Patent ID: 8260446
Filing Date: 2012-09-04
Classification: B24B,G05B

Abstract:
1. A computer-implemented method, comprising: storing a library having a plurality of reference spectra, each reference spectrum of the plurality of reference spectra having a stored associated index value, each index value representing a time during a polishing operation at which the reference spectrum of the plurality of reference spectra with the associated index value is expected to be observed; measuring a sequence of spectra in-situ during polishing of a substrate to obtain measured spectra, wherein each stored associated index value was generated prior to polishing of the substrate; binning spectra from the measured spectra into two or more radial zones; for each measured spectrum of the sequence of spectra, finding a best matching reference spectrum from the plurality of reference spectra to generate a sequence of best matching reference spectra; determining the associated index value for each best matching spectrum from the sequence of best matching reference spectra to generate a sequence of index values; fitting a linear function to the sequence of index values; and halting the polishing either when the linear function matches or exceeds a target index or when the associated index value from the determining step matches or exceeds the target index, wherein the steps of finding a best matching reference spectrum to generate a sequence of best matching reference spectra, determining an associated index value for each best matching spectrum from the sequence of best matching reference spectra to generate a sequence of index values and fitting a linear function to the sequence of index values are performed for each of the two or more radial zones independently of one another.