OPTICAL DETECTION OF METAL LAYER CLEARANCE

摘要

A method of controlling polishing includes polishing a metal layer of a substrate. The metal layer overlies an underlying layer structure. During polishing of the metal layer, a light beam is directed onto the first substrate. The metal layer is sufficiently thin that a portion of the light beam reflects from an exposed surface of the metal layer and a portion of the light beam passes through the metal layer and reflects from the underlying layer structure to generate a reflected light beam. The reflected light beam is monitored during polishing and a sequence of measured spectra is generated from the reflected light beam. At least one of a polishing endpoint or an adjustment for a polishing rate is determined from the sequence of measured spectra.