In-situ measurement of VUV optical materials under F2 laser irradiation

Yasuo Itakura; Akira Sumitani; Fumika Yoshida; Youichi Kawasa; Jing Zhang; Osamu Wakabayashi; Hakaru Mizoguchi

doi:10.1117/12.456904

25 February 2002 In-situ measurement of VUV optical materials under F₂ laser irradiation

Yasuo Itakura, Akira Sumitani, Fumika Yoshida, Youichi Kawasa, Jing Zhang, Osamu Wakabayashi, Hakaru Mizoguchi

Proceedings Volume 4426, Second International Symposium on Laser Precision Microfabrication; (2002) https://doi.org/10.1117/12.456904
Event: Second International Symposium on Laser Precision Micromachining, 2001, Singapore, Singapore

Abstract

The 157nm molecular fluorine laser is regarded as the next generation light source for semiconductor exposure technology in the vacuum ultraviolet (VUV) region. Research for high performance F₂ laser optical materials is therefore indispensable. In this paper, we describe methods and results of evaluating optical materials used in the 157nm region. In order to evaluate F₂ laser optical materials, we have developed in-situ system, which measures the real-time transmittance at 157nm during laser irradiation and the transmittance in the vacuum ultraviolet (VUV) region directly after laser irradiation to avoid airborne contamination. The system is purged with high purity nitrogen gas during irradiation to reduce laser light absorption and to keep contamination at a minimum. Due to F₂ laser irradiation cleaning, the transmittance of uncoated calcium fluoride (CaF₂) samples initially rapidly then gradually increased during 50 million pulses (Mpls). Thereafter the transmittance remained constant. In addition, durability test results of CaF₂ substrates and coatings are also presented. Especially coating quality varied enormously between suppliers.

Citation Download Citation

Yasuo Itakura, Akira Sumitani, Fumika Yoshida, Youichi Kawasa, Jing Zhang, Osamu Wakabayashi, and Hakaru Mizoguchi "In-situ measurement of VUV optical materials under F₂ laser irradiation", Proc. SPIE 4426, Second International Symposium on Laser Precision Microfabrication, (25 February 2002); https://doi.org/10.1117/12.456904

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