Basic Studies of the Effects of Microfabrication, Environment, and Cyclic-Loading on the Long-Term Durability of Thin-Film Microstructures

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DMI-9872324 Komvopoulos This research in Long Term Durability of Materials and Structures will study the effects of design and micro-fabrication on the micromechanical properties of polysilicon microstructures. In order to develop a better understanding of the relationship between cyclic stress (or strain) amplitude and fatigue life for polysilicon processed under different conditions and exposed to different environments, an innovative experimental scheme based upon surface micromachining technology will be used. The ultimate objective is to investigate the effects of fabrication process parameters (doping, etching, and annealing), specimen size, microstructure characteristics (grain size), type and amplitude of loading, and environmental conditions on the mechanical behavior and endurance of polysilicon thin-film microstructures. The relationship between design considerations, processing parameters, and subsequent durability of the resulting microstructures to resist crack initiation will be investigated. Characterization techniques will include imaging and surface force microprobe experimentation, with a novel vacuum probe station specifically designed to simulate typical micromachine operating conditions, to analyze the fatigue behavior and crack initiation. This project will provide an excellent opportunity for training graduate students in high endurance design of microeletromechanical systems devices. The knowledge base for material deterioration at the microscale will be advanced with this work.