At-wavelength characterization of the extreme ultraviolet Engineering Test Stand Set-2 optic

• Published in: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 2001-11, Vol.19 (6), p.2396-2400
• Main Authors: Naulleau, Patrick, Goldberg, Kenneth A., Anderson, Erik H., Batson, Phillip, Denham, Paul E., Jackson, Keith H., Gullikson, Eric M., Rekawa, Senajith, Bokor, Jeffrey
• Format: Article
• Language: English
• Subjects: Diffractive optics; Imaging techniques; Interferometers; Interferometry; Projection systems; Ultraviolet radiation; Wavefronts
• ISSN: 0734-211X; 1071-1023; 1520-8567
• DOI: 10.1116/1.1421545

At-wavelength interferometric characterization of a new 4×-reduction lithographic-quality extreme ultraviolet (EUV) optical system is described. This state-of-the-art projection optic was fabricated for installation in the EUV lithography Engineering Test Stand (ETS) and is referred to as the ETS Set-2 optic. EUV characterization of the Set-2 optic is performed using the EUV phase-shifting point diffraction interferometer (PS/PDI) installed on an undulator beamline at Lawrence Berkeley National Laboratory’s Advanced Light Source. This is the same interferometer previously used for the at-wavelength characterization and alignment of the ETS Set-1 optic. In addition to the PS/PDI-based full-field wave front characterization, we also present wave front measurements performed with lateral shearing interferometry, the chromatic dependence of the wave front error, and the system-level pupil-dependent spectral-bandpass characteristics of the optic; the latter two properties are only measurable using at-wavelength interferometry.