Light scattering analysis for undiluted slurry management

Continuous, real-time process monitoring of undiluted CMP slurry has been used in production fabs now for over three years. This field experience has brought to light several critical issues, two of which are discussed here. The first concerns the handling of dense ceria slurries which have high counts that can exceed the algorithm of the original SlurryScope™ system. A new algorithm that analyzes all of the light scattering data has been developed to address this for high density slurries. The second is that some facility layouts do not allow for locating the SlurryScope close to the slurry sampling tap-off point. The information lost as a result of long sampling lines is quantified.