Multilayer phase-only diffraction gratings: Fabrication and application to extreme ultraviolet optics

Abstract

The use of phase-only diffractive devices has long played an important role in advanced optical systems in varying fields. Such devices include gratings, diffractive and holographic optical elements, diffractive lenses, and phase-shift masks for advanced lithography. Extending such devices to the increasingly important regime of extreme ultraviolet (EUV) wavelengths, however, is not trivial. Here, we present an effective fabrication and etch process enabling high-resolution patterning of Mo/Si multilayers for use in EUV phase devices, providing another method for fabrication of high numerical aperture diffractive devices or high-resolution EUV phase shift masks

Wavelength separation from extreme ultraviolet mirrors using phaseshift reflection

“…mask thickness) of 2-3 μm, the requirement of R a 0.025 would allow for downscaling to pitches of 100 μm. Etching in a multilayer, making use of embedded etch-stop layers, could also be considered [11].…”