Electrostatically actuated failure of microfabricated polysilicon fracturemechanics specimens

Polysilicon fracture mechanics specimens have been fabricated using standar d microelectromechanical systems (MEMS) processing techniques, and thus hav e characteristic dimensions comparable with typical MEMS devices. These spe cimens are fully integrated with simultaneously fabricated electrostatic ac tuators, which are capable of providing sufficient force to ensure catastro phic crack propagation from blunt notches produced using micromachining. Th us, the entire fracture experiment takes place on-chip, without any externa l loading source. Fracture has been initiated using both monotonic and cycl ic resonance loading. A reduction in the nominal toughness under cyclic loa ding is attributed to subcritical growth of sharp cracks from the micromach ined notches in the fracture mechanics specimens. Fatigue fracture has been observed in specimens subjected to as many as 10(9) cycles, and environmen tal corrosion is implicated in at least some aspects of the fatigue.