Waferlevel vacuum packaging: Essential for microscanners in mobile applications

MEMS scanning mirrors are a key part of miniaturized laser based display systems. Due to their small outline and high performance these systems are supposed to be integrated into next generation mobile devices such as cellular phones or PDAs. But mobile applications demand for ruggedness against harsh environmental conditions, which can only be guaranteed by a hermetic package. Packaging of MEMS is an important expense factor within the production costs and to ensure mass producibility the packaging has to be done on a wafer level. While for inertial MEMS this is state of the art, it has not yet been reported for MOEMS. Therefore, Fraunhofer ISIT has developed a complete process technology for the manufacturing of wafer level vacuum packaged MEMS scanning mirrors. It allows the fabrication of vertical stacked combdrives for quasistatic mirror operation and a low damping environment for the reduction of needed driving signals. It has been achieved that scan angles of above 50 deg can be reached even at a low driving voltage of below 6 V.