Nanofabrication of hard X-ray optics by metal electroplating in a dry etched mechanically stable inorganic template

A nanofabrication process for high resolution X-ray optics and X-ray lithography masks was developed. The process is based on the plasma etching of a sacrificial hard inorganic interlayer (Si, Si(3)N(4), SiO(x) or HSQ) used for pattern transfer and aspect ratio amplification. The structures are first defined on a top thin metal film by electron beam lithography and lift-off; a thin nickel layer at the bottom of the hard interlayer is used as etch stop. A base plating (Cr/Au) under the nickel serves as seed layer for the electroplating of an X-ray absorber or phase shifting material. The fabrication is completed by the stripping of the hard template by wet or dry etching. Compared to methods based on analogous process schemes, in which the aspect ratio of nanostructures is instead amplified by pattern transfer into a sacrificial polymer interlayer by oxygen plasma, the investigated method is advantageous for the higher mechanical stability of the nanostructured hard templates with respect to the polymer ones, thus enabling the realization of higher aspect ratio features. (C) 2011 Elsevier B.V. All rights reserved.