Cu–Cu hybrid bonding technology: from physical mechanisms to system integration for 3D ICs

Abstract With the rapid development of microelectronic technology toward high-performance and high-density integration, traditional bonding methods face dual challenges of interconnection density and bonding temperature. The Cu–Cu hybrid bonding, leveraging its outstanding benefits in sub-micron interconnection and efficient thermal management, has emerged as an innovative solution to overcome the limitations of traditional packaging. This paper systematically explores the physical mechanisms, integration technologies, key process breakthroughs, and macroscopic applications of Cu–Cu hybrid bonding. The study highlights the revolutionary advantages of hybrid bonding, such as ultra-fine vertical interconnection spacing. A detailed analysis of two major physical mechanisms in key technical pathways is presented. In practical applications, Cu–Cu hybrid bonding has demonstrated success in high-bandwidth memory, three-dimensional heterogeneous integration, and complementary metal–oxide–semiconductor image sensors. A notable example is Sony’s Cu/SiO₂-bonded image sensor, markedly improving imaging quality and integration density. However, challenges such as thermal boundary resistance control, process complexity, and large-scale production costs remain barriers to industrialization. Future advancements, including novel passivation materials and integration with ultra-wide bandgap semiconductors, promise to further propel the performance and reliability of radio frequency (RF) devices, power electronics, and artificial intelligence chips. This review provides a comprehensive framework for both theoretical exploration and practical implementation of Cu–Cu hybrid bonding technology.