In this work, the effect of process residual stress has been studied on three different designs of membranes for RF MEMS switch application. Expressions for the pull-in voltage of stressed membranes have been developed by simple modification of existing relation for unstressed membranes. To validate the results, gold membranes have been fabricated and released successfully using silicon dioxide as the sacrificial layer. The theoretical results show a very good match with experimental results. This expression allows the estimation of the pull-in voltage of stressed membranes without the need for numerical simulations. The stress in the membranes can also be extracted from pull-in voltage measurements. Our results show that high spring constant (K) structures are less prone to deflection and change in the pull-in voltage. Also, for a high stress value, the pull-in voltages of the structures become almost independent of the spring constant.
Design, fabrication, and characterization of a highperformance micromachined lamellar-grating-interferometerbased Fourier transform spectrometer are presented. The device is designed to give high deflections with very low dynamic deformation and good mode separation. Mechanical self-stoppers are introduced to withstand accelerations larger than 500 g due to shock. The clear aperture area of the grating is about 10 mm 2 . The maximum deflection while electrostatically actuated at ambient conditions is ±356 µm at 71.2 V and 340 Hz, setting a record for comparable devices. At a pressure of 8.6 Pa, the same deflection is reached at 4.3 V. Six hundred eighty spectra per second can be recorded with a resolution of 14 cm −1 . With a HeNe laser at 633 nm, a spectral resolution of 0.54 nm (22 cm −1 ) is reached using electrostatic actuation. The microelectromechanical systems device is integrated into a compact Fourier transform spectrometer setup including a blackbody source, an infrared (IR) detector, and a visible laser using the device back side for reference. Early results with IR interferograms are also reported. In addition, the devices are actuated with pressure waves in the ambient air to reach deflections up to ±700 µm. With this setup, the spectrum of a red laser is measured with a resolution of 0.3 nm (12.4 cm −1 ).[2011-0252] Index Terms-Fourier transform spectroscopy (FTS), infrared (IR) spectroscopy, interferometer, lamellar grating, microoptoelectromechanical systems.
I. INTRODUCTIONF OURIER transform spectroscopy (FTS) has evolved into a standard analytical technique in the fields of physical, biological, and chemical sciences, as well as a tool for quality and process control, bomb detection, mining industry, and gas detection. Compared to other spectroscopy methods, it provides high accuracy, high throughput, a compact form factor, and low cost. The conventional FTS devices make use of a Michelson Manuscript
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