Interferometric testing of EUV lithography cameras

Phase-measuring, lateral-shearing interferometry has been carried out on a multilayer-coated extreme-ultraviolet (EUV) Schwarzschild camera at the multilayer coating's center wavelength. The measured wavefront error was 0.096 waves rms at a wavelength of 13.5 nm. The interferometer employed in the measurement was developed to evaluate the image quality and improve the alignment of cameras for EUV lithography and was previously shown to have a sensitivity of 0.021 waves rms or better at an operating wavelength of 13 nm.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.