Cu Pumping Analysis During $\text{Cu}/\text{SiO}_{2}$ Hybrid Bonding Using In-Situ SPM Imaging

The assessment of Cu pumping (also known as Cu extrusion) during thermal annealing is vital information for the successful execution of hybrid bonding as well as defect-free processing of the through silicon vias (TSV). Unpredicted Cu pumping can pose major reliability issues. Correspondingly, in this study, high-temperature analysis of Cu pumping was conducted utilizing in-situ scanning probe microscopic (SPM) imaging. Cu / $\text{SiO}_{2}$ surfaces with recessed and protruded Cu topographies were produced by chemical mechanical polishing (CMP) and used for Cu pumping investigations. The amount of Cu pumping upon thermal annealing up to $400^{\circ}\mathrm{C}$ and cooling down to room temperature was precisely quantified. The SPM results were compared with FEM simulation results, and a numerical equation for Cu pumping was proposed, accordingly. It was shown that by using in-Situ SMP imaging, valuable information on the behavior of hybrid Cu / dielectric surfaces can be generated.