1 July 2002 Ion beam sputter deposition of low-defect EUV mask blanks on 6-in. LTEM substrates in a real production environment
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Abstract
EUV mask blanks consist of two thin film systems deposited on low thermal expansion 6 inch substrates (LTEM). First there is the multilayer stack with around 100 alternating layers of elements with different optical properties which are topped by a capping layer. Beside optimal optical properties it is also necessary to improve the heat stability of the layer system. The absorber stack which consists of a buffer and an absorber layer is next. Here a minimum absorption of EUV light of 99 percent is required. The stress in both layer systems should be as low as possible. The reduction of defects to an absolute minimum is one of the main challenges. The high-reflective Mo/Si multilayer coatings were designed for normal incidence reflectivity and successfully deposited on 6-inch LTEM substrates by ion-beam sputtering. X-ray scattering, transmission electron microscopy and atomic force microscopy were used for characterization of the multilayer interfaces and the surface morphology. The results are correlated to the measured normal incidence reflectivity using synchrotron radiation at the PTB reflectometer at BESSY II, Berlin, Germany.
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Hans Willy Becker, Lutz Aschke, Birgit Schubert, Juergen Krieger, Frank Lenzen, Sergey A. Yulin, Torsten Feigl, Thomas Kuhlmann, Norbert Kaiser, "Ion beam sputter deposition of low-defect EUV mask blanks on 6-in. LTEM substrates in a real production environment", Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); doi: 10.1117/12.472326; https://doi.org/10.1117/12.472326
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