A blazed diffraction grating for the EUV lithography Beamline 12.0.1 of the Advanced Light Source has been fabricated using optical direct write lithography and anisotropic wet etching technology. A variable line spacing pattern was recorded on a photoresist layer and transferred to a hard mask layer of the grating substrate by a plasma etch. Then anisotropic wet etching was applied to shape triangular grating grooves with precise control of the ultralow blaze angle. Variation of the groove density along the grating length was measured with a Long Trace Profiler (LTP). Fourier analysis of the LTP data confirmed high groove placement accuracy of the grating. The grating coated with a Ru coating demonstrated diffraction efficiency of 69.6% in the negative first diffraction order which is close to theoretical efficiency at the wavelength of 13.5 nm. This work demonstrates an alternative approach to fabrication of highly efficient and precise x-ray diffraction gratings with ultra-low blaze angles.

Date Published: 15 September 2016
PDF: 7 pages
Proc. SPIE 9963, Advances in X-Ray/EUV Optics and Components XI, 996306 (15 September 2016); doi: 10.1117/12.2238303

Published in SPIE Proceedings Vol. 9963:
Advances in X-Ray/EUV Optics and Components XI
Ali M. Khounsary; Shunji Goto; Christian Morawe, Editor(s)