Novel EUV mask absorber evaluation in support of next-generation EUV imaging

Vicky Philipsen*, Kim Vu Luong, Karl Opsomer, Christophe Detavernier, Eric Hendrickx, Andreas Erdmann, Peter Evanschitzky, Robbert W.E. Van De Kruijs, Zahra Heidarnia-Fathabad, Frank Scholze, Christian Laubis

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

22 Citations (Scopus)
350 Downloads (Pure)


In next-generation EUV imaging for foundry N5 dimensions and beyond, inherent pitch- and orientation-dependent effects on wafer level will consume a significant part of the lithography budget using the current Ta-based mask. Mask absorber optimization can mitigate these so-called mask 3D effects. Thin metal absorbers like Ni and Co have been experimentally investigated due to their high EUV absorption, but they pose challenges on the current technology of subtractive mask patterning [1]. A simulation study of attenuated EUV phase shift masks has identified through multiobjective optimization superior imaging solutions for specific use cases and illumination conditions [2]. Evaluating novel EUV mask absorbers evolves on two levels, demonstrating (1) improvements from lithographic perspective and (2) compatibility with the full mask supply chain including material deposition, absorber patterning, scanner environment compatibility and mask lifetime. On the lithographic level, we have identified regions based on the material optical properties and their gain in imaging performance compared to the reference Ta-based absorber. Within each improvement region we engineered mask absorber materials to achieve both the required imaging capabilities, as well as the technical requirements for an EUV mask absorber. We discuss the material development of Te-based alloys and Ag-based layered structures, because of their high EUV extinction. For the attenuated phase shift materials, we start from a Ru-base material, due to its low refractive index, and construct Ru-alloys. On the experimental level, we examined our novel mask absorber materials against an initial mask absorber requirement list using an experimental test flow. Candidate materials are evaluated on film morphology and stability through thermal, hydrogen, EUV loading, and chemical cleaning, for their EUV optical constants by EUV reflectometry, as well as preliminary for selective dry etch. The careful mask absorber evaluation, combining imaging simulations and experimental material tests, allowed us to narrow down to promising combinations for novel EUV mask absorbers.

Original languageEnglish
Title of host publicationPhotomask Technology 2018
EditorsEmily E. Gallagher, Jed H. Rankin
ISBN (Electronic)9781510622159
Publication statusPublished - 10 Oct 2018
Event2018 SPIE Photomask Technology - Monterey, United States
Duration: 17 Sep 201819 Sep 2018

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


Conference2018 SPIE Photomask Technology
Country/TerritoryUnited States


  • Absorber characterization
  • EUV mask absorber
  • Mask 3D effects
  • Rigorous mask 3D lithography simulation


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