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Proceedings Paper

Short-range electron backscattering from EUV masks
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Paper Abstract

Electron backscattering from Extreme Ultraviolet (EUV) masks during Electron Beam (EB) exposure was studied by simulations and experiments. The film structure of EUV masks is quite different from that of photomasks. The Mo/Si multilayer on the EUV substrate is very thick (280 nm) and heavy metal material such as Ta is used for the absorber. Monte Carlo simulations suggest that the absorbed energy inside the resist caused by the backscattered electrons from these films is non-negligible, about 1/10 of the forward scattering electrons and 1/4 of the backscattered electrons from the substrate. Also the simulations show that the influence range is very short because the backscattering happens near the mask surface. These simulations were verified by conducting EB exposure experiments. Short-range proximity effect was clearly observed by measuring the resist Critical Dimentions (CDs) of short bars laid beside the large exposed area. The data were fitted by assuming a backscattering electron distribution which has an exponential form with 0.4 μm range. The range is very short compared with the conventional proximity range of 10 μm. We conclude that the conventional EB proximity effect correction method needs to be revisited for EUV masks.

Paper Details

Date Published: 11 June 2010
PDF: 8 pages
Proc. SPIE 7748, Photomask and Next-Generation Lithography Mask Technology XVII, 774823 (11 June 2010); doi: 10.1117/12.862641
Show Author Affiliations
Hiroyoshi Tanabe, Intel K.K. (Japan)
Tsukasa Abe, Dai Nippon Printing Co. Ltd. (Japan)
Yuichi Inazuki, Dai Nippon Printing Co. Ltd. (Japan)
Naoya Hayashi, Dai Nippon Printing Co. Ltd. (Japan)

Published in SPIE Proceedings Vol. 7748:
Photomask and Next-Generation Lithography Mask Technology XVII
Kunihiro Hosono, Editor(s)

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