Wafer-to-wafer hybrid bonding technology for 3D IC

In this research, the wafer-level metal/adhesive hybrid bonding technology was developed to perform the 3D integration platform. Four kinds of polymer materials, BCB, SU-8, AL-Polymer, and PI, were evaluated as the bonding adhesive for hybrid collocation with metal. After realizing the bonding properties, the qualified ones were patterned on wafers, and sequentially bonded by metal bonding conditions. Two kinds of conditions were simulated, one is Cu-Sn eutectic bonding, and the other is Cu-Cu thermo-compression bonding. The compatibility between each polymer and metal was evaluated, and the application range of each material was established thereof. Furthermore, samples with hybrid scheme were fabricated to perform hybrid bonding and realize the compatibility in whole process. The micro-bump/Cu-pad size less than 20µm and thickness less than 5µm were designed for interconnection. The bonding quality and interface investigation on metal/adhesive were analyzed to make sure the interconnection and micro-gap filling between stacked wafers. The evaluation results of wafer-level hybrid bonding and material candidates will be disclosed in the paper.