摘要
Advanced packaging technologies such as 2.5D and three-dimensional integration require fine-pitch, high-reliability interconnects. However, Cu-Cu direct bonding and hybrid bonding remain challenged by surface nonuniformity, coplanarity control, and the need for additional planarization and activation processes. In this study, nanoporous copper (NP Cu) was proposed as an interconnect material to enable improved surface conformity and ultralow-temperature bonding. Dome-shaped NP Cu bumps were fabricated by a dealloying method. SEM and TEM analyses revealed a three-dimensional nanoporous structure composed of ultrafine nanocrystallites with sizes below 50 nm, while X-ray diffraction confirmed a random crystallographic orientation. Thermocompression bonding was performed at 100 °C under applied pressures of 0.5 and 5 MPa. Cross-sectional SEM and HRTEM observations showed effective interfacial bonding under both pressure conditions. Electrical characterization using a nanoprobe demonstrated nearly identical values and linear I-V behavior for joints bonded under different pressures. These results demonstrate that NP Cu enables reliable Cu-Cu direct bonding at temperatures as low as 100 °C, providing a promising CMP-free interconnect solution for advanced packaging applications.