EUV Laser Sources

Computer chips are manufactured in a way similar to developing a photograph. A pattern is projected with light onto a disc of silicon, and wherever the light hits, a light-sensitive layer changes. How fine this pattern can be depends on the wavelength of the light, that is, the distance between two wave crests. The shorter the wavelength, the smaller the structures that can be imaged. EUV laser sources are machines that generate particularly short-wavelength light: extreme ultraviolet radiation with a wavelength of 13.5 nanometers. A nanometer is a millionth of a millimeter, so this light has a wavelength around forty times shorter than visible blue light.

Why no modern chips can be made without 13.5 nanometers

For decades, the industry exposed chips using laser light with a wavelength of 193 nanometers. With clever tricks, they got remarkably far with it, but eventually the limit was reached. The structures on current processors are only a few nanometers wide. Such fine details require shorter light, and this is exactly the gap that EUV closes.

Every modern smartphone processor and every AI accelerator for data centers now goes through EUV exposure. Without this technology, there would be no chips of the current generation. That is why the light source is not a peripheral component, but a bottleneck for the entire global economy.

On top of this comes an unusual power dynamic. Worldwide, only one company builds complete EUV lithography machines: the Dutch corporation ASML. The laser source inside comes from the German manufacturer Trumpf, and the mirrors from Zeiss. Depending on the configuration, a machine costs between 150 and 350 million euros. This concentration turns EUV into a matter of foreign policy: the export of such systems to China is heavily restricted by regulations.

Tin droplets, two laser pulses, and a flash of plasma

EUV light cannot simply be generated directly with a laser. Instead, a detour is taken via extremely hot gas. Inside the source, about 50,000 tiny tin droplets per second fall through a vacuum chamber. Each droplet is around 25 micrometers in size, thinner than a human hair.

Each droplet is hit twice. A first, weaker laser pulse flattens it into a flat disc. A second, very powerful pulse vaporizes this disc into plasma, a gas of charged particles. The plasma reaches over 200,000 degrees in the process and radiates in the EUV range for a fraction of a second. The driving laser for this is a carbon dioxide laser with about 30 kilowatts of power.

The effort involved is enormous, the efficiency low. Only a few percent of the energy used is converted into usable EUV light. Another problem: EUV is absorbed by air and even by glass. The system therefore has to operate in a vacuum, and instead of lenses, dozens of special mirrors are used. Each mirror consists of around a hundred ultra-thin layers and still absorbs part of the light.

EUV in stock market news and in your own phone

You never see an EUV source directly, it sits in only a few chip factories worldwide. Nevertheless, it appears regularly in the news. Reports on ASML’s quarterly figures, on new factories from TSMC, Samsung or Intel, and on export bans almost always revolve around this technology.

In everyday life, you encounter it in the product. Every current smartphone, every modern graphics card, and the chips behind AI services are exposed using EUV. When a manufacturer advertises a three-nanometer process, this light source is behind it.

A common misconception: EUV light does not write the structures point by point like a laser printer. It projects an entire pattern at once through a mask, a kind of stencil. The next step is called High-NA EUV, where NA stands for numerical aperture, that is, the light-gathering capability of the optics. These machines use the same 13.5-nanometer source, but larger mirrors, and cost considerably more still.