Monitoring of polishing pad texture in chemical mechanical polishing

Abstract

An apparatus for chemical mechanical polishing includes a platen having a surface to support a polishing pad, a carrier head to hold a substrate against a polishing surface of the polishing pad, a pad conditioner to press an abrasive body against the polishing surface, an in-situ polishing pad monitoring system including an imager disposed above the platen to capture an image of the polishing pad, and a controller configured to receive the image from the monitoring system and generate a measure of polishing pad surface roughness based on the image. The controller can use machine-learning based image processing to generate the measure of surface roughness.

What is claimed is: 
     
         1 . An apparatus for chemical mechanical polishing, comprising:
 a platen having a surface to support a polishing pad;   a carrier head to hold a substrate against a polishing surface of the polishing pad;   a pad conditioner to press an abrasive body against the polishing surface;   an in-situ polishing pad monitoring system including an imager disposed above the platen to capture an image of the polishing pad; and   a controller configured to receive the image from the monitoring system, to receive other data including a value for a parameter, and to generate a measure of polishing pad surface texture based on the image and the value of the parameter.   
     
     
         2 . The apparatus of  claim 1 , wherein the parameter comprises a polishing control parameter, a state parameter, a measurement from a sensor in the polishing system or a measurement of the polishing pad by a sensor outside the polishing system. 
     
     
         3 . The apparatus of  claim 2 , herein the parameter comprises a platen rotation rate, a slurry dispense rate, a slurry composition, a number of substrates since the polishing pad was changed, or a measurement of the surface roughness of the polishing pad by a stand-alone metrology station before the polishing pad was installed on the platen. 
     
     
         4 . The apparatus of  claim 1 , wherein the controller is configured to at least one of halt a conditioning process or adjust a conditioning parameter based on the measure of polishing pad surface texture. 
     
     
         5 . The apparatus of  claim 1 , wherein the controller is configured to operate as a machine learning based image processing system, and to input the image to the image processing system. 
     
     
         6 . The apparatus of  claim 5 , wherein the machine learning based image processing system comprises a supervised learning module. 
     
     
         7 . The apparatus of  claim 6 , wherein the machine learning based image processing system comprises a dimensional reduction module to receive the image and output component values, and wherein the controller is configured to input the component values to the image to the supervised learning module. 
     
     
         8 . The apparatus of  claim 6 , wherein the controller is configured to input the image directly to the supervised learning module. 
     
     
         9 . The apparatus of  claim 6 , wherein the controller is configured to operate the supervised learning module as an artificial neural network. 
     
     
         10 . An apparatus for chemical mechanical polishing, comprising:
 a platen having a surface to support a polishing pad;   a carrier head to hold a substrate against a polishing surface of the polishing pad;   a pad conditioner to press an abrasive body against the polishing surface;   an in-situ polishing pad monitoring system including an imager disposed above the platen to capture an image of the polishing pad, wherein the imager is radially movable over the platen; and   a controller configured to receive the image from the monitoring system, to receive other data including a value for a parameter,   
     
     
         11 . The apparatus of  claim 10 , wherein the imager is mounted on a pivotable arm to swing laterally over the platen. 
     
     
         12 . A method of polishing, comprising:
 bringing a substrate into contact with a polishing pad on a platen;   generating relative motion between the substrate and the polishing pad;   capturing an image of the polishing pad with an optical sensor;   receiving other data including a value for a parameter; and   generating a measurement of surface texture of the polishing pad by inputting the image and the value of the parameter to a machine learning based image processing system.   
     
     
         13 . The method of  claim 12 , wherein the parameter comprises a polishing control parameter, a state parameter, a measurement from a sensor in the polishing system or a measurement of the polishing pad by a sensor outside the polishing system. 
     
     
         14 . The method of  claim 12 , herein the parameter comprises a platen rotation rate, a slurry dispense rate, a slurry composition, a number of substrates since the polishing pad was changed, or a measurement of the surface roughness of the polishing pad by a stand-alone metrology station before the polishing pad was installed on the platen. 
     
     
         15 . The method of  claim 12 , comprising receiving training data including a plurality of pairs of training images and training values, and training a supervised learning algorithm in the learning based image processing system using the training data. 
     
     
         16 . The method of  claim 15 , wherein the training values comprise surface texture values. 
     
     
         17 . The method of  claim 16 , wherein the training values comprise surface roughness values. 
     
     
         18 . The method of  claim 12 , comprising halting a conditioning process or adjusting a conditioning parameter based on the measure of polishing pad surface texture.