Flatness correction of NZTE mask blank substrates

Lutz Aschke; Fredi Schubert; Joerg Kegeler; Axel Schindler; Thomas Haensel; Konrad Knapp

doi:10.1117/12.436634

20 August 2001 Flatness correction of NZTE mask blank substrates

Lutz Aschke, Fredi Schubert, Joerg Kegeler, Axel Schindler, Thomas Haensel, Konrad Knapp

Proceedings Volume 4343, Emerging Lithographic Technologies V; (2001) https://doi.org/10.1117/12.436634
Event: 26th Annual International Symposium on Microlithography, 2001, Santa Clara, CA, United States

Abstract

For EUV lithography mask blank substrates of the 6025 type will be made from Near Zero Thermal Expansion (NZTE) materials. The low thermal expansion of EUV substrates shall provide for the required better thermal stability during mask-writing and lithography exposure. The manufacturing of such NZTE mask blank substrates requires modified finishing processes in comparison to standard mask blanks. Super polishing takes place to provide high spatial frequency roughness of less than 2 Angstroms RMS. To improve the flatness and the roughness at the mid spatial frequencies another correction step is required. Such step can be Ion Beam Figuring for example. We evaluate the results for the different spatial frequencies by interferometry and atomic force microscopy. We have a closer look how the additional finishing steps improve the flatness and mid spatial frequency roughness. The impact of these newly introduced finishing steps for the high spatial frequency roughness is studied. We examine the processes for two different substrate materials with near zero thermal expansion (ZERODUR and ULE).

Citation Download Citation

Lutz Aschke, Fredi Schubert, Joerg Kegeler, Axel Schindler, Thomas Haensel, and Konrad Knapp "Flatness correction of NZTE mask blank substrates", Proc. SPIE 4343, Emerging Lithographic Technologies V, (20 August 2001); https://doi.org/10.1117/12.436634

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