Micromotion analysis by deep-UV speckle interferometry

Abstract

In the last decades, electronic speckle pattern interferometry (ESPI) was successfully used for detecting deformation, vibration, and strain on specimens and components with dimensions on the macroscopic level. The outstanding features of ESPI are it's ability for fully automatic operation combined with the excellent sensitivity controlled by the wavelength of laser light. In the field of MEMS' (MicroElectroMechanicalSystems) testing, however, where the object size scales down below one millimeter, a number of problems arises when speckle techniques are to be applied. On the other hand, speckle solutions sound really promising to satisfy certain demands in MEMS technology. In this situation, some recent research concentrated on the further development of speckle interferometry to serve best for the specifics of MEMS characterization and quality assurance. The paper explains the benefits and the application limits of micro speckle interferometry (MSI) and it shows the potential for improvements when a deep UV laser source is used. For the experiments, a new deep ultraviolet micro speckle interferometer (DUV-MSI) was designed operating at 266 nm of wavelength. The implemented optics enables for the measurement of both, in-plane and out-of-plane movements on the microparts. In this way, a complete motion analysis can be performed with nanometer accuracy.