Method of recycling abrasive slurry

Abstract

A method of recycling an abrasive slurry for recycling a slurry that: contains colloidal silica; and has been used in polishing semiconductor wafer(s) is provided. The method includes: adding a dispersant to the used slurry having been collected so as to prevent the used slurry from being gelled; irradiating ultrasound to the used slurry having been added with the dispersant so as to disperse a gelled portion and aggregated silica in the used slurry; and, by using a filter, removing a foreign substance contained in the used slurry having been irradiated with the ultrasound.

1 . A method of recycling an abrasive slurry for recycling a slurry containing colloidal silica, the slurry being a used slurry having been used in polishing semiconductor wafer(s), the method comprising:
 adding a dispersant to the used slurry having been collected so as to prevent the used slurry from being gelled;   irradiating ultrasound to the used slurry having been added with the dispersant so as to disperse a gelled portion and aggregated silica in the used slurry; and   removing a foreign substance contained in the used slurry having been irradiated with the ultrasound, the foreign substance being removed by a filter.   
   
   
       2 . The method of recycling an abrasive slurry according to  claim 1 , wherein
 a pH value of the used slurry is measured and the pH value is adjusted by adding an alkali solution before the dispersant is added to the used slurry.   
   
   
       3 . The method of recycling an abrasive slurry according to  claim 1 , wherein
 viscosity of the used slurry is measured and the viscosity is adjusted by adding a water-soluble polymer before the dispersant is added to the used slurry.   
   
   
       4 . The method of recycling an abrasive slurry according to  claim 1 , wherein
 a temperature of the used slurry is measured and the temperature is adjusted by using a heat exchanger before the dispersant is added to the used slurry.   
   
   
       5 . The method of recycling an abrasive slurry according to  claim 1 , wherein
 metal ion contained in the used slurry is removed after the ultrasound is irradiated to the used slurry.   
   
   
       6 . The method of recycling an abrasive slurry according to  claim 5 , wherein
 the metal ion contained in the used slurry is removed by adding a chelate agent to the used slurry.