Patent ID: 7998358

Claim:
A non-transitory computer program product, tangibly embodied on a computer readable storage device, comprising instructions to cause a polishing system to perform the operations of: storing a predetermined criterion for detecting an end point using a selected peak in a spectrum of light; polishing a substrate; measuring a sequence of current spectra of light reflected from the substrate while the substrate is being polished, wherein the selected peak persists with at least an evolving location or width through the sequence of current spectra; for each current spectrum in the sequence of current spectra, measuring one or more of a current location and a current width of the selected peak in the current spectrum; determining whether the current location or the current width, respectively, of the selected peak in a latest current spectrum in the sequence of current spectra satisfies the predetermined criterion; and ceasing to polish the substrate when the current location or the current width, respectively, of the selected peak is determined to satisfy the predetermined criterion.