Measurement of thin-film residual stress based on single-beam lever method

In order to measure the residual stress of thin film, an automatic measurement system based on single-beam light lever method was designed in this paper. The total system, composed of light path system, laser system, sample support system and speckle tracking measurement system, measured the variation of the sample´s radius before and after depositing the thin film, which would be used to calculate the film residual stress based on Stoney formula. Taking optical concave reflectors with given radius as the samples, this method belonging to nondestructive test was compared to the contour method, and the results shown that the measuring precision of radius was within ± 2%, which was better than the contour method. In addition, the system was relatively simple, effective and low cost and the radius of curvature measurement range could be as low as 0.2 meter.