Adaptively tracking spectrum features for endpoint detection

摘要

A method of controlling polishing includes polishing a substrate having a second layer overlying a first layer, detecting exposure of the first layer with an in-situ monitoring system, receiving an identification of a selected spectral feature and a characteristic of the selected spectral feature to monitor during polishing, measuring a sequence of spectra of light from the substrate while the substrate is being polished, determining a first value for the characteristic of the feature at the time that the first in-situ monitoring technique detects exposure of the first layer, adding an offset to the first value to generate a second value, and monitoring the characteristic of the feature and halting polishing when the characteristic of the feature is determined to reach the second value.

主权项

1. A method of controlling polishing, comprising:
polishing a substrate having a first layer; receiving an identification of a selected optical spectral feature and a characteristic of the selected optical spectral feature to monitor during polishing; measuring a sequence of spectra of light from the substrate while the substrate is being polished; determining from at least one spectrum in the sequence of spectra a first value for the characteristic of the optical spectral feature at a time that the first layer is exposed; adding an offset to the first value to generate a second value; monitoring the characteristic of the optical spectral feature by, for each spectrum in the sequence of spectra, determining from the spectrum a value of the characteristic, wherein the spectral feature comprises a peak or valley in the spectrum that persists with an evolving location, width or intensity, respectively, through the sequence of spectra, and the characteristic comprises a position, width or intensity of the peak or valley in the spectrum; and halting polishing when the characteristic of the optical spectral feature is determined to reach the second value.