Method for controlling polysilicon removal

Abstract

The invention is directed to a method of chemically-mechanically polishing a substrate comprising polysilicon and a material selected from silicon oxide and silicon nitride with a chemical-mechanical polishing system comprising an abrasive, a polyethylene oxide/polypropylene oxide copolymer, water, and a polishing pad.

1 . A method of chemically-mechanically polishing a substrate, which method comprises: 
 (i) contacting a substrate comprising polysilicon and a material selected from silicon oxide and silicon nitride with a chemical-mechanical polishing system comprising: 
 (a) an abrasive,  
 (b) a liquid carrier,  
 (c) about 1 ppm to about 1000 ppm, based on the weight of the liquid carrier and any components dissolved or suspended therein, of a polyethylene oxide/polypropylene oxide copolymer having an HLB of about 15 or less, and  
 (d) a polishing pad,  
   (ii) moving the polishing pad relative to the substrate, and    (iii) abrading at least a portion of the substrate to polish the substrate.    
     
     
         2 . The method of  claim 1 , wherein the amount of copolymer is about 100 ppm to about 800 ppm.  
     
     
         3 . The method of  claim 1 , wherein the copolymer has a molecular weight of about 4000 g/mol or less.  
     
     
         4 . The method of  claim 1 , wherein the copolymer has an HLB of about 8 or less.  
     
     
         5 . The method of  claim 1 , wherein the copolymer is terminated with a hydroxyl group.  
     
     
         6 . The method of  claim 1 , wherein the abrasive is selected from the group consisting of alumina, ceria, silica, zirconia, and combinations thereof.  
     
     
         7 . The method of  claim 6 , wherein the abrasive is fumed silica.  
     
     
         8 . The method of  claim 6 , wherein the abrasive is ceria.  
     
     
         9 . The method of  claim 1 , wherein the abrasive is suspended in the liquid carrier.  
     
     
         10 . The method of  claim 9 , wherein the amount of abrasive is about 5 wt. % to about 20 wt. %, based on the weight of the liquid carrier and any components dissolved or suspended therein.  
     
     
         11 . The method of  claim 10 , wherein the amount of abrasive is about 8 wt. % to about 15 wt. %.  
     
     
         12 . The method of  claim 9 , wherein the liquid carrier comprises water.  
     
     
         13 . The method of  claim 12 , wherein the pH is about 5 to about 12.  
     
     
         14 . The method of  claim 13 , wherein the pH is about 7 to about 9.  
     
     
         15 . The method of  claim 1 , wherein the polishing system further comprises a complexing agent dissolved or suspended in the liquid carrier.  
     
     
         16 . The method of  claim 1 , wherein the polishing system further comprises an amine dissolved or suspended in the liquid carrier.  
     
     
         17 . The method of  claim 1 , wherein the substrate comprises both silicon oxide and silicon nitride.  
     
     
         18 . The method of  claim 1 , wherein the polishing removal rate of the polysilicon is substantially the same as the removal rate under the same conditions except for the absence of the copolymer.