Testing a capped MEMS gyroscope by an infrared technique

Sealing MEMS devices by wafer capping is an important step during MEMS fabrication. Induced stress during capping may alter system behavior or may even reduce yield. Therefore, it is desirable for MEMS development and fabrication to have a technique to inspect and monitor dynamic behavior of mechanical structures in capped MEMS devices. MEMS gyroscopes in general are sensitive to stress introduced by the capping process because the resonances of mechanical structures have an influence to the sensor properties. In this paper we present the analysis of a MEMS gyroscope performed with an infrared confocal laservibrometer microscope. Vibration spectra and geometric parameters of capped MEMS structures are measured rapidly. We demonstrate that accurate vibration spectra can be obtained which we have utilized to analyze the influence of thermal loading in the capped device.