Height and Vibration Measurements of Spiral-shaped Accelerometers

Problem

In prototyping and calibration of MEMS accelerometers, it is crucial to assess both the 3D geometry and the vibrational response of the device. Conventional tools often struggle with complex topologies like spirals, especially when height and mode shape information must be correlated.

Solution

The PICOSCALE Vibrometer offers two key capabilities:

1. Height reconstruction via phase-unwrapped interferometry

2. Modal vibration imaging using on-the-fly amplitude and phase detection

Together, these functions provide a full picture of structural and dynamic performance.

Implementation

• A spiral-shaped accelerometer was scanned to reconstruct its 3D topography.

• Height mapping revealed that the outer spiral arms are ~25 µm above the substrate, and the core ~10 µm above it.

• Modal analyses were performed at 2, 4, 14, and 46 kHz using the system’s internal shaker stage and lock-in amplifier.

• Deflection images combining amplitude and phase were used to identify bending modes, with the fundamental mode at 2 kHz defining the prototype’s bandwidth.

Results

• Accurate height images were obtained using automated phase unwrapping, even on a non-flat and partially reflective sample.

• Modal imaging revealed distinct resonance patterns at all tested frequencies, confirming proper actuation and sensor functionality.

• These insights can be directly used to refine mechanical models and improve sensor design.

Conclusion

By combining height and vibration analysis, the PICOSCALE Vibrometer provides essential tools for validating and optimizing MEMS accelerometers, especially during early-stage development. Its integrated software enables fast, one-click processing for both structural and dynamic characterization.