Complex species and pressure dependence of intensity scaling laws for contamination rates of EUV optics determined by XPS and ellipsometry

S. B. Hill; N. S. Faradzhev; L. J. Richter; T. B. Lucatorto

doi:10.1117/12.846849

19 March 2010 Complex species and pressure dependence of intensity scaling laws for contamination rates of EUV optics determined by XPS and ellipsometry

S. B. Hill, N. S. Faradzhev, L. J. Richter, T. B. Lucatorto

Author Affiliations +

Proceedings Volume 7636, Extreme Ultraviolet (EUV) Lithography; 76360E (2010) https://doi.org/10.1117/12.846849
Event: SPIE Advanced Lithography, 2010, San Jose, California, United States

Abstract

The goal of our ongoing optics-contamination program is to estimate the magnitude and scaling laws of the contamination rates of optics exposed to extreme-ultraviolet (EUV) radiation in the presence of various contaminant species expected in the EUV-lithography-tool environment by exposing samples to in-band 13.5 nm light from our synchrotron in the presence of fixed partial pressures of admitted gases. We report contamination rate measurements on TiO₂-capped samples for species observed in separate resist-outgassing measurements (benzene, isobutene, toluene and tert-butylbenzene) in the pressure range (10^-8 to 10^-5) Pa. We use two spatially-resolved surface probe techniques, spectroscopic ellipsometry and X-ray photoelectron spectroscopy, to determine the thickness of deposited carbon. The correlation and sensitivities of these techniques are discussed. The high sensitivity of ellipsometry shows that contamination rates for some species have a pronounced non-linear intensity dependence and can be strongly influenced by admixtures of water vapor, while the rates for other species are linear over the same intensity range and are less affected by ambient water. Understanding scaling laws is critical when estimating optic lifetimes or cleaning cycles by extrapolating over the 3-to-6 orders of magnitude between accelerated-testing and tool-environment partial pressures.

Citation Download Citation

S. B. Hill, N. S. Faradzhev, L. J. Richter, and T. B. Lucatorto "Complex species and pressure dependence of intensity scaling laws for contamination rates of EUV optics determined by XPS and ellipsometry", Proc. SPIE 7636, Extreme Ultraviolet (EUV) Lithography, 76360E (19 March 2010); https://doi.org/10.1117/12.846849

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