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  4. Vol 7, Issue 1, 2024

Study on Enhancing Adhesion and Reliability in Wafer-Level Fan-Out Packaging

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DOI: 10.23977/jeeem.2024.070112 | Downloads: 1 | Views: 84

Author(s)

Wenjing Cui 1, Ziyu Liu 2, Jieyu Zhou 3, Hongye Liu 1, Yabin Sun 3, Lin Chen 2,4, Qingqing Sun 2

Affiliation(s)

1 School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
2 School of Microelectronics, Fudan University, Shanghai, 200433, China
3 Department of Electrical Engineering, East China Normal University, Shanghai, China
4 State Key Laboratory of Integrated Chips and Systems, Fudan University, Shanghai, China

Corresponding Author

Ziyu Liu

ABSTRACT

Wafer-level Fan-out packaging (FOWLP) with multi-layer redistribution layers (RDL) emerges as a pivotal technology in 3D integration. Polyimide (PI) as an insulation layer in the construction of RDL is essential for FOWLP. The adhesion of PI has become a focal point of multi-layer RDL. This study focuses on solving the adhesion technologies for PI photoresist lithography to achieve four layer RDL. The adhesion of PI to both the complex substrate and varying RDL layouts is investigated as a significant determinant of package reliability, characterized predominantly by surface free energy (SFE). It reveals that improving the substrate morphology by flattening can significantly enhance the PI adhesion, thereby addressing fluctuations caused by temporary bonding defects. Techniques such as CF4 dry etching and optimization of the temporary bonding process were found effective in mitigating substrate imperfections. Furthermore, various surface treatments applied to the RDL layers were investigated to boost the interface adhesion between the RDL and PI. Notably, after subjecting the plated copper to a 180W, 3-minute Argon plasma atmosphere, we observed an increase in roughness to 12 nm and an elevation in SFE to 80.82 mN/m, markedly improving copper surface adhesion. Additionally, employing Plasma-Enhanced Chemical Vapor Deposition (PECVD) to deposit SiO2 on the surface of the RDL layer substantially increased the SFE to 83.1±0.7 mN/m, demonstrating the most significant enhancement in PI adhesion. These advancements propose promising pathways to improve the structural integrity and reliability of FOWLP.

KEYWORDS

Wafer Level Packaging, Plasma, Descum, Adhesion, Surface roughness, Polyimide

CITE THIS PAPER

Wenjing Cui, Ziyu Liu, Jieyu Zhou, Hongye Liu, Yabin Sun, Lin Chen, Qingqing Sun, Study on Enhancing Adhesion and Reliability in Wafer-Level Fan-Out Packaging. Journal of Electrotechnology, Electrical Engineering and Management (2024) Vol. 7: 92-99. DOI: http://dx.doi.org/10.23977/jeeem.2024.070112.

REFERENCES

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[7] Liu W W, Wu L H, Weng B, et al. Plasma Treatment for Robust Interface Adhesion of Wafer Level Packaging[C]//2021 16th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT). IEEE, 2021: 64-67
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