Strength analysis of a micromechanical acceleration sensor by fracture mechanical approaches

The strength properties of a micromechanical acceleration sensor for airbag application fabricated from single crystalline silicon were analyzed using fracture mechanical concepts. The investigations revealed that the strength of the suspended seismic mass depends on local stress concentrations, either on the anisotropic etched notch or on the passivation pattern on the surface of the suspension. Different fracture concepts had to be applied for the strength analysis of both cases. The experimental results were found to agree very well with the theoretical prediction. It can be concluded that the strength of the sensor is high enough to ensure its reliability during application. In general, appropriate fracture mechanical concepts have a great potential to consider the strength and reliability properties of micromechanical components during the layout and design stage which contributes to reducing the development efforts.