Susceptibility of CMP slurries to agglomeration
MR Litchy, DC Grant - CT Associates, Inc.
R Schoeb - Levitronix GmbH
Particles in some CMP slurries agglomerate when circulated in CMP slurry delivery systems. The agglomerated particles can limit filter life or reduce integrated circuit device yield by causing wafer defects. The rate of agglomeration depends on both the slurry type and the type of pump used to transport it. In this study, the susceptibility of nine different CMP slurries to agglomeration in simulated delivery systems incorporating bellows, diaphragm, or magnetically levitated centrifugal pumps was investigated. The CMP slurries evaluated incorporated fumed and colloidal silica, alumina, and ceria particles and are used in five different slurry applications (ILD, copper barrier, tungsten, copper step 1, and STI).
A number of slurry health parameters were monitored in the study including zeta potential, total percent solids, pH, specific gravity, and hydrogen peroxide concentration. The large particle tail (particles ? 0.5 ?m) of the slurry particle size distribution (PSD) was the only parameter that changed significantly in most slurries. Significant changes in the large particle tail were observed with at least one pump in seven of the nine slurries. The working PSD was the only other health parameter that indicated significant change, but only during experiments with one of the nine slurries. No significant changes were observed in other slurry health parameters.
CTA publication #109: International Conference of Planarization/CMP Technology, Seoul, Korea, November 2011.