Optical endpoint detection for buff module on CMP tool

摘要

The invention includes a polishing station and a buffing station for chemically mechanically polishing a wafer. The buffing station preferably includes a pair of rotating opposing buffing pads that receive a portion of the wafer. In the buffing station, a measurement instrument may be positioned adjacent an exposed portion of the wafer for detecting an endpoint of the buffing process. A first slurry may be used in the polishing station and a second slurry may be used in the buffing station. For planarizing a wafer with a metal layer over a barrier layer, the metal layer may be removed at the polishing station while the barrier layer is removed at the buffing station. For planarizing a dielectric layer, the top portion of the dielectric layer may be removed at the polishing station with an additional amount removed at the buffing station thereby leaving a dielectric layer with a desired thickness.