20 August 2004 Actinic detection and screening of multilayer defects on EUV mask blanks using dark-field imaging
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Proceedings Volume 5446, Photomask and Next-Generation Lithography Mask Technology XI; (2004) https://doi.org/10.1117/12.557773
Event: Photomask and Next Generation Lithography Mask Technology XI, 2004, Yokohama, Japan
Abstract
MIRAI Project has developed a novel actinic (at-wavelength) inspection tool for detecting critical multilayer defects on EUV mask blanks using a dark-field imaging and a laser-produced plasma (LPP) light source. The first milestone of proof-of-concept was successfully achieved by demonstration of programmed defect detection accurate to 70nm in width and 2nm in height without any detection of false defects. Characterization of this experimental actinic inspection tool is ongoing to define the detailed specification of a proto-type tool. One of the important factors that define the sensitivity of the inspection tool is the signal to noise ratio available from the inspection image. In this paper, characterization results of background fluctuation and through focus imaging are presented. The characterization of background fluctuation suggested that the pixel-to-pixel fluctuation by spatial fluctuation of roughness is smaller than originally assumed possibly because of the smoothing by the aberration of the imaging optics. The negative impact of the degradation of defect signal by the aberration at the best focus is relaxed due to the smoothed fluctuation of the background intensity.
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Yoshihiro Tezuka, Masaaki Ito, Tsuneo Terasawa, Toshihisa Tomie, "Actinic detection and screening of multilayer defects on EUV mask blanks using dark-field imaging", Proc. SPIE 5446, Photomask and Next-Generation Lithography Mask Technology XI, (20 August 2004); doi: 10.1117/12.557773; https://doi.org/10.1117/12.557773
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