Fundamental Characteristics of Condensed Chemical Mechanical Polishing Waste Slurry

We investigated the possibility of efficiently reclaiming fumed silica slurry in an oxide chemical-mechanical polishing (CMP) process for environmental load reduction with regard to waste disposal, as well as for reduction in CMP consumable cost. The characteristics of the reclaimed slurry were determined according to pH value, specific gravity, conductivity, particle size, zeta potential, and trace-metal levels. We also determined whether the reclaimed slurry was functionally comparable to the original one. Experimental results showed that reclamation affected the large particle count (LPC) of particles larger than 0.56 mu m in the slurry. The reclaimed slurry had a ten-fold increase in LPC over the original slurry. However, there was significant decrease in the number of particles larger than 1.01 mu m in the reclaimed slurry compared with that in the original one because depth filters used during reclamation effectively remove agglomerated particles and foreign materials from the condensed waste slurry. The removal rate and uniformity of the reclaimed slurry were comparable with those of the original one. Even though there was a slight increase in slurry residues on the wafers, no changes in micro-scratch defects on wafers was observed. Therefore, we demonstrated the feasibility of reclaiming condensed waste slurry for reuse. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3599950] All rights reserved.