A test device and test method for optical thin film stress

Abstract

The invention provides a testing device and a testing method for optical thin film stress. Surface sound waves with the same frequency are generated at specific positions of the front surface and the back surface of a prepared long-strip sample by a surface sound wave generator; the surface sound waves are used as a diffraction grating for incident light; when a film is not plated, the wavelengths of the surface sound waves on the front surface and the back surface of a substrate are equal and the symmetrical diffraction grating is formed, and diffraction zero-grade or + / -1-grade light intensity is uniformly distributed; after the film is plated, the substrate is bent by the stress; the sound wave speeds on the two surfaces are changed so that the wavelengths of the sound waves on the front surface and the back surface are different and the diffraction grating is not symmetrical, and furthermore, the zero-grade or + / -1-grade light intensity is not uniformly distributed; the light intensity is periodically distributed and is converted into the bending curvature of the substrate according to the size of the period; and the stress of a thin film is calculated according to a Stoney formula. The testing device has the advantages of simple structure, simplicity in manufacturing and high sensitivity; and the system errors of a traditional substrate bending method are eliminated, and the testing device can be applied to the detection of the stress of all the thin films prepared on the transparent substrate.

Description

technical field [0001] The invention belongs to the field of optical thin film testing, in particular to an optical thin film stress testing device and a testing method with simple structure and high sensitivity. Background technique [0002] Existing thin film stress testing techniques mainly include cantilever method, diffraction method and so on. However, the cantilever method and optical interference method require one end of the substrate to be fixed and the other end to be freely suspended, and then a thin film is deposited under the substrate. The substrate is bent due to the internal stress of the film, causing a displacement at the free end. The deformation of the film will have a certain impact on the displacement. The support conditions of the two measurements before and after the film preparation cannot be exactly the same, so the contribution of gravity to the displacement is different, which cannot be completely eliminated and affects the test accuracy. The di...

AI Technical Summary

Problems solved by technology

The traditional ultrasonic method needs to measure the sound velocity. Due to the very small amount of sound velocity changed by the stress and the current technical limitations, the accuracy of the measured sound velocity is not high, which makes it difficult to apply the ultrasonic method in the stress test of optical thin films.

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