3D microstructures fabricated by partially opaque X-ray lithography masks

X-ray lithography has several advantages over optical or e-beam techniques, since x-ray proximity printing can overcome typical limitations of such techniques, enabling the imaging of ultra thick resist layers (micro-mechanical application). In this work we will discuss the fabrication of a multilevel x-ray mask capable of producing a radiation dose modulation when used in a typical proximity x-ray lithography set-up. The aim of our investigation is to develop a process that in a single x-ray exposure can replicate a multilevel mask profile. The mask was realised by e-beam lithography and made by a number of overlapped gold layers, so producing a modulation of the x-ray dose absorption. We describe in some detail the process for the fabrication of the mask and the first result of the x-ray exposure.