Patent ID: 8563335
Filing Date: 2013-10-22
Classification: B24B,G01N,H01L

Abstract:
1. A method of controlling a polishing operation, comprising: polishing a substrate; during polishing, obtaining a sequence over time of measured spectra from the substrate with an in-situ optical monitoring system; for each measured spectrum from the sequence of measured spectra, applying a Fourier transform to the measured spectrum to generate a transformed spectrum thus generating a sequence of transformed spectra; for each transformed spectrum, selecting a peak of interest from a plurality of peaks in the transformed spectrum, wherein selecting the peak of interest includes identifying a highest peak and a second-highest peak within a range of position values, determining a height and a position for each of the highest peak and the second-highest peak, and determining whether the highest peak has a lower position value than the second-highest peak; for each transformed spectrum, determining a position value for the peak of interest in the transformed spectrum thus generating a sequence of position values; and determining at least one of a polishing endpoint or an adjustment of a pressure to the substrate from the sequence of position values.