Optical characterization of dynamics on Si-capped MEMS

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 innovative and patented MSA-650 IRIS Micro System Analyzer 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 indispensible.

Highlights

  • Superior separation of individual device layers in capped MEMS delivers the true dynamical MEMS behaviour
  • Extracting real-time motion data even from complex-structured Si-capped MEMS
  • High resolution modal data up to 25 MHz
  • Straighforward FE model validation of MEMS in final state
  • Integrated high performance IR microscope allows for measuring through Si walls
  • Video microscope measuring mode revealing in-plane motion up to 2.5 MHz
  • Standard data export formats for modal data, graphics and video for direct post-processing

Modal testing of silicon encapsulated MEMS 

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 worldwide 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. 

Accessories and components

Tripods, test stands, positioning stages

A-STD-TST-01 Test Stand

Test stand providing ample workspace. With motorized z-axis, travel range 200 mm.

A-STD-BAS-02 Base Stand

Rigid support for the sensor head. Includes manual focus block with 100 mm travel range with coarse and fine drive. Interfaces to commercially available optical tables.

A-STD-F50 Focus Block

Travel Range 50 mm. With coarse and fine drive for manual z-axis adjustment of the sensor head. Interfaces with commercially available wafer probe stations.

Vibration isolation, breadboards

A-TAB-AIR-01 Active Vibration Isolation Table

Air-damped vibration isolation table with active level adjustment. Compatibility: A-STD-TST-01 Test Stand, A-STD-BAS-02 Base Stand.

A-TAB-ELC-01 Active Vibration Isolation Table

Electronically controlled voice coil stabilization for highest isolation performance. Compatibility: A-STD-TST-01 Test Stand, A-STD-BAS-02 Base Stand.

A-BBO-ME02 Breadboard

Breadboard with metric hole pattern. Footprint 900 mm x 600 mm. Compatibility: A-STD-BAS-02 Base Stand.

A-AVI-MELA Active Vibration Isolation Breadboard

Electronically controlled for highest vibration isolation performance. With metric hole pattern. Footprint 600 x 800 mm. Compatibility: A-STD-BAS-02 Base Stand.

Miscellaneous

MSA-A-WPM Wafer Prober Module

Together with the A-PST-200P XY Positioning Stage, the wafer prober module forms a motorized platform for electrical contacting and high-precision measurement of wafers and substrates up to 200 mm in diameter.


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