Investigation of the fatigue origin and propagation in submicrometric silicon piezoresistive layers

The work investigates fatigue damage accumulation in a 250-nm thick Silicon layer that can be integrated in surface micromachining processes to realize piezoresistive sensing elements, as an alternative to capacitive detection. The investigation is done through a suitably designed structure which combines a 20-μm-thick layer, used to apply cyclic stresses, to the nanometric layer, where stress accumulation is obtained. Fatigue results are compared to previous works on micrometric Silicon and put in the context of the current theories about the origin and propagation of fatigue in micro- and nano-machined Silicon.