Pattern inspection of etched multilayer extreme ultraviolet mask

Susumu Iida; Ryoichi Hirano; Tsuyoshi Amano; Hidehiro Watanabe

doi:10.1117/1.JMM.15.2.021002

29 January 2016 Pattern inspection of etched multilayer extreme ultraviolet mask

Susumu Iida, Ryoichi Hirano, Tsuyoshi Amano, Hidehiro Watanabe

Journal of Micro/Nanolithography, MEMS, and MOEMS, Vol. 15, Issue 2, 021002 (January 2016). https://doi.org/10.1117/1.JMM.15.2.021002

Abstract

Patterned mask inspection for an etched multilayer (ML) extreme ultraviolet mask was investigated. In order to optimize the mask structure from the standpoint of a pattern inspection the mask structure not only from the standpoint of a pattern inspection by using a projection electron microscope but also by using a projection electron microscope but also by considering the other fabrication processes using electron beam techniques such as critical dimension metrology and mask repair, we employed a conductive layer between the ML and substrate. By measuring the secondary electron emission coefficients of the candidate materials for the conductive layer, we evaluated the image contrast and the influence of the 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 half pitch 44, 40, and 32 nm line-and-space 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 and etching residues remained detectable. The 16-nm-sized defects were also detected after the etched part was refilled with Si. A double-layer structure with 2.5-nm-thick 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.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Susumu Iida, Ryoichi Hirano, Tsuyoshi Amano, and Hidehiro Watanabe "Pattern inspection of etched multilayer extreme ultraviolet mask," Journal of Micro/Nanolithography, MEMS, and MOEMS 15(2), 021002 (29 January 2016). https://doi.org/10.1117/1.JMM.15.2.021002

Published: 29 January 2016

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