Metrology, static and dynamic characterization of microstructures using acousto-optic-modulated-stroboscopic-interferometry Murali Manohar Pai, Gino Rinaldi, Muthukumaran Packirisamy, Narayanswamy Sivakumar * Optical Microsystems Laboratory, CONCAVE Research Center, Department of Mechanical and Industrial Engineering, Concordia University, 1455 de Maisonneuve Bl. West, Montreal, Canada H3G 1M8 article info Article history: Received 11 January 2008 Received in revised form 9 July 2008 Accepted 14 July 2008 Available online 26 July 2008 Keywords: Microstructures MEMS Acousto-optic-modulator Surface metrology Static and dynamic characterization abstract Mechanical and electro-mechanical advancements to the nano-scale require comprehen- sive and systematic testing at the micro-scale in order to understand the underlying influ- ences that define the micro/nano device both from a fabrication and operational point of view. In this regard, surface metrology measurements, as well as static and dynamic char- acteristics will become very important and need to be experimentally determined in order to describe the system fully. These integrated tests are difficult to implement at dimen- sions where interaction with the device can seriously impact the results obtained. Hence, a characterization method to obtain valid experimental information without interfering with the functionality of the device needs to be developed. In this work, an Acousto Optic Modulated Stroboscopic Interferometer (AOMSI) is presented and employed to obtain surface, static and dynamic properties of micro-scale structures. This method has the advantage of being a high-speed visualization technique that can provide details of surface metrology as well as static/dynamic displacements and modal profiles. In this regard, it is a non-contacting approach that can be implemented without negatively impacting struc- turally sensitive devices especially at the nano-scale. The experimental setup can incorpo- rate both thermo-mechanical and electro-mechanical loading in order to quantify operational and/or environmental influences. This method has the advantage of obtaining real time vibrating shape modes when compared to single point scanning methods. This approach is applied to cantilever microstructures. Sample test results are presented and compared with theory and are in good agreement. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction The main concern, when testing micro-scale integrated systems, is how to carry out experimental measurements in such a manner that they will not interfere with the oper- ation of the device, in order to extract information that re- flects the operation of the device in a realistic manner. Hence, the excitation mechanism whether it is electro- static, thermal or mechanical must be carefully considered prior to the testing. In this regard, it is possible to deduce or extract material and mechanical properties of the device from the static and dynamic investigations, which will en- able designers to improve and validate the theoretical model. High-speed visualization is a tool to improve the understanding and testing of microstructures. This versa- tile diagnostic technique can be used for developing reli- able and enhanced micro-electro-mechanical-systems (MEMS) [1,2]. The characterization tool should have the capability to measure various parameters such as displace- ment and vibrations in order to understand the perfor- mance of the microdevice. Real-time measurement of surface displacement using laser Doppler vibrometry (LDV) has been used for both macro and micro-scale systems [3–5]. However, in widely 0263-2241/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.measurement.2008.07.004 * Corresponding author. Tel.: +1 514 848 2424x7923; fax: +1 514 848 3175. E-mail address: nrskumar@encs.concordia.ca (N. Sivakumar). Measurement 42 (2009) 337–345 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement