How pump-induced particles affect low-k CMP detectivity

High shear flow generated by positive displacement pumps increases the distribution of oversized particles, leading to increased water surface defectivity during chemical mechanical planarization (CMP). The magnitude of pump-induced slurry agglomeration depends on the shear stress and chemical nature of the slurry. The normalized oversized particle distributions show that the maglev centrifugal pump caused less shear flow and did not show any significant particle agglomeration in low-k slurries. High shear flow generated by positive displacement pumps increased the distribution of oversized particles, leading to significantly increased surface defectivity during CMP, whereas less defectivity was found in slurries circulated by centrifugal pumps. Excellent correlation was established between the roughness/defect density and the degree of agglomeration.