Physical and Chemical Characterization of Reused Oxide Chemical Mechanical Planarization Slurry

The recycle of Chemical Mechanical Planarization (CMP) slurries has been actively considered in the industry to reduce the cost-of-consumables (COC) because of the sharp increase of the consumption of slurry in CMP. The main purpose of this study was to characterize the used oxide slurry physically and chemically to establish a means of reprocessing it. The characteristics of slurry were determined according to pH, solid content, specific gravity and particle size. These characteristics were affected and varied by deionized water inflow during the CMP process. The tetraethylorthosilicate removal rate was strongly dependent on the solid content and pH of slurry solutions. The solid content played a major role in determining the removal rates. Regardless of the number of polishings, the removal rate was almost the same at a solid content when it was modified by adding new slurry. The mean particle size of slurries did not change at all even in the five times recycled slurry. Even though there was a slight increase in the fraction of large particles in the range of 20 to 120 µm in the recycled slurries, no changes in thickness uniformity or defect density were observed when polishing was performed in either new or recycled slurry.