Broadband transmission masks, gratings and filters for extreme ultraviolet and soft X-ray lithography

Abstract

Lithography and patterning on a nanometre scale with extreme ultraviolet (EUV) and soft X-ray radiation allow creation of high resolution, high density patterns independent of a substrate type. To realize the full potential of this method, especially for EUV proximity printing and interference lithography, a reliable technology for manufacturing of the transmission masks and gratings should be available. In this paper we present a development of broadband amplitude transmission masks and gratings for extreme ultraviolet and soft X-ray lithography based on free-standing niobium membranes. In comparison with a standard silicon nitride based technology the transmission masks demonstrate high contrast not only for in-band EUV (13.5nm) radiation but also for wavelengths below Si L-absorption edge (12.4nm).The masks and filters with free standing areas up to 1000×1000μm2 and 100nm to 300nm membrane thicknesses are shown. Electron beam structuring of an absorber layer with dense line and dot patterns with sub-50nm structures is demonstrated. Diffractive and filtering properties of obtained structures are examined with EUV radiation from a gas discharge plasma source.