Investigations on the mechanism of silica particle removal during the Cu buff cleaning process

A new buff cleaning method to remove particles remaining on the Cu surface after chemical mechanical polishing was developed. Because the van der Waals force is the dominant adhesion force when silica particles are attached to a blanket Cu film, an alkaline solution or hot water was previously recommended to increase the lifting force and weaken the van der Waals force, thereby improving the cleaning efficiency by 92.58% and 92.71%, respectively. In this study, the temperature effects on physical and chemical bonding were thoroughly compared for silica and ceria samples. Soft pads are recommended to improve the particle removal efficiency and prevent scratching the Cu surface during the buff process. Almost all of the particles were dislodged and scratching was successfully prevented after optimization. This work elucidates the mechanisms of particle adhesion and removal in Cu buff cleaning from the standpoints of force and energy, thus optimizing Cu buff cleaning and achieving an ideal cleaning efficiency.