Tuesday  |  Virtual Track 4  |  09:24 AM–09:36 AM

#11379, Experimental Evaluation of Non-Uniform Thin Film Stress

Generally speaking, the thin film stress has been obtained by Stoney's formula. That is because the use of Stoney's formula only requires the measurement of the radii of curvature of substrate before and after coating the thin film. In the earlier work of the authors, it can be found out that the thin film stress is almost non-uniform when the substrate after coating. However, the Stoney's formula just can employ to the uniform and equibiaxial thin film stress. Therefore, the application of Stoney's formula is not available for actual situations. Hence, in the literatures, the extended Stoney's formulas have been developed to determine the non-uniform thin film stress. By using the extended Stoney's formulas, the coherent gradient sensing (CGS) technique has to apply to measure the whole-field curvature of substrate. The use of the extended Stoney's formulas with CGS technique can apparently obtain the non-uniform thin film stress. However, the extended Stoney's formulas have not been estimated by experimental. In this paper, the whole-field stress and curvature of circular disks made of PSM-1 photoelastic material and coated with the silicon dioxide (SiO2) thin film of different thicknesses were measured by photoelasticity and CGS technique, respectively. The non-uniform thin film stresses can be estimated by comparing the results of the two methods.

Wei-Chung Wang   National Tsing Hua University
Po-Yu Chen   National Tsing Hua University
Yue-Shuan Lin   National Tsing Hua University