In-Sequence Spectrographic Sensor

Abstract

A method of controlling a polishing system includes polishing a substrate at a first polishing station, transporting the substrate to an in-line optical metrology system positioned between the first polishing station and a second polishing station, at the in-line optical metrology system measuring a spectrum reflected from the substrate, and generating a characterizing value from the spectrum, determining that the substrate needs rework based on the characterizing value, returning the substrate to the first polishing station and performing rework of the substrate at the first polishing station; and transporting the substrate to the second polishing station and polishing the substrate at the second polishing station.

What is claimed is: 
     
         1 . A method of controlling a polishing system, comprising:
 polishing a substrate at a first polishing station;   transporting the substrate to an in-line optical metrology system positioned between the first polishing station and a second polishing station;   at the in-line optical metrology system measuring a spectrum reflected from the substrate, and generating a characterizing value from the spectrum;   determining that the substrate needs rework based on the characterizing value;   returning the substrate to the first polishing station and performing rework of the substrate at the first polishing station; and   transporting the substrate to the second polishing station and polishing the substrate at the second polishing station.   
     
     
         2 . The method of  claim 1 , wherein the substrate is held by a carrier head and the carrier head is suspended from a track, and the transporting the substrate is performed by moving the carrier head along the track. 
     
     
         3 . The method of  claim 1 , wherein generating the characterizing value comprises obtaining a plurality of measured spectra with the optical metrology system from a plurality of different measurement spots within an area on the substrate, generating a plurality of values based on the plurality of measured spectra, and combining the values to generate the characterizing value. 
     
     
         4 . The method of  claim 3 , wherein generating a plurality values comprises comparing each of the plurality of measured spectra to a reference spectrum to generate a similarity value. 
     
     
         5 . The method of  claim 3 , wherein the substrate comprises a plurality of dies, and the area is substantially equal to an area of one of the dies. 
     
     
         6 . The method of  claim 1 , wherein generating the characterizing value comprises at least one of identifying a matching reference spectrum from a library of reference spectra and determining the characterizing value associated with the matching reference spectrum, determining a wavelength or width of a peak or valley in the spectrum, or fitting an optical model to the spectrum. 
     
     
         7 . The method of  claim 1 , comprising measuring another spectrum reflected from the substrate at the in-line optical metrology system positioned between the first polishing station and a second polishing station after performing rework and before transporting the substrate to the second polishing station. 
     
     
         8 . The method of  claim 1 , wherein the polishing the substrate at the first polishing station comprises a filler layer clearing recipe, and polishing the substrate at the second polishing station comprises an underlying layer polishing recipe. 
     
     
         9 . The method of  claim 1 , wherein polishing the substrate at the first polishing station comprises a bulk polishing step of a copper damascene process. 
     
     
         10 . The method of  claim 9 , wherein polishing the substrate at the second polishing station comprises a dielectric exposure step of a copper damascene process. 
     
     
         11 . The method of  claim 1 , comprising transporting the substrate to a cassette and performing polishing of at least one other substrate at the first polishing station before returning the substrate to the first polishing station and performing rework of the substrate at the first polishing station. 
     
     
         12 . A polishing system, comprising:
 a first polishing station including a first support for a first polishing pad;   a second polishing station including a second support for a second polishing pad;   a carrier head to hold a substrate, the carrier head supported by a support structure and movable between the first polishing station and the second polishing station;   an in-line optical metrology system positioned between the first polishing station and the second polishing station, the optical metrology system configured to measure a spectrum reflected from the substrate and generate a characterizing value from the spectrum; and   a controller configured to cause the carrier head to move to the first polishing station, to cause the substrate to be polished at the first polishing station, to cause the carrier head to move to the in-line metrology system, to determining whether the substrate needs rework based on the characterizing value, to cause the carrier head to return to the first polishing station and performing rework of the substrate at the first polishing station, to cause the carrier head to move to the second polishing station, and to cause the substrate to be polished at the second polishing station.   
     
     
         13 . The system of  claim 12 , wherein the support structure comprises a track and the carrier head is movable along the track. 
     
     
         14 . The system of  claim 13 , wherein the carrier head is suspended from a carriage on the track. 
     
     
         15 . The system of  claim 12 , wherein the controller is configured to cause the carrier head to move to the in-line optical metrology system and to receive another spectrum reflected from the substrate at the in-line optical metrology system after performing rework and before transporting the substrate to the second polishing station. 
     
     
         16 . The system of  claim 12 , comprising a cassette and a robot to transfer the substrate from the carrier head to the cassette, and wherein the controller is configured to cause the robot to transport the substrate from the carrier head to the cassette before the substrate is returned to the first polishing station and rework of the substrate is performed at the first polishing station. 
     
     
         17 . The system of  claim 16 , wherein the controller is configured to cause polishing of at least one other substrate at the first polishing station before the substrate is returned to the first polishing station and rework of the substrate is performed at the first polishing station.