LIGA technology for R&D and industrial applications

Abstract

The LIGA process[1] was first developed at the Forschungszentrum Karlsruhe GmbH. It is currently used worldwide by numerous other research institutes and by industry. LIGA allows for the manufacturing of microcomponents with almost arbitrary lateral geometry and resolution in the micron range, but with structure heights into the millimeter range. The typical materials used are polymers, metals, and ceramics, thus covering a wide range of nonsilicon candidates. The main process steps have given the technique its name, LIGA, a German acronym consisting of LI (Lithographie for lithography), G (Galvanik for electroplating), and A (Abformung for replication techniques, such as molding). In the classical understanding of LIGA, the lithography step is performed using the highly collimated and energetic X-rays of a synchrotron that can penetrate with little scattering into hundreds of microns of polymer resist and hence pattern it with extremely sharp, smooth, and vertical sidewalls. In addition, due to the short wavelengths of the X-rays, the spatial resolution of the process is very high, thus allowing for extremely high aspect ratios, i.e., the ratio of width over thickness of a structure. The overall process development requires establishing an entire process chain, e.g., a mask-making procedure, since X-ray masks need to be patterned with relatively high-aspect-ratio absorbing structures in a LIGA-like process, or an adopted sacrificial layer technique. © 2006 Springer-Verlag Berlin Heidelberg.