Measurement of pad thickness and control of conditioning

Abstract

A conditioning process includes rotating a polishing pad about an axis of rotation, conditioning the polishing pad by sweeping an abrasive disk in a path across a surface of the polishing pad between an inner radial distance from the axis of rotation and an outer radial distance from the axis of rotation, sweeping a sensor across the polishing pad while conditioning the polishing pad, measuring a thickness of the polishing pad at a plurality of positions between the inner radial distance and the outer radial distance with the sensor, and adjusting at least one of a dwell time or a pressure of the abrasive disk against the polishing pad for a portion of the path based on measurements of the thickness by the sensor such that the polishing pad wears to a more uniform thickness than without such adjustment.

1 . A method of controlling a conditioning process, comprising:
 rotating a polishing pad about an axis of rotation;   conditioning the polishing pad by sweeping an abrasive disk in a path across a surface of the polishing pad between an inner radial distance from the axis of rotation and an outer radial distance from the axis of rotation;   sweeping a sensor across the polishing pad while conditioning the polishing pad;   measuring a thickness of the polishing pad at a plurality of positions between the inner radial distance and the outer radial distance with the sensor; and   adjusting at least one of a dwell time or a pressure of the abrasive disk against the polishing pad for a portion of the path based on measurements of the thickness by the sensor such that the polishing pad wears to a more uniform thickness than without such adjustment.   
     
     
         2 . The method of  claim 1 , comprising adjusting the dwell time of the abrasive for the portion of the path. 
     
     
         3 . The method of  claim 1 , comprising adjusting the pressure of the abrasive disk against the polishing pad for the portion of the path. 
     
     
         4 . The method of  claim 1 , wherein sweeping the abrasive disk includes suspending the abrasive disk from an arm and pivoting the arm between a first angle and a second angle. 
     
     
         5 . The method of  claim 4 , comprising storing a pressure profile for the conditioning disk, the pressure profile identifying a pressure to apply as a function of an angular position of the arm, and wherein adjusting the pressure comprises adjusting the pressure profile. 
     
     
         6 . The method of  claim 4 , comprising storing an position profile for the conditioning disk, the position profile being an angular position for the arm as function of a time, and wherein adjusting the dwell time comprises adjusting the position profile. 
     
     
         7 . The method of  claim 4 , comprising suspending the sensor from the arm. 
     
     
         8 . The method of  claim 7 , wherein the sensor is positioned adjacent the disk. 
     
     
         9 . The method of  claim 7 , further comprising storing each measurement of the thickness by the sensor with an angular position of the arm at a time an associated measurement was made. 
     
     
         10 . The method of  claim 1 , wherein the sensor comprises an eddy current sensor. 
     
     
         11 . A method of operating a polishing system, comprising:
 installing a polishing pad on a rotatable platen;   sweeping a sensor across the polishing pad while the polishing pad is on the platen;   measuring a distance between the sensor and the platen at a plurality of positions between an inner radial distance and an outer radial distance with the sensor; and   detecting an air bubble trapped between the polishing pad and the sensor based on measurements of the distance by the sensor.   
     
     
         12 . The method of  claim 11 , further comprising removing the polishing pad prior to polishing a substrate with the polishing pad. 
     
     
         13 . The method of  claim 11 , further comprising suspending the sensor from an arm of a conditioner apparatus. 
     
     
         14 . The method of  claim 13 , wherein sweeping the sensor includes pivoting the arm. 
     
     
         15 . The method of  claim 1 , wherein the sensor comprises an eddy current sensor. 
     
     
         16 . A conditioner system, comprising:
 a base secured to a frame of a chemical mechanical polishing system;   an arm connected to the frame and pivotally movable by the base over a polishing pad of the chemical mechanical polishing system;   a conditioning head suspended from the arm to hold an abrasive disk against the polishing pad; and   an eddy current sensor suspended from the arm and positioned to measure a thickness of the polishing pad.   
     
     
         17 . The conditioner system of  claim 16 , wherein the eddy current sensor is suspended from the conditioning head. 
     
     
         18 . The conditioner system of  claim 16 , wherein the eddy current sensor is configured to contact the polishing pad. 
     
     
         19 . The conditioner system of  claim 16 , wherein the eddy current sensor is separated from the polishing pad by a gap. 
     
     
         20 . The conditioner system of  claim 16 , wherein the conditioning head and arm are configured such that pivoting the arm sweeps the abrasive disk in a path across a surface of the polishing pad between an inner radial distance from an axis of rotation of a platen and an outer radial distance from the axis of rotation, and comprising a controller configured to adjust at least one of a dwell time or a pressure of the abrasive disk against the polishing pad for a portion of the path based on measurements of the thickness by the sensor such that the polishing pad wears to a more uniform thickness than without such adjustment.