aalto1 untyped-item.component.html
Low-temperature solid-liquid interdiffusion bonding for heterogeneous integration
Loading...
URL
Journal Title
Journal ISSN
Volume Title
School of Electrical Engineering |
Doctoral thesis (article-based)
| Defence date: 2025-02-28
Electronic archive copy is available via Aalto Thesis Database.
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
Major/Subject
Mcode
Degree programme
Language
en
Pages
68 + app. 45
Series
Aalto University publication series Doctoral Theses, 24/2025
Abstract
There has been a notable transition in the electronics industry towards the heterogeneous integration strategy to achieve a compact yet multifunctional devices. However, this approach present challenges when incorporating materials with differing characteristics, particularly regarding temperature-induced constraints for the assembly process. Low-temperature bonding techniques are one of the key technologies to address this problem and fully realize the potential of heterogeneous integration. Among the numerous bonding methods, this dissertation explores the low-temperature bonding processes based on the solid–liquid interdiffusion (SLID) technique utilizing Cu–Sn–In metallurgy. The eutectic behaviour of Sn–In allows a significant reduction of the bonding temperatures from a typical bonding temperature above 250 °C down to 150 °C.
Microstructural characterization of the bonds formed at temperatures between 150 °C and 200 °C reveals a homogeneous interconnect featuring an intermetallic phase with a remelting temperature above 450 °C, which makes it thermally stable. Electrical measurements confirm the interconnects’ small resistance that is comparable to those obtained from well-known Cu–Sn bonding technique, underscoring the capability of this low-temperature process for vertical integration. Hermeticity assessment, conducted using seal-ring shaped bond, highlight the technique’s potential for microelectromechanical system (MEMS) or micro-optoelectromechanical system (MOEMS) packaging. Moreover, the bond exhibited tensile strength of a similar magnitude with the popular Cu–Cu thermocompression bonding method.
Some challenges in the implementation of the low-temperature bonding process have been identified, including limitations for process integration, squeeze-out, and defect formations. These issues can be mitigated through optimization of the design and processing parameters. Despite these challenges, the results from this work highlight the prospect to fully demonstrate the capabilities of heterogeneous integration by addressing temperature-induced limitations.
Description
Supervising professor
Paulasto-Kröckel, Mervi, Prof., Aalto University, Department of Electrical Engineering and Automation, FinlandThesis advisor
Vuorinen, Vesa, Dr., Aalto University, Department of Electrical Engineering and Automation, FinlandOther note
Parts
- [Publication 1]: O. Golim, V. Vuorinen, N. Tiwary, R. Glenn, and M. Paulasto-Kröckel, "Lowtemperature Metal Bonding for Optical Device Packaging," in 23rd European Microelectronics and Packaging Conference & Exhibition, Gothenburg, Sweden 2021: IEEE, pp. 1-4.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-2021123111201DOI: 10.23919/EMPC53418.2021.9585007 View at publisher
- [Publication 2]: O. Golim, V. Vuorinen, G. Ross, T. Wernicke, M. Pawlak, N. Tiwary, M. Paulasto-Kröckel, "Achieving low-temperature wafer level bonding with Cu– Sn–In ternary at 150 °C," Scripta Materialia., vol. 222, pp. 1-3, 2023.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202209075348DOI: 10.1016/j.scriptamat.2022.114998 View at publisher
- [Publication 3]: O. Golim, V. Vuorinen, T. Wernicke, M. Pawlak, and M. Paulasto-Kröckel, "Low-Temperature Wafer-Level Bonding with Cu-Sn-In Solid Liquid Inter-diffusion for Microsystem Packaging," Microelectronics Engineering, vol. 286, no. 112140, pp. 1-9, 2024.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202402072372DOI: 10.1016/j.mee.2024.112140 View at publisher
- [Publication 4]: O. Golim, V. Vuorinen, G. Ross, S. Suihkonen, and M. Paulasto-Kröckel, "Investigative characterization of delamination at TiW–Cu interface in low-temperature bonded interconnects," Materials Characterization, vol. 209, 2024.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202403062528DOI: 10.1016/j.matchar.2024.113772 View at publisher
- [Publication 5]: O. Golim, V. Vuorinen, M. Paulasto-Kröckel, "Facilitating Small Pitch Interconnects with Low-Temperature Solid-Liquid Interdiffusion Bonding,", is conditionally accepted in IEEE Transactions on Component, Packaging, and Manufacturing Technology, November 2024.
DOI: 10.1109/TCPMT.2025.3540665 View at publisher