Thermoelastic analysis of interfacial stress and stress singularity between a thin film and its substrate

From advances in microelectronics and microelectromechanics, the area of applications for thin-film devices has been widely expanding. The thermal environment is severe in an increasing number of locations for thin-film devices. Thin-film devices are subjected to thermoelastic load due to a thermal expansion mismatch between a thin film and a substrate. In this study, interfacial stress between a thin film and its substrate and the behavior of singular stress at the edge are discussed on the basis of thermoelasticity. A boundary element method using fundamental solutions for dissimilar materials is extended to the thermoelastic problem. This method uses the solution that satisfies boundary conditions at the interface. Analytical treatment of the singular integral along the interface is used to evaluate the derivative of displacement. The method does not require discretization along the interface in the boundary element analysis. The interfacial stress is shown in detail, and the behavior of singular stress at the edge of the film is discussed from the results of the interfacial stress.