EFFECT OF SLURRY VISCOSITY MODIFICATION ON OXIDE AND TUNGSTEN CMP

Chemical mechanical polishing (CMP) of semiconductor substrates is a c omplex phenomenon that involves chemical and mechanical interactions b etween substrate material, slurry and pad. The effect of the physical properties of the slurry on the polishing rates is not very well under stood. The rheological properties of polishing slurries affect materia l removal rate and surface quality of the semiconductor wafers. In thi s work, we have studied the effect of changing viscosity of a commerci al colloidal silica-based slurry on removal rate. The pad material sel ected was a commercial pad. The results show that the effect of viscos ity modifiers is very different for oxide and tungsten CMP. This can b e related to the fundamental difference in the mechanism of material r emoval in the two cases. We have discussed those viscosity effects in relation to the mechanism of materials removal pertaining to both oxid e and metal CMP. (C) 1998 Elsevier Science S.A.