Experiments and simulations were performed to investigate the characteristics of staining on pad surface. Experiments were performed on a table-top axisymmetric polishing system, consisting of a 12-inch non-rotating platen and a 4-inch rotating wafer carrier. Stain deposited on each land area was found to be darker in the direction of wafer rotation and in the radial direction, suggesting that the staining agent was produced by mechanical action during polishing and subsequently was advected downstream by slurry flow. While staining increased with polishing pressure, wafer rotation rate and polishing time, it did not seem to affect removal rate. Slurry velocity simulations showed shear flow on the land areas and wafer-driven circulation in the grooves. Temperature simulations showed a 12 °C rise in the reaction temperature on the surface of the copper wafer. Simulated stain images were in qualitative agreement with experimental results.