Analysis of removal mechanism on oxide CMP using mixed abrasive slurry

Mixed abrasive slurry (MAS) is one of the non-traditional slurries with more than two different sizes, shapes or materials of abrasives which are to improve a chemical mechanical polishing (CMP) performance such as a removal rate. This paper focuses on the MAS mixed with two different sized abrasives and controlled by mixing ratio. Hybrid effect of the MAS was investigated from the removal mechanism of the mixed abrasives on oxide film. Experiments have been implemented with a 4-inch wafer with silicon dioxide film and KOH-based colloidal silica slurries. The slurry has two different sizes, 30 nm and 70 nm, with concentration of 1~30 wt%. The effects of abrasive concentration and mixing ratio were investigated in the oxide CMP in order to achieve high removal rate. During the oxide CMP with the MAS, the contact condition of abrasives was changed by mixing ratio. Through the experiment, it could be seen that two-body and three-body abrasions occur in mixed abrasive slurry according to the particle concentration. Finally, we could see that the proper ratio to achieve high removal rate was 2:1 (D30:D70) since most of the abrasives were active in material removal and carried out two-body abrasion.