Mechanical Integrity of Hybrid Bonding

(22:42 + Q&A) Oguzhan Orkut Okudur, imec
From the 2024 IEEE Symposium on Reliability for Electronics and Photonics Packaging
Summary: As the demand for high-performance chips grows, we approach the limits of transistor scaling and turn to 3D integration to enhance power and performance. One promising technique is direct wafer-to-wafer bonding, or hybrid bonding, which allows dies or wafer stacking at room temperature using the Van der Waals attraction forces between clean dielectric surfaces. One of the primary challenges in direct wafer-to-wafer bonding is managing the mechanical aspects of the process. During bonding, the wafers are deformed mechanically resulting in misalignment and distortions that limits the yield of the process. These deformations are influenced by factors such as tool configurations, residual stresses, wafer warpage, and surface adhesion. Experimental approaches to optimize all these variables are often time-consuming and costly, therefore, simulations can help us better understand bonding dynamics and the deformation mechanisms involved. We will also present some thermal-mechanical stress and strain analysis at the nanoscale level, particularly the impact of this stress at extremely scaled Cu hybrid bond pads. From our experimental and modeling experience, when scaling bond pads from pitches above 2 ?m to pitches below 500 nm, the dominant mechanism for pad contacting shifts from elasto-plastic expansion to surface diffusion.
Finally, another critical aspect of hybrid bonding is the measurement of bond strength between wafers. Surface roughness, chemical composition, and post-bonding treatments all affect bonding integrity. Therefore, developing accurate characterization methods is essential to optimize processes and ensure reliability in the final devices. In this presentation we will compare different methods for evaluating the interface adhesion energy of hybrid bonded wafers with silicon carbon nitride (SiCN) as primary bonding surface.
Bio: Oguzhan Orkut Okudur has been working in the field of mechanical reliability of semiconductors since 2011. He received his PhD degree from the University of Leuven (Belgium) in the field of materials engineering and has been working at imec’s mechanical modeling and characterization team for the last 10 years, currently as the R&D Team Leader.

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