Fabrication of microstructures by ion beam micromachining

The use of non-focused and focused ion beams as tools for fabrication and assembly of microstructures is described. Non-focused, low energy (< 1.5 keV) and high current density (< 100 mA cm-2) argon ion beams produced by a Kaufman-type source have been used for ultra-precision micromachining of materials for microelectromechanical systems applications. Uniform material removal rates of up to 1 micrometers min-1 without reactive etching are achieved during stencil-mask milling of micro-parts or during pattern transfer into ceramic or semiconductor substrates by photolithography followed by ion milling. Micro-components with typical dimensions in the 1 - 100 micrometers range and having dimensional tolerances of order 0.1 micrometers have been demonstrated, consisting of ultra-thin plates, beams, shafts and cantilevers. Self supporting nickel, aluminium, stainless steel and mu-metal plates with thicknesses down to 1 micrometers have then been used for fabricating more complex micro-parts such as disks, gears and cogs by direct writing using focused ion beam (FIB) micromachining with a resolution of 50 nm. The FIB instrument allows in situ imaging during microfabrication using secondary elements or ions, and can be used for inspection during micro-part assembly. A novel process applicable to the production of 3D micro-parts is also described.