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Proceedings Paper

Evaluation of outgassing from a fluorinated resist for 157-nm lithography
Author(s): Shigeo Irie; Kiyoshi Fujii; Yasuo Itakura; Youichi Kawasa ; Keiji Egawa; Ikuo Uchino; Akira Sumitani; Toshiro Itani
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Paper Abstract

We have evaluated the outgassing products and the in-situ transmittance of a contaminated CaF2 substrate for monocyclic fluoropolymers with four protecting groups: methoxymethyl (MOM), tert-butoxycarbonyl (t-BOC), menthoxymethyl (MM), and 2-cyclohexylcyclohexyloxymethyl (CCOM). We have also evaluated the same type of fluoropolymer with seven kinds of photo-acid generators (PAGs) added to a base fluoropolymer solution. We found little correlation between the total amount of outgassing from the polymer and the decreasing rate of the CaF2 substrate transmittance caused by outgassing adhesion. Although the MOM protecting group generated the largest amount of outgassing products, the most substantial decrease in the transmittance was observed for the t-BOC protecting group. Also, the outgassing products due to use of a PAG did not greatly reduce the absorption coefficient of a CaF2 substrate regardless of the kind of PAG. Therefore, the absorption coefficient of the outgassing-contaminated CaF2 substrate appears to be more sensitive to the type of protecting group, especially the t-BOC protecting group including a t-butyl unit, rather than the type of fluoropolymer or PAG. We analyzed the substrate surface contaminant due to the t-butyl unit by x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS), and found that increasing amounts of organic compounds, containing mainly C- and H-atoms, were adhered to and deposited on the substrate surface with an increasing irradiation dose. We speculate that the contaminants on a CaF2 surface with or without an anti-reflective coating were formed not only through mere physical adsorption, but also through certain chemical combinations. We conclude that in terms of material design of the fluoropolymer resist for 157-nm lithography, we need to pay attention to the protecting group of polymers, especially the t-BOC or t-butyl protecting group, which generates isobutene product during 157-nm irradiation.

Paper Details

Date Published: 14 May 2004
PDF: 12 pages
Proc. SPIE 5376, Advances in Resist Technology and Processing XXI, (14 May 2004); doi: 10.1117/12.535110
Show Author Affiliations
Shigeo Irie, Semiconductor Leading Edge Technologies, Inc. (Japan)
Kiyoshi Fujii, Semiconductor Leading Edge Technologies, Inc. (Japan)
Yasuo Itakura, Komatsu Ltd. (Japan)
Youichi Kawasa , Komatsu Ltd. (Japan)
Keiji Egawa, Komatsu Ltd. (Japan)
Ikuo Uchino, Komatsu Ltd. (Japan)
Akira Sumitani, Komatsu Ltd. (Japan)
Toshiro Itani, NEC Electronics Corp. (Japan)

Published in SPIE Proceedings Vol. 5376:
Advances in Resist Technology and Processing XXI
John L. Sturtevant, Editor(s)

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