Cu Pumping Analysis during Cu/SiO2 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/SiO2 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°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.