In-situ Study on Thermal Compression Bonding of Nanotwinned Cu Pillars
ABSTRACT
Cu-Cu pillars thermal compression bonding (TCB) technique has emerged as a promising solution for ultrafine pitch packaging in 3D integrated circuit technologies. In-situ micropillar compression is a technique extensively used to investigate the deformation behavior and deformation mechanisms of metallic materials at microscale. Here, we demonstrated the approach of using in-situ micropillar compression technique to investigate TCB of nanotwinned Cu. The in-situ studies enabled the real-time monitoring of the bonding of Cu interfaces under constant stress. Focused ion beam microscopy and transmission electron microscopy revealed the local microstructure and crystallography along the bonded Cu-Cu interfaces. The investigation from in-situ TCB was also combined with the existing bonding models to discuss the influence of diffusion on bonding development.
BIOGRAPHY
Nanomechanics provides us with an opportunity to study fundamental mechanical properties of physical systems under nanometer scale. Our research focuses on the nanomechanical behavior investigation of metallic thin film materials. This work spans not only the physical vapor deposition like magnetron sputtering, but also the use of in-situ micropillar compression technique under scanning electron microscopy, focus ion beam fabrication and transmission electron microscopy to better understanding the deformation behavior and deformation mechanisms. Leveraging my knowledge and experience in materials science and advanced characterization approaches, I successfully applied our research capabilities on different metallic systems or application scenarios like Co based alloys, high entropy alloys and nanotwinned Cu bumps. In my SRC Research Scholars program, we successfully utilized our in-situ micropillar compression technique to achieve the real-time monitoring of nanotwinned Cu to Cu bump bonding development and investigate the bonding mechanism under nanoscale. This work features a strategy to advance our understanding of the bonding process and provides an insight into tailoring the microstructure of Cu for bonding under lower temperature and lower pressure.