Generation of Pad Debris during Oxide CMP Process and Its Role in Scratch Formation

The generation of pad debris during the chemical mechanical planarization (CMP) process was studied. A fresh pad was conditioned with deionized water alone without polishing any wafer in order to characterize the pad debris exclusively. It was found that the pad debris presented in several size ranges with irregular shapes, mostly in agglomerated form. Polishing experiments were performed continuously without conditioning the pad, and the byproducts were gathered several times during the process. No pad debris was found in the gathered slurry during this process, but dispersion of some agglomerated silica particles was observed. The slurry was gathered during CMP processes conducted under both in situ and ex situ pad conditions. The generation of pad debris during polishing was observed with in situ conditioning but not observed with ex situ conditioning. The effect of the presence of pad debris on scratch formation was also studied, and it was found that the occurrence of pad debris seriously increased the number of scratches. An increase in the number of diamonds per unit area of a conditioner could ultimately avoid the generation of pad debris, eventually reducing the scratch formation by sustaining the same removal rate and nonuniformity after the CMP process.