Correlation of large particle count data in CMP slurry with production wafer defects

A Vantage SlurryScope was installed in an IMFT production fab CMP tool for slurry monitoring at point of use (POU). Data gathered over several weeks was compared to four different wafer yield metrics, including wafer defects associated with CMP scratching. A strong correlation was found between defects and the total particle count in the smallest (1.0-1.2μm) particle bin reported by the SlurryScope system. Discrete particle excursion events did not play a role in these correlations. The SlurryScope was then moved to the equipment chase to monitor large particles continuously in the slurry distribution system (SDS) main loop. Using the correlation methods learned at POU, a similar correlation was found between defects and drift in the measured total particle count. The SlurryScope data was also compared to a traditional offline monitoring method. The correlation coefficient was significantly higher for SlurryScope data in all four defect metrics included in this study.