Dresden 2006 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 5: Internal Symposium “Functional thin films - future applications and challenges”

DS 5.3: Hauptvortrag

Montag, 27. März 2006, 15:30–16:15, GER 37

EUV Optical Coatings — •Hartmut Enkisch, Stephan Müllender, and Peter Kürz — Carl Zeiss SMT AG; 73446 Oberkochen; Germany

In the semiconductor community, the extreme ultra-violet lithography (EUVL) at 13.5 nm wavelength is considered to be the next-generation technology ensuring both optimum quality and throughput. Presently built lithographic tools make use of deep ultra-violet (DUV, 193 nm) radiation and are based on conventional refractive elements made of glass or transparent single crystals. Since radiation of 13.5 nm wavelength is strongly absorbed by virtually any material this approach is not possible in the EUV range. Therefore, EUVL tools exclusively consist of reflective elements. In order to obtain a sufficiently high reflectance, all mirrors to be operated near normal incidence have to be coated with multilayer coatings. They consist of a periodic stack of spacer and absorber layers possessing different refractive indices at the desired wavelength. These multilayer stacks work analogously to Bragg’s Law and thus have a periodic length of about half the wavelength. Therefore, single-layer thicknesses of 3 to 4 nm have to be obtained. The requirements of the optical performance put stringent demands on the quality of the multilayer coatings, such as periodicity, temporal and thermal stability, lateral uniformity, absolute thickness, and film stress.