Effects of film stress on the chemical mechanical polishing process

A theoretical model is constructed to simulate the pressure distribution ar ising from wafer curvature (film stress) during chemical mechanical polishi ng (CMP), based on theories of elastic contact stress. Results from oxide C MP experiments suggest that the wafer curvature results in a nonuniform pol ish rate distribution across the wafer, in agreement with the simulation ba sed on the model. This stress-dependent polish nonuniformity is attributed to the nonuniform pressure distribution across the wafer, induced by the wa fer radius of curvature (film stress). Also, it was found that the magnitud e of bride film stress itself has little effect on removal rate. Oxides wit h tensile stress tend to have a weakened bond structure and enhanced chemic al reactivity, both of which result in slightly higher removal rates. The r everse is true for oxides with compressive stress. Deviations from the mode l prediction mag. result from the stress induced by slurry flow, local vari ations in wafer shape and form, and pad surface properties. (C) 1999 The El ectrochemical Society. S0013-4651(99)03-063-3. All rights reserved.