Fatigue rates of monocrystalline silicon thin films in harsh environments: Influence of stress amplitude, relative humidity, and temperature

This study investigates the separate influence of stress, temperature, and relative humidity (RH) on the fatigue behavior of 10-mu m-thick, monocrystalline silicon (Si) films at 40 kHz, under fully reversed loading. The fatigue rates are most sensitive to stress, with four orders of magnitude decrease from 3.2 to 1.5-2 GPa, confirming a size effect associated with the fatigue behavior of Si under bending load. The fatigue rates are also much more sensitive to RH than temperature or partial pressure of water, indicating that the effective environmental parameter is the adsorbed water layer. The implications on the relevant fatigue process(es) are discussed.