Microscale interfacial adhesion assessment in a multilayer by a miniaturised four-point bending test

Abstract

Microscale techniques capable of selectively isolating and delaminating embedded multilayer interfaces in a stable manner have the potential to be powerful characterisation tools for improving the reliability of microelectronic devices. Here we propose an analytical approach to assess the steady-state strain energy release rate during the delamination of an embedded multilayer interface, initiated by our recently developed miniaturised four-point bending technique. Stable delamination of a SiN-GaAs interface was initiated via nanoindentation induced bending of microbridges that had been milled into the surface of an Al-SiN-GaAs multilayer using a focused ion beam. Analytical models quantify the strain energy released within a section of a microbridge using the load-displacement relation obtained during delamination. The models are validated by demonstrating their capacity to approximate the experimentally observed linear-elastic deformation of a reference microbridge under both three- and four-point bending. We find that deformation of the clamped-ends as well as indenter penetration of a microbridge contribute significantly to the total indenter displacement. We then show this can be accounted for through a combination of Euler–Bernoulli beam and Hertzian contact theory. A mean steady-state strain energy release rate of G¯SS=2.20±0.36Jm−2 is obtained for the SiN–GaAs interface.