Single stage re-circulation filtrations were performed to remove oversized particles from colloidal silica based Chemical-Mechanical Polishing (CMP) slurry. Proper filtration was demonstrated to achieve rapid removal of oversized particles while not altering the percent solids of the CMP slurry. Mathematical models were developed to simulate particle reduction in CMP slurry distribution systems. The models predict particle concentration as a function of the flow rate, the particle removal efficiency of the filter, and filtration time. The models show that flow rate is the most critical parameter in order to achieve rapid removal of oversized particles. The major role of pre-filtration is to capture a portion of the oversized particles and protect the final filtration from premature plugging in order to deliver maximum filter service life. Based on examination of the limited data, the re-circulation flow model adequately predicts the particle concentration profile. Ultimately, selection of the optimum filters depends on flow rate, particle removal efficiency of the filter, filtration scheme (single vs. multi-stage filtration), and filter service life.
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