Method for Producing Polishing Agent, Polishing Agent Produced Thereby and Method for Producing Silicon Wafer

Abstract

The present invention is a method for producing a polishing agent in which silica particles are dispersed in an aqueous solution, comprising at least a step of removing metal compound ions from a prepared silica sol by ion exchange (B); a step of purifying further the ion-exchanged silica sol (D); a step of adding alkali metal hydroxide to the purified silica sol (F); and a step of adding an acid to the silica sol to which the alkali metal hydroxide is added (G). There is provided a method for producing a polishing agent which can extremely effectively suppress metal contamination when a silicon wafer or the like is polished can be produced.

1 - 13 . (canceled) 
   
   
       14 . A method for producing a polishing agent in which silica particles are dispersed in an aqueous solution, comprising at least a step of removing metal ions from a prepared silica sol by ion exchange; a step of purifying further the ion-exchanged silica sol; a step of adding alkali metal hydroxide to the purified silica sol; and a step of adding an acid to the silica sol to which the alkali metal hydroxide is added. 
   
   
       15 . The method for producing a polishing agent according to  claim 14 , wherein a strong acid is used as the acid. 
   
   
       16 . The method for producing a polishing agent according to  claim 14 , wherein after the alkali metal hydroxide is added, quaternary ammonium salt is added either together with the acid, or before or after the acid is added. 
   
   
       17 . The method for producing a polishing agent according to  claim 15 , wherein after the alkali metal hydroxide is added, quaternary ammonium salt is added either together with the acid, or before or after the acid is added. 
   
   
       18 . The method for producing a polishing agent according to  claim 16 , wherein tetramethylammonium hydroxide is used as the quaternary ammonium salt. 
   
   
       19 . The method for producing a polishing agent according to  claim 17 , wherein tetramethylammonium hydroxide is used as the quaternary ammonium salt. 
   
   
       20 . The method for producing a polishing agent according to  claim 14 , wherein after the alkali metal hydroxide is added, an organic chelating agent is added either together with the acid, or before or after the acid is added. 
   
   
       21 . The method for producing a polishing agent according to  claim 19 , wherein after the alkali metal hydroxide is added, an organic chelating agent is added either together with the acid, or before or after the acid is added. 
   
   
       22 . The method for producing a polishing agent according to  claim 20 , wherein at least one selected from the group consisting of polyamino-polycarboxylic acid derivatives and salts of polyamino-polycarboxylic acid derivatives is used as the organic chelating agent. 
   
   
       23 . The method for producing a polishing agent according to  claim 21 , wherein at least one selected from the group consisting of polyamino-polycarboxylic acid derivatives and salts of polyamino-polycarboxylic acid derivatives is used as the organic chelating agent. 
   
   
       24 . The method for producing a polishing agent according to  claim 14 , wherein ion exchange is carried out as the step of purifying. 
   
   
       25 . The method for producing a polishing agent according to  claim 23 , wherein ion exchange is carried out as the step of purifying. 
   
   
       26 . The method for producing a polishing agent according to  claim 14 , wherein an alkaline silica sol having a pH in the range of 8 to 13 is used as the prepared silica sol. 
   
   
       27 . The method for producing a polishing agent according to  claim 25 , wherein an alkaline silica sol having a pH in the range of 8 to 13 is used as the prepared silica sol. 
   
   
       28 . The method for producing a polishing agent according to  claim 14 , wherein a silica sol containing spherical-silica particles having an average particle size in the range of 11 to 13 nm is used as the prepared silica sol. 
   
   
       29 . The method for producing a polishing agent according to  claim 27 , wherein a silica sol containing spherical-silica particles having an average particle size in the range of 11 to 13 nm is used as the prepared silica sol. 
   
   
       30 . The method for producing a polishing agent according to  claim 14 , wherein after the ion exchange is carried out, the silica sol has a pH in the range of 2 to 4. 
   
   
       31 . The method for producing a polishing agent according to  claim 29 , wherein after the ion exchange is carried out, the silica sol has a pH in the range of 2 to 4. 
   
   
       32 . The method for producing a polishing agent according to  claim 14 , wherein the silica sol after the acid is added has a pH in the range of 10 to 12. 
   
   
       33 . The method for producing a polishing agent according to  claim 31 , wherein the silica sol after the acid is added has a pH in the range of 10 to 12. 
   
   
       34 . The polishing agent produced by the method according to  claim 14 . 
   
   
       35 . The polishing agent produced by the method according to  claim 33 . 
   
   
       36 . A method for producing a silicon wafer comprising at least a polishing step, wherein as the polishing step, the wafer is polished by contacting and rubbing with a polishing pad with providing the polishing agent produced by the method according to  claim 14  to the polishing pad. 
   
   
       37 . A method for producing a silicon wafer comprising at least a polishing step, wherein as the polishing step, the wafer is polished by contacting and rubbing with a polishing pad with providing the polishing agent produced by the method according to  claim 33  to the polishing pad.