In-situ AFM observation of enhanced thermal expansion in downscaled nanotwinned-Cu/SiO2 vias for 3D IC integration
Three-dimensional integrated circuit (3D IC) packaging offers viable solutions to sustain Moore's Law. Hybrid bonding, a key process in 3D IC packaging, enables high-density interconnections between stacked chips but faces fabrication challenges as the pitch continues to scale down. This study...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-05-01
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| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425013353 |
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| Summary: | Three-dimensional integrated circuit (3D IC) packaging offers viable solutions to sustain Moore's Law. Hybrid bonding, a key process in 3D IC packaging, enables high-density interconnections between stacked chips but faces fabrication challenges as the pitch continues to scale down. This study explores the use of nanotwinned Cu (NT-Cu) to enhance hybrid bonding. The thermal expansion of NT-Cu pads in SiO2 vias and the effects of downscaling pad size on expansion behaviors were investigated using in-situ heating atomic force microscopy (AFM). At 200 °C, the 3-μm regular Cu pad expanded uniformly by 3.9 nm, while the 3-μm NT-Cu pads exhibited uneven expansion, with the periphery expanding by 11.7 nm and the center expanding by 2.6 nm. Despite the uneven expansion, the enhanced expansion in the 3-μm NT-Cu pad is beneficial for broadening the process window for chemical mechanical planarization (CMP) and hybrid bonding processes. Grain-boundary diffusion was identified as the underlying mechanism behind this behavior. Finally, successful bonding with NT-Cu/SiO2 vias at a low temperature of 200 °C demonstrates their potential for fine-pitch hybrid bonding. |
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| ISSN: | 2238-7854 |