Process and Reliability of Cu-SiO2 Hybrid Bonds for 3D IC Heterogeneous Integration

(30:02 + Q&A) Prof. Chih Chen, National Yang Ming Chiao Tung University — 3D ICs have emerged as a key solution for high-performance computing devices, with Cu/SiO2 hybrid joints serving as vertical interconnects for ultra-fine-pitch packaging. To fabricate these joints, recessed Cu pads are formed within SiO2 vias. The bonding process begins with room-temperature SiO2–SiO2 bonding, followed by heating to induce Cu pad expansion, enabling Cu–Cu direct bonding. We employed in-situ atomic force microscopy (AFM) to directly measure the extent of Cu expansion. The results reveal that the microstructure of the Cu plays a critical role in this expansion behavior. Furthermore, thermo-mechanical stress arising from the mismatch in thermal expansion coefficients between SiO2 and the Cu pads significantly affects the reliability of Cu/SiO2 hybrid joints. The impact of this stress on temperature-cycling performance will be discussed in the conference presentation.
Bio: Professor Chih Chen obtained his Ph.D. in Materials Science in 1999 from the research group of Professor King-Ning Tu at the University of California, Los Angeles (UCLA). In 2000, he joined the faculty of National Yang Ming Chiao Tung University (NYCU) and served as the Chair of the Department of Materials Science and Engineering from February 2017 to January 2023. Professor Chen discovered the direct current electroplating technique for (111)-oriented nanotwinned copper, which was published in Science in 2012. In 2016, he transferred this technology to Chemleader Inc. for large-scale production. As a result, he received several prestigious awards, including the National Innovation Award (2016), the Materials Innovation Award from the Taiwan Materials Research Society (2016), the Outstanding Technology Transfer Award (2017), the Taiwan Outstanding Researcher Award from the National Science and Technology Council (2017 and 2022), and the TMS 2018 Research to Industrial Practice Award from The Minerals, Metals & Materials Society (TMS). In 2022, he was recognized as a Fellow of the Taiwan Materials Research Society (MRS-T). Professor Chen's current research interests include low-temperature Cu-to-Cu direct bonding, high-strength nanotwinned copper wires and films for 3D IC integration, and the reliability of flip-chip solder joints and microbumps in microelectronic packaging, with a focus on electromigration, thermomigration, and metallurgical reactions. He has published over 230 journal papers and holds more than 35 patents in Taiwan and the United States. Additionally, he co-authored a book on Science and Technology of Electronic Packaging with Professors King-Ning Tu and Hung-Ming Chen, which was published by Wiley in 2021.

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