Mechanical analysis of polycrystalline and single-crystalline silicon microstructures

Abstract Polycrystailine silicon (polysilicon) microstructures are fabricated with surface micromachining using a sacrificial layer technique. Due to the internal residual stress in LPCVD polysilicon layers, only a free-standing length of up to a maximum value for such microstructures, e.g., cantilevers, bridges, membranes, can be obtained. Single-crystalline silicon microstructures are fabricated with bulk micromachining techniques using appropriate etchstop techniques. Unstructured and structured single-crystal membranes have been fabricated. Due to the lower residual stress in single-crystalline membranes, a different range of geometries and hence of mechanical properties is available. For both polysilicon and bulk silicon structures, finite-element analysis with the ANSYS® simulation program has been used to determine the mechanical sensitivity and resonance frequency.