Optimization of triangular-profiled Si-grating fabrication technology for EUV and SXR applications

Abstract

Anisotropic wet etching of vicinal monocrystalline Si (111)4o wafers was used to obtain blazed gratings that are highly efficient in the soft X-ray (SXR) and extreme ultraviolet (EUV) applications. An improved experimental technology for the fabrication of triangular-grooved Si gratings, both medium-frequency (250 and 500 mm-1) and high-frequency (2500 mm-1) ones, is presented. The stages of forming a Cr-mask for grooves etching, removing Si nubs in order to smooth the profile, and polishing the surface to reduce nanoroughness have been optimized. This paper describes the way of simultaneously (in one process) obtaining a smoothed triangular profile of the Si grating and a polished surface of facets by wet etching. Keywords: diffraction grating, Si wet etching, triangular groove profile, AFM, SEM.