Plasma and Fusion Research

Volume 17, 1406005 (2022)

Regular Articles

Evaluation of Hydrogen-Induced Blistering of Mo/Si Multilayers with a Capping Layer

Hiroaki TOMURO^1,2), Mengran JI¹⁾, Ryo NAGATA¹⁾, Koichiro KOUGE^1,2), Tatsuya YANAGIDA²⁾, Masayuki MORITA²⁾, Masahiko ANDOU²⁾, Yoshiyuki HONDA²⁾, Kiichiro UCHINO¹⁾ and Tsuyoshi YOSHITAKE¹⁾

1): Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
2): Gigaphoton Inc. Hiratsuka facility, Shinomiya, Hiratsuka, Kanagawa 254-8567, Japan

(Received 30 September 2021 / Accepted 20 January 2022 / Published 21 February 2022)

Abstract

Mo/Si multilayer mirrors are used for extreme ultraviolet (EUV) lithography. The formation of hydrogen-induced blisters in the Mo/Si multilayer is a problem that reduces the reflectance of the mirror. To evaluate the blister-resistance of EUV mirrors, the blister formation processes of Mo/Si multilayers with a capping layer were investigated using a high-frequency hydrogen plasma system as a hydrogen ion source under varying hydrogen ion exposure conditions. As a result, it was observed that blister formation by low-energy hydrogen ion irradiation of about 10 eV increases the blister-occupied area, depending on the amount of the ion dose. Furthermore, the sample was heated to promote the diffusion of hydrogen atoms, and the activation energy of blister formation was examined using the Arrhenius plot of the ion dose required for blister formation with respect to the heating temperature. The analysis showed that when the ion flux is known, the blister formation time can be predicted.

Keywords

EUV lithography, Mo/Si multilayer, capping layer, CCP plasma, blister

DOI: 10.1585/pfr.17.1406005

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