Measurement of Young´s modulus on microfabricated structures using a surface profiler

A point-force, load-deflection method using a stylus-type surface profiler to determine the Young´s moduli (E_Y) of thin-film microstructural materials is introduced. In this method both force and deflection in microstructures are measured simultaneously by the profiler to provide a convenient and accurate means to obtain Young´s modulus directly. Measurements on two types of micromechanical structures are described: a doubly supported bridge and a bridge-slider (a beam with one fixed end and one end that can slide in a flanged housing). The influence of residual stress in the doubly supported beam is described and accounted for theoretically to interpret measurements made on low-stress silicon-nitride films. For this material E _Y is 373 GPa. In the bridge-slider structure, residual strain is relaxed to zero. Measurements on a polycrystalline-silicon bridge slider show a value for E_Y of 123 GPa in unannealed material that is doped heavily with phosphorous, and grown at 650°C