Hybrid Bonding of Nanotwinned Copper/organic Dielectrics with Low Thermal Budget

The temperature for hybrid bonding is favorably to be lower than 250 °C, and thus nanotwinned Cu (nt-Cu) and low curing temperature dielectrics were combined to achieve that. To facilitate the fabrication of highly (111)-oriented surface of nt-Cu, Cu first process was chosen. In contrast to damascene Cu process, Cu first process changed the sequences of dielectric coating and Cu electroplating processes. In this study, patterned nt-Cu was plated first, and then dielectric was added in the process before or after chemical mechanical planarization (CMP). Low-temperature polyimide (PI) and non-conductive paste (NCP) were used to conduct two kinds of processes of hybrid bonding. If PI was coated and partially cured on a patterned wafer before CMP, co-planarization of nt-Cu/PI should be done afterwards to fabricate Cu/PI structure. The Cu/PI hybrid bonding can be achieved at 200 °C for 30 min. If a patterned wafer was planarized firstly, NCP was dropped on the samples and bonding process can be carried out at 180 °C for 2 h. This process was denoted as Cu + NCP hybrid bonding. The above two methods of hybrid bonding could be achieved under 250 °C, and might be the solutions for hybrid bonding technology with low thermal budget.