Mechanical properties study of nano-scale thin films on the novel paddle cantilever using optical interferometer with four step phase-shifting method

A paddle-like cantilever beam was designed and developed as a specimen to measure the mechanical behavior of thin films. This beam is in triangle shape in order to provide uniform plane strain distribution and standard clean room processing was used to prepare the sample. The residual stress measurement of thin films application for MEMS were studied with the deflections of silver, gold, and copper films (50-250 nm) driven by the electrostatic force and measured using four step phase-shifting method. The results present that the test structure and the optical (FSPS) method work excellently. Furthermore, silver presents that the deflection decreases after deposition to demonstrate that the tensile residual stress in the film. Oppositely, gold and copper films show compressive residual stress in them.