• Journal of the Microelectronics and Packaging Society
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• v.28 no.3
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• pp.9-15
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• 2021

Miniaturization of semiconductor devices has recently faced a physical limitation. To overcome this, 3D packaging in which semiconductor devices are vertically stacked has been actively developed. 3D packaging requires three unit processes of TSV, wafer grinding, and bonding, and among these, copper bonding is becoming very important for high performance and fine-pitch in 3D packaging. In this study, the effects of Ti nanolayer on the antioxidation of copper surface and low-temperature Cu bonding was investigated. The diffusion rate of Ti into Cu is faster than Cu into Ti in the temperature ranging from room temperature to 200℃, which shows that the titanium nanolayer can be effective for low-temperature copper bonding. The 12nm-thick titanium layer was uniformly deposited on the copper surface, and the surface roughness (R_q) was lowered from 4.1 nm to 3.2 nm. Cu bonding using Ti nanolayer was carried out at 200℃ for 1 hour, and then annealing at the same temperature and time. The average shear strength measured after bonding was 13.2 MPa.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.91-97
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• 2022

The wettability and rheological properties of solder paste with the size of the solder powder were evaluated. To formulate the solder paste, three types of solder powder were used: T4 (20~28 ㎛), T5 (15~25 ㎛), and T6 (5~15 ㎛). The viscosities of the T4, T5, and T6 solder pastes at 10 RPM were 155, 263, and 418 Pa·s, respectively. After 7 days, the viscosity of the T4 solder paste slightly increased by 2.6% and that of T5 was increased by 20.6%. The viscosity of the T6 solder paste after 7 days could not be measured due to high viscosity. The viscosity variation with solder particle size also affected on the printability of the solder. In the case of the T4 solder paste, printability, slump, bridging, and soldering properties were excellent. On the other hand, T5 showed slight dewetting and solder ball defects. Especially, T6, which the smallest powder size, showed poor printability and dewetting at the edge of solder.