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Proceedings Paper

Interference patterning of gratings with a period of 150 nm at a wavelength of 157 nm
Author(s): Gerald Fuetterer; Waltraud Herbst; Joerg Rottstegge; Margit Ferstl; Michael Sebald; Johannes Schwider
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Paper Abstract

A system producing an optical pattern with a high spatial frequency at (lambda) equals 157 nm has been built to be used as a photoresist tool for the 157 nm lithography. In order to generate a test pattern with a high spatial frequency, two-beam interference was used to overcome the limits of existing mask-projection systems using numerical apertures up to 0.65. In order to work without phase lock techniques a e-beam phase grating was used for providing the two interfering wave fronts for the generation of 150 nm-structures. The phase grating is illuminated under the Bragg-angle. Only two diffraction orders propagate and the other orders are evanescent. The interference pattern resulting in the region of the overlap of the propagated orders is a true two-beam pattern of the same period as the e-beam mask. The photoresist coated wafer is placed in the plane of the interference pattern and is rigidly held by a mechanical fixture. The contrast of the interference pattern depends on the degree of spatial coherence of the excimer laser, on the coherence length, the polarization state of the beam used to illuminate the surface relief phase grating, and on the distance between the wafer and the surface relief phase grating. The degree of spatial coherence was increased by a restriction of the plane wave spectrum which has been attained at the cost of energy throughput. In addition, the TM-polarization was blocked. This was done by a polarizer and a spatial filter. The theoretical background of the experiment will be discussed as well as practical problems.

Paper Details

Date Published: 30 July 2002
PDF: 11 pages
Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474559
Show Author Affiliations
Gerald Fuetterer, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)
Waltraud Herbst, Infineon Technologies AG (Germany)
Joerg Rottstegge, Infineon Technologies AG (Germany)
Margit Ferstl, Heinrich-Hertz-Institut fuer Nachrichtentechnik Berlin GmbH (Germany)
Michael Sebald, Infineon Technologies AG (Germany)
Johannes Schwider, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)

Published in SPIE Proceedings Vol. 4691:
Optical Microlithography XV
Anthony Yen, Editor(s)

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