A simple analytical method for residual stress measurement on suspended MEM structures using surface profilometry

This paper presents an analytical method to calculate residual stress and Young's modulus in clamped-clamped beams. These types of structures are a typical building block of many MEMS devices, and this guarantees accurate transferability of the measured parameters. The method is based on the determination of beam bending as a function of applied load by means of a surface profiler, and as a function of beam length. By modeling analytically both the elastic and the stress contribution to beam bending, it is possible to obtain both the stress value and Young's modulus by a simple fitting of the experimental data. Results are presented for electrodeposited gold beam arrays of different widths, but the method is in principle exploitable for every type of suspended film where the residual stress strongly influences the material properties. Accuracy and limitations of the method are also discussed.