Torsional stress, fatigue and fracture strength in silicon hinges of a micro scanning mirror

Special micro scanning mirrors have been designed for the investigation of torsional stress in micro-scale hinges made of crystalline silicon. The setup with precise logging of resonant frequency and deflection amplitude of the MEMS-scanners is described. First results on fatigue and fracture strength are presented. Fracture of torsion beams with 6.6 μm x 30 μm cross-section occurred at 2.0 GPa to 2.4 GPa. No sign of fatigue was observed in operation for 512 h at 1.4 GPa torsional stress in resonance at 2260.7 Hz oscillation frequency. Measured frequency variation was 0.06% without any trend.

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