Failure of a brittle layer on a ductile substrate: Nanoindentation experiments and FEM simulations

Functional devices such as microelectronic systems, solar cells and power are composed of complex stacks various materials, including semiconductors, ceramics metallic alloys. The knowledge the mechanical response those is a key point, they submitted to harsh stresses during fabrication process (induced by thermal treatments, polishing, packaging processes, ...) well device lifetime. We report study microelectronic-dedicated stack where silicon nitride (Si 3 N 4 ) layer was deposited on top thick alloy (AlSiCu) layer. In chips, Si widely used passivation layer, while AlSiCu electrical connection structure has been tested experimentally nanoindentation. Multiple pop-in events were observed loading curves, indicating multiple cracking, with cracks initiated at stages. high reproducibility curves then allowed their full analysis numerical modeling. complete damage multilayer indentation analyzed using modeling Finite Element Method (FEM), accounting for plasticity in AlSiCu, crack propagation possible delamination interface between two layers. stages occurring elucidated, showing particular occurrence first region underneath indenter (hence not visible surface observation), followed second forming further away from indenter, Moreover, novel procedure identification tensile strength presented, an inverse method based FEM simulations experimental data. results (cracking patterns locations) also validated observation cross-sections Scanning Electron Microscope (SEM) after Focused Ion Beam (FIB) milling sample. addition, proposed quite generic can be adapted other systems similar multiple-cracking under indentation.