Cerium salt, producing method thereof, cerium oxide and cerium based polishing slurry

Abstract

A cerium salt wherein, when 20 g of the cerium salt is dissolved in a mixed liquid of 12.5 g of 6N nitric acid and 12.5 g of a 30% hydrogen peroxide aqueous solution, a concentration of an insoluble component present in the solution is 5 ppm or less by mass ratio to the cerium salt before dissolution and cerium oxide produced by processing the cerium salt at high temperatures. Scratch on a surface to be polished can be reduced when a cerium based polishing slurry containing the cerium oxide particles is used, since an amount of impurities in cerium oxide particles and cerium salt particles, raw material thereof, is reduced for high purification.

1 . A cerium salt wherein, when 20 g of the cerium salt is dissolved in a mixed liquid of 12.5 g of 6N nitric acid and 12.5 g of a 30% hydrogen peroxide aqueous solution, a concentration of an insoluble component present in the solution is 5 ppm or less by mass ratio.  
   
   
       2 . The cerium salt according to  claim 1 , wherein the insoluble component is a substance containing silicon.  
   
   
       3 . A producing method of a cerium salt where through obtaining at least one kind of cerium-containing intermediate from a cerium compound a precipitating agent is added to obtain a precipitate of a cerium salt, comprising at least one time of separating and removing an insoluble component from the cerium-containing intermediate in a solution state.  
   
   
       4 . The producing method of a cerium salt according to  claim 3 , comprising adding a precipitating agent to the cerium-containing rare earth salt solution to obtain a precipitate of the cerium salt, wherein a precipitating agent from which an insoluble component is removed in advance is added to the cerium-containing rare earth salt solution to precipitate.  
   
   
       5 . The producing method of a cerium salt according to  claim 3 , comprising obtaining a solution by mixing the cerium salt and 6N nitric acid, separating and removing an insoluble component in the solution, and adding after the removal a precipitating agent to precipitate a purified cerium salt.  
   
   
       6 . The producing method of a cerium salt according to  claim 3 , wherein the precipitating agent is in a solution state where the precipitating agent is dissolved in advance in a solvent and the insoluble component is separated and removed.  
   
   
       7 . Cerium oxide obtained by subjecting the cerium salt obtained according to  claim 1  to a high temperature process of  250 ° C. or more.  
   
   
       8 . The cerium oxide according to  claim 7 , wherein when 20 g of the cerium oxide is dissolved in a mixed liquid of 12.5 g of 6N nitric acid and 12.5 g of a 30% hydrogen peroxide aqueous solution, a concentration of an insoluble component present in the solution is 10 ppm or less by mass ratio.  
   
   
       9 . Cerium oxide in which when 20 g of the cerium oxide is dissolved in a mixed liquid of 12.5 g of 6N nitric acid and 12.5 g of a 30% hydrogen peroxide aqueous solution, a concentration of an insoluble component present in the solution is 10 ppm or less by mass ratio.  
   
   
       10 . A cerium based polishing slurry, comprising the cerium oxide according to  claim 7  or  9 .  
   
   
       11 . A cerium based polishing slurry in which when 20 g of the cerium based polishing slurry is dissolved in a mixed liquid of 12.5 g of 6N nitric acid and 12.5 g of a 30% hydrogen peroxide aqueous solution, a concentration of an insoluble component present in the solution is 10 ppm or less by mass ratio.  
   
   
       12 . Cerium oxide obtained by subjecting the cerium salt obtained according to the producing method of  claim 3  to a high temperature process of 250° C. or more.