Multi-technique platform for dynamic and static MEMS characterisation

摘要

MEMS characterisation is an important application area for interferometry. In this paper a Mach-Zehnder interferometer configuration is presented that combines both coherent and low coherent techniques in one setup. It incorporates the application of classical Laser Interferometry (LI) and Electronic Speckle Pattern Interferometry as well as classical Low Coherence Interferometry (LCI), full-field Optical Coherence Tomography and Low Coherence Speckle Interferometry. Digital Holography can be applied by minor modifications of the setup. The setup, working principle, and applications of the interferometer will be described. Measurements on a MEMS-based pressure sensor are presented. The sensor consists of a glass wafer attached to a silicon membrane. A cavity is etched into the glass wafer. The wafers are bonded and form a vacuum cavity. Membrane deformations are measured through the window using LI and LCI. LCI provides information about the shape of the glass window. Results from speckle techniques are compared with similar results from plane wave techniques. The influence of the glass window and the illumination of the object are investigated.