Recently ceria-based slurries, which show high removal selectivity of silicon oxide to silicon nitride, have been applied to shallow trench isolation (STI) CMP process. While wafer-to-wafer nonuniformity (WTWNU) and within-wafer nonuniformity (WIWNU) are superior to conventional silica-based slurries, the level of defects caused by slurry-induced scratches is relatively high. Filtration of ceria-based slurry in the recirculation loop, with absolute performance filters, has been found to be very effective in reducing CMP defects (microscratches) and in improving process consistency. This paper/presentation discusses the possible cause of scratches when using ceria-based slurry and the defect reduction results obtained using Pall's Profile Star filters from a study on a ceria based CMP slurry process.
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