Ultrashallow EUV and Soft X‐Ray Gratings Fabricated by Broad‐Beam Nitrogen Ion Irradiation

Controlled and precise fabrication of structures with heights in the range of single‐digit nanometers is one of the challenges for diffraction gratings operating near‐normal incidence in the extreme ultraviolet (EUV) and soft X‐ray range. Here, we expand on previous research utilizing swelling of silicon after irradiation with ions as an alternative to conventional dry etching. By irradiating silicon through a mask with a broad beam of nitrogen ions, we realized lamellar gratings in a precise and well‐controlled process. We were able to fabricate gratings with structure heights between 1.00 ± 0.05 and 10 ± 0.5 nm and a pitch of 1 µm, which is suitable for both EUV and soft X‐ray applications. A variation of ion energy from 20 to 40 keV further expands the foundations of this process and yields an additional parameter to control the resulting structure height and shape.