Fabrication of 200 nm period x-ray transmission gratings using electron beam lithography

摘要

X-ray transmission gratings (TG) have attracted much interest because of its wide use in x-ray telescope, synchrotron radiation facilities, and target diagnostic in inertial confinement fusion, etc. In this work, a 200 nm period master TG to diffract x-ray in the energy range 0.1-8keV has been successfully fabricated by electron beam lithography followed by gold electroplating. In fabrication processes, 500 nm resist was exposed by focused electron beam on polyimide free-standing-membrane coated with a Cr/Au plating base. According to numerical simulation, the proximity effect due to electron back-scattering from the substrate can be sharply reduced because of the thin polyimide free-standing membrane substrates. PMMA resist was chosen due to its high resolution and good performance in subsequent processes. After delicate dose test and shape modification of the proximity effect caused by electron front-scattering, resist grating bars with 95 nm width and 200 nm period were achieved. Subsequently, resist patterns were transferred to gold layer by electroplating. In future work, with this master mask of TG, thousands of TG to diffract x-ray can be sufficiently replicated using x-ray lithography.