Fast and easy fabrication methodology of Fresnel zone plates for the extreme ultraviolet and soft x-ray regions

摘要

Zone plate design and efficient methods for the fabrication of zone plates for extreme ultraviolet (EUV) and soft x-ray applications in a newly developed scanning reflection microscope are presented. Based on a-beam lithography, three types of transmission zone plates with focal lengths between 6 and 15 mm are reported: (i) phaseshifting zone plates made by 190 nm thick PMMA rings on Si3N4 membranes, (ii) absorbing zone plates made by 75 nm thick Au ring structures on Si3N4 , and (iii) freestanding Au rings of 50 nm thickness and increased transmission in the EUV range. Experiments at the DELTA synchrotron facility reveal a minimum spot size and resulting spatial resolution of 9 +/- 3 mu m, which is the theoretical limit resulting from the synchrotron beam parameters at 60 eV photon energy. Images of a Ti/Si chessboard test pattern are recorded exploiting the energy dependence of the element-specific reflectance. (C) 2019 Optical Society of America