Diffraction Efficiency Of A Small-Period Astronomical X-Ray Reflection Grating Fabricated Using Thermally Activated Selective Topography Equilibration

We have fabricated a blazed x-ray reflection grating with a period of 160 nm using thermally activated selective topography equilibration (TASTE) and electron-beam (ebeam) physical vapor evaporation. TASTE makes use of grayscale ebeam lithography to create three-dimensional (3-D) structures in resist, which can then be thermally reflown into a desired profile. A blazed grating profile can be fabricated by selectively reflowing a periodic staircase structure into a wedge. This was done for the first time at a grating period of 160 nm, 2.5 times smaller than previous x-ray gratings fabricated using TASTE. The grating was patterned over a 10 mm by 60 mm area in a 147-nm-thick layer of poly(methyl methacrylate) resist and coated with 5 nm of chromium and 15 nm of gold using ebeam evaporation. The diffraction efficiency of the grating was measured using beamline 6.3.2 at Lawrence Berkeley National Laboratory's Advanced Light Source. The results show a total absolute diffraction efficiency greater than or similar to 40% at lower energies, with maximum single-order diffraction efficiency ranging from 20% to 40%. The total diffraction efficiency was greater than or similar to 30% across the measured bandpass of 180 to 1300 eV. (C) 2020 Society of Photo-Optical Instrumentation Engineers (SPIE)