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Proceedings Paper

Direct phase-shift measurement of thin and thick absorber EUV masks
Author(s): Tetsunori Murachi; Hiroyoshi Tanabe; Seh-Jin Park; Eric Gullikson; Taichi Ogase; Tsukasa Abe; Naoya Hayashi
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Paper Abstract

The measurement and extraction method of phase-shift values for thin and thick absorber Extreme Ultra-Violet (EUV) masks has been studied by both of experiments and simulations. We fabricated 4 EUV masks with different absorber thicknesses. We first estimated the phase-shift values from the absorber thicknesses of each mask and the nandk values which were derived in advance by other experiments. This method is indirect and may contain plate-by-plate errors. In order to extract the phase-shift values directly, we developed a phase-shift measurement method based on scatterometry. We measured the reflectivity of the open and dark area of the 4 masks by using the EUV reflectometer at Lawrence Berkeley National Laboratory (LBNL). We also measured the diffracted light intensities of grating pattern. The phaseshift values were derived from these data assuming an interference of reflected and diffracted lights. We calibrated the method by including the shadowing effect of 6 degree incident angle, and adding the information on the measured mask patterns. The extraction results of phase-shift values by this method agreed well within the error bar. The absorber thickness having 180 degree phase-shift, which works as an embedded attenuated phase-shifting mask, could be somewhere between 66 nm and 76 nm. The measurement accuracy of this method depends on the phase-shift values. The error becomes the largest at 180 degree phase-shift, and the worst one in this experiment was much larger than the proposed phase-shift measurement accuracy of ± 2 degree [1]. Much effort will be required to achieve this target.

Paper Details

Date Published: 30 June 2012
PDF: 10 pages
Proc. SPIE 8441, Photomask and Next-Generation Lithography Mask Technology XIX, 84411M (30 June 2012); doi: 10.1117/12.976817
Show Author Affiliations
Tetsunori Murachi, Intel K. K. (Japan)
Hiroyoshi Tanabe, Intel K. K. (Japan)
Seh-Jin Park, Intel Corp. (United States)
Eric Gullikson, Lawrence Berkeley National Lab. (United States)
Taichi Ogase, Dai Nippon Printing Co., Ltd. (Japan)
Tsukasa Abe, Dai Nippon Printing Co., Ltd. (Japan)
Naoya Hayashi, Dai Nippon Printing Co., Ltd. (Japan)


Published in SPIE Proceedings Vol. 8441:
Photomask and Next-Generation Lithography Mask Technology XIX
Kokoro Kato, Editor(s)

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