Detection of planarization from acoustic signal during chemical mechanical polishing

Abstract

A chemical mechanical polishing apparatus includes a platen, a polishing pad supported on the platen, a carrier head to hold a surface of a substrate against the polishing pad, a motor to generate relative motion between the platen and the carrier head so as to polish an overlying layer on the substrate, an in-situ acoustic monitoring system comprising an acoustic sensor that receives acoustic signals from the surface of the substrate, and a controller configured to detect planarization of topology on the substrate based on a signal from the in-situ acoustic monitoring system.

What is claimed is: 
     
         1 . A chemical mechanical polishing apparatus, comprising:
 a platen;   a polishing pad supported on the platen;   a carrier head to hold a surface of a substrate against the polishing pad;   a motor to generate relative motion between the platen and the carrier head so as to polish an overlying layer on the substrate;   an in-situ acoustic monitoring system comprising an acoustic sensor that receives acoustic signals from the surface of the substrate; and   a controller configured to detect planarization of topology on the substrate based on a signal from the in-situ acoustic monitoring system.   
     
     
         2 . The apparatus of  claim 1 , wherein the controller is configured to cause a dispenser to switch from dispensing a first polishing liquid to dispensing a second polishing liquid upon detection of the planarization. 
     
     
         3 . The apparatus of  claim 1 , wherein the controller is configured to cause a carrier head to switch from applying a first pressure to applying a second pressure to the substrate upon detection of the planarization. 
     
     
         4 . The apparatus of  claim 1 , wherein the controller is configured to perform a Fourier transform on the signal and to sum a spectral power density over a frequency range to generate a power signal. 
     
     
         5 . The apparatus of  claim 4 , wherein the controller is configured to detect a change in slope of the power signal to detect the planarization of topology. 
     
     
         6 . The apparatus of  claim 4 , wherein the controller is configured to detect a decrease in the magnitude of the slope of the power signal to detect the planarization of topology. 
     
     
         7 . A method of chemical mechanical polishing apparatus, comprising:
 bringing a substrate into contact with a polishing pad and generating relative motion between the substrate and polishing pad so as to polish an overlying layer on the substrate;   acoustically monitoring the substrate during polishing with a sensor of an in-situ acoustic monitoring system; and   detecting planarization of topology on the substrate based on a signal from the sensor.   
     
     
         8 . The method of  claim 7 , comprising switching from dispensing a first polishing liquid to dispensing a second polishing liquid upon detection of the planarization. 
     
     
         9 . The method of  claim 7 , comprising switching from applying a first pressure to applying a second pressure to the substrate upon detection of the planarization. 
     
     
         10 . The method of  claim 7 , comprising performing a Fourier transform on the signal and summing a spectral power density over a frequency range to generate a power signal. 
     
     
         11 . The method of  claim 10 , comprising detecting a change in slope of the power signal to detect the planarization of topology. 
     
     
         12 . The method of  claim 10 , comprising detecting a decrease in the magnitude of the slope of the power signal to detect the planarization of topology. 
     
     
         13 . A non-transitory computer readable medium encoded with a computer program comprising instructions to cause one or more computers to:
 receive signals a sensor of an in-situ acoustic monitoring system during polishing of a substrate; and   detect planarization of topology on the substrate based on the signals from the sensor.   
     
     
         14 . The computer readable medium of  claim 13 , comprising instructions to switch from dispensing a first polishing liquid to dispensing a second polishing liquid upon detection of the planarization. 
     
     
         15 . The computer readable medium of  claim 13 , comprising instructions to switch from applying a first pressure to applying a second pressure to the substrate upon detection of the planarization. 
     
     
         16 . The computer readable medium of  claim 13 , comprising instructions to perform a Fourier transform on the signal and summing a spectral power density over a frequency range to generate a power signal. 
     
     
         17 . The computer readable medium of  claim 16 , comprising instructions to detect a change in slope of the power signal to detect the planarization of topology. 
     
     
         18 . The computer readable medium of  claim 16 , comprising instructions to detect a decrease in the magnitude of the slope of the power signal to detect the planarization of topology.