Grouping Spectral Data From Polishing Substrates

A computer program product residing on a computer readable medium, the computer program product comprising instructions for causing a processor to:

• receive a plurality of measured spectra reflected from a substrate at a plurality of different positions on the substrate, the substrate comprising at least two regions having different structural features;
• perform a clustering algorithm on the plurality of measured spectra to separate the plurality of measured spectra into a number of groups based on the spectral characteristics of the plurality of measured spectra, wherein the instructions to perform the clustering algorithm include instructions to initialize a plurality of centroids by selecting at least a pair of spectra from the plurality of measured spectra with the pair of spectra meeting a distance metric criterion, and to set the plurality of centroid to have the spectral characteristics of the selected spectra;
• select one of the number of groups to provide a selected group having a subset of spectra from the plurality of measured spectra;
• determine at least one characterizing value for the substrate based on the subset of spectra of the selected group;
• and
• control polishing of the substrate based on the characterizing value, wherein the instructions to control polishing of the substrate comprise instructions to determine a polishing endpoint based on the characterizing value and cause a polishing system to stop polishing at the polishing endpoint based.

A polishing system, comprising:

• a support to hold a polishing pad;
• a carrier head to hold a substrate comprising at least two regions having different structural features in contact with the polishing pad;
• an in-situ optical monitoring system to measure a plurality of measured spectra reflected from a substrate at a plurality of different positions on the substrate;
• and
• a controller configured to
• receive the plurality of measured spectra from the in-situ optical monitoring system;
• perform a clustering algorithm on the plurality of measured spectra to separate the plurality of measured spectra into a number of groups based on the spectral characteristics of the plurality of measured spectra, wherein the instructions to perform the clustering algorithm include instructions to initialize a plurality of centroids by selecting at least a pair of spectra from the plurality of measured spectra with the pair of spectra meeting a distance metric criterion, and to set the plurality of centroid to have the spectral characteristics of the selected spectra;
• select one of the number of groups to provide a selected group having a subset of spectra from the plurality of measured spectra;
• determine at least one characterizing value for the substrate based on the subset of spectra of the selected group;
• and
• control polishing of the substrate based on the characterizing value, wherein the controller is configured to determine a polishing endpoint based on the characterizing value and stop polishing at the polishing endpoint.