The Benefits of Multi-Stage Filtration for Improved CMP Slurry Large Particle Retention

It is well understood that large particles and agglomerates in CMP (chemical mechanical planarization) slurries can generate defects on wafer which can result in yield loss. To minimize defects caused by large particles/agglomerates many fabs filter the slurry in the sub-fab's SDS (slurry delivery system). It is less common to employ filtration at the Point of Use (POU), the POT (point of tool) or POD (point of dispense), to further mitigate large particles that form in the slurry loop during recirculation. A bench setup using a combination of filters, representing those that are commonly used in the SDS and POU systems, was used to simulate both single-pass and recirculation modes. Optical particle measurement data showed a reduction in LPC (large particle count) (>0.5 um) of 60% with improved SDS filtration, and an even more significant reduction (80-90%) with additional POU filtration, which should result in fewer defects on wafer.