Fabrication process development for silicon micro and nanosystems

Micromechanical devices have been fabricated out of silicon for decades, but only recently even smaller structures - nanodevices have become experimentally possible. Traditionally silicon devices are fabricated using separate lithography and various etching methods. This thesis work concentrates on developing fabrication techniques for silicon micro and nanostructures. The goal was to achieve nanometer-scale feature size and simultaneously significantly speed up the most time consuming phases. For testing purposes also functional devices were designed and fabricated. Main discoveries are related to the use of ion beam writing in a nonstandard manner. Instead of direct milling, methods were developed to directly use the beam to replace time consuming lithography step by the substrate treatment by ions. As a result, several silicon-based fabrication techniques were developed that require only a few processing steps and therefore can be realized in less than one day. The main achievement is in overcoming some of the limitations of serial writing methods such as those required in electron beam lithography or focused ion beam processing. High aspect ratio (laterally small, but tall) structures were successfully obtained using both technologies for the pattern transfer. Fabrication techniques, described in this thesis, open up an opportunity for the developers to almost instantly test their ideas using functional components by altering the way nanosystems are developed. The presented methods cannot easily be extended to mass production but are appropriate in basic research and prototyping.