Material removal regions in chemical mechanical planarization for submicron integrated circuit fabrication: Coupling effects of slurry chemicals, abrasive size distribution, and wafer-pad contact area

A material removal rate (MRR) model as a function of abrasive weight concentration has been proposed for chemical mechanical planarization/polishing (CMP) by extending a material removal model developed earlier in 2001 and 2002. With an increase of the weight concentration of abrasives, three regions of material removal exist: a chemically dominant and rapid increasing region, a mechanically dominant linear region, and a mechanical dominant saturation region. A detailed model is proposed to explain that the transition from the first to the second region is due to a transition from a wafer surface covered with a single soft material to a surface covered with both soft and hard materials. The slope of the linear region is a function of abrasive size distribution, and the saturation removal rate is a function of abrasive size distribution and wafer-pad contact area. The model can help to clarify the roles of chemicals, wafer-pad contact area, and abrasive size distribution in CMP.