Patent ID: 8808059
Filing Date: 2014-08-19
Classification: B24B,G01B,H01L

Abstract:
1. A method of controlling a polishing operation, comprising: storing an optical model for a layer stack having a plurality of layers, the optical model having a plurality of input parameters, the plurality of input parameters defining a parameter space; generating a plurality of model spectra by calculating a model spectrum using the optical model for each of a first plurality of different points in the parameter space; measuring a test spectrum of a test substrate; for each model spectrum of the plurality of model spectra, comparing the test spectrum to the model spectrum to determine a difference value, thereby generating a plurality of difference values; determining a plurality of minima in the plurality of difference values; for at least one local minimum of the plurality of minima, determining a plurality of reference spectra, the plurality of reference spectra for each local minimum generated using the optical model with a second plurality of different points in the parameter space clustered at a point in the parameter space corresponding to the local minimum; measuring a spectrum of a substrate with an in-sequence or in-situ monitoring system to provide a measured spectrum; determining a best matching reference spectrum from the plurality of reference spectra that provides a best match to the measured spectrum; determining a value associated with the best matching reference spectrum; polishing the substrate with a polishing apparatus; and adjusting a polishing endpoint or a polishing parameter of the polishing apparatus based on the value associated with the best matching reference spectrum.