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Micro System Analyzer Provides Optical Characterization of Si-capped MEMS Dynamics

Visualization of dynamic response is key to testing and developing MEMS devices. This is indispensable for validating FE calculations and determining cross-talk effects. The new innovative and patented MSA-650 IRIS Micro System Analyzer from Polytec allows for measuring true MEMS dynamics by characterizing both in-plane and out-of-plane motions through silicon encapsulation without contact, without need for preparing nor decapping the device.

The step of MEMS capping in fabrication processes may result in additional stress, which might alter the device performance. Therefore, a comprehensive characterization of the MEMS device in its final and encapsulated state is needed and indispensable.

Modal testing of silicon encapsulated MEMS 

Polytec MSA-650 integrated into MPI probe station

Laser-Doppler-Vibrometry (LDV) is a well-established technique to study the mechanical dynamics of MEMS with utmost precision. However, most laser vibrometers work at visible wavelengths for which the silicon encapsulation is opaque and inhibits MEMS inspection. Thus, LDV testing of such MEMS via visible wavelengths requires either un-encapsulated MEMS or to decap the device.

With a dedicated IR camera and a low-coherence SLD source the MSA-650 IRIS is the first measurement system with this technology to measure in-plane vibration on encapsulated silicon MEMS with down to 30 nm resolution and real-time out-of-plane vibrations up to 25 MHz with picometer resolution and below. Polytec’s brand new interferometer technology now delivers supreme data quality due to superior separation of individual device layers in capped MEMS devices.

The high-performance laser Doppler vibrometer delivers fast, real-time response measurement with sub-pm displacement resolution. The integrated stroboscopic video microscope enables the straightforward characterization and live-animation of in-plane motion. And the white-light interferometer option provides millions of 3D surface data in seconds.

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