Real-time detection of fracture mode at the direct bonded Chevron-notch Si chip via acoustic emission

In this study, the bonding strength and fracture behavior of wafer-to-wafer (W2W) bonding chip-scale Chevron-notch (CN) Si specimen was investigated using the tensile test with real-time acoustic emission (AE) monitoring. Fracture analysis could be identified into two failure modes, “interface open type” and “matrix crack type”. The bonding strength of the interface open type was slightly higher (6.41 J/m 2 ) than the matrix crack type (6.12 J/m 2 ). On the other hand, the interface open type exhibited higher AE absolute energy (4.0 × 10 7 aJ), 2.7 s of signal detection duration, and more detected signals (14.7 counts) compared to the matrix crack type, 2.3 × 10 7 aJ, 1.6 s, and 10.4 counts, respectively. Conventionally, both bonding strength measurement and microstructural analysis were required to classify fracture types, but AE monitoring enabled real-time identification during the tensile test.