Fabrication of large area ultrathin silicon membrane: Application for high efficiency extreme ultraviolet diffraction gratings

Abstract

Silicon membranes of 100nm thick (and below) over several mm2 have been fabricated for high efficiency extreme ultraviolet (EUV) transmission grating. The perfect planarity (<1nm) and the high transparency (>80%) at 13.5nm wavelength have been measured. In comparison to SiNx membranes (40% transmission), the silicon membranes allow high resolution EUV interference lithography using the second order diffraction of the molybdenum grating. The fabrication of such phase gratings has been performed and the diffraction efficiency measurement is 27% for the silicon membrane and the Mo grating.