Comparison of Organic and Inorganic Dielectric Hybrid Bonding with Highly <111>-Oriented Nanotwinned Cu

Cu hybrid joints have appeared to be the solution for fine-pitch advanced packaging. A multitude of options are available for selecting dielectric materials for the hybrid bonding, which includes SiO₂, SiCN and polymer dielectrics, and all the materials have their pros and cons. In this paper, we have examined low-thermal-budget (≦220 °C), high bonding strength (≧ 30 MPa) and low contact resistance (< 1.7 × 10^-8 Ω•cm²) hybrid bonding without a post-bond annealing process via film-to-film bonding with low-curing-temperature polyimide, PI, and die-to-die hybrid bonding with low-curing-temperature polyimide and highly <111>-oriented nanotwinned Cu, NT-Cu; and compared it to inorganic hybrid bonding in previous literature. The thermal properties of NT-Cu and the surrounding dielectric need to be compatible with each other to achieve the best bonding quality and lowest cost. NT-Cu can be bonded and even eliminate the bonding interface at 150~250 °C within 1 h, while the inorganic dielectrics need post-bond annealing process to eliminate the seams for at least 1~4 h at 200~350 °C. As for low-curing-temperature PI, bonding can be achieved, and its interface can be eliminated at only 100 °C for 30 min and even lower. It also possesses low dielectric constants, processing simplicity, strong mechanical properties, great thermal stability, and very low process cost, making NT-Cu/PI a potential new choice for 3D IC hybrid bonding.