Precision Metrology for Hybrid Bonding: Nova’s Engineering-Driven Approach to Advanced Packaging
As the semiconductor industry advances beyond the limitations of traditional 2D scaling, the focus has shifted toward 3D integration and heterogeneous packaging. Among the most promising technologies enabling this shift is Hybrid Bonding, a method that allows for direct copper-to-copper and dielectric-to-dielectric connections at extremely fine pitches. This capability is essential for achieving the performance, power efficiency, and form factor requirements of modern logic, memory, and AI-centric devices.
Hybrid Bonding supports interconnect pitches below 5 microns, eliminating the need for micro-bumps and reducing parasitic effects that hinder signal integrity and power delivery. However, the precision required for successful implementation introduces a new class of metrology challenges. These include controlling surface planarity, managing wafer warpage, and ensuring alignment accuracy, all of which are critical to achieving high yield and long-term reliability in 3D-stacked architectures.
Figure 1: A wide range of metrology challenges in Hybrid Bonding
Nova has developed a comprehensive suite of metrology solutions tailored to these challenges. These solutions are designed not only for high-resolution and high-throughput performance but also for seamless integration into high-volume manufacturing environments.
One of the most critical steps in the Hybrid Bonding process is ensuring that the bonding surfaces are exceptionally flat and uniform. Post-CMP (Chemical Mechanical Planarization) topography, particularly copper recess or dishing, must be tightly controlled to avoid bonding defects. Nova’s Prism platform addresses this with a unique combination of spectral interferometry and optical critical dimension (OCD) spectrometry. Enhanced by unique algorithms and data analysis, this approach enables accurate, high-throughput measurements of Cu/SiCN surface topography, even in structures with thick metal layers and complex underlayers. The ability to reduce reliance on reference data significantly shortens time to solution, making it ideal for dynamic production environments.
Figure 2: Cu Recess (Dishing)
While the inner wafer area is of high importance, the edge and bevel regions are equally critical. These areas influence bonding uniformity, contamination risk, and mechanical integrity. Nova’s edge metrology capabilities provide high-resolution measurements of edge roll-off and bevel trim, using direct OCD-based profiling. This non-destructive, contamination-free approach ensures that even the most peripheral regions of the wafer meet the stringent requirements of Hybrid Bonding, particularly in wafer-to-wafer configurations where edge topography can affect carrier bonding and thermal stress distribution.
Figure 3: Wafer Edge Topography
Beyond surface-level precision, Hybrid Bonding also demands a deep understanding of the wafer’s internal structure. Variations in total thickness, bow, and warp can lead to misalignment and bonding voids. Nova’s WMC platform offers full-wafer and die-level geometry mapping with nanometer-scale accuracy. With over a million points per wafer measured at high throughput, this solution bridges the gap between inspection and metrology. The system’s dual-sensor configuration allows for simultaneous measurement of bow, warp, and thickness, even for buried or opaque layers, providing comprehensive data for process optimization.
Figure 4: Pre-bonding Bow/Warp measurement of full wafers
As dies are and prepared for stacking, each one can exhibit unique warpage characteristics due to stress release and material heterogeneity. This is particularly relevant in die-to-wafer Hybrid Bonding, where the absence of a compliant interlayer means that even minor die warpage can compromise alignment and bonding integrity. Nova’s tools provide high-resolution die-level bow and warp measurements, both pre- and post-singulation. The system’s ability to perform continuous measurement across die gaps on ring frames, combined with SFQR (Site Flatness Quality Rating) metrics, enables precise assessment of individual die flatness—an essential factor in ensuring bonding success.
Figure 5: Die Warpage measurement on a diced wafer
Nova’s metrology solutions are engineered for the realities of advanced packaging, where precision, speed, and scalability are non-negotiable. By combining optical scatterometry, interferometry, and machine learning, Nova delivers a comprehensive toolkit for Hybrid Bonding process control. These innovations empower engineers to push the boundaries of 3D integration, enabling the next generation of semiconductor devices.
The metrology challenges and solutions highlighted in this post were presented by Nova Ltd. At the VLSI Symposium 2025 as part of a professional workshop on Hybrid Bonding – Breaking Boundaries in Advanced Packaging and Heterogeneous Integration in the Era of Chiplets and AI.
