Measurement of anisotropic fatigue life in micrometre-scale single-crystal silicon specimens

The fatigue life of micrometre-scale single-crystal silicon specimens was measured using the resonant vibration of a micromachined resonator device. Two kinds of identically shaped specimens oriented to < 110 > and < 100 > crystal directions on the (001) plane were tested. On the deflection-life relationship, the deflection amplitudes of the < 100 > oriented specimens were approximately 1.56 times higher than that of < 110 > oriented ones at the same fatigue life. Observation by scanning electron microscope showed that the fracture surfaces differed depending on the specimen orientation and deflection amplitude. The life-shortening effect of the surface roughness was also demonstrated.