Cross comparison of direct strength testing techniques on polysilicon films

Several direct and indirect testing techniques to characterize the strength and distribution in strength of structural thin films have been developed with widely varying results appearing in the literature (roughly 1 to 4 GPa for polysilicon). Much of the variation between authors has been explained in terms of microstructural differences, sample size effects, and release techniques. Five laboratories participated in a cross comparison of direct tensile testing techniques in an effort to study these variations; all samples were fabricated and released simultaneously at Sandia National Labs to eliminate material variations. Sample lengths ranged from 15 to 1000 μm long. All the samples were fabricated with a thickness of 2.5 μm. The distributions in strength are reported along with a tabulation of mean, standard deviation, and Weibull modulus of fracture strength for each lab.