Cheemalamarri, H. K., Fujino, M., Bhesetti, C. R., Long, L. B., Dileep, M., Vempati, S. R., & Singh, N. (2025). Novel Selective Metal Capping on Cu pad Enabling Void-Free Hybrid Bonding at Low Thermal Budgets, Irrespective of Cu Topography and Microstructure. 2025 IEEE 75th Electronic Components and Technology Conference (ECTC), 576–581. https://doi.org/10.1109/ectc51687.2025.00102
Abstract:
Cu/dielectric hybrid bonding is a pivotal technology for high-density and reliable interconnects in 3D IC integration. However, the incorporation of temperature-sensitive components, such as memory devices, necessitates a stringent reduction in the overall thermal budget to prevent thermal-induced degradation and ensure device reliability. Lowering both dielectric and Cu bonding temperatures presents significant challenges. Even though Alternative dielectrics are making the dielectric bonding at low temperatures, Cu bonding is still a challenging. Cu bonding suffers from uncontrolled Cu dishing, surface roughness, and oxidation, which hinder low-temperature processing. This study introduces a novel approach to achieving hybrid bonding below 250˚C by implementing an innovative metal passivation engineering technique for Cu bond pads. The passivation mechanism is implemented tested its feasibility for both μm and sub-0.5μm (400 nm) pitches. Void-free interfaces at this reduced thermal budget are confirmed through FIB, X-SEM, C-SAM, and TEM analyses, demonstrating substantial improvements over conventional un-passivated Cu/dielectric hybrid bonding. Additionally, this passivation technique addresses two persistent challenges in hybrid bonding: mitigating metal-dielectric overlap-induced nonbonding area and bonding voids caused by galvanic corrosion. TEM-EDS investigations reveal efficient interdiffusion across the passivation layer, reinforcing the viability of this approach in enabling robust, high-performance interconnects for next-generation 3D IC applications.
License type:
Publisher Copyright
Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - Center of Excellence in Advanced Packaging 3.0
Grant Reference no. : I2101E0008