Search for copper diffusion at hybrid bonding interface through chemical and electrical characterizations

• Published in: Microelectronics and reliability 2021-11, Vol.126, p.114217, Article 114217
• Main Authors: Jourdon, Joris, Lhostis, Sandrine, Moreau, Stéphane, Lamontagne, Patrick, Frémont, Hélène
• Format: Article
• Language: English
• Subjects: 3D integration; Copper diffusion; Engineering Sciences; Hybrid bonding; Micro and nanotechnologies; Microelectronics; ToF-SIMS; Voltage breakdown
• ISSN: 0026-2714; 1872-941X
• DOI: 10.1016/j.microrel.2021.114217

Cu/SiO2 diffusion at hybrid bonding interface without diffusion barrier was investigated in order to validate the electrical insulation of interconnects. The Cu thermal diffusion was studied by ToF-SIMS analysis of the dielectrics stack facing bonding pads after a bonding annealing (400 °C, 2 h) and a diffusion annealing (400 °C, 14 h). No trace of copper was found above the limit of detection 1017 at·cm−3. Cu ions drift was followed by I-V measurements on specially designed comb-serpentine that maximize the electrical field at bonding interface. Their efficiency was confirmed since physical failure analysis located the dielectric breakdown damage between bonding pads. Breakdown voltages coupled to wafer-to-wafer misalignments enabled the extraction of the SiO2 breakdown strength: 3.4 MV·cm−1. This study proves that at room temperature, hybrid bonding interconnects remain electrically insulated despite thermal budgets involved by the bonding process. •Evaluation of Cu diffusion through SiO2 at hybrid bonding interface under stresses•No Cu trace above 1017 at·cm−3 detected after a 400 °C-16 h thermal budget•I-V measurements evidenced that the voltage breakdown is misalignment dependent.