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Proceedings Paper

Surface characterization of optically polished CaF2 crystal by quasi-Brewster angle technique
Author(s): Jue Wang; Robert L. Maier; John H. Bruning
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Paper Abstract

With the development of 157nm laser lithography, calcium fluoride (CaF2) has become a very important material for excimer laser components. The optical performance of CaF2 at 157nm is strongly related to its surface quality. By analyzing the phase change of reflected p-polarization near the Brewster angle at wavelengths between 150nm and 1000nm, a quasi-Brewster angle technique (qBAT) was developed to characterize the surface quality of CaF2. This technique suggests that the slope of the quasi-Brewster angle is dominated by top surface roughness, while the displacement of the quasi-Brewster angle is determined by subsurface damage. A simple model developed to describe the surface quality of CaF2 includes both top surface and subsurface effects. The relationship between subsurface damage and quasi-Brewster angle shift was determined. Using an ultraviolet ozone (UVO) cleaning process, four surface characteristics, e.g., top surface roughness, top surface contamination, subsurface damage, and subsurface contamination could be distinguished.

Paper Details

Date Published: 4 November 2003
PDF: 9 pages
Proc. SPIE 5188, Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies, (4 November 2003); doi: 10.1117/12.507180
Show Author Affiliations
Jue Wang, Corning Tropel Corp. (United States)
Robert L. Maier, Corning Tropel Corp. (United States)
John H. Bruning, Corning Tropel Corp. (United States)


Published in SPIE Proceedings Vol. 5188:
Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies
Angela Duparre; Bhanwar Singh, Editor(s)

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