In recent years, optical lithography was increasingly reaching its physical limits. The leap to EUV lithography was necessary to realize semi-conductor structures on the nanometer scale. However, this step required an entirely new way of thinking about how production processes should run. The entire technology, from the light source to the optical system in a vacuum to the surface coating, had to be developed from scratch. Extreme ultraviolet light is absorbed by air, making it unsuitable for use in conventional production environments. Moreover, this light cannot be shaped and focused by lenses which is the common practice in optical lithography. To avoid this physical problem, researchers at Carl Zeiss SMT have developed a lithographic system consisting exclusively of mirrors. It is adapted for use in a high vacuum, for example, in an environment with almost no air molecules. The mirrors used in this technology must meet extremely high requirements. The requirements for the mirror layers are equally high. They consist of approximately 100 individual layers that are applied with atomic precision.
A further decisive factor is that the mirrors need to have a diameter of more than half a meter to make it work.
The Fraunhofer Institute for Applied Optics and Precision Engineering IOF, based in Jena, Germany, is a long-standing customer of Bühler Leybold Optics and one of the key partners in the development of this mirror coating.