Thermo-Mechanical Stress and Its Effect on the Fabrication and Reliability of Cu-SiO₂ Hybrid Bonds for 3D IC Heterogeneous Integration (Invited)

As the required performance for artificial intelligence and high-performance computing devices continue to increase, the interconnect density has to increase accordingly. Cu/SiO2 hybrid joints have emerged to be the solutions for ultra-fine pitch interconnects for advanced packaging. To fabricate the hybrid joints, recessed Cu pads in SiO2 vias are prepared. Temperature is increased to form Cu-Cu metal bonding. Thermo-mechanical stress is generated due to mismatch of coefficients of thermal expansion (CTE) between the SiO2 and the Cu pads, and it plays a very important role in the fabrication. In addition, during the reliability tests, such as electromigration and temperature cycling, temperatures may vary from -55 °C to 200 °C. Therefore, the thermo-mechanical stress is generated again and it may affect the reliability tests. This paper will discuss the effect of the thermo-mechanical stress on the fabrication and reliability tests.