Point of use regeneration of oxide chemical mechanical planarization slurry by filtrations

Abstract

The main Purpose of this study was to regenerate the used oxide slurry using filters. The solid content in regenerated slurry was controlled by ultra fine (UF) filtration that extracts only the solution from diluted slurry. Reverse osmosis (RO) filtration was adapted to recover chemicals added in the original slurry formulation by rejecting pure deionized (DI) water from slurry solutions collected by UF filtration. The specific gravity, conductivity, and pH were adjusted by the filtration and addition of KOH in the regenerated slurry. The new slurry was intentionally added into the regenerated slurry to reduce the process time and increase the lifetime of used slurry. The same removal rate of tefraethylorthosilicate (TEOS) oxide was observed when chemical mechanical planarization (CMP) was performed using the regenerated oxide slurry. The particles size of the regenerated slurry was, smaller than that of the original slurry. No microscratches were observed in the wafer polished by the regenerated slurry. Also, the defect densities of polished oxides were decreased after polishing with the regenerated slurry.