Effect of soft agglomerates on CMP slurry performance

The stability of the polishing slurries under extreme environments of pH, ionic strength, pressure, and temperature is required for their optimal performance in chemical mechanical polishing (CMP) operations. Agglomeration of the abrasive particles during polishing due to fluctuations in local particle or salt concentration under dynamic processing conditions may alter the slurry performance. It is known that the presence of hard and larger size particles in the CMP slurries increases the defect density and surface roughness of the polished wafers. However, the consequences of particle agglomeration or in other words "soft" agglomerate formation (even those transient in nature) on the polishing performance are not known. In this study, silica CMP performance was evaluated with partially dispersed slurries and it was observed that even the soft agglomerates adversely impacted the surface quality of the polished wafers, indicating that optimal slurry performance requires development of robust dispersion schemes. (C) 2002 Elsevier Science (USA).