edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 28 NO. 2 12 INSPECTION AND METROLOGY CHALLENGES IN HYBRID BONDING Himanandhan Reddy Kottur, Pavanbabu Arjunamahanthi, Liton Kumar Biswas, Istiaq Firoz Shiam, Katayoon Yahyaei, and Navid Asadizanjani Department of Electrical and Computer Engineering, University of Florida, Gainesville h.kottur@ufl.edu EDFAAO (2026) 2:12-24 1537-0755/$19.00 ©ASM International® INTRODUCTION The semiconductor industry is experiencing a paradigm shift from traditional monolithic system-on-chip (SOC) architectures toward heterogeneous integration (HI) based on chiplet design.[1,2] This evolution stems from the growing demand for higher performance, energy efficiency, and design flexibility as transistor scaling reaches physical and economic limits. Instead of a single large die, complex systems are now partitioned into multiple smaller chiplets, each optimized for specific functions such as logic processing, memory, or I/O operations. Subsequently, these chips are interconnected within a single package, achieving system-level performance comparable to that of monolithic SOCs while improving manufacturing yield, scalability, and cost efficiency.[3] At the heart of this transformation lies hybrid bonding, a key enabler for fine-pitch, high-density interconnects essential for 3D integration and chipletbased architectures.[4] Unlike conventional solder-based interconnects, hybrid bonding establishes direct copperto-copper (Cu-Cu) and dielectric-to-dielectric contacts, eliminating the need for solder bumps and underfill.[5] This advancement reduces parasitic resistance and capacitance, leading to enhanced electrical performance and lower power consumption. The technology has rapidly become foundational for stacking logic-memory modules, integrating high-bandwidth memory (HBM), and assembling artificial intelligence (AI) accelerators that demand compact form factors and superior signal.[6,7] The various applications of hybrid bonding are illustrated in Fig. 1. Additionally, hybrid bonding offers superior thermal conductivity and mechanical stability, critical for mitigating the heat and stress challenges inherent in dense 3D systems.[8] However, the inspection and metrology of hybrid bonding remain among the most critical challenges to ensuring bonding quality, process control, and long-term reliability. The bonding process demands nanometerscale planarity and cleanliness, where even minor surface roughness, contamination, or misalignment can degrade bond integrity. As bonding pitches continue to scale down, the difficulty of detecting and characterizing such defects increases dramatically. Traditional inspection techniques often lack the spatial resolution or sensitivity required to identify interfacial anomalies such as voids, delamination, or incomplete copper contact, especially when these features are buried beneath dielectric layers. Moreover, conventional metrology methods struggle to differentiate between mild topographical variations and defects Fig. 1 Hybrid bonding interconnects in various electronic technologies.
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