11 November 1999 Visible light interferometer for EUVL system alignment
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Abstract
A visible wavelength interferometer has been developed for the alignment of an extreme ultraviolet lithography (EUVL) camera. Although the EUVL camera will operate at 13.4 nm, the alignment is far more conveniently done at visible wavelengths, at ambient pressure. Traditional visible interferometers are not capable of reaching the better than 1 nm accuracy required for EUVL camera alignment; so a phase shifting diffraction-limited interferometer was constructed and used to align and quantify the EUVL wavefront to an accuracy better than (lambda) visible/2000. The interferometer and alignment process are described, and camera wavefront measurements presented.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard J. Gaughan, "Visible light interferometer for EUVL system alignment", Proc. SPIE 3782, Optical Manufacturing and Testing III, (11 November 1999); doi: 10.1117/12.369216; https://doi.org/10.1117/12.369216
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