Micro 3D measurement applied to interfacial deformation of bilayer thin film/substrate structure under thermal cycling loads

Failures resulting from thermal mismatch between the layers in a multilayer thin Film/Substrate structure (F/S) are fatal for the reliability of F/S-based electron devices. In this paper, a bilayer F/S consisting of a silicon substrate, a chromium film layer and a copper film layer is investigated under external thermal cycling loads. Grid method combining with the stereovision model in a Scanning Electron Microscope (SEM) system is developed to realize the measurement of three-dimensional deformation at microscale. The Focused Ion Beam (FIB) deposition technology is employed to fabricate micro-scale grid pattern with the spatial frequency of 1000 lines/mm on the test sample surface. The thermal fatigue mismatch between the film layers gives rise to intense 3D deformation near the interface area. The out-of-plane deformation as well as the in-plane deformation of the interface area is measured to achieve the genuine 3D deformation characterization. The accuracy analysis validates the feasibility of the proposed method.