20 August 2024 Zone plate-based extreme ultraviolet mask microscope with through-pellicle imaging capability
Markus Benk, Dmytro Zaytsev, Chris Orman, Brandon Vollmer, Daniel Santos, Jeffrey Gamsby, Jeremy Mentz, Farhad Salmassi, Arnaud Allezy, Senajith Rekawa, Ryan Miyakawa, Weilun Chao, Eric Gullikson, Scott Chegwidden, Guojing Zhang, Patrick Naulleau, Bruno La Fontaine
Author Affiliations +
Abstract

Mirror-based and zone plate-based imaging systems are being used in actinic extreme ultraviolet (EUV) reticle review tools. With regard to zone plates, a short working distance is advantageous in terms of the required spectral bandwidth, manufacturability, and potential throughput and imaging performance. Zone plates therefore typically have a short working distance. The industry has adopted the use of an EUV pellicle to protect the photomask. Imaging photomask through-pellicle requires a working distance larger than 2.5 mm. A zone-plate-based EUV mask microscope with a 3-mm working distance has been commissioned at beamline 11.3.2 of the Advanced Light Source. Through-pellicle imaging at an exposure time of 2 s is demonstrated. The instrument achieves an image contrast of 95% on large features on a photomask with a tantalum-based absorber. Imaging down to 45-nm half pitch (mask scale) is demonstrated. A NILS of 2.55 is achieved on 60-nm half-pitch (mask scale) lines and spaces. These results demonstrate that zone-plate-based imaging systems can meet the requirements of an actinic EUV mask review tool in terms of imaging performance and throughput in an instrument compatible with EUV pellicles.

© 2024 Society of Photo-Optical Instrumentation Engineers (SPIE)
Markus Benk, Dmytro Zaytsev, Chris Orman, Brandon Vollmer, Daniel Santos, Jeffrey Gamsby, Jeremy Mentz, Farhad Salmassi, Arnaud Allezy, Senajith Rekawa, Ryan Miyakawa, Weilun Chao, Eric Gullikson, Scott Chegwidden, Guojing Zhang, Patrick Naulleau, and Bruno La Fontaine "Zone plate-based extreme ultraviolet mask microscope with through-pellicle imaging capability," Journal of Micro/Nanopatterning, Materials, and Metrology 23(4), 041404 (20 August 2024). https://doi.org/10.1117/1.JMM.23.4.041404
Received: 31 May 2024; Accepted: 25 July 2024; Published: 20 August 2024
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KEYWORDS
Microscopes

Extreme ultraviolet

Pellicles

Photomasks

Mirrors

Zone plates

Imaging systems

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