| Summary: | Fine pitch Cu/SiO<sub>2</sub> hybrid bonding has been successfully demonstrated at a low temperature of 120 °C, a breakthrough, using Au passivation method in this work. To explore the bonding mechanism of passivation structures for hybrid bonding in details, Cu-Cu direct bonding with Au passivation on both wafer-level and chip-level has been discussed, including analyses of AFM, SAT, TEM, electrical measurements, and reliability test. Cu/SiO<sub>2</sub> hybrid bonding with the fine pitch structure with stable electrical performance can be achieved at low bonding temperature under an atmospheric environment. Accordingly, this Au passivation scheme for Cu/SiO<sub>2</sub> hybrid bonding with excellent bonding quality, low thermal budget, and high reliability shows a great feasibility for the 3D IC and heterogenous integration applications.
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