Hybrid bonding technology is an advanced 3D chip packaging technology that provides higher connection density and bandwidth than traditional microbumps by enabling direct copper-to-copper interconnects between chips in a very small size. This technology has shown its importance in a number of areas, including CMOS image sensors, high-performance computing, 3D NAND, and DRAM memory. In the field of 3D chip stacking and advanced packaging, it allows for tight electrical and mechanical connections between different chip layers or chips and substrates, which is of great significance for improving chip performance, reducing size, and reducing power consumption. In recent years, chipmakers have been looking to reduce the size of circuits, and some industry insiders say that hybrid bonding technology will be equally important in the next five years.
The important role of hybrid bonding in 3D chips
Increase the number of transistors: Hybrid bonding technology allows two or more chips to be stacked in the same package, which allows chipmakers to significantly increase the number of transistors in the processor and memory without increasing the physical size of the chip. This is critical to continue to improve chip performance, especially in the context of a general slowdown in transistor size reduction.
Improved integration and performance: Hybrid bonding technology significantly increases the level of chip integration by stacking chips vertically. This high level of integration not only helps to reduce the size of the final product, but also greatly improves data transfer speed and system performance. In 3D chips, the cable distribution area is expanded to the entire surface of the processor, effectively shortening the length of the cable between each processor, thereby improving data transmission efficiency and reducing power consumption.
Figure: Hybrid bonding technology plays an important role in 3D chips (Source: IEEE Spectrum)
Enabling high-density interconnects: Hybrid bonding enables interconnect pitches in the sub-micron and even nanometer ranges compared to traditional bonding technologies. This extremely high-density interconnect allows more connection points to be placed in a smaller area, greatly increasing the bandwidth for data communication between chips. In 3D chip packaging, millions of connection points per square millimeter of silicon can be reached, providing a solid foundation for high-speed, efficient data transmission.
Reduced Resistance and Delay: Hybrid bonding reduces resistance and energy loss for signal transmission by eliminating the need for intermediate media such as solder through a direct copper-to-copper connection. At the same time, this direct connection also reduces the time delay of signal propagation, which helps to improve the overall performance of the system.
Improved heat dissipation: The compact construction and direct conductive path help improve thermal management and reduce heat generation issues. This is especially important for high-performance computing, artificial intelligence, and other high-speed computing applications, which tend to generate a lot of heat. Hybrid bonding technology improves heat dissipation efficiency and ensures stable operation of the system by optimizing the chip stacking structure.
At present, hybrid bonding technology has been widely used in image sensors, high-end processors, HBM memory stacks, AI accelerators and other fields. For example, in the field of image sensors, hybrid bonding technology is used to connect the pixel array at the bottom layer with the circuit layer at the top, reducing optical path loss and enabling smaller camera module designs. In high-end processors, hybrid bonding technology is used to tightly stack compute cores and caches on top of each other, significantly improving system performance.
As the technology continues to mature and become more cost-effective, it is expected that hybrid bonding technology will be widely used in more complex and demanding system-in-package solutions in the future. At the same time, hybrid bonding technology will continue to promote the development and innovation of 3D chips, providing strong support for the miniaturization and high performance of modern electronic products.
