PIEZOELECTRIC FILMS IN SILICON-BASED MICROACTUATION STRUCTURES - Active Drives for Microengineering Applications, IEE Colloquium on

The mechanisms for micromechanical actuation that are most practical, and have been the most applied, are electrostatic attraction and piezoelectric effect. Both scale well into mirro-dimensions, are relatively compatible with microfabrication processes, and are also suitable for displacement sensing. Of the two, piezoelectric devices are much better able to provide strong forces, and while electrostatic devices require no special material, their geometrical requirements are much less compatible with planar processing. For these reasons, piezoelectric actuation is very attractive for many applications in microsystems. The primary difficulties in developing micro-actuators based on piezoelectric effect lie in depositing or attaching an appropriate material to the mechanical, typically silicon, parts of the structure, and in developing compatible processes for machining these structures. In most actuators demonstrated to date, the approach has been to bond a micromachined silicon structure to a piece of bulk piezoelectric ceramicl. This eliminates the need for a suitable deposition process, but imposes severe restrictions on the size, geometry and position of the active element, and is not well suited to integration.