Fabrication of parallel-plate nanomirror arrays for extreme ultraviolet maskless lithography

A micromirror array for extreme ultraviolet (EUV) maskless lithography was designed and fabricated. The arrays are composed of devices with less than a 350 nm actuation gap and a surface area ranging from 1 μm2 to 20 μm2. The mirror layer is composed of silicon in lieu of the Mo/Si stack used for EUV mirrors in order to debug the process and to simplify the initial fabrication. Germanium was used as a sacrificial material while α-Si acts as a hinge for this parallel-plate design. Silicon migration into germanium was observed, so the thermal budget was restrained to 450 °C for the entire process. Scanning electron microscope images of working devices are provided.