Published: Jan 2001
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Specimens have been developed to measure the strength and fracture toughness, of polycrystalline silicon and silicon carbide at the micron scale. The specimens have been fabricated using standard microelectromechanical systems (MEMS) processing techniques, and so have characteristic dimensions comparable to typical MEMS devices (notches, cracks and uncracked ligaments of several microns). They are fully integrated with simultaneously fabricated electrostatic actuators that are capable of providing sufficient force to ensure failure under monotonic loading. Thus the entire experiment takes place on-chip, eliminating the difficulties associated with attaching the specimen to an external loading source. Polycrystalline specimens containing cracks formed by indentation were associated with a microstructure independent average fracture toughness of 1.0 MPa√m. The strength of specimens containing micromachined blunt notches demonstrated a strong dependence on processing procedures and resulting surface roughness. Fractographic investigation suggests that this dependence is related to the size of processing-related flaws on the side surfaces of the films.
polysilicon, fracture toughness, strength, microstructure, actuator, fractography, amorphous, polycrystalline
Professor of Civil Engineering, Case Western Reserve University, Cleveland, Ohio
Kyocera Professor of Materials Science and Engineering,