Full-field hard X-ray microscopy below 30 nm: A challenging nanofabrication achievement. Nanotechnology 2008

Abstract The fabrication of devices to focus hard x-rays is one of the most difficult-and important-challenges in nanotechnology. Here we show that Fresnel zone plates combining 30 nm external zones and a high aspect ratio finally bring hard x-ray microscopy beyond the 30 nm Rayleigh spatial resolution level and measurable spatial frequencies down to 20-23 nm feature size. After presenting the overall nanofabrication process and the characterization test results, we discuss the potential research impact of these resolution levels. The nanofabrication of hard x-ray Fresnel zone plates (FZPs) is a very difficult task because of extreme and conflicting technical requirements We show here that by direct electron beam writing and a careful optimization of crucial processing parameters we obtained Au FZPs for >8 keV photon energy delivering a Rayleigh criterion spatial resolution of 29 nm in full-field imaging. Most important was the ad hoc adjustment of the duty cycle of the Au nanostructure to compensate for the line distortion induced by the resist development and electrodeposition. We cross-validated the spatial resolution with three different methods: the modulation transfer function (MTF) approach Efficiency is another good characteristic of our FZPs: it exceeds 6% at 8 keV, substantially better than competing 0957-4484/08/395302+05$30.0