Mask absorber/tone and process impact on resist line-edge-roughness

Eisuke Ohtomi; Vicky Philipsen; Joren Severi; Ulrich Welling; Laurence S. Melvin III; Yosuke Takahata; Yusuke Tanaka; Danilo De Simone

doi:10.1117/12.2657287

28 April 2023 Mask absorber/tone and process impact on resist line-edge-roughness

Eisuke Ohtomi, Vicky Philipsen, Joren Severi, Ulrich Welling, Laurence S. Melvin III, Yosuke Takahata, Yusuke Tanaka, Danilo De Simone

Author Affiliations +

Proceedings Volume 12494, Optical and EUV Nanolithography XXXVI; 1249410 (2023) https://doi.org/10.1117/12.2657287
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Abstract

High numerical-aperture (NA) extreme ultraviolet lithography (EUVL) system has been highly desired [1-3] and is now under construction at imec-ASML high-NA laboratory in Veldhoven. However, there are still many challenges to realize high-volume manufacturing (HVM) by high-NA EUVL; Line edge roughness (LER) mitigation is one of the key elements. In our previous research, we studied how normalized image log slope (NILS) and resist film thickness (FT) affect resist LER by exposure at NA 0.33 on NXE:3400 and S-Litho EUV [4] . However, mask absorber/tone, exposure dose and postexposure bake (PEB) temperature were not focused on for decreasing LER. They have the potential to mitigate resist roughness as illumination and resist thickness also have. Unbiased LER (uLER) values of metal oxide resists (MOR) were experimentally measured on half pitch 14 nm line and space (L/S) under several mask absorber/tonality, dose and PEB temperature. Per mask absorber/tone the NILS was varied by using different illumination shapes. Low-n masks exhibited higher NILS for the same illumination shape, which resulted in lower resist LER on wafer. It was also found that mask tone can contribute to LER mitigation. According to detailed investigations about mask roughness, mask error enhancement factor (MEEF) and flare by CD-SEM measurements and S-Litho EUV, the most likely reason for LER difference is flare increase given by mask tone change. From dose and PEB temperature variation study, dose was apparently more dominant to resist roughness than PEB temperature.

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Eisuke Ohtomi, Vicky Philipsen, Joren Severi, Ulrich Welling, Laurence S. Melvin III, Yosuke Takahata, Yusuke Tanaka, and Danilo De Simone "Mask absorber/tone and process impact on resist line-edge-roughness", Proc. SPIE 12494, Optical and EUV Nanolithography XXXVI, 1249410 (28 April 2023); https://doi.org/10.1117/12.2657287

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KEYWORDS

Line edge roughness

Extreme ultraviolet lithography

Light sources and illumination

Extreme ultraviolet

Scanners

3D mask effects

Metal oxides

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