Methanol-containing silica-based cmp compositions

Abstract

The invention provides a polishing composition comprising (a) a silica abrasive, (b) methanol, and (c) a liquid carrier, wherein the polishing composition has a pH of 1 to 6, and the polishing composition is colloidally stable. The invention also provides a method for polishing a substrate comprising a silicon-based dielectric layer using the polishing composition. The invention further provides a method of stabilizing a silica abrasive in a polishing composition by contacting the abrasive with methanol.

1 . A polishing composition comprising: 
 (a) silica abrasive,    (b) methanol, and    (c) a liquid carrier,    wherein the polishing composition has a pH of about 1 to about 6 and the interaction between the silica abrasive and the methanol provides colloidal stability to the polishing composition.    
     
     
         2 . The polishing composition of  claim 1 , wherein the silica abrasive is selected from the group consisting of fumed silica, colloidal silica, silica-coated abrasive particles, and combinations thereof.  
     
     
         3 . The polishing composition of  claim 1 , wherein the polishing composition has a pH of about 1.5 to about 4.  
     
     
         4 . The polishing composition of  claim 1 , wherein the liquid carrier comprises water.  
     
     
         5 . The polishing composition of  claim 1 , wherein the methanol is present in an amount of about 100 ppm to about 1500 ppm.  
     
     
         6 . The polishing composition of  claim 5 , wherein the methanol is present in an amount of about 100 ppm to about 800 ppm.  
     
     
         7 . The polishing composition of  claim 1 , wherein the silica abrasive is present in an amount of about 0.5 wt. % to about 5 wt. %.  
     
     
         8 . The polishing composition of  claim 5 , wherein about 200 ppm to about 3000 ppm of methanol is present per wt. % of silica abrasive.  
     
     
         9 . The polishing composition of  claim 6 , wherein about 200 ppm to about 1600 ppm of methanol is present per wt. % of silica abrasive.  
     
     
         10 . The polishing composition of  claim 1 , wherein the composition further comprises an oxidizer.  
     
     
         11 . The polishing composition of  claim 1 , wherein the composition further comprises a complexing agent.  
     
     
         12 . A method of polishing a substrate comprising (i) contacting a substrate comprising a silicon-based layer with the polishing composition of  claim 1 , and (ii) abrading at least a portion of the substrate with the polishing composition to polish the substrate.  
     
     
         13 . The method of  claim 12 , wherein the substrate further comprises a tungsten layer.  
     
     
         14 . The method of  claim 12 , wherein the substrate further comprises a copper or nickel layer.  
     
     
         15 . The method of  claim 12 , wherein the silicon-based layer is silicon dioxide and the substrate further comprises a silicon nitride layer.  
     
     
         16 . A method of stabilizing a polishing composition comprising a silica abrasive and a liquid carrier comprising (i) providing silica abrasive, (ii) providing a liquid carrier for the silica abrasive, and (iii) contacting the silica abrasive with methanol to form a stabilized polishing composition.  
     
     
         17 . The method of  claim 16 , wherein the polishing composition has a pH of about 1 to about 6.