By Mark R. Litchy, Donald C. Grant, CT Associates, Inc., USA and Reto Schoeb, Levitronix GmbH, Switzerland

ABSTRACT

Delivery systems used to supply slurry to CMP planarization tools can damage slurry.  In this experiment, four slurries were circulated in a simulated slurry delivery loop at a fixed flow rate and pressure using a variety of pumps (bellows, diaphragm, and magnetically levitated centrifugal) to determine the effect of circulation on the slurry health.  During each test, a number of slurry health parameters were monitored including the size distribution of the particles in the slurry. Most slurry health parameters were unaffected during the tests.  However, significant changes in the large particle tail (particles ≥ 0.5μm) of the slurry particle size distributions (PSD) were observed.  Both the pump and slurry type played important roles in the magnitude of the change.  In some slurries, large increases in the large particle concentrations were observed during circulation with diaphragm and bellows pumps, while in other slurries increases were not observed.  With the magnetically levitated centrifugal pumps, minimal changes were observed, regardless of the type of slurry tested.