Role of slurry chemistry on pump induced particle agglomeration during CMP of copper/low K dielectrics

Oversize particles in CMP slurries are one of the most important sources of defectivity during chemical mechanical planarization (CMP) of dielectrics and metals. We have investigated the effect of pump induced particle agglomeration during the slurry handling process. The stress effects induced by positive displacement pumps were investigated in the polishing of copper/low k dielectric materials. These studies were carried out by measuring the oversize particle distribution and the surface defectivity generated during the CMP polishing process. Good correlations between the pump induced agglomeration effects and defectivity in copper/low K polishing were developed. Inter-particle force measurements were also conducted as a function of slurry type and pH to understand the role of such forces in pump induced agglomeration of particles. The agglomeration of the slurries was found to depend both on the external stress applied on the slurries and the inter-particle forces acting on the slurries. The mechanisms for pump induced agglomeration and defect generation during copper, and low k dielectric polishing have been developed.