Methodologies for Characterization of W2W Bonding Strength

In this paper, we compare different methods for evaluating the interface adhesion energy of hybrid bonded wafers with silicon carbon nitride (SiCN) as the primary bonding surface. The bonded wafers or coupons were submitted to different annealing conditions and their adhesion energy was evaluated. In this study we compared different methods that include Maszara test, four-point bending and nanoindentation based techniques (wedge and cube corner indenter tip) to demonstrate the different techniques produce similar results for the measurement of adhesion energy. In all cases, a steep increase in the bonding energy was observed after 200 degrees C and reached their maximum at 250 degrees C. This is consistent with previous studies that have shown that higher annealing temperatures can improve the interfacial adhesion and reduce the defects in SiCN layers. We conclude that all three methods can provide useful information for W2W bonding strength characterization, but they have different strengths and limitations.