A Novel NH₄OH-assisted Self-Aligned Cu/SiO₂ Bonding for High-Precision and High-Speed Hybrid Bonding

Under the explosive demand for computing power in the core areas of the digital economy, such as artificial intelligence, high-performance computing, and the Internet of Things, interconnection technology faces the triple challenge of high bandwidth, low power consumption, and high density. Hybrid Bonding has become a key technology to support the heterogeneous integration of large computing power chips, which can achieve sub-micron or even nanometer interconnect spacing, reduce signal delay and power consumption, and improve chip bandwidth and capacity. Die-to-wafer bonding (D2W) technology has significant advantages in supporting heterogeneous integration, improving yield, and breaking through the limitations of three-dimensional packaging interconnect layers. However, its alignment bonding process is complex and faces challenges in alignment accuracy and production efficiency. This article proposes a Cu/SiO₂ bonding process based on NH₄OH-assisted self-aligned bonding technology at 200 °. After activation by Ar plasma, 5 μl of NH₄OH droplets were dropped onto the surface of the chip to be bonded. Under the capillary action of the interface between liquid and air, the upper and lower chips were continuously adjusted, achieving self-alignment while bonding. This scheme significantly increases the -OH and -NH₂ functional groups on the surface of the chip, which is beneficial for achieving Cu-Cu and SiO₂-SiO₂ hybrid bonding under low temperature and low-pressure conditions, ultimately obtaining a continuous and tightly bonded interface. In summary, this method provides a critical path for establishing high-precision and high-speed self-aligning hybrid bonding technology.