Measurement of Young´s modulus and residual stress of micromembranes

A novel method for the determination of the Young´s modulus and residual stress of micromembranes is described. Since thin film structures are frequently used in micro devices, characterization of mechanical properties of thin films is desired by the design and fabrication of micro devices. This paper characterizes the mechanical properties of thin micromembranes under compressive stresses with or without initial deflections, which are fabricated by silicon micromachining techniques. The relation between the deflection and the pressure applied to a square membrane is induced by modeling the membrane as a square plate having large deflection with clamped boundaries and the presence of internal compressive stress. The Young modulus and residual stress are simultaneously determined by using the load deflection behavior of a square membrane. The deflection of the membrane is measured using a micro interferometer. The mechanical properties of silicon nitride and silicon oxide membranes and polycrystalline silicon compound membranes with silicon nitride film are measured. This method use simple apparatus, and the fabrication of samples is very easy