Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper

Jing Ye Juang; Kai Cheng Shie; Po-Ning Hsu; Yu Jin Li; K. N. Tu; Chih Chen

doi:10.1109/ECTC.2019.00102

Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper

Jing Ye Juang^*
, Kai Cheng Shie
, Po-Ning Hsu
, Yu Jin Li
, K. N. Tu
, Chih Chen

^*Corresponding author for this work

Research output: Chapters, Conference Papers, Creative and Literary Works › RGC 32 - Refereed conference paper (with host publication) › peer-review

18 Citations (Scopus)

Abstract

In this study, we fabricated (111)-oriented nt-Cu microbumps with 30 μm in diameter, and bonded them together using chip-to-chip bonding scheme in N₂ ambient, without vacuum. A well bonded interface in the Cu-to-Cu joint was identified by the microstructure observation. Scanning electron microscope (SEM) images showed a void-less bonding interface within the bonded Cu joint. In addition, a die shear test was conducted. The test results revealed that the shear strength is 124 MPa, which is nearly two times higher than the SnAg solder joint (64 MPa). It indicates that the Cu joint is more robust than the SnAg joint. In addition, fracture analysis showed that the joint fractured in a ductile manner. Besides, we also performed the resistance measurement by using Kelvin probes on the bonded chip-to-chip test vehicles. The resistance is 4.12 mΩ for a single joint and its contact resistivity is 4.26 × 10^-8 Ω·cm². More than 30% resistance reduction has been confirmed as compared to the SnAg solder joint (6.32 mΩ). Moreover, we can further reduce the joint resistance by the second annealing process. The resistance can be brought down to 3.27 mΩ with a resistivity of 3.14 × 10^-8 Ω·cm². There is a nearly 50% resistance reduction, as compared to SnAg solder joint. The resistance value after the second annealed Cu joint is close an ideal Cu joint. In summary, low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper has been successfully achieved. © 2019 IEEE

Original language	English
Title of host publication	Proceedings - ECTC: The 2019 IEEE 69th Electronic Components and Technology Conference
Publisher	IEEE
Pages	642-647
ISBN (Electronic)	9781728114989, 978-1-7281-1499-6
ISBN (Print)	978-1-7281-1500-9
DOIs	https://doi.org/10.1109/ECTC.2019.00102
Publication status	Published - 2019
Externally published	Yes
Event	69th IEEE Electronic Components and Technology Conference (ECTC 2019) - The Cosmopolitan of Las Vegas, Las Vegas, United States Duration: 28 May 2019 → 31 May 2019 https://www.ectc.net/about/69highlights.cfm

Publication series

Name	Proceedings - Electronic Components and Technology Conference
ISSN (Print)	0569-5503
ISSN (Electronic)	2377-5726

Conference

Conference	69th IEEE Electronic Components and Technology Conference (ECTC 2019)
Place	United States
City	Las Vegas
Period	28/05/19 → 31/05/19
Internet address	https://www.ectc.net/about/69highlights.cfm

Research Keywords

Cu joint resistance
Cu-to-Cu direct bonding
Fracture modes
Grain growth
Nanotwinned Cu
Shear strength
Surface diffusion creep

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10.1109/ECTC.2019.00102

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Juang, J. Y., Shie, K. C., Hsu, P.-N., Li, Y. J., Tu, K. N., & Chen, C. (2019). Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper. In Proceedings - ECTC: The 2019 IEEE 69th Electronic Components and Technology Conference (pp. 642-647). (Proceedings - Electronic Components and Technology Conference). IEEE. https://doi.org/10.1109/ECTC.2019.00102

@inproceedings{257ac5b6a115470b8ce1acf06c502085,

title = "Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper",

abstract = "In this study, we fabricated (111)-oriented nt-Cu microbumps with 30 μm in diameter, and bonded them together using chip-to-chip bonding scheme in N2 ambient, without vacuum. A well bonded interface in the Cu-to-Cu joint was identified by the microstructure observation. Scanning electron microscope (SEM) images showed a void-less bonding interface within the bonded Cu joint. In addition, a die shear test was conducted. The test results revealed that the shear strength is 124 MPa, which is nearly two times higher than the SnAg solder joint (64 MPa). It indicates that the Cu joint is more robust than the SnAg joint. In addition, fracture analysis showed that the joint fractured in a ductile manner. Besides, we also performed the resistance measurement by using Kelvin probes on the bonded chip-to-chip test vehicles. The resistance is 4.12 mΩ for a single joint and its contact resistivity is 4.26 × 10-8 Ω·cm2. More than 30\% resistance reduction has been confirmed as compared to the SnAg solder joint (6.32 mΩ). Moreover, we can further reduce the joint resistance by the second annealing process. The resistance can be brought down to 3.27 mΩ with a resistivity of 3.14 × 10-8 Ω·cm2. There is a nearly 50\% resistance reduction, as compared to SnAg solder joint. The resistance value after the second annealed Cu joint is close an ideal Cu joint. In summary, low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper has been successfully achieved. {\textcopyright} 2019 IEEE",

keywords = "Cu joint resistance, Cu-to-Cu direct bonding, Fracture modes, Grain growth, Nanotwinned Cu, Shear strength, Surface diffusion creep",

author = "Juang, \{Jing Ye\} and Shie, \{Kai Cheng\} and Po-Ning Hsu and Li, \{Yu Jin\} and Tu, \{K. N.\} and Chih Chen",

year = "2019",

doi = "10.1109/ECTC.2019.00102",

language = "English",

isbn = "978-1-7281-1500-9",

series = "Proceedings - Electronic Components and Technology Conference",

publisher = "IEEE",

pages = "642--647",

booktitle = "Proceedings - ECTC : The 2019 IEEE 69th Electronic Components and Technology Conference",

address = "United States",

note = "69th IEEE Electronic Components and Technology Conference (ECTC 2019) ; Conference date: 28-05-2019 Through 31-05-2019",

url = "https://www.ectc.net/about/69highlights.cfm",

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Juang, JY, Shie, KC, Hsu, P-N, Li, YJ, Tu, KN & Chen, C 2019, Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper. in Proceedings - ECTC: The 2019 IEEE 69th Electronic Components and Technology Conference. Proceedings - Electronic Components and Technology Conference, IEEE, pp. 642-647, 69th IEEE Electronic Components and Technology Conference (ECTC 2019), Las Vegas, Nevada, United States, 28/05/19. https://doi.org/10.1109/ECTC.2019.00102

Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper. / Juang, Jing Ye; Shie, Kai Cheng; Hsu, Po-Ning et al.
Proceedings - ECTC: The 2019 IEEE 69th Electronic Components and Technology Conference. IEEE, 2019. p. 642-647 (Proceedings - Electronic Components and Technology Conference).

Research output: Chapters, Conference Papers, Creative and Literary Works › RGC 32 - Refereed conference paper (with host publication) › peer-review

TY - GEN

T1 - Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper

AU - Juang, Jing Ye

AU - Shie, Kai Cheng

AU - Hsu, Po-Ning

AU - Li, Yu Jin

AU - Tu, K. N.

AU - Chen, Chih

PY - 2019

Y1 - 2019

N2 - In this study, we fabricated (111)-oriented nt-Cu microbumps with 30 μm in diameter, and bonded them together using chip-to-chip bonding scheme in N2 ambient, without vacuum. A well bonded interface in the Cu-to-Cu joint was identified by the microstructure observation. Scanning electron microscope (SEM) images showed a void-less bonding interface within the bonded Cu joint. In addition, a die shear test was conducted. The test results revealed that the shear strength is 124 MPa, which is nearly two times higher than the SnAg solder joint (64 MPa). It indicates that the Cu joint is more robust than the SnAg joint. In addition, fracture analysis showed that the joint fractured in a ductile manner. Besides, we also performed the resistance measurement by using Kelvin probes on the bonded chip-to-chip test vehicles. The resistance is 4.12 mΩ for a single joint and its contact resistivity is 4.26 × 10-8 Ω·cm2. More than 30% resistance reduction has been confirmed as compared to the SnAg solder joint (6.32 mΩ). Moreover, we can further reduce the joint resistance by the second annealing process. The resistance can be brought down to 3.27 mΩ with a resistivity of 3.14 × 10-8 Ω·cm2. There is a nearly 50% resistance reduction, as compared to SnAg solder joint. The resistance value after the second annealed Cu joint is close an ideal Cu joint. In summary, low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper has been successfully achieved. © 2019 IEEE

AB - In this study, we fabricated (111)-oriented nt-Cu microbumps with 30 μm in diameter, and bonded them together using chip-to-chip bonding scheme in N2 ambient, without vacuum. A well bonded interface in the Cu-to-Cu joint was identified by the microstructure observation. Scanning electron microscope (SEM) images showed a void-less bonding interface within the bonded Cu joint. In addition, a die shear test was conducted. The test results revealed that the shear strength is 124 MPa, which is nearly two times higher than the SnAg solder joint (64 MPa). It indicates that the Cu joint is more robust than the SnAg joint. In addition, fracture analysis showed that the joint fractured in a ductile manner. Besides, we also performed the resistance measurement by using Kelvin probes on the bonded chip-to-chip test vehicles. The resistance is 4.12 mΩ for a single joint and its contact resistivity is 4.26 × 10-8 Ω·cm2. More than 30% resistance reduction has been confirmed as compared to the SnAg solder joint (6.32 mΩ). Moreover, we can further reduce the joint resistance by the second annealing process. The resistance can be brought down to 3.27 mΩ with a resistivity of 3.14 × 10-8 Ω·cm2. There is a nearly 50% resistance reduction, as compared to SnAg solder joint. The resistance value after the second annealed Cu joint is close an ideal Cu joint. In summary, low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper has been successfully achieved. © 2019 IEEE

KW - Cu joint resistance

KW - Cu-to-Cu direct bonding

KW - Fracture modes

KW - Grain growth

KW - Nanotwinned Cu

KW - Shear strength

KW - Surface diffusion creep

UR - https://www.scopus.com/pages/publications/85072302774

UR - https://www.scopus.com/record/pubmetrics.uri?eid=2-s2.0-85072302774&origin=recordpage

U2 - 10.1109/ECTC.2019.00102

DO - 10.1109/ECTC.2019.00102

M3 - RGC 32 - Refereed conference paper (with host publication)

SN - 978-1-7281-1500-9

T3 - Proceedings - Electronic Components and Technology Conference

SP - 642

EP - 647

BT - Proceedings - ECTC : The 2019 IEEE 69th Electronic Components and Technology Conference

PB - IEEE

T2 - 69th IEEE Electronic Components and Technology Conference (ECTC 2019)

Y2 - 28 May 2019 through 31 May 2019

ER -

Juang JY, Shie KC, Hsu PN, Li YJ, Tu KN, Chen C. Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper. In Proceedings - ECTC: The 2019 IEEE 69th Electronic Components and Technology Conference. IEEE. 2019. p. 642-647. (Proceedings - Electronic Components and Technology Conference). Epub 2019 Aug 26. doi: 10.1109/ECTC.2019.00102

Low-resistance and high-strength copper direct bonding in no-vacuum ambient using highly (111)-oriented nano-twinned copper

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