterning with DUV meant exposing the same wafer layer two, three, or even four times with slightly shifted masks, a slow and expensive process that introduced alignment errors at every step.
EUV simplifies the process by printing complex patterns in fewer exposures. This doesn’t just improve resolution. It reduces the total number of processing steps, which lowers manufacturing cost and improves yield (the percentage of chips on a wafer that actually work). DUV systems are still widely used for less critical chip layers and for older, larger process nodes, but every leading-edge chip today relies on EUV for its finest features.