DFG-RSF: Beryllium based multilayer optics for the EUV spectral range

• Applicant: Dr. Andrey Sokolov
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310360704

• Final Report Year: 2020

Final Report Abstract

The expertise of two world-standard facilities of high reputation was merged in this project: (1) Institute for Physics of Microstructure of the Russian Academy of Science (IPM-RAS), Nizhny Novgorod, which owns a well-equipped laboratory for XUV-multilayer optics fabrication and (2) the synchrotron radiation facility BESSY-II with a state-of-the-art At-Wavelength Metrology station to characterize such optical elements. The goal of this project was the development, characterization and application of novel types of multilayer stacks with promising innovative properties, namely beryllium (Be)-containing optical devices to be used in the VUV, EUV, and soft x-ray region for various applications. The high scientific, optical and technological interest in this material contrasts to the limited experimental data set available. This is due to the high toxicity of Be and the special laboratory certification required to handle this material, which was only recently acquired at the laboratory of our partners in Nizhny Novgorod. We identified three main areas of potential applications, for which Be-optics might be superior to the commonly used optical approaches: EUV-lithography optics; Optics for astronomy; High-pass filter optics. In all of these cases simulations on the basis of the available optical constants had demonstrated already clearly their improved performance. Since experimental data on the optical behavior of Be is scarce, the project started by determining it’s optical constants in the UV-, VUV and EUV-range of interest and by development of an analytical, self-calibrating approach to describe the manufactured (multi- )layer stacks as a depth-profile of the electron density on the basis of a global fit to the experimental reflectivity and transmission data. For all of the above mentioned application fields the project was more than successful and resulted up to now in nine publications in peer-reviewed journals. The results for reflectivity, transmission, thermal (long-term) stability etc. exceeded our expectations. Remaining discrepancies between simulated (expected) and measured results could be clearly traced to boundary (interface) inhomogeneity which are in turn described by the global fit model as well. Some highlights of the project results are the following: 1) Outstanding optical properties of Be/Al multilayers in the UV-range. 2) Mo/Be multilayer with C, B4C, and Si interlayers – better interfaces. 3) Freestanding Be-containing membranes - long term stability. 4) Be-containing multilayer mirrors for EUV-lithography – record reflectivity. 5) Heat load on mirrors - annealing of Mo/Be multilayers – improved performance.

Publications

• "Be/Albased multilayer mirrors with improved reflection and spectral selectivity for solar astronomy above 17 nm wavelength" Thin Solid Films 631 (2017) 106–111
  N.I. Chkhalo, D.E. Pariev, V.N. Polkovnikov, N.N. Salashchenko, R.A. Shaposhnikov, I.L. Stroulea, M.V. Svechnikov, Yu.A. Vainer, S.Yu. Zuev
  
• "Effect of ion beam etching on the surface roughness of bare and silicon covered beryllium films" Surface and Coatings Technology, 311, (2017) 351-356
  N.I.Chkhalo, M.S.Mikhailenko, A.V.Mil'kov, A.E.Pestov, V.N.Polkovnikov, N.N.Salashchenko, I.L.Strulya, M.V.Zorina, S.Yu.Zuev
  
• “High-reflection Mo/Be/Si multilayers for EUV lithography” Optics Letters 42(24) (2017) 5070-5073
  Nikolai I. Chkhalo, Sergei A. Gusev, Andrey N. Nechay, Dmitry E. Pariev, Vladimir N. Polkovnikov, Nikolai N. Salashchenko, Franz Schäfers, Mewael G. Sertsu, Andrey Sokolov, Mikhail V. Svechnikov, Dmitry A. Tatarsky
  
• "Study of oxidation processes in Mo/Be multilayers" AIP Advances 8, 075202 (2018)
  A. N. Nechay, N. I. Chkhalo, M. N. Drozdov, S. A. Garakhin, D. E. Pariev, V. N. Polkovnikov, N. N. Salashchenko, M. V. Svechnikov, Yu. A. Vainer, E. Meltchakov, and F. Delmotte
  
• “Influence of barrier interlayers on the performance of Mo/Be multilayer mirrors for next-generation EUV lithography” Optics Express, Vol. 26, Issue 26, pp. 33718-33731 (2018)
  M. V. Svechnikov, N. I. Chkhalo, S. A. Gusev, A. N. Nechay, D. E. Pariev, A. E. Pestov, V. N. Polkovnikov, D. A. Tatarskiy, N. N. Salashchenko, F. Schäfers, M. G. Sertsu, A. Sokolov, Y. A. Vainer, and M. V. Zorina
  
• “Beryllium- Based Multilayer Mirrors and Filters for the Extreme Ultraviolet Range” Journal of Nanoscience and Nanotechnology Vol. 19, 1–8, 2019
  Chkhalo Nikolay, Lopatin Alexey, Nechay Andrey, Pariev Dmitriy, Pestov Alexey, Polkovnikov Vladimir, Salashchenko Nikolay, Schäfers Franz, Sertsu Mewael, Sokolov Andrey, Svechnikov Mikhail, Tsybin Nikolay, and Zuev Sergey
  
• “Mo/Si Multilayer Mirrors with B4C and Be Barrier Layers”, J. of Surface Investigation. (2019) 13(2), pp. 169-172
  S. Yu. Zuyev, D. E. Pariev, R. S. Pleshkov, V. N. Polkovnikov, N. N. Salashchenko, M. V. Svechnikov, M. G. Sertsu, A. Sokolov, N. I. Chkhalo, F. Schäfers
  
• “Stable high-reflection Be/Mg multilayer mirrors for solar astronomy at 30.4 nm”, Opt. Lett. 44, 263-266 (2019)
  V. Polkovnikov, N. Chkhalo, R. Pleshkov, N. Salashchenko, F. Schäfers, M. Sertsu, A. Sokolov, M. Svechnikov, and S. Zuev
  
• "Beryllium-Based Multilayer Mirrors for the Soft X-Ray and Extreme Ultraviolet Wavelength Ranges" Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques, 14, 124–134 (2020)
  Yu. A. Vainer, S. A. Garakhin, S. Yu. Zuev, A. N. Nechay, R. S. Pleshkov, V. N. Polkovnikov, N. N. Salashchenko, M. V. Svechnikov, M. G. Sertsu, R. M. Smertin, A. Sokolov, N. I. Chkhalo & F. Schäfers