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Proceedings Paper

Pattern inspection of etched multilayer EUV mask
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Paper Abstract

Patterned mask inspection for an etched multilayer (ML) EUV mask was investigated. In order to optimize the mask structure from the standpoint of not only a pattern inspection by using a projection electron microscope (PEM), but also by considering the other fabrication processes using electron beam (EB) techniques such as CD metrology and mask repair, we employed a conductive layer between the ML and substrate. By measuring the secondary electron emission coefficients (SEECs) of the candidate materials for conductive layer, we evaluated the image contrast and the influence of charging effect. In the cases of 40-pair-ML, 16 nm sized extrusion and intrusion defects were found to be detectable more than 10 sigma in hp 44 nm, 40 nm, and 32 nm line and space (L/S) patterns. Reducing 40-pair-ML to 20-pair-ML degraded the image contrast and the defect detectability. However, by selecting B4C as a conductive layer, 16 nm sized defects remained detectable. These defects were also detected after the etched part was refilled with Si. Moreover, the simulation shows a high sensitivity for detecting the residual-type defects (etching residues). A double layer structure with 2.5-nm-thik B4C on metal film used as a conductive layer was found to have sufficient conductivity and also was found to be free from the surface charging effect and influence of native oxide.

Paper Details

Date Published: 23 October 2015
PDF: 14 pages
Proc. SPIE 9635, Photomask Technology 2015, 96350Y (23 October 2015); doi: 10.1117/12.2203123
Show Author Affiliations
Susumu Iida, EUVL Infrastructure Development Ctr., Inc. (Japan)
Ryoichi Hirano, EUVL Infrastructure Development Ctr., Inc. (Japan)
Tsuyoshi Amano, EUVL Infrastructure Development Ctr., Inc. (Japan)
Hidehiro Watanabe, EUVL Infrastructure Development Ctr., Inc. (Japan)

Published in SPIE Proceedings Vol. 9635:
Photomask Technology 2015
Naoya Hayashi, Editor(s)

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