We investigated the effects of the pad surface response during polishing and conditioning on the removal rate variation in a tungsten chemical mechanical polishing (CMP) process. We examined the coefficient of friction (COF) to identify the tribology of the pad conditioning. The variation in the removal rate was dependent on the COF during conditioning. We also evaluated the effects of diamond edge degradation of the pad conditioner disk on its cutting ability from the viewpoint of mechanical wear. The results showed that the decline in pad wear rate was caused by a decrease in the cutting ability as the diamond sharp edges rounded off, while the diamond contact area with the pad surface depended little on the diamond abrasive degradation. Furthermore, we demonstrated the usefulness of measuring the height ratio of the asperity called "top surface area (TSA) ratio" as an appropriate topographical parameter to study the dependence of COF during conditioning on the decay of the removal rate. We present a clear correlation between the pad wear rate degradation and the TSA ratio after CMP to elucidate an increase in the conditioning COF related to truncation of the asperity tip by wear and plastic deformation. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3368700] All rights reserved.