Fatigue Characteristics of Silicon Micromechanism for Micromachine

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Elastic deformation of the microstructure such as an elasticity hinge was used for a movable mechanism of MEMS.The fabrication process of the microstructure often yielded the stress concentration. Static and fatigue strength are evaluated for notched type specimens fabricated from silicon wafers by micromachining, that is, PVD and the photo-etching processes. Results are summarized as follows :1. A micromaterial testing machine is developed for four points bending under statically and cyclic loading. An algorithm for the computer image processing to measure the specimen deformation is improved.2. Limitation between the loading frequency and deformation of the specimen is examined base on the energy law. Maximum frequency experimentally obtained under the fatigue test is half of the theory.3. An anisotropy etching has been applied to single crystalline silicon and V-groove is introduced. From the SEM observation a notch root has a radius of sub-micron order.4. It is found that the static strength of the notched specimen can be evaluated by the stress intensity factor, except for the extremely shallow notch.5. Fatigue test for 10^6 cycles is done for notched specimen, however no change is observed around the root of the notch.