Closed-loop control of cmp slurry flow

Abstract

Embodiments of the present invention generally relate to methods for chemical mechanical polishing a substrate. The methods generally include measuring the thickness of a polishing pad having grooves or other slurry transport features on a polishing surface. Once the depth of the grooves on the polishing surface is determined, a flow rate of a polishing slurry is adjusted in response to the determined groove depth. A predetermined number of substrates are polished on the polishing surface. The method can then optionally be repeated.

1 . A method, comprising:
 (a) measuring a thickness of a polishing pad, the polishing pad having grooves disposed in a polishing surface of the polishing pad;   (b) determining a depth of the grooves disposed in the polishing surface;   (c) adjusting a flow rate of a polishing slurry introduced to the polishing surface in response to the determined depth of the grooves disposed in the polishing surface;   (d) polishing a predetermined number of substrates; and   (e) repeating (a)-(e).   
     
     
         2 . The method of  claim 1 , wherein the predetermined number of substrates is about 500 substrates. 
     
     
         3 . The method of  claim 1 , wherein the predetermined number of substrates is about 1000 substrates. 
     
     
         4 . The method of  claim 1 , wherein the grooves disposed in the polishing pad surface have an initial depth of about 40 mils. 
     
     
         5 . The method of  claim 1 , wherein the adjusting the flow rate comprises reducing the flow rate of the polishing slurry as the depth of the grooves decreases. 
     
     
         6 . The method of  claim 5 , wherein the measuring a thickness of a polishing pad comprises measuring the thickness using an inductive sensor. 
     
     
         7 . The method of  claim 6 , wherein the adjusting the flow rate comprises associating the determined depth of the grooves to a predetermined slurry flow rate located in a look-up table, the look-up table stored on a computer-readable medium. 
     
     
         8 . A method, comprising:
 (a) measuring a thickness of a polishing pad, the polishing pad having grooves disposed in a polishing surface of the polishing pad;   (b) comparing the measured thickness of the polishing pad to an initial pre-polish thickness of the polishing pad to calculate a reduction in polishing pad thickness;   (c) calculating a depth of the grooves disposed in the polishing surface;   (d) adjusting a flow rate of a polishing slurry introduced to the polishing surface in response to the determined depth of the grooves disposed in the polishing surface;   (e) polishing a predetermined number of substrates, the polishing comprising contacting each of the predetermined number of substrates to the polishing pad, and introducing the polishing slurry to the polishing pad at the adjusted flow rate for each of the predetermined number of substrates; and   (f) repeating (a)-(e).   
     
     
         9 . The method of  claim 8 , wherein the adjusting a flow rate of a polishing slurry comprises reducing the flow rate of the polishing slurry as the depth of the grooves disposed in the polishing surface decreases, such that a substantially constant polishing removal rate is maintained. 
     
     
         10 . The method of  claim 9 , wherein the predetermined number of substrates is at least about 500 substrates. 
     
     
         11 . The method of  claim 10 , wherein the adjusting a flow rate comprises associating the determined depth of the grooves to a slurry flow rate located in a look-up table stored in a computer-readable medium. 
     
     
         12 . The method of  claim 11 , wherein the grooves disposed in the polishing pad surface have an initial depth of about 60 mils. 
     
     
         13 . The method of  claim 12 , wherein the measuring a thickness of a polishing pad comprises measuring the thickness using an inductive sensor. 
     
     
         14 . A method, comprising:
 (a) measuring a thickness of a polishing pad, the polishing pad having grooves disposed in a polishing surface of the polishing pad;   (b) comparing the measured thickness of the polishing pad to an initial pre-polish thickness of the polishing pad to determine a reduction in polishing pad thickness;   (c) calculating a depth of the grooves disposed in the polishing surface;   (d) comparing the calculated depth of the grooves to a value stored in a look-up table;   (d) introducing a slurry to the polishing pad at a predetermined flow rate; the predetermined flow rate dependent upon the calculated depth of the grooves;   (e) polishing a predetermined number of substrates; and   (f) repeating (a)-(e).   
     
     
         15 . The method of  claim 14 , wherein the grooves disposed in the polishing pad surface have an initial depth of about 40 mils. 
     
     
         16 . The method of  claim 15 , further comprising replacing the polishing pad when the grooves have a depth of about 5 mils or less. 
     
     
         17 . The method of  claim 16 , wherein the introducing a slurry to the polishing pad comprises reducing the flow rate of the polishing slurry as the depth of the grooves disposed in the polishing surface decreases, such that a substantially constant polishing removal rate is maintained. 
     
     
         18 . The method of  claim 17 , wherein the measuring a thickness of the polishing pad comprises measuring the thickness using an inductive sensor. 
     
     
         19 . The method of  claim 18 , wherein the predetermined number of substrates is at least about 500 substrates. 
     
     
         20 . The method of  claim 18 , wherein the calculating a depth of the grooves disposed in the polishing surface further comprises determining the volume of the grooves disposed in the polishing surface.