We report, for the first time to our knowledge, experimental demonstration of wave-front analysis via the Hartmann technique in the extreme ultraviolet range. The reference wave front needed to calibrate the sensor was generated by spatially filtering a focused undulator beam with 1.7- and 0.6-μm -diameter pinholes. To fully characterize the sensor, accuracy and sensitivity measurements were performed. The incident beam’s wavelength was varied from 7 to 25 nm. Measurements of accuracy better than λEUV/120 (0.11 nm) were obtained at λEUV=13.4 nm . The aberrations introduced by an additional thin mirror, as well as wave front of the spatially unfiltered incident beam, were also measured.
© 2003 Optical Society of America
(120.3940) Instrumentation, measurement, and metrology : Metrology
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
(220.3740) Optical design and fabrication : Lithography
(260.7200) Physical optics : Ultraviolet, extreme
Pascal Mercère, Philippe Zeitoun, Mourad Idir, Sébastien Le Pape, Denis Douillet, Xavier Levecq, Guillaume Dovillaire, Samuel Bucourt, Kenneth A. Goldberg, Patrick P. Naulleau, and Senajith Rekawa, "Hartmann wave-front measurement at 13.4 nm with λEUV/120 accuracy," Opt. Lett. 28, 1534-1536 (2003)