Effects of Fluid Handling Components on Slurry Health
Mark Litchy, Donald C. Grant and Gary Van Schooneveld
CT Associates, Inc., 7121 Shady Oak Road, Eden Prairie, MN 55344 USA
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This study investigated the effects of pumping systems and diaphragm valves on the physical properties, or “health,” of a CMP slurry. Health was determined by measuring changes in the slurry particle size distribution. Three types of pumping systems were tested: bellows, diaphragm and magnetically-levitated centrifugal. The bellows and diaphragm systems caused significant increases in concentrations of large particles in the slurry while the centrifugal pump had little effect. The increased concentrations resulted in shorter lifetimes of filters used to remove large particles from the slurry. Valves had little effect on the properties of slurry flowing through them, but increased large particle concentrations when the valves were cycled. The rate of increase was substantially less than that seen with the bellows and diaphragm pumping systems. Overall, this paper shows that how a slurry is handled following its manufacture can have a significant effect on the concentration of large particles in the slurry. Some handling techniques substantially increase large particle concentrations and can be expected to decrease slurry polishing effectiveness. Other techniques that are available cause significantly less change in slurry properties.
In Proceedings of Pac-Rim-CMP 2005 Symposium, pp. 417-429