Reliability test and failure analysis of optical MEMS

Modern UV-lithography is searching for new highly parallel writing concepts. Spatial light modulation (SLM) with optical MEMS devices offers such possibilities. Special emphasis must be put on the ability of SLM devices to handle ultraviolet light (UV). For deep UV laser mask writing (248 nm) we designed and fabricated a 2048×512 pixel optical MEMS with individually addressable aluminum micro-mirrors. In order to support the small volume production and the qualification of such devices we have set up test and characterization systems for failure analysis and lifetime testing. In order to ensure a high quality of the optical MEMS e.g. a map of the device under test is needed showing the exact position of defective pixels together with the type of defect like not responding, always deflected, wrong spring constant, or poorly reflecting surface. Additionally information on the flatness of the mirrors and on their lifetime under UV pulsed illumination are required. This paper describes the concepts of our test systems, their experimental realization, and results obtained for our optical MEMS chips.