MEMS characterization using new hybrid laser Doppler vibrometer/strobe video system

Abstract

Laser Doppler Vibrometry (LDV) is a widely accepted tool for dynamic characterization of MEMS. Using automated scan capability, the Polytec system can measure structural resonance and display out-of-plane deflection shapes with amplitudes down to the picometer level and frequencies to 30 MHz. By adding stroboscopic video microscopy for in-plane motion analysis, our combined Micro Motion Analysis (MMA) system is capable of three-dimensional dynamic characterization. The MMA system opens up new possibilities to measure in-plane actuators previously difficult or impossible for LDV measurements. To exemplify the use of this technology, we present characterization measurements on MEMS devices fabricated by Sandia National Labs SUMMiT V process. Multi-axis measurements reveal the complex motions exhibited by an electrostatic comb drive driven at resonance. Also, ultra-high resolution velocity measurements are made on passive cantilever structures oscillating under thermal excitation. Picometer resolution makes possible detection of these purely mechanical resonances. Both comb drive and cantilever data are used to determine mechanical properties important to evaluate the reliability of fabrication processes. This study demonstrates the unique performance of our hybrid LDV / strobe video measurement system for quick, accurate, high-resolution dynamic response measurements.