Multiscale fracture studies of polycrystalline silicon-based MEMS

Micro-electro-mechanicalsystems(MEMS)made of polycrystalline silicon are widely used in several engineering fields. The fracture properties of polycrystalline silicon directly affect their reliability. The effect of the orientation of grains on the fracture behaviour of polycrystalline silicon is investigated out of the several factors. This is achieved, firstly, by identifying the statistical variation of the fracture strength and critical strain energy release rate, at the nanoscopic scale, over a thin freestanding polycrystallinesiliconfilm,havingmesoscopicscaledimensions.The fracturestressandstrainatthemesoscopiclevelarefoundto be closely matching with uniaxial tension experimental results.Secondly,thepolycrystallinesiliconfilmisconsidered at the continuum MEMS scale, and its fracture behaviour is studiedbyincorporatingthenanoscopicscaleeffectofgrain orientation. The entire modelling and simulation of the thin film is achieved by combining the discontinuous Galerkin method and extrinsic cohesive law describing the fracture