Characterization of Interfacial Fracture Strength in Hybrid Bonded Wafers: A Novel Approach for High-Resolution Spatial Profiling

Hybrid bonding revolutionizes 2.5D and 3D microelectronic packaging by enabling high-density, low-resistance interconnects between chips. However, to ensure device reliability under thermo-mechanical stress, the key metric to study is interfacial fracture strength of hybrid bonded interfaces. Traditional testing methodologies often fall short in capturing spatial variability in fracture strength across the wafer from edge to center. Furthermore, they also need additional tooling and have limited accuracy in crack length measurement. To address these limitations, we propose a novel approach for characterizing the interfacial fracture strength across a 300 mm hybrid bonded wafer. First, the wafer is diced into 4 mm wide strips which are subjected to the extended razor blade test (E-RBT). The E-RBT employs a thin blade manually inserted into the hybrid bonding interface starting from the wafer edge. Sample deformation is monitored using an optical profilometer. Data processing techniques are employed to determine crack length. This procedure is then repeated as the blade is inserted deeper into the sample—thus generating a detailed spatial profile of the interfacial fracture strength. In contrast with traditional test methods, the E-RBT enables us to determine the spatial variation of interfacial bond strength across the entire wafer. A complementary finite-element model is developed to verify the applicability of Maszara’s wafer-based equations to beam samples. The models indicate that Maszara’s wafer-based equations are able to capture the trends but underpredict magnitude. Our results indicate that for blanket oxide-oxide bonded wafers, the fracture strength at the wafer center is approximately 20% higher compared to wafer edge. This novel characterization method not only refines measurement precision but also delivers a comprehensive fracture strength profile, offering valuable insights into the variability of bond strength within hybrid bonded interfaces. The improved resolution and precision of this technique contribute significantly to the reliability assessments of advanced semiconductor packaging, highlighting its potential for broader application in the industry.