International Journal of Fracture 119/120: 449–474, 2003.

High-cycle fatigue of micron-scale polycrystalline silicon films: fracture mechanics analyses of the role of the silica/silicon interfac

Fatigue of polycrystalline silicon for MEMS applications: Crack growth and stability under resonant loading conditions

Although bulk silicon is not known to exhibit susceptibility to cyclic fatigue, micron-scale structures made from silicon films are known to be vulnerable to degradation by fatigue in ambient air environments, a phenomenon that has been recently modeled in terms of a mechanism of sequential oxidation and stress-corrosion cracking of the native oxide layer

High cycle fatigue of polycrystalline silicon thin films in laboratory air

When subjected to alternating stresses, most materials degrade, e.g., suffer premature failure, due to a phenomenon known as fatigue. It is generally accepted that in brittle materials, such as ceramics, cyclic fatigue can only take place where there is some degree of toughening, implying that premature fatigue failure would not be expected in polycrystalline silicon where such toughening is absent. However, the fatigue failure of polysilicon is reported in the present work, based on tests on thirteen thin-film (2 µm thick) specimens cycled to failure in laboratory air (~25ºC, 30-50 % relative humidity), where damage accumulation and failure of the notched cantilever beams were monitored electrically during the test. Specimen lives ranged from about 10 seconds to 34 days (5 x 10 5 to 1 x 10 11 cycles) with the stress amplitude at failure being reduced to ~50 % of the low-cycle strength for lives in excess of 10 9 cycles

Mechanism of fatigue in micron-scale films of polycrystalline silicon for microelectromechanical applications

Reported nearly a decade ago, cyclic fatigue failure in silicon thin films has remained a mystery. Silicon does not display the room temperature plasticity or extrinsic toughening mechanisms necessary to cause fatigue in either ductile (e.g., metals) or brittle (e.g., ceramics and ordered mintermetallic) materials

A reaction-layer mechanism for the delayed failure of micron-scale polycrystalline silicon structural films subjected to high-cycle fatigue loading

A study has been made of high-cycle fatigue in 2um thick structural films of n+- type, polycrystalline silicon for MEMS applications

The effects of cubic stiffness on fatigue characterization resonator performance

Micromachined, kHz-frequency resonators are now routinely employed as testing structures to characterize the fatigue degradation properties of thin film materials such as polycrystalline silicon (polysilicon). In addition to stress-life (S-N) fatigue curves, important properties such as crack propagation rates may be inferred from proper resonant frequency measurements throughout a fatigue test. Consequently, any nonlinear dynamic behavior that would complicate the interpretation of resonant frequency changes should be avoided. In this paper, nonlinear frequency-response curves of a polysilicon fatigue structure are measured in a vacuum environment. Finite element models of the structure are used to identify the source of geometric nonlinearity leading to a Duffing-type cubic stiffness. Given the origin of the behavior, a parametric optimization strategy is performed to minimize the cubic stiffness. This study highlights the importance of considering the dynamic behavior when designing resonating structures, especially when they are used for mechanistic studies in various environments