Following over 20 years of intensive, collaborative development work, European companies and research institutes have created a revolutionary new manufacturing technology for mass-producing powerful microchips: EUV lithography.
EUV stands for extreme ultraviolet, meaning light with an extremely short wavelength. This “new light” makes it possible to manufacture microchips that are much more powerful, energy-efficient, and affordable than ever before. Until now, the leading optical lithography process has relied on light sources with a wavelength of 193 nanometers. By contrast, the new manufacturing process works with only 13.5 nanometers. EUV thus enables chip structures 5,000 times thinner than a human hair.
World market leaders like Samsung and TSMC have based the production of their state-of-the-art chips on this new process since 2018. Smartphones with microchips manufactured using EUV lithography have been available on the mass market since the fall of 2019.
Teams from ZEISS Semiconductor Manufacturing Technology (SMT), TRUMPF Lasersystems for Semiconductor Manufacturing and the Fraunhofer Institute for Applied Optics and Precision Engineering IOF made a decisive contribution to the leap from laboratory to market:
Sergiy Yulin is Senior Principal Scientist at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena, where he is responsible for the development of EUV optics.
As Vice President in the EUV High-NA team at SMT in Oberkochen, Germany, Peter Kürz is responsible for development and product launch of the next generation of EUV optics.
Michael Kösters is a group leader at TRUMPF Lasersystems for Semiconductor Manufacturing in Ditzingen, where he is jointly responsible for the development of the high-power laser that makes it possible to generate EUV light.
In order to generate the EUV light, ASML and TRUMPF designed a unique light source. In a plasma source developed by ASML, 50,000 droplets of tin per second are fired into a vacuum chamber, where they are struck by two consecutive pulses from a high-power CO2 laser from TRUMPF.
To generate EUV light, the plasma has to be heated to a temperature of nearly 220,000 degrees Celsius – almost 40 times hotter than the average surface temperature of the sun. With 30 kilowatts of power, the TRUMPF laser required for this process is the most powerful industrial laser in the world.
Since ultraviolet light is absorbed by all materials – including air – ZEISS SMT created an optical system for the EUV lithography machine that operates in the vacuum chamber and is made up of mirrors. Because the mirrors have to be held in position as precisely as possible during the exposure process, an entirely new mechatronics concept was required for maximum tilt stability. The results speak for themselves: If one of these EUV mirrors were to redirect a laser beam and aim it at the Moon, it would be able to hit a ping pong ball on the Moon’s surface.
The mirrors are also the product of significant innovations. Since even the smallest irregularities cause aberrations, the world’s “most precise” mirror had to be developed for EUV lithography. If this mirror were to be enlarged to the size of Germany, the height of the Zugspitze mountain would be just 0.1 millimeters. In addition to such high precision, EUV mirrors require maximum quality and reflectivity.
The Fraunhofer IOF served as an important research partner for the development of EUV mirrors through special multi-layer coatings, so-called Bragg mirrors. Here, a layer stack consisting of more than 100 layers, each one just a few nanometers thick, is applied with atomic precision. The particular challenge is achieving the highest reflexivity possible over the entire mirror surface as well as the longevity of the coating during exposure to EUV light.