KAIST Develops "Nano Sandpaper" to Enhance HBM Surface Quality

A technology capable of uniformly processing semiconductor surfaces down to the atomic level has been developed in Korea. The key is extending the everyday concept of sandpaper that smooths surfaces into the realm of nanotechnology. This technology shows potential for improving surface quality and processing precision in advanced semiconductor processes such as high-bandwidth memory (HBM).

KAIST announced on the 11th that a research team led by Professor Kim Sanha of the Department of Mechanical Engineering has developed "nano sandpaper" that uses carbon nanotubes as an abrasive material.

Nano sandpaper image (AI-generated). Korea Advanced Institute of Science and Technology

Sandpaper is a familiar tool used to smooth surfaces by rubbing. However, it is difficult to apply in fields that require extremely precise surface processing, such as semiconductors. This is because conventional sandpaper is made by attaching abrasive particles with an adhesive, which makes it difficult to fix very fine particles evenly.

To compensate for this, the semiconductor industry has used a planarization process called Chemical Mechanical Polishing (CMP), which employs a chemical solution, or so-called slurry, in which abrasive particles are dispersed in a liquid. However, this method requires additional cleaning steps and generates a large amount of waste, creating a significant environmental burden.

In contrast, the nano sandpaper developed by the research team is evaluated as a new planarization technology that not only processes surfaces more precisely than existing semiconductor manufacturing processes, but also reduces the environmental burden generated during processing.

To overcome the shortcomings of planarization processes that use slurry, the research team extended the concept of sandpaper down to the "nano" scale. They succeeded in implementing "nano sandpaper" by vertically aligning carbon nanotubes that are thinner than a human hair, fixing them inside polyurethane, and exposing only part of them on the surface.

This structure structurally suppresses the detachment of the abrasive material, eliminating concerns about surface damage and maintaining stable performance even with repeated use.

(From left) Dr. Kang Seokgyeong and Professor Kim Sanha, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology.

In particular, the nano sandpaper exhibits an abrasive density that is 500,000 times higher than that of the finest commercial sandpaper currently available.

The precision of sandpaper is expressed as "abrasive density (grit number)," which indicates how densely abrasive grains are arranged on the surface. This value is used as an indicator of the number of abrasive grains per unit area of the sandpaper.

For example, the grit number of sandpaper used in everyday life is typically in the range of about 40 to 3,000, whereas the grit number of the nano sandpaper exceeds 1 billion. This extremely dense structure means that it is possible to process surfaces with precision down to a few nanometers (equivalent to the thickness of several atoms).

The research team also verified the effectiveness of the nano sandpaper through actual experiments. Using nano sandpaper, they were able to smooth copper surfaces down to the nanometer scale, and when they tested semiconductor pattern planarization, they obtained results showing that dishing defects were reduced by up to 67% compared with conventional CMP processes.

Dishing defects, in which the center of the wiring becomes concave, are regarded as a major defect that affects the performance and reliability of advanced semiconductors such as HBM.

Because the abrasive material in nano sandpaper is fixed to the sandpaper surface, there is no need to continuously supply slurry solution as in existing processes. As a result, cleaning steps can be reduced, and no waste slurry is generated, enabling a more environmentally friendly semiconductor manufacturing process.

The research team expects that this technology can be applied to planarization processes for advanced semiconductors such as HBM used in AI servers, as well as to hybrid bonding processes, which are attracting attention as next-generation semiconductor interconnection technologies.

This study is also significant in that it extends the everyday concept of sandpaper into a nano-precision processing technology, thereby suggesting the possibility of securing core technologies needed for semiconductor manufacturing.

Professor Kim said, "This research is an original case that demonstrates that the concept of sandpaper, which is commonly used in everyday life, can be extended to the nano scale and applied to ultra-fine semiconductor manufacturing," adding, "We expect that nano sandpaper technology will not only enhance semiconductor performance but also enable environmentally friendly manufacturing processes."

Meanwhile, Dr. Kang Sukkyung of the KAIST Department of Mechanical Engineering participated in this research as the first author. The research results (paper) were recently published online in the international journal Advanced Composites and Hybrid Materials, which focuses on composite materials and nanoengineering.

This content was produced with the assistance of AI translation services.