EAGER: Collaborative Research: In situ Thermal-mechanical Localization Metrology for Advanced 3D Packaging

Advanced three-dimensional (3D) packaging plays a critical role in the performance of miniaturized semiconductor devices. Owing to reduced component dimension, high-density stacking, and complex interconnection inherent to 3D packaging, significant temperature rise and complex thermal-mechanical stress are generated inside multiple hierarchical levels, degrading transistor performance and accelerating device failure. To improve the reliability of semiconductor devices, it is essential to gain a comprehensive understanding of the thermal-mechanical environment within the 3D packaging. However, accessing the critical regions inside advanced 3D packaging remains challenging because they are often buried beneath densely stacked components and interconnected microstructures. This EArly-concept Grant for Exploratory Research (EAGER) project will develop in situ metrology capabilities to directly probe localized temperature and stress inside advanced 3D packaging. By resolving thermal-mechanical interactions at submicron spatial resolution, the project will not only identify critical regions prone to hotspot formation and thermal stress concentration, but also provide design guidelines for next-generation 3D packaging with improved performance and reliability. Educational activities, including curriculum development and student research opportunities, will complement the research activities and broaden the project impact. The overarching goal of this project is to develop an in situ, high-resolution internal thermal-mechanical characterization technique for advanced 3D packaging. The approach integrates optical diagnostics and nanophotonics with semiconductor packaging. Micro-Raman spectroscopy will serve as a temperature- and stress-sensitive optical probe, while photonic waveguides co-designed with a 3D packaging test vehicle will deliver the Raman probe to critical regions buried within stacked architectures. To enable accurate thermal-mechanical characterization, the project will first explore photonic integration design strategies that preserve strong Raman scattering without altering surrounding thermal-mechanical environment. Then, a reliable fabrication process for photonic integrated 3D packaging will be established. Finally, the project will demonstrate in situ characterization of localized temperature rise and thermal-mechanical stress at critical regions inside the 3D packaging during the device operation. This project will expand the localized metrology toolkit needed for the inspection and design of advanced 3D packaging. Insights gained from systematic characterizations will advance fundamental understanding of how the interplay between localized heat generation and microstructures impacts thermal-mechanical interactions within 3D stacking architecture. Moreover, the photonic integration strategy can provide a versatile platform to make various optical probes accessible to high-resolution diagnostics for advanced 3D packaging. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.