Focused ion beam micromachining of three-dimensional structures and three-dimensional reconstruction to assess their shape

Focused ion beam (FIB) systems are ideal tools for micromachining three-dimensional structures. To mill a shape correctly numerous factors, such as the shape of the ion beam and the re-deposition of the sputtered materials have to be accounted for during the ion milling. In order to alter the ion milling process to account for these and other factors, the shape of the milled structure and how it differs to the intended shape has to be determined. For a non-symmetrical structure with high depth-to-width aspect ratios a cross-section through its centre, prepared using the FIB system, will not be representative and atomic force microscopy cannot be used because of the geometry of the atomic force microscope's tip. Here, the use of three-dimensional reconstruction from a sequential set of FIB-prepared two-dimensional cross-sections milled through a structure to determine its shape is outlined.