Mechanical reliability of surface-micromachined self-assembling two-axis MEMS tilting mirrors

The Polytec(TM) laser Doppler vibrometer was used to characterize the dynamics, mechanical reliability and lifetimes of surface-micromachined self-assembling MEMS tilting mirrors. The mechanical modes of micromirror can be identified and corresponding resonance frequencies measured. It was found, for certain experimental conditions, that micromirror operation simulating contact between poly-Si surfaces may result in device lifetime reduction due to stiction at the point of contact. The appropriate modifications in device design eliminate the effect of stiction on device lifetime. Moreover, for up to 10(9) mechanical cycles completed no friction-related device degradation has been observed. In controled dry ambient at room temperature, micromirrors have been able to complete about 2x10(10) switching operations without signs of mechanical degradation. The results validate the robustness and long term mechanical reliability of evaluated micromirror devices.