Economical Characterization of Cu/Dielectric Hybrid Bonded Interfaces Using Ion Milling Method

In chip-to-wafer (C2W) hybrid bonding process, Cu metal pads and dielectric from top component and bottom substrate are simultaneously bonded. Subsequently, there is a need to perform characterization of the bonded Cu metal pads quickly, efficiently, and cheaply to check the integrity of the Cu bond pads, such as defects, bondability, diffusion across the interface, dimensions, or misalignment to facilitate optimization for better hybrid bonding. Using ion milling to characterize the Cu bond pads, the C2W die is first grinded by mechanical polishing close to the region of interest (and also grinded to a smaller size in order to be able to mount on the sample holder), and then the C2W die is ion milled to expose the Cu bond pads the size of approximately 3μm by 3 μm. This way of characterization performed on the bonded Cu metal pads helps quickly check the integrity of the Cu bond pads.