Dynamically tracking spectrum features for endpoint detection

A computer program product, tangibly embodied in a machine readable storage device, comprising instructions for causing a processor to:

• receive user input selecting a fixed wavelength range that is a subset of wavelengths measured by an in-situ monitoring system;
• receive an identification of a selected spectral feature, and a characteristic of the selected spectral feature to monitor during polishing;
• receive a sequence of spectra of light from a substrate while the substrate is being polished;
• for each spectrum in the sequence of spectra, search the fixed wavelength range of the each spectrum for the selected spectral feature, and determine a value of the characteristic of the selected spectral feature to generate a sequence of values;
• and
• determine at least one of a polishing endpoint or an adjustment for a polishing rate based on the sequence of values.

A chemical mechanical polishing system, comprising:

• a platen to hold a polishing pad;
• a carrier head to hold a substrate in contact with the polishing pad;
• an in-situ optical monitoring system configured to measure a sequence of spectra of light from the substrate while the substrate is being polished;
• and
• a controller configured to
• receive an identification of a selected spectral feature, a wavelength range having a width, and a characteristic of the selected spectral feature to monitor during polishing,
• receive the sequence of spectra of light from the in-situ optical monitoring system,
• generate a sequence of values of the characteristic of the selected spectral feature from the sequence of spectra, wherein the controller is configured to generate the sequence of values by, for at least some spectra from the sequence of spectra, generating a modified wavelength range based on a position of the spectral feature within a previous wavelength range used for a previous spectrum in the sequence of spectra, searching the modified wavelength range for the selected spectral feature, and determining a value of the characteristic of the selected spectral feature, and
• determine at least one of a polishing endpoint or an adjustment for a polishing rate based on the sequence of values.

A chemical mechanical polishing system, comprising:

• a platen to hold a polishing pad;
• a carrier head to hold a substrate in contact with the polishing pad;
• an in-situ optical monitoring system configured to measure a sequence of spectra of light from the substrate while the substrate is being polished;
• and
• a controller configured to:
• receive user input selecting a fixed wavelength range that is a subset of wavelengths measured by the in-situ optical monitoring system,
• receive an identification of a selected spectral feature, and a characteristic of the selected spectral feature to monitor during polishing,
• receive the sequence of spectra of light from the in-situ optical monitoring system,
• for each spectrum in the sequence of spectra, search the fixed wavelength range of the each spectrum for the selected spectral feature, and determine a value of the characteristic of the selected spectral feature to generate a sequence of values, and
• determine at least one of a polishing endpoint or an adjustment for a polishing rate based on the sequence of values.