A NEW TECHNIQUE FOR MEASURING THE MECHANICAL-PROPERTIES OF THIN-FILMS

Accurate measurement of mechanical properties is very difficult for fi lms that are only a few microns thick, Previously, these properties ha ve been determined by indirect methods such as cantilever beam and dia phragm bulge tests. This paper presents a new technique to measure the Young's modulus of thin films in a direct manner consistent with its definition, Strain is measured by a laser-based technique that enables direct and accurate recording of strain on a thin-film specimen, Load is recorded with a 1-lb load cell, and an air bearing is used to elim inate friction in the loading system, The specimen is phosphorus-doped polysilicon that has a gage cross section of 3.5 mu m thick by 600 mu m wide. All 29 uniaxial tensile tests show brittle behavior, and the average values of Young's modulus and fracture strength are measured t o be 170+/-6.7 GPa and 1.21+/-0.16 GPa, respectively, One fatigue test is also reported in this paper.