Date of Award

Spring 2026

Language

English

Embargo Period

4-30-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Engineering

First Advisor

Kathleen Dunn

Committee Members

James Lloyd, Christophe Vallee, Vidya Kaushik, Thomas Murray

Keywords

Electroplating, Hybrid Bonding, Low tempertaure, Cu Alloys, Fine grain Cu

Subject Categories

Materials Chemistry | Metallurgy | Nanoscience and Nanotechnology | Nanotechnology Fabrication | Semiconductor and Optical Materials

Abstract

Hybrid bonding has emerged as a key enabler for next-generation three-dimensional (3D) integration, offering fine-pitch interconnects and improved electrical performance. However, conventional Cu–Cu hybrid bonding typically requires elevated temperatures to achieve sufficient diffusion and interface quality, posing challenges for temperature-sensitive device integration and process compatibility. This work investigates materials engineering approaches to enable low-temperature Cu–Cu bonding through both microstructure design and alloying strategies.

This work begins by examining grain refinement in Cu as a pathway to enhance diffusion through increased grain boundary density, providing efficient atomic transport without introducing additional elements. Three Cu-based systems Cu–Co, Cu–Ag, and Cu–Al were systematically studied to understand the role of alloying and diffusion behavior on mechanical, thermal, and structural properties. Co-deposited Cu–Co and Cu–Ag alloys were investigated to understand their influence on grain structure and diffusion behavior along with their impact on electrical performance. Additionally, a Cu–Al bi-layer anneal approach was employed to study an alternative alloying pathway that avoids complex chemistries, offering a more scalable and fabrication-friendly solution due to the widespread use and compatibility of Al in semiconductor processing. A combination of advanced characterization techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and nanoindentation, was used to establish correlations between microstructure, composition, and properties. Diffusion behavior was analyzed to distinguish between lattice and grain boundary contributions, highlighting the critical role of microstructural pathways in enabling low-temperature bonding.

The results demonstrate that both microstructure engineering through grain refinement and controlled alloying can significantly enhance atomic mobility and bonding performance at reduced temperatures. These approaches provide complementary pathways toward reliable, scalable hybrid bonding. The findings offer insight into materials-driven strategies for next-generation interconnect technologies and support the development of low-temperature 3D integration platforms for advanced electronic systems.

License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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