Polishing slurry for ionic materials, method for selecting a dispersant to be contained in the polishing slurring, method for determining a mixing concentration of the selected dispersant and polishing method using said polishing slurry

Abstract

A polishing slurry is disclosed, which is to be used for polishing an ionic material, the polishing slurry including a dispersant which is to form a nonionic adsorbing layer on a surface of the ionic material. The dispersant may be selected by separately preparing first and second solutions containing first and second different dispersants, immersing test pieces each made of said ionic material into the first and second solutions, respectively, comparing a step between an etched portion and a non-etched portion of the test piece immersed in the first solution with a step between an etched portion and a non-etched portion of the test piece immersed in the second solution, and selecting the dispersant used in the solution in which the test piece having the smaller step is immersed.

1 . A polishing slurry to be used for polishing an ionic material, said polishing slurry comprising a dispersant which is to form a nonionic adsorbing layer on a surface of the ionic material.  
   
   
       2 . The polishing slurry claimed in  claim 1 , wherein said dispersant is a nonionic water-soluble synthetic polymer.  
   
   
       3 . The polishing slurry claimed in  claim 2 , wherein the nonionic water-soluble synthetic polymer is sodium carboxylmethyl cellulose (CMC).  
   
   
       4 . A dispersant-selecting method, which is adapted to select the dispersant to be incorporated into the polishing slurry claimed in  claim 1 , comprises separately preparing a first solution containing a first dispersant and a second solution containing a second dispersant different from the first one, immersing test pieces each made of said ionic material into the first and second solutions, respectively, while a portion of each of the test pieces is masked or not immersed, comparing a step between an etched portion and a non-etched portion of the test piece immersed in the first solution with a step between an etched portion and a non-etched portion of the test piece immersed in the second solution, and selecting the dispersant used in the solution in which the test piece having the smaller step is immersed.  
   
   
       5 . A dispersant-selecting method, which is adapted to select the dispersant to be incorporated into the polishing slurry claimed in  claim 1 , comprises separately preparing a first solution containing a first dispersant and a second solution containing a second dispersant different from the first one, immersing test pieces each made of said ionic material into the first and second solutions, respectively, comparing an average size of pits formed on the test piece immersed in the first solution by etching with an average size of pits formed on the test piece immersed in the second solution by etching, and selecting the dispersant used in the solution in which the test piece having the smaller pit size is immersed.  
   
   
       6 . A method for determining a mixing concentration of the dispersant selected by the selecting method in  claim 4 , which sets the mixing concentration of the above-selected dispersant to be incorporated into the claimed polishing slurry, comprises preparing a plurality of solutions having different concentrations of the dispersant, respectively, immersing test pieces made of an ionic material into the plurality of the solutions, respectively, while a portion of each of the test pieces is masked or not immersed, determining a relation between a step between an etched portion and a non-etched portion of each of the test pieces immersed in the plurality of the solutions, respectively, and the concentration of a corresponding one of the solutions, and setting the mixing concentration of the dispersant to be used in actual polishing based on the thus determined relation.  
   
   
       7 . A method for determining a mixing concentration of the dispersant selected by the selecting method in  claim 5 , which sets the mixing concentration of the above-selected dispersant to be incorporated into the claimed polishing slurry, comprises preparing a plurality of solutions having different concentrations of the dispersant, respectively, immersing test pieces made of an ionic material into the plurality of the solutions, respectively, while a portion of each of the test pieces is masked, determining a relation between a step between an etched portion and a non-etched portion of each of the test pieces immersed in the plurality of the solutions, respectively, and the concentration of a corresponding one of the solutions, and setting the mixing concentration of the dispersant to be used in actual polishing based on the thus determined relation.  
   
   
       8 . A polishing method comprises polishing an ionic material with a polishing slurry comprising a dispersant which forms a nonionic adsorbing layer on a surface of the ionic material, the dispersant being selected by a selecting method comprising separately preparing a first solution containing a first dispersant and a second solution containing a second dispersant different from the first one, immersing test pieces each made of said ionic material into the first and second solutions, respectively, while a portion of each of the test pieces is masked or not immersed, comparing a step between an etched portion and a non-etched portion of the test piece immersed in the first solution with a step between an etched portion and a non-etched portion of the test piece immersed in the second solution, and selecting the dispersant used in the solution in which the test piece having the smaller step is immersed, at a mixing concentration determined by the mixing concentration-determining method in  claim 6 .  
   
   
       9 . The polishing method comprises polishing an ionic material with a polishing slurry comprising a dispersant which is a nonionic water-soluble polymer and which forms a nonionic adsorbing layer on a surface of the ionic material, the dispersant being selected by a selecting method comprising separately preparing a first solution containing a first dispersant and a second solution containing a second dispersant different from the first one, immersing test pieces each made of said ionic material into the first and second solutions, respectively, while a portion of each of the test pieces is masked or not immersed, comparing a step between an etched portion and a non-etched portion of the test piece immersed in the first solution with a step between an etched portion and a non-etched portion of the test piece immersed in the second solution, and selecting the dispersant used in the solution in which the test piece having the smaller step is immersed, at a mixing concentration determined by the mixing concentration-determining method in  claim 6 .  
   
   
       10 . A polishing method comprises polishing an ionic material with a polishing slurry comprising a dispersant which forms a nonionic adsorbing layer on a surface of the ionic material, the dispersant being selected by a selecting method comprising separately preparing a first solution containing a first dispersant and a second solution containing a second dispersant different from the first one, immersing test pieces each made of said ionic material into the first and second solutions, respectively, comparing an average size of pits formed on the test piece immersed in the first solution by etching with an average size of pits formed on the test piece immersed in the second solution by etching, and selecting the dispersant used in the solution in which the test piece having the smaller pit size is immersed, at a mixing concentration determined by the mixing concentration-determining method in  claim 6 .  
   
   
       11 . The polishing method comprises polishing an ionic material with a polishing slurry comprising a dispersant which is a nonionic water-soluble polymer and which forms a nonionic adsorbing layer on a surface of the ionic material, the dispersant being selected by a selecting method comprising separately preparing a first solution containing a first dispersant and a second solution containing a second dispersant different from the first one, immersing test pieces each made of said ionic material into the first and second solutions, respectively, comparing an average size of pits formed on the test piece immersed in the first solution by etching with an average size of pits formed on the test piece immersed in the second solution by etching, and selecting the dispersant used in the solution in which the test piece having the smaller pit size is immersed, at a mixing concentration determined by the mixing concentration-determining method in  claim 6.