This SPIE Spotlight focuses on the micro-/nano-structuring aspects of focused ion beam (FIB) instrumentation. It is designed as a tutorial with examples of real structures of increasing complexity. Readers with no previous experience with FIB/SEM instrumentation can quickly grasp the basics of ion/matter interactions, surface modification methods, initial alignment and structuring, fabrication of various micro-optic elements, and an outlook of up-and-coming FIB technologies.
Over the last few decades, the focused ion beam (FIB) microscope has become an increasingly important and capable tool for nanotechnology. Its initial application in circuit editing and mask repair has considerably broadened to include a multitude of uses in materials science and engineering, life sciences, electronics, chemistry, and physics, both as an analytical tool and a microfabrication instrument. This popularity comes from the ability to directly manipulate surfaces at the finest scale and in various ways. As a rapid prototyping tool, it enables a user to watch in real time as a design turns into a device without the mask design and manufacturing cycle of various lithography techniques. As a metrology tool, FIBs, in combination with scanning electron microscopy in two-beam systems, are used for structural characterization via cross sections of fabricated structures as well as for chemical analysis and high-resolution tomography in conjunction with x-ray analysis or electron-backscatter-diffraction methods. Such an instrument with strong nanofabrication and analytical capabilities will undoubtedly become more and more vital in the future. This Spotlight is a tutorial on the micro- and nanostructuring aspects of FIBs with a particular emphasis on micro- and nano-optics. Although it contains references to the most relevant texts in the field, it is not intended to be an extensive review of the literature. Instead, as a tutorial, it provides examples of real structures of increasing complexity. This text will give the reader with no previous experience with FIB/SEM instrumentation a chance to quickly grasp the basics of the FIB and ion beam–sample interactions directed toward micro-/nano-optics fabrication applications. The text starts with a few basics and then introduces case studies with increasing complexity. In the introductory part, the basic structure of the FIB instrumentation is described to the uninitiated by giving an (ultra-)short overview. The tutorial continues by introducing the fundamentals of ion–matter interactions from a practical point of view. Then an overview of surface modification methods will be given with a focus on the direct-writing/milling methods, including grayscale ion beam lithography (IBL) as it is an essential approach for fabricating micro-optical components. The second part will contain more practical knowledge, such as the initial alignment procedure followed by some simple structuring examples discussing the influences of beam scan directions, number of passes and dwell times, and other process parameters. This is followed by three case studies that will concentrate on the fabrication of various micro-optic elements via binary and grayscale directwrite IBL. The third and fourth parts will present an outlook of the emerging FIB technologies such as three-beam systems, helium ion microscopy, and heavy ion instrumentation, followed by a summary.