19.01.2022
Figure: The complex refractive index n=1-δ-iβ of different materials relevant for EUV lithograpghy at 13.5 nm wavelength
The introduction of EUV lithography in semiconductor industry has significantly expanded the technologically relevant spectral range of electromagnetic radiation to include extreme UV radiation (EUV). For the development of optical components such as mirrors, gratings or photomasks in this spectral range, the optical properties of the relevant materials must be accurately known. For many chemical elements and especially for compounds and alloys, the existing databases usually only contain estimates based on some measured and theoretical values. In EU-wide research projects and long-term cooperations with leading research institutes and companies from the semiconductor industry, PTB has investigated the optical properties of technologically relevant materials, e.g. the optical properties of potential absorber materials for EUV photomasks. Using this data, such photomasks can be optimized to improve the optical contrast of the structures to be imaged on the semiconductor chips. The results for a first set of materials have now been published and are thus available for technology development. For quick and easy access, they have been made freely accessible as the cornerstone of a database that is to be constantly expanded with new results.
Publication:
R. Ciesielski, Q. Saadeh, V. Philipsen et al., “Determination of optical constants of thin films in the EUV”, Appl.Opt. 61 (2022)
Link to database: https://www.ocdb.ptb.de/home
DOI: https://doi.org/10.1364/AO.447152
Contact:
R. Ciesielski, 7.14, E-Mail: 
Richard.Ciesielski(at)ptb.de