Direct e-beam writing of high aspect ratio nanostructures in PMMA: A tool for diffractive X-ray optics fabrication

We present a fast and reliable fabrication method of dense, periodic and high aspect ratio PMMA and metallic nanostructures. Biased lines are directly exposed by a 100 keV electron beam in thick layers of polymethyl-methacrylate (PMMA) resist to produce polymer mold which is later used to grow Au high aspect ratio structures by electroplating. Dense PMMA and Au nanostructures with aspect ratios >11 were manufactured in 520 nm and with aspect ratios >12 in ∼1 μm thick layers of PMMA. This method was successfully applied to produce various X-ray optics devices, such as beam shaping condensers, Fresnel zone plates and diffraction gratings. The performance of a beam shaper was tested at 10 keV photon energy showing a good diffraction efficiency of 10%.