As interconnect pitches approach sub‑micrometer size, hybrid bonding pushes semiconductor manufacturing into a regime where metrology tolerances tighten to the nanometer scale and margins for error disappear. At these dimensions, Cu pads and dielectric surfaces must be exceptionally planar, clean, and precisely aligned, because even a few nanometers of height variation, wafer bow, or residual contamination can prevent reliable Cu–Cu contact and lead to latent yield loss. In this regime, traditional optical inspection alone is no longer sufficient, and AFM becomes indispensable.

Metrology must measure surface topography with very high vertical and lateral resolution to accurately capture Cu pad dishing and roll‑off. These values are critical for the following bonding steps and must be tightly controlled and optimized. As a result, AFM‑based CMP process control is essential: CMP quality and uniformity directly define bonding performance, and only by minimizing post‑bonding defects such as voids or unbonded regions can yield loss be avoided.