Microfabrication of actuators

The author discusses general principles and main components of linear micromechanical actuators. The different actuators have some commonality in their construction. In each case, it is required to fabricate stiff mechanical parts from a conductor, so that voltages may be applied to generate electric fields. The parts must be spaced from the substrate to allow motion, and electrically isolated from each other and the substrate. The author presents two common methods of fabrication on Si. In the first method the substrate is n-(100)Si, which can be etched by anisotropic etchants such as EDP and KOH. Mechanical parts are defined by a heavy boron diffusion prior to etching. This method is most appropriate for piezoelectric devices. The second method is a more sophisticated multilayer process, in which a sacrificial insulator is placed between the substrate and the mechanical parts