Effects of pad properties on material removal in chemical mechanical polishing

The surface roughness among the properties of the polishing pad is known as the dominant factor that determines the removal rate of the thin film because the material on a wafer surface is removed by direct contact with the rough pad surface. In this paper, the authors investigated the effect of pad surface roughness on material removal process in chemical mechanical polishing (CMP). The reduced peak height (Rpk) is an estimate of the peaks above the main plateau and is related to the wear characteristics of the pad. In addition, the pad conditioning process acts to define and maintain the structure of the pad surface asperities and as such affects the material removal rate, material removal stability. Without regeneration of the pad surface during polishing, the material removal rate rapidly declines according to the polishing time. And the material removal rate is in direct proportion to Rpk from the experimental results. In conclusion, the surface roughness of the pad has a strong correlation with the material removal in CMP.