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21 January 1993 Large-area soft x-ray projection lithography using multilayer mirrors structured by RIE
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SXPL (soft X-ray projection lithography) is one of the most promising applications of X-ray reflecting optics using multilayer mirrors. Within our collaboration, such multilayer mirrors were fabricated, characterized, laterally structured and then used as reflection masks in a projecting lithography procedure. Mo/Si-multilayer mirrors were produced by electron beam evaporation in UHV under thermal treatment with an in-situ X-ray controlled thickness in the region of 2d equals 14 nm. The reflectivities measured at normal incidence reached up to 54%. Various surface analysis techniques have been applied in order to characterize and optimize the X-ray mirrors. The multilayers were patterned by reactive ion etching (RIE) with CF4, using a photoresist as the etch mask, thus producing X-ray reflection masks. The masks were tested in the synchrotron radiation laboratory of the electron accelerator ELSA at the Physikalisches Institut of Bonn University. A double crystal X-ray monochromator was modified so as to allow about 0.5 cm2 of the reflection mask to be illuminated by white synchrotron radiation. The reflected patterns were projected (with an energy of 100 eV) onto the resist (Hoechst AZ PF 514), which was mounted at an average distance of about 7 mm. In the first test-experiments, structure sizes down to 8 micrometers were nicely reproduced over the whole of the exposed area. Smaller structures were distorted by Fresnel-diffraction. The theoretically calculated diffraction images agree very well with the observed images.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Steffen Rahn, Andreas Kloidt, Ulf Kleineberg, Bernt Schmiedeskamp, Klaus Kadel, Werner K. Schomburg, F. J. Hormes, and Ulrich Heinzmann "Large-area soft x-ray projection lithography using multilayer mirrors structured by RIE", Proc. SPIE 1742, Multilayer and Grazing Incidence X-Ray/EUV Optics for Astronomy and Projection Lithography, (21 January 1993);

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