Feed forward parameter values for use in theoretically generating spectra

Abstract

A method of controlling a polishing operation is described. A controller stores an optical model for a layer stack having a plurality of layers and a plurality of input parameters including a first parameter and a second parameter. The controller stores data defining a plurality of default values for the first parameter and measures an optical property of a substrate and generates a second value. Using the optical model and the second value and iterating over the first values, a number of reference spectra are calculated. A spectrum is measured and the measured spectrum is matched to the reference spectra and the best matched reference spectrum is determined. The first value of the best matched reference spectrum is determined and is used to adjust a polishing endpoint or a polishing parameter of a polishing apparatus.

What is claimed is: 
     
         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 including a first parameter and a second parameter;   storing data defining a plurality of default first values for the first parameter;   measuring an optical property of a substrate at a stand-alone or in-sequence metrology station to generate a second value for the second parameter;   for each first value from the plurality of first values, calculating a reference spectrum using the optical model based on the first value and the second value, to generate a plurality of reference spectra;   transporting the substrate from the stand-alone or in-sequence metrology station to an in-sequence or in-situ monitoring system of a chemical mechanical polishing apparatus;   measuring a spectrum with the 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 the first value associated with the best matching reference spectrum;   polishing the substrate with the polishing apparatus; and   adjusting a polishing endpoint or a polishing parameter of the polishing apparatus based on the first value associated with the best matching reference spectrum.   
     
     
         2 . The method of  claim 1 , wherein the first parameter comprises a thickness of an outermost layer of the substrate. 
     
     
         3 . The method of  claim 2 , wherein the second parameter comprises an index of refraction or extinction coefficient of the outermost layer or a thickness of an underlying layer of the substrate. 
     
     
         4 . The method of  claim 1 , comprising measuring the optical property of the substrate at the stand-alone metrology station to generate the second value, and measuring the spectrum with the in-sequence monitoring system to provide the measured spectrum. 
     
     
         5 . The method of  claim 1 , comprising measuring the optical property of the substrate at the in-sequence metrology station to generate the second value, and measuring the spectrum with the in-situ monitoring system to provide the measured spectrum. 
     
     
         6 . The method of  claim 1 , comprising calculating a plurality of second values based on the second value, a default range, and a default increment. 
     
     
         7 . The method of  claim 6 , comprising calculating a reference spectrum using the optical model for each combination of a first value from the plurality of first values and a second value from the plurality of second values. 
     
     
         8 . 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 including a first parameter and a second parameter;   measuring an optical property of a substrate at a stand-alone or in-sequence metrology station to generate a second value for a second parameter of the plurality of optical parameters;   transporting the substrate from the stand-alone or in-sequence metrology station to an in-sequence or in-situ monitoring system of a chemical mechanical polishing apparatus;   measuring a spectrum with the in-sequence or in-situ monitoring system to provide a measured spectrum;   fitting the optical model to the measured spectrum, the fitting including finding a first value of the first parameter that provides a minimum difference between an output spectrum of the optical model and the measured spectrum, the fitting including holding the second parameter at the second value or using the second value of the second parameter as a seed value in searching for the minimum difference;   polishing the substrate with the polishing apparatus; and   adjusting a polishing endpoint or a polishing parameter of the polishing apparatus based on the first value associated with the fitted optical model.   
     
     
         9 . The method of  claim 8 , wherein the first parameter comprises a thickness of an outermost layer of the substrate. 
     
     
         10 . The method of  claim 9 , wherein the second parameter comprises an index of refraction or extinction coefficient of the outermost layer or a thickness of an underlying layer of the substrate. 
     
     
         11 . The method of  claim 8 , comprising measuring the optical property of the substrate at the stand-alone metrology station to generate the second value, and measuring the spectrum with the in-sequence monitoring system to provide the measured spectrum. 
     
     
         12 . The method of  claim 8 , comprising measuring the optical property of the substrate at the in-sequence metrology station to generate the second value, and measuring the spectrum with the in-situ monitoring system to provide the measured spectrum. 
     
     
         13 . The method of  claim 8 , wherein the fitting includes holding the second parameter at the second value. 
     
     
         14 . The method of  claim 8 , wherein the fitting includes using the second value of the second parameter as a seed value in searching for the minimum difference.