What were the biggest hurdles you had to overcome?
One important challenge was the size of the substrates to be coated. The objective was not only to develop new coatings on a laboratory scale, but to scale them directly to dimensions that are relevant to the application. The implementation of gradients over large substrate surfaces requires precise knowledge and high stability of distribution in the system. It is therefore an elaborate process that requires a lot of test processes and extensive measurements. And, as I said, the number of cathodes plays a significant role for the possibilities of layer design and interface engineering. Of course, it took a great deal of work to convince the demanding high-end customers of the value of our technology.
In cooperation with Bühler Leybold Optics, the coating technology has been further developed in line with the continuous stream of new discoveries. How important was the collaboration with the system supplier for you?
The remote service option was a great help in discussing and solving problems during the first campaigns with the new technology. The exceptional demands relating to coating homogeneity and the implementation of precise coating thickness gradients was a very big challenge as well as being in an uncharted territory both in research at our company and in plant construction at Bühler Leybold Optics. Without a direct and open discussion in both directions, we would certainly not have come this far. I think Leybold Optics found us very challenging at times, but in the end this was the key to the breakthrough and both sides learned a great deal.
In addition to the basic development, commercial implementation is also a very important issue with EUV technology. What role did Fraunhofer IOF play in the practical implementation?
At the Fraunhofer Institute, we are closely involved with the industrial implementation of our research work. The interplay between research and application-oriented development as well as a solid value chain consisting of design, optics manufacturing, cleaning, characterization, coating, and logistics are a special strength at Fraunhofer IOF that also brings us international success in other fields, such as space optics. The boundaries between application-oriented research and production are sometimes not well-defined. Fraunhofer Institutes often act as an “enabler” for innovations in companies, because demonstrators can already be implemented due to their broad competence and comprehensive technology platforms, even when supply chains have not yet been established due to the small quantities and high risks entailed in the development phase. The importance of Fraunhofer, especially in this phase in the field of EUV lithography, is shown clearly, for example by projects with Intel, Cymer and ASML, that have even honored us with distinctions such as the “Cymer Supplier Award” – which was really wonderful. We then applied our discoveries to the industry in various ways, on the one hand through know-how transfer based on more than 15 patents, and also by intelligence – and more than 10 of our experts are now working in relevant companies. Finally, in 2015, the spinoff optiXFab was founded by my longstanding colleague Torsten Feigl, which has been successful in the market ever since. At the same time, we are continuing our research activities, for example moving towards even shorter wavelengths and other applications, such as microscopy in the so-called water window. There is still a lot to do.