A comparative study on the roles of velocity in the material removal rate during chemical mechanical polishing

Abstract

Relative velocities between the flowing slurry and selected points on a 150 mm wafer and nonuniformity of velocity are calculated given the known carrier speed, platen speed, and pad-to-wafer distance. Based on simulation results, the combination of a high pad rpm, a medium wafer rpm, and a large pad-to-wafer distance should give rise to a minimum nonuniformity of velocity. Chemical mechanical polish (CMP) removal rates data are fitted to the original Preston equation, Tseng's model,(1) and a modified Preston equation which incorporates the deterioration characteristics of abrasives into the removal rate model. Theoretical removal rate data predicted by Tseng's model and the modified Preston equation exhibit much better agreement with experimental removal rates than those by the original Preston equation. The nonlinear dependence of removal rate on velocity can be explained by the deterioration in slurry abrasion capability. (C) 1999 The Electrochemical Society. S0013-4651(97)11-028-X. All rights reserved.