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A reliable technique for rapid monitoring of critical dimensional and material parameters during the fabrication of microelectromechanical systems (MEMS) is still an open task. Electrical excitation is sometimes simply not possible, or an electrical test does not reveal sufficient information for a complete characterization. In this paper, we present a new approach that employs optical testing of MEMS vibration frequencies. It is not necessary to have electrical connections because we have developed probes with transparent electrodes to excite vibrations electrostatically without contact on the wafer level. Broadbandwidth excitation is applied to detect all relevant resonances interferometrically through the probes in a single broad-band measurement. Peak detection of the resonances results in a measurement vector containing the resonant frequencies. We demonstrate a new method to estimate system parameters by model identification. The analytical models are derived from a general approach based on finite-element analysis. The parameters with uncertainties are finally determined by guaranteed parameter estimation.[2012-0315]

A tunable dual-band MEMS Fabry-Pérot filter for simultaneous use of the spectral ranges from 8 µm to 10.5 µm and from 4 µm to 5 µm is reported. A peak transmittance of at least 75 % and a FWHM of less than 200 nm were measured. The maximum control voltage is 41 V. Two movable reflector carriers compensate the influence of gravitational force on the central wavelength. The device can withstand mechanical shocks according to Mil-Std-883G, method 2002.4, test condition B. The filter is integrated in a tiny, robust and fast microspectrometer module with the size of a TO-8 housing.

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As is generally known, miniature infrared spectrometers have great potential, e. g. for process and environmental analytics or in medical applications. Many efforts are being made to shrink conventional spectrometers, such as FTIR or grating based devices. A more rigorous approach for miniaturization is the use of MEMS technologies. Based on an established design for the MWIR new MEMS Fabry-Perot filters and sensors with expanded spectral ranges in the LWIR have been developed. The range 5.5 - 8 m is particularly suited for the analysis of liquids. A dual-band sensor, which can be simultaneously tuned from 4 - 5 m and 8 - 11 m for the measurement of anesthetics and carbon dioxide has also been developed. A new material system is used to reduce internal stress in the reflector layer stack. Good results in terms of finesse ( 60) and transmittance ( 80 %) could be demonstrated. The hybrid integration of the filter in a pyroelectric detector results in very compact, robust and cost effective microspectrometers. FP filters with two moveable reflectors instead of only one reduce significantly the acceleration sensitivity and actuation voltage