Discover EUV lithography by yourself

Visitors to the Deutsches Museum in Munich can now explore how EUV mirror optics work on a new demonstrator

EUV lithography can be used to produce smaller and more powerful microchips than ever before. A team of researchers from the Fraunhofer-Institute for Applied Optics and Precision Engineering IOF and industrial partners ZEISS and TRUMPF were awarded the German Future Prize 2020 for their development. An exhibition at the Deutsches Museum in Munich commemorates the previous prize winners and their technological breakthroughs. On July 15, the exhibition on EUV lithography was inaugurated there.

EUV stands for "extreme ultraviolet", i.e., light with an extremely short wavelength. However, the use of EUV light in chip production is demanding and complex: It can only be used in a vacuum. In addition, only special mirror optics instead of lenses can be used to guide the light.
 

Highly reflective mirrors instead of lenses

Conventional mirrors do not reflect EUV light very well. Only when they are coated with special multilayer coatings can they reflect EUV light. Dr. Sergiy Yulin from Fraunhofer IOF in Jena has developed this coating technology for EUV lithography with his team over many years. The demonstrator provided by the institute and now inaugurated at Deutsches Museum in Munich addresses specifically the coating of EUV optics.

It exemplifies how the coating technique for large-scale mirrors developed by Dr. Yulin can be used to reflect significantly more light than conventional coating methods. The demonstrator illustrates two things that are particularly important for EUV lithography: First, it shows how individual structures of a microchip can be imaged on a wafer with a mask using reflective mirrors. The actual microchip is later created on this wafer in chip production after many exposures with different masks. Second, the demonstrator shows that the mirrors in the exposure system need an extremely smooth coating in order to be able to produce a sharp image on the wafer to begin with.

But how exactly does the demonstrator display this process? In the demonstration, a mask – in this case the EUV logo – is first imaged on a screen in two quality levels. The light first reaches the mask from the light source and then hits the large mirror. There it is reflected and forwarded to one of two smaller mirrors – one of these small mirrors is coated with a layer comparable to the technology developed by Dr. Yulin. The other one is not. This layer was optimized for the demonstrator's visible LED light for the purpose of demonstration at the museum. True EUV light would not be visible to visitors' eyes.

The logo is reflected again from this small mirror, allowing it to pass through the hole in the large mirror and onto the screen. There, depending on the properties of the small mirror, the logo is either sharp or blurred. A sharp image is achieved when the coated mirror is in the path of the beam. When visitors press a button on the demonstrator, they swap the coated mirror with the uncoated one, clearly showing the effect of the different coatings.

EUV lithography enables next-generation microchips 

Artificial intelligence, autonomous driving, big data or even virtual reality - all these things are already a reality today. In the future, however, we will encounter them much more frequently - provided that we have even more powerful microchips than before. Such chips can be manufactured with the aid of so-called EUV lithography. The chips are more powerful because the use of EUV light allows significantly more integrated circuits to be accommodated on them for the same size.

The production of such fine structures is possible with the aid of very short-wave light – namely, extreme ultraviolet light, or EUV for short – in a photolithography process. With the aid of lithography, the structures for electronic components are transferred to a silicon wafer in a multi-stage projection process, from which the actual microchip is later created. The smaller the wavelength used in the lithography process, the smaller the structures that can be produced on the chips. A complex process is required for chip production with EUV light: In addition to a powerful plasma light source and extremely precise mirror optics, highly reflective coatings are required for the manufacturing process.

After more than 25 years of research and development work, a team of researchers from ZEISS, TRUMPF and Fraunhofer IOF has succeeded in developing the most important key components for the first EUV lithography system in the form of mirror optics, mirror coating and a laser for the light source. For this achievement, Dr. Peter Kürz (ZEISS), Dr. Michael Kösters (TRUMPF) and Dr. Sergiy Yulin (Fraunhofer IOF) were awarded the German Future Prize in 2020, presented by German Federal President Frank-Walter Steinmeier.

Honoring for innovative engineering and scientific achievements

The German Future Prize has been presented every year since 1997. It is one of the highest accolades for scientific achievement in Germany and is worth 250,000 euros. It honors exceptional achievements in technology, engineering and the life sciences that have resulted in viable products. Every year, during a multistage selection process, the prestigious jury selects three research teams and their innovation for the final round from among a large number of different projects, the "shortlist". Alongside their innovative achievements, the jury also evaluates the development's economic and social potential. For Fraunhofer, the award in 2020 has been the 9th award of the "Deutsche Zukunftspreis". Of these, the prize went to Fraunhofer IOF for the third time.