Paper
18 September 2024 High-NA EUV mask pattern characterization using advanced mask CD-SEM metrology
Author Affiliations +
Proceedings Volume 13273, 39th European Mask and Lithography Conference (EMLC 2024); 132730S (2024) https://doi.org/10.1117/12.3029528
Event: 39th European Mask and Lithography Conference (EMLC 2024), 2024, Grenoble, France
Abstract
Development of High-NA EUV scanners is maturing and reached the stage of first exposures. Due to the anamorphic 0.55 NA optics, High-NA EUV masks are designed at (4x,-8x) magnification compared to wafer scale (X,Y). Consequently, while dimensions further shrink in X-direction on mask, they relax in Y-direction, resulting in asymmetric mask patterns and new mask perceptions. In this paper, we present a CD-based characterization for a variety of generic patterns on a state-of-the-art High-NA EUV mask, with emphasis on feature dimensions which are specifically relevant to High-NA EUV lithography. The mask metrology is done using an Advantest E3650 mask CD-SEM at imec, with image capture and metrology settings optimized for EUV masks. Besides providing insight into achievable pitches, we touch upon CD linearity for line-space patterns on mask, local roughness and non-uniformity at different length scales, and include a simulation to discuss the transfer of mask variability to wafer variability for a dense contact hole case. Another important aspect which we highlight in this study, is related to the effect of CD errors on mask. Namely, because of the anamorphic imaging, an X/Y symmetric CD offset on mask will lead to asymmetric CD errors at wafer level which can no longer be absorbed e.g. by choice of exposure dose. To avoid these asymmetries at wafer level, it is important to make sure that the mask is well targeted. The latter, however, also depends on choices in metrology settings, which may be ‘historic defaults’ and based on larger dimensions on DUV masks, yet applied to (High-NA) EUV masks. We therefore appeal to mask vendors for a careful verification of metrology settings applied for measurement on (High-NA) EUV masks.
(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.
Joost Bekaert, Balakumar Baskaran, Lieve Van Look, Joern-Holger Franke, Vicky Philipsen, Ardavan Niroomand, Eric Hendrickx, Hideaki Komami, Tatsuro Okawa, Soichi Shida, Shinichi Kojima, and Toshimichi Iwai "High-NA EUV mask pattern characterization using advanced mask CD-SEM metrology", Proc. SPIE 13273, 39th European Mask and Lithography Conference (EMLC 2024), 132730S (18 September 2024); https://doi.org/10.1117/12.3029528
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KEYWORDS
Semiconducting wafers

Critical dimension metrology

Extreme ultraviolet

Metrology

Scanning electron microscopy

Smoothing

Extreme ultraviolet lithography

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