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

Lin, Jie An; Lin, Chung‐Kuang; Liu, Chen Min; Huang, Yongheng; Chen, Chih; Chu, David S.H.; Tu, King‐Ning

doi:10.3390/cryst6010012

Cited by 28 publications

(8 citation statements)

References 17 publications

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“…Figure 18 shows the cross-section morphology of the interface between the Cu and Sn layers in the samples with and without the TFMG barrier layer just after solder joining and after aging at 125 • C for 500 h. In the sample without the barrier layer, bilayer IMCs with a thick scallop-like Cu 6 Sn 5 of 7-8 µm close to the Sn matrix and a thin Cu 3 Sn of 0.5 µm close to the Cu substrate were formed at both interfaces after solder joining. These experimental results are in good agreement with the data in the literature [44]. When aged at 125 • C after 500 h, the interfacial Cu 6 Sn 5 and Cu 3 Sn IMCs grew to 9-10 µm and 0.5-1 µm in thickness, respectively.…”

Section: Imc Formation With Different Barrier Layers Via Experimentssupporting

confidence: 92%

Material Properties of Zr–Cu–Ni–Al Thin Films as Diffusion Barrier Layer

Sung

Chen

2020

Crystals

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Due to the rapid increase in current density encountered in new chips, the phenomena of thermomigration and electromigration in the solder bump become a serious reliability issue. Currently, Ni or TiN, as a barrier layer, is widely academically studied and industrially accepted to inhibit rapid copper diffusion in interconnect structures. Unfortunately, these barrier layers are polycrystalline and provide inadequate protection because grain boundaries may presumably serve as fast diffusion paths for copper and could react to form Cu–Sn intermetallic compounds (IMCs). Amorphous metallic films, however, have the potential to be the most effective barrier layer for Cu metallization due to the absence of grain boundaries and immiscibility with copper. In this article, the diffusion properties, the strength of the interface between polycrystalline and amorphous ZrCuNiAl thin film, and the effects of quenching rate on the internal microstructures of amorphous metal films were individually investigated by molecular dynamics (MD) simulation. Moreover, experimental data of the diffusion process for three different cases, i.e., without barrier layer, with an Ni barrier layer, and with a Zr53Cu30Ni9Al8 thin film metallic glass (TFMG) barrier layer, were individually depicted. The simulation results show that, for ZrCuNiAl alloy, more than 99% of the amorphous phase at a quenching rate between 0.25 K/ps and 25 K/ps can be obtained, indicating that this alloy has superior glass-forming ability. The simulation of diffusion behavior indicated that a higher amorphous ratio resulted in better barrier performance. Moreover, a very small and uniformly distributed strain appears in the ZrCuNiAl layer in the simulation of the interfacial tension test; however, almost all the voids are initiated and propagated in the Cu layer. These phenomena indicate that the strength of the ZrCuNiAl/Cu interface and ZrCuNiAl layer is greater than polycrystalline Cu. Experimental results show that the Zr53Cu30Ni9Al8 TFMG layer exhibits a superior barrier effect. Almost no IMCs appear in this TFMG barrier layer even after aging at 125 °C for 500 h.

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Section: Imc Formation With Different Barrier Layers Via Experimentssupporting

confidence: 92%

Material Properties of Zr–Cu–Ni–Al Thin Films as Diffusion Barrier Layer

Sung

Chen

2020

Crystals

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“… Scanning electron microscopy (SEM) images of Cu/Sn diffusion coupled with Kirkendall void formation at the Cu 3 Sn layer (a) without electromigration effect [ 76 ] and (b) with electromigration effect [ 95 ]. …”

Section: Reliability Issues Concerning Imcsmentioning

confidence: 99%

Intermetallic compounds in 3D integrated circuits technology: a brief review

Annuar

Mahmoodian

Hamdi

et al. 2017

Science and Technology of Advanced Materials

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The high performance and downsizing technology of three-dimensional integrated circuits (3D-ICs) for mobile consumer electronic products have gained much attention in the microelectronics industry. This has been driven by the utilization of chip stacking by through-Si-via and solder microbumps. Pb-free solder microbumps are intended to replace conventional Pb-containing solder joints due to the rising awareness of environmental preservation. The use of low-volume solder microbumps has led to crucial constraints that cause several reliability issues, including excessive intermetallic compounds (IMCs) formation and solder microbump embrittlement due to IMCs growth. This article reviews technologies related to 3D-ICs, IMCs formation mechanisms and reliability issues concerning IMCs with Pb-free solder microbumps. Finally, future outlook on the potential growth of research in this area is discussed.

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“…Therefore, the equation: Cu 6 Sn 5 → 2 Cu 3 Sn + 3 Sn would become Cu 6 Sn 5 → 2 Cu 3 Sn + void which the void ratio was 41.4% calculated by material density. [12] Based on the conditions, an ideal cubic unit cell representing the effective porous Cu 3 Sn was shown in the Fig.6a. There were 8 voids at corners and 6 voids in the 6 sides representing uniform porous structure.…”

Section: Td2-2mentioning

confidence: 99%

Electromigration in microbumps with Cu-Sn intermetallic compounds

Chu

Zhan

Lin

et al. 2016

2016 International Conference on Electronics Packaging (ICEP)

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The electromigration test of the microbump interconnects with Cu/Cu6Sn5/Cu structure is reported in this study. This Cu6Sn5 intermetallic compound layer was singlecrystal like. The diameter of the microbumps in die-to-die stacking was 30 μm. Test vehicles were applied by a current density of 2.2x10 5 A/cm 2 and settled on a hotplate at 150 o C. The resistances of the microbumps were simultaneously monitored by the four point probe during the test procedure. The Cu6Sn5 transformed into Cu3Sn in the early stage and porous Cu3Sn generated in the Cu6Sn5 layer at later stages. The morphology of porous Cu3Sn could be caused by the current direction. The decomposition of Cu6Sn5 into Cu3Sn and Sn occurs during the EM test. The migration of Sn atoms to the periphery of the underbump-metallization was forced by the current stress, which may be the mechanism of the pore formation with the pore volume of 41.4%. More porous Cu3Sn was found in the cathode end which was an evidence of the EM effect. Finite element analysis was used to do some calculation based on theoretical stoichiometry and microstructures in the test results. The resistivity of porous Cu3Sn structure which was about 30 μΩ−cm which was three times larger than that of Cu3Sn. The porous Cu3Sn may threaten the reliability issues of microbumps.

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

Cited by 28 publications

References 17 publications

Material Properties of Zr–Cu–Ni–Al Thin Films as Diffusion Barrier Layer

Material Properties of Zr–Cu–Ni–Al Thin Films as Diffusion Barrier Layer

Intermetallic compounds in 3D integrated circuits technology: a brief review

Electromigration in microbumps with Cu-Sn intermetallic compounds

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