Mitsui Chemicals launches new adhesive for 3D stacking that can be permanently bonded under low temperature conditions

In Japan, Mitsui Chemicals is aggressively probing into the business of new bonding materials for the 3D stacking application increasingly appreciated in advanced semiconductor packaging. The composition can be bonded temporarily at room temperature and can achieve permanent bonding at a lower temperature of 150 degrees. It has the further advantage that the wafers will not displace after bonding and is expected to help reduce the distance between the wafers. Dense package. 

In order to achieve high performance in advanced semiconductors related to generative artificial intelligence (AI), the importance of 3D stacking technology of vertically stacking wafers is increasing. In terms of IC chip stacking technology, it is expected that hybrid bonding, which simultaneously connects copper electrodes and insulating layers, will replace the existing solder connection and become mainstream. Mitsui Chemicals has developed a new adhesive material for hybrid bonding that is used in stacked wafers (CoW) to bond copper (Cu) electrodes together.

The new material can be temporarily bonded at room temperature and under low load, and permanently bonded at low temperatures of 150°C. After hardening, chemical mechanical polishing (CMP) can be performed without slurry or Cu residue. There will be no positional shift due to deformation after joining.

After the new adhesive is applied and hardened on the substrate with the Cu electrode, even if foreign matter remains during the dicing process, voids will not be formed and bonding defects will not easily occur. The subsequent material will not be removed from the wafer. The protruding edges can reduce the distance between chips and achieve high-density packaging. In addition, permanent bonding can be achieved at room temperature through plasma treatment.

Existing hybrid bonding materials use inorganic materials such as silicon oxide films, but foreign matter can be caught in and create voids, which can lead to related problems. On the other hand, bonding technology using resin continues to develop. Although it is possible to join after covering foreign matter, the temporary joining is performed in a flowing state, so positional deviation is likely to occur.

The new materials developed by Mitsui Chemicals have the advantage of solving these problems. With the progress of customer evaluation, the new bonding materials are expected to be commercialized as soon as 2025. Mitsui Chemicals also plans to develop them into the world's first process application After the protective tape "ICROS" and the photomask protective film "PELLICLE", it became a part of the semiconductor business, with annual sales of more than 10 billion yen as a mid- to long-term goal.