Fast prototyping of high-aspect ratio, high-resolution X-ray masks by gas-assisted focused ion beam

The capacity of chemically-assisted focused ion beam (FIB) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number {Z}) coatings on X-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing for fast prototyping of high-aspect ratio, high-resolution masks for deep X-ray lithography for the LIGA process. In preliminary demonstrations, an automated FIB system operating at 30 keV with a gallium liquid metal source and an iodine gas injection system was used for direct milling into a few micrometer thick gold of microstructures into the sub-hundred nanometer regime. Three-dimensional micromachining in bulk diamond is also reported to illustrate the capability of the technique.This work was made possible under funding for California Institute of Technology from NASA general contract (# NAS7-1407), the partial funding for CAMD from the DARPA grant HI-MEMS Development and Manufacturing (contract # N66001-98-1-8926). Patrick Deshaye (Norsam) microsculpting work is also gratefully acknowledged.This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.