Novel piezoelectric polyimide MEMS

We have demonstrated a fabrication process for fabricating MEMS cantilever and bridge structures using a novel high-temperature piezoelectric polyimide as the structural material. The process consists of conventional lithography and metallization processes and uses a sacrificial layer of photoresist. Electrodes are fabricated on the upper and lower surfaces of the suspended structures and a self-test electrode is fabricated underlying each suspended component for testing. Particular attention is paid to the baking and curing of the polymer films used for structural, sacrificial and lithography layers in order to maintain the structural integrity of the devices throughout the fabrication process. A key aspect to accomplishing this is the use of a chemically imidized polyimide solution to eliminate the high curing temperature normally required to form polyimide. Using this approach, the entire process sequence, through the removal of the sacrificial layer, is kept below 125/spl deg/C. This process has application to building a variety of microelectromechanical sensors and actuators.