A novel and simple method of low temperature, low process time, pressureless interconnection for 3D packaging

• Main Authors: Huang, Jeng-Hau, Shih, Po-Shao, Shen, Chang-Hsien, Renganathan, Vengudusamy, Grafner, Simon Johannes, Lin, Yu-Chun, Kao, Chin-Li, Lin, Yung-Sheng, Hung, Yun-Ching, Chiang, Chun-Wei, Kao, C.R.
• Format: Conference Proceeding
• Language: English
• Subjects: 3D integration; Copper; Electroless Cu plating; Electroless Cu plating solution; Low-temperature bonding; Mass production; Packaging; Plating; Pressure free bonding; Surface morphology; Surface roughness; Three-dimensional displays
• ISSN: 2377-5726
• DOI: 10.1109/ECTC51909.2023.00282

3D IC technology has been widely used in the packaging field to achieve lighter weight, higher interconnect density and finer pitch. Hybrid bonding is considered a promising technology for realizing these concepts in 3D packaging. However, the implementation can be challenging due to the high temperatures and extremely low surface roughness required for the process which can significantly increase the cost of manufacturing. Researchers are constantly looking for ways to overcome these challenges and make 3D IC technology more accessible and cost-effective for mass production. Microfluidic electroless interconnection (MELI) process, a hybrid bonding alternative, has been shown to be a promising technique with the capability of bonding pillar joints at low temperatures and pressures. However, the long processing time and complex fluid mechanics of the MELI process could become a challenge for the application in mass production. To address these limitations, this study proposes a new bonding method that utilizes an optimized plating solution to eliminate fluid flow and reduce reaction time, with the aim of a higher suitability for mass production. This new bonding method uses a copper-glycerin complex solution with a high copper concentration to allow a significant reduction of processing time and temperature. With this method, Cu pillars could be bonded in less than 10 minutes at room temperature. The joints and cross-sectional morphology are investigated as well. Overall, this new method is simple, low temperature, short process time, and pressureless, making it a more promising technology for 3D integration for the future.