A new method for measuring residual stress in the isotropic and anisotropic thin film is proposed. A modified Twyman-Green interferometer is used to measure the surface topography of thin film. This invention is combined with 2D fast Fourier transform (FFT), phase unwrapping algorithm and numerical analysis methods for measuring the radius of curvature of a substrate before and after film deposition.

Various coating processes has residual stress in thin films. The distribution of thin film stress may be isotropic or anisotropic. For the  literature and patents , the general measuring methods are suitable for isotropic film stress. The measurement method of anisotropic stress is rarely discussed.

This technology can be applied to film residual stress measurement of ophthalmic lenses, optical component coatings, solar cell panels, touch panels, optoelectronic components, and semiconductor component products etc. The residual stress measurement of thin films has the market development potential.