Korea Takes Early Lead in 'Ultrafine Competition'... Semiconductor Packaging Technology Innovation

KAIST Research Team Achieves 27% Reduction in Bending and 40% Increase in Strength Compared to Existing Materials

Domestic researchers have succeeded in innovating semiconductor packaging technology that can gain an edge in the increasingly intense competition in semiconductor ultra-fine technology.

KAIST announced on the 2nd that Professor Seongsu Kim's research team from the Department of Mechanical Engineering at KAIST, together with Professor Brian Wardle's research team from the Massachusetts Institute of Technology (MIT), succeeded in developing a "curing process based on bonding temperature control to enhance the reliability of semiconductor packages."

Semiconductor packaging is a post-process after semiconductor manufacturing, gaining attention as a next-generation technology as the miniaturization of circuits in the front-end process reaches its limits. It refers to the process of connecting multiple semiconductor chips into one and protecting them from external environments. The temperature of the semiconductor package is also important because if the temperature of semiconductor components rises, the semiconductor's lifespan drastically decreases and it may stop functioning.

The main material of semiconductor packages, EMC, undergoes a chemical reaction and hardens when heated; this phenomenon is called a curing reaction. During the curing process, changes in temperature and pressure over time cause warpage due to differences in thermal contraction between materials after the process as the thickness of the semiconductor package becomes thinner. To solve this problem, the research team developed a curing process that can accurately predict the bonding temperature between EMC and the substrate and control the warpage phenomenon.

EMC curing process system based on bonding temperature consisting of rapid cooling and reheating. Image source: Provided by KAIST

In this study, the research team developed an EMC curing process technology based on bonding temperature control that rapidly lowers the temperature just before the bonding of the two materials occurs to reduce the bonding temperature of the semiconductor package. Thermosetting polymer EMC, when rapidly cooled to room temperature just before bonding with the substrate during the curing process, suppresses the curing reaction and induces the bonding temperature close to room temperature. Subsequently, EMC can be fully cured through reheating. This process reduces the difference between the bonding temperature and the operating temperature of the package, minimizing length changes caused by differences in thermal contraction between elements and thus reducing warpage. For this, it is important to analyze the exact bonding temperature between the two materials. The research team derived a formula to calculate the bonding temperature considering the chemical shrinkage of EMC occurring during the curing process and verified it using a strain measurement system.

Through the new curing process that introduces rapid cooling just before the precisely measured bonding temperature, warpage of the semiconductor package decreased by 27% compared to the conventional EMC curing process, and the mechanical strength at the EMC-substrate interface increased by about 40%. Additionally, the mechanical properties of EMC subjected to the curing process including rapid cooling showed no difference from those of the conventional process.

Professor Kim explained, "The new EMC curing process based on bonding temperature control solved the warpage issue, which has been continuously emerging in semiconductor packages that are becoming thinner and smaller," adding, "It will be a foundational technology that not only improves the yield of semiconductor packages but also enhances durability."

This research was published on March 1 in the international academic journal ‘ACS Applied Materials & Interfaces.’

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