Patent ID: 8014004

Claim:
A method of determining a polishing endpoint of a substrate, the method comprising: polishing a surface of a substrate; storing in a database a plurality of previously recorded spectra, each of the previously recorded spectra having a physical property value associated therewith stored in the database; during polishing, directing a beam of white light to impinge the surface of the substrate and generate a reflected light beam and measuring a sequence of first spectra of the reflected light beam; for each first spectrum from the first spectra, determining a second spectrum from the plurality of previously recorded spectra stored in the database that matches the first spectrum to generate a sequence of second spectra, wherein the second spectrum matches the first spectrum when the second spectrum is similar to the first spectrum; for each second spectrum in the sequence of second spectra, identifying from the database the physical property value stored in the database associated with the second spectrum to generate a sequence of physical property values; and determining a polishing endpoint from the sequence of physical property values.