Removal rate results obtained from a 150 mm Speedfam-IPEC 472 polisher, coupled with a proven removal rate model has allowed for the determination of effective pressure (i.e., the actual pressure exerted on the structures of a patterned wafer) during chemical mechanical planarization (CMP) of high-density plasma-filled shallow trench isolation (STI) wafers. Results showed that the ratio of derived effective pressure to applied wafer pressure was 2.2, 1.7, and 1.3 for 10, 50, and 90% density wafers, respectively. The relative consistency of these ratios indicates that the effective pressure experienced during polishing is not impacted by pattern density in a proportionate manner. (C) 2004 The Electrochemical Society.