Rupture tests on polysilicon films through on-chip electrostatic actuation

A set of rotational test structures for on-chip fracture characterization of 0.9 mu m thick polysilicon film have been designed, modelled, and fabricated. The structures are actuated by a large number of comb-fingers capacitors which develop a force sufficient to load the specimens in bending up to rupture. A 3D FE model of the whole structures was used during the design phase. Tests were carried out at room temperature and at atmospheric humidity The measured Young's modulus of the tested polysilicon was 175 +/- 4 GPa. The low dispersion around the mean value confirms the quality and the good reliability of the whole procedure. The maximum stress at rupture was 2898 +/- 325 MPa; Weibull parameters found taking into account size effects and the effect of nonuniform stress distribution on the failure probability were sigma(0) = 2234 MPa, and m = 10.3.