Statistical strength investigation of poly-silicon membranes using microscopic loading tests and numerical simulation

The strength of poly-silicon membranes was investigated by experimental tests and numerical simulations. A new fracture test has been developed that replicates the loading situation under real service conditions well but with higher stress level. A set of 45 membranes was tested at each of the three positions on the wafer in order to assure statistical accuracy and to evaluate the strength distribution across the wafer. Using finite element simulation, fracture stresses were calculated and analyzed by means of a two-parametric Weibull distribution subsequently. High values were found for the characteristic fracture stresses. They are in the range of 5,400-6,000 MPa.