Patent ID: 7403270
Filing Date: 2008-07-22
Classification: G01L

Abstract:
1. A method for evaluating a whole field stress in a thin film, comprising: (a) preparing a substrate; (b) measuring a wavefront for said substrate with a laser having a wavelength of λ so as to obtain a first wavefront phase; (c) depositing an optical thin film on said substrate as a specimen; (d) measuring a wavefront for said specimen so as to obtain a second wavefront phase; (e) determining a phase difference between said first wavefront phase and said second wavefront phase by means of an image subtraction; (f) fitting said phase difference with Zernike polynomials so as to obtain a fitting result for a respective surface topography of said substrate and said specimen; (g) retaining a coefficient of a specific term of said Zernike polynomials according to said fitting result, wherein said specific term is corresponding to a strain for said whole field stress; and (h) obtaining said whole field stress according to said coefficient of said specific term.