Characterization and failure analysis of MEMS: high resolution optical investigation of small out-of-plane movements and fast vibrations

A high resolution optical tool is required to investigate the mechanical behavior and failure modes of micro-electromechanical systems (MEMS). We report on the possibilities of a newly developed optical characterization tool for MEMS devices. Both slow movements and fast mechanical vibrations up to 15 MHz can be monitored. The instrument can perform an imaging operation for a complete image at once by employing laser TV holography, which is a large advantage over scanning laser Doppler vibrometers. For vibration measurements, this new, interference based instrument uses a beat frequency between object excitation and reference beam excitation. A normal CCD camera is used to obtain 3D images and movies of periodic mechanical motions of MEMS devices. Excitation can be by means of a PZT, or by using electronic excitation. We show that the instrument is a very useful tool for the characterization and failure analysis of MEMS devices.The whole MEMS team at IMEC and their coworkers in projects are thanked for providing many of the samples shown in this paper. In particular, we would like to thank the following people. Melexis is thanked for providing the membrane sample of Fig. 4–6 and 14. Figs. 7–9 were measured in the frame of the MISTRA project (IWT contract 000167). Theo Rijks (Philips Natlab) provided the sample of Figs. 10 and 11. Chris Muhlstein sent the sample of Fig. 12 to us. Hans de Vries (Philips Centre for Industrial Technology/EP&A) is thanked for providing the sample of Fig. 13. The switch of Fig. 15 was made in the MIRS project (5012352345). Laurent Francis (IMEC) is thanked for providing the sample of Fig. 16. Sjoerd van de Geijn of Océ-Technologies B.V. provided the sample of Fig. 17.