2018, Volume 13, Issue 3
Frontiers of Mechanical Engineering >> 2018, Volume 13, Issue 3 doi: 10.1007/s11465-017-0457-7
Analysis on annealing-induced stress of blind-via TSV using FEM
1. State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
2. School of Mechanical Engineering, Jiangnan University, Wuxi 214122, China.
3. School of Mechanical and Electrical Engineering, Jiangsu Normal University, Xuzhou 221116, China
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Abstract
Copper-filled through silicon via (TSV) is a promising material owing to its application in high-density three-dimensional (3D) packaging. However, in TSV manufacturing, thermo-mechanical stress is induced during the annealing process, often causing reliability issues. In this paper, the finite element method is employed to investigate the impacts of via shape and SiO2 liner uniformity on the thermo-mechanical properties of copper-filled blind-via TSV after annealing. Top interface stress analysis on the TSV structure shows that the curvature of via openings releases stress concentration that leads to ~60 MPa decrease of normal stresses, sxx and syy, in copper and ~70 MPa decrease sxx of in silicon. Meanwhile, the vertical interface analysis shows that annealing-induced stress at the SiO2/Si interface depends heavily on SiO2 uniformity. By increasing the thickness of SiO2 linear, the stress at the vertical interface can be significantly reduced. Thus, process optimization to reduce the annealing-induced stress becomes feasible. The results of this study help us gain a better understanding of the thermo-mechanical behavior of the annealed TSV in 3D packaging.
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