According to the latest report from ETNews, citing supply chain sources, TSMC is reportedly still holding back from investing in the silicon packaging technology known as hybrid bonding for HBM memory integration. For those unfamiliar, hybrid bonding creates a permanent bond between two silicon chips using embedded metal bumps that are fused together to form a single chip. Multiple dies or entire silicon wafers can be connected by stacking the back ends of two chips together. This technology eliminates traditional chip bumps and directly bonds copper interconnections between the two chips. In modern packaging, chip solder bumps, which stick out before the chip is soldered to the PCB, are roughly 100 micrometers in size, while microbumps are approximately 20 micrometers. Hybrid bonding reduces this size to 1 micrometer. Microbumps are used to interconnect silicon with other chips inside a package, as seen in CoWoS-S and CoWoS-L, where microbumps are prevalent for chip-to-interposer connections.

For TSMC, the future may involve bypassing hybrid bonding technology for packaging HBM memory and investing in microbumps that are 5 micrometers in size. Reportedly, TSMC is preparing its supply chain for 5-micrometer microbumps, which will be even smaller than what is currently available, to enhance performance in packaging. South Korean and Japanese suppliers are reportedly collaborating with TSMC to achieve this, with mass production of 5-micrometer microbumps expected in the second half of 2028. As a reminder, AMD's 3D V-Cache technology uses hybrid bonding to put SRAM on top of logic, but TSMC reportedly plans to keep integration of HBM memory into packaging on microbumps for now.This isn't the first instance where TSMC has opted not to adopt the latest packaging technology in manufacturing. For example, TSMC still believes that Low-NA EUV lithography will suffice for advancing next-generation nodes. TSMC has been committed to using Low-NA with multi-patterning, where the EUV machine takes multiple passes to etch a design on a single layer, until manufacturing begins for nodes at 1 nanometer and below. This trend continues with microbumps, even as the entire industry, including SK hynix, views hybrid bonding as the most efficient and high-performance method for stacking chips.