Stress distribution in chemical mechanical polishing

This paper describes a first principles, three-dimensional, wafer scale model that relates chemical mechanical polishing (CMP) nonuniformity (NU) to the distribution of Von Mises stress on the wafer surface. The model describes mechanical aspects of the polishing process including the effects of down pressure and the physical properties of the carrier, carrier film, wafer and pad. The finite element model is solved using ANSYS (Version 5.2, ANSYS Inc.) to obtain the Von Mises stress distributions. The calculated Von Mises stress distributions correlate well with observed removal rate (RR) profiles obtained during oxide polishing. Analysis of the model predictions reveals that the applied down force causes radial deformation of the pad and carrier film during polishing. This deformation induces radial and angular (theta) stresses on the wafer surface, and these stresses account for the variation in the calculated Von Mises stress. (C) 1997 Elsevier Science S.A.