White Paper: In-line refractive index (RI) measurements are the technique of choice for qualifying the hydrogen peroxide content in CMP slurries. However, peroxide content is not the only slurry metric of interest. Typically, slurries are delivered from the manufacturer in concentrated form, then diluted with water and peroxide at the fab. Though slurry density is a critical parameter for CMP performance, incoming density can vary from batch to batch.

Simply adding specified amounts of peroxide and water will give inconsistent results at the process tool. Provided the blender system can circulate incoming slurry through the refractive index unit, RI can be used to monitor the density of slurry in the blender tank, ensuring that the specified density is maintained regardless of fluctuations in the incoming material.