Characterizing Interfacial Sliding of Through-Silicon-Via by Nano-Indentation

In this paper, an experimental method is proposed to determine the shear sliding behavior of the interface between a copper through-silicon-via (TSV) and silicon. This interface was loaded in a nano-indentation experiment on specimens that were fabricated using focused-ion-beam milling. The elastic and plastic properties of the copper via were first characterized by micro-pillar compression experiments. The interfacial sliding is described by a cohesive zone model with a traction-separation relation including a linearly elastic part followed by frictional sliding at a constant shear traction. Both analytical and numerical models were developed for extracting the parameters of the traction-separation relation for the shear behavior of the interface. The average critical shear traction required to initiate interfacial sliding was found to be 77.2 MPa and the corresponding relative displacement across the interface was 182.7 nm, while the frictional shear strength was 25 MPa. The traction-separation relation with the extracted parameters may be used to study via extrusion and associated reliability analysis for integrated TSV structures.