Mechanism of the Local Cu Protrusion in Cu-Filled Through Silicon Vias Under Heat Treatment
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Reliability of through silicon via (TSV) structures is a critical issue in the industrialization of TSV technology. One of the most important problems for TSV reliability is the thermal stress induced by a large coefficient of thermal expansion mismatch between different materials in the TSV structure. This mismatch could seriously deteriorate the performance of the TSVs, and even lead to failure. Here, the influence of heating temperature on the microstructure evolution in the TSV structure was investigated. The microstructures of Cu-filled TSV samples under different annealing conditions were characterized, and the phenomenon of global Cu protrusion and local grain-like Cu protrusion were observed in Cu-filled TSVs. Mechanisms of Cu protrusion in TSVs during heat treatment were analyzed, and possible factors involving thermal stress, grain growth, and void formation are discussed. The results showed that the origin of local grain-like TSV-Cu protrusion might be related to grain growth of Cu and the elastic modulus mismatch between coarse Cu grains.
KeywordsThrough silicon via reliability Cu protrusion voiding elastic modulus
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The authors thank the support of the Beijing Nova Program (Z161100004916155), Natural Science Foundation of Beijing Municipality (2172006 and 2172009), Beijing Municipal Excellent Talents Foundation (CIT&TCD201804007), and General Project of Science and Technology of Beijing Municipal Education Commission (SQKM201610005024).
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