EUV technology on a steep growth curve
In 2020, TRUMPF, ZEISS and the Fraunhofer Institute for Applied Optics and Precision Engineering IOF received the German Future Prize for developing EUV (Extreme Ultraviolet) lithography into an industry-ready process. Since then, a fast-growing multi-billion market has emerged around EUV technology.
In the PHOTONICS interview, the spokesperson for the award-winning team, ZEISS researcher Dr. Peter Kürz, explained the core of EUV lithography in one sentence: “In the system, 50,000 tin droplets per second are fired into a high vacuum, where they are each hit twice by pulses from a high-power CO2 laser from TRUMPF. This ignites the tin plasma, which emits the EUV radiation. It was the Dutch technology group ASML that brought this process to series maturity and has been marketing it with great success ever since. It was recently announced that the semiconductor group Intel has bought all of the EUV lithography systems that ASML will produce in 2024 in one go. The order volume is likely to be just under two billion US dollars. Chip manufacturers are lining up at ASML to equip themselves with the technology, which makes chip structures in the low single-digit nm scale possible. The key to this is that the Dutch company combines the laser plasma source from TRUMPF with high-end optics from ZEISS. “If you were to scale one of our EUV mirrors to the size of Germany, the largest deviations from the target shape would only be 0.1 mm high,” Kürz reported in an interview at the time.
EUV radiation can only be generated artificially
The finest nanostructuring of wafers to date requires EUV radiation with a wavelength of 13.5 nanometers (nm). This does not occur in nature, but has to be generated by a laser-ignited plasma using a so-called secondary source. At the heart of the process is the 30 kW laser from TRUMPF, which uses the double hits to put the tin droplets into a state of plasma at over 220,000°C. It is this plasma that then emits light with the required wavelength. A Dutch-American research team from the Advanced Research Center for Nanolithography ARCNL in Amsterdam and the Los Alamos National Laboratory in New Mexico got to the bottom of the question of how exactly this light emission from the plasma takes place. According to the study, the tin atoms in the plasma decay into free electrons and positively charged ions with different charges. Many of the ions are in an excited state, in other words, they are orbited by electrons with an additional portion of energy which they emit as EUV radiation when they change to an orbit that is closer to their nucleus. It was unclear for a long time how these additional energy packets are distributed among one or more electrons, and to what extent this depends on whether they orbit the atomic nucleus in the first, second, third, or even fourth shell. The team solved the mystery with the help of a supercomputer that calculated all—more than ten billion—possible energy transitions in the tin plasma. The result: It’s not only electrons returning from the first excited energy state that emit 13.5 nm, but also the electrons in higher shells. Every electron that returns to a lower energy state contributes to the EUV emission, which is precisely why tin plasma is unique and particularly suitable for EUV beam sources.
Global EUV market growing rapidly
EUV technology is the first industrial application of so-called secondary sources to trigger the development of a multi-billion dollar market. And, according to current market studies, this market will grow rapidly in the coming years. In its Global Forecast, the market research company Research and Markets predicts annual growth rates of just under 22% for EUV lithography through 2028. At the end of the period under review, the forecast expects a market volume of 25.3 billion US dollars. An outlook from Data Bridge Market Research is almost as optimistic. This forecast talks of 20.1% annual growth, which means that the global market for EUV lithography will increase from USD 9.38 billion to more than USD 40 billion in the period from 2023 to 2031. This fascinating technology was therefore not only worthy of a German Future Prize, but is also boosting the semiconductor industry with steep growth rates, both economically and in terms of the performance of modern chips. The basis for this is provided by photonics in the form of a laser plasma source.