Current density effects on the electrical reliability of ultra fine-pitch micro-bump for TSV integration

Electromigration tests of SnAg solder bump samples with 15 µm bump height and Cu under-bump-metallization (UBM) were performed. The test conditions were 1.45ˆ10 4 A/cm 2 at 185˝C and 1.20ˆ10 4 A/cm 2 at 0˝C. A porous Cu 3 Sn intermetallic compound (IMC) structure was observed to form within the bumps after several hundred hours of current stressing. In direct comparison, annealing alone at 185˝C will take more than 1000 h for porous Cu 3 Sn to form, and it will not form at 170˝C even after 2000 h. Here we propose a mechanism to explain the formation of this porous structure assisted by electromigration. The results show that the SnAg bump with low bump height will become porous-type Cu 3 Sn when stressing with high current density and high temperature. Polarity effects on porous Cu 3 Sn formation is discussed.

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“…Park et al reported that a high stressing current may lead to a serious side wall reaction effect [16]. Figure 6a shows the side wall of a bump.…”

Section: Formation Of Porous Cu3snmentioning

confidence: 99%

Formation Mechanism of Porous Cu3Sn Intermetallic Compounds by High Current Stressing at High Temperatures in Low-Bump-Height Solder Joints

Lin

Liu

et al. 2016

Crystals

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“…This phenomenon is similar to resistance change of general micro-bumps. The diameter of the flip-chip solder bump is larger than that of the micro-bump so the current density through the flipchip solder bump is less than the micro-bump [10]. Thus, the high current density of micro-bumps results in faster IMC formation and growth and leads to the rapid resistance change of the micro-bump [10].…”

Section: Resultsmentioning

confidence: 94%

“…Therefore, these structures are observed using the in-situ SEM during current stressing. Figure 3 showed the enlarged BSE image of the crosssectioned Cu/Sn-Ag micro-bump interface before and after current stressing at 1.5×10 5 A/cm 2 , 150℃ for 150h [10]. Most of Sn was transformed into the Cu 6 Sn 5 phase ( Figure 3b).…”

Section: Methodsmentioning

confidence: 96%

“…The schematic structure of (a) Cu/Sn-Ag microbump [10], (b) Cu/Ni/Sn-Ag micro-bump Figure 1(b) is Cu pillar/ Ni/ Sn-Ag structure. Cu, Ni and Sn-Ag layer are formed by electroplating.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, the excessive IMC growth in micro-bump can degrade the mechanical and electrical reliability. Therefore, it is essential to understand the fundamental mechanisms of IMC growth kinetics [10].…”

Section: Introductionmentioning

confidence: 99%

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Structure effects on the electrical reliability of fine-pitch Cu micro-bumps for 3D integration

Lee

Kim

et al. 2014

2014 IEEE 64th Electronic Components and Technology Conference (ECTC)

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Recently, flip chip solder bumps have been replaced by the fine-pitch solder micro-bump due to the miniaturization of electronic devices and the high performance requirement, and so on. Because of the fast decreasing size of the micro-bump and increasing power consumption needs in logic through-Si via applications, the significance of electromigration among major reliability issues have been increased. There are several important electrical current-induced reliability issues such as current crowding, polarity effect and thermomigration. And the excessive intermetallic compound (IMC) growth and Kirkendall voiding or micro voiding in micro-bump can degrade the mechanical reliability as well as electrical reliability. Therefore, the understanding of fundamental IMC growth mechanism is essential. This study systematically investigated the effects of bump structures such as solder height and UBM structure on the IMC growth kinetics and electromigration performance of Cu micro-bump. Quantitative analyses on the IMC growth kinetics during in-situ electromigration test were performed in a scanning electron microscope chamber under current stressing conditions with current density of 1.5 x 10 5 A/cm 2 at 150℃. Under high temperature and electric current stressing, the IMCs growth is accelerated by electron wind force. And the IMC phase transition time became shorter because IMC growth rates increased. In Cu/Sn-Ag and Cu/Ni/Sn-Ag system, the effect of current crowding and Joule heating was negligible in fully IMC-transformed micro-bump. Finally, microvoid formation mechanisms during IMC growth in the Cu/Ni/thin Sn system were discussed in detail.

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Effect of Joule heating on the reliability of microbumps in 3D IC

Yao,

An,

Dong

et al. 2024

Journal of Materials Research and Technology

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Current density effects on the electrical reliability of ultra fine-pitch micro-bump for TSV integration

Cited by 6 publications

References 16 publications

Formation Mechanism of Porous Cu3Sn Intermetallic Compounds by High Current Stressing at High Temperatures in Low-Bump-Height Solder Joints

Formation Mechanism of Porous Cu3Sn Intermetallic Compounds by High Current Stressing at High Temperatures in Low-Bump-Height Solder Joints

Structure effects on the electrical reliability of fine-pitch Cu micro-bumps for 3D integration

Effect of Joule heating on the reliability of microbumps in 3D IC

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