Degradation Mechanisms in Die-to-Wafer Hybrid Bonding Governed by Surface Activation Lifetime and Moisture Evaporation

While direct placement die-to-wafer (D2W) hybrid bonding is essential for advanced packaging, its performance is often compromised by an extended storage time between surface activation and bonding. However, the underlying chemical degradation mechanisms have not been fully elucidated because of the challenge of correlating macroscopic bond strength with molecular-scale interfacial changes. Here, we introduce a comprehensive analytical approach, combining a novel, highly accurate bonding energy measurement with multi-modal surface spectroscopy. This method reveals that degradation is governed by a dual-factor mechanism: the loss of interfacial water and the depletion of surface silanol groups. The direct correlation between these interfacial changes and the reduction in bonding energy was quantitatively confirmed by thermal desorption and sum-frequency generation spectroscopy. This study provides the first quantitative insight into the degradation kinetics during storage, offering a clear scientific basis for optimizing D2W hybrid bonding processes.