Apparatus and method for treating etching solution

Abstract

An apparatus and method for treating an etching solution, where the replacement frequency of the etching solution is reduced, while the inclusion of impurities in the treated etching solution is prevented. An apparatus for treating an etching solution in order to reuse the etching solution used in etching treatment of silicon, where the apparatus includes: membrane separation means 3 which performs membrane separation treatment on the etching solution supplied from an etching bath 2 ; and circulating means 6 which circulates a permeated solution supplied from the membrane separation means 3 to the etching bath 2 . The membrane separation means 3 includes a UF membrane module 4 and an NF membrane module 5 . Alkaline and organic substances may be added to the etching solution supplied from the membrane separation means 3.

1 . An apparatus for treating an etching solution in order to circulate and reuse an etching solution used in etching treatment of silicon, comprising:
 membrane separation means which performs membrane separation treatment on the etching solution supplied from an etching bath; and   circulating means which circulates a permeated solution of the membrane separation means to the etching bath.   
     
     
         2 . The apparatus for treating an etching solution according to  claim 1 , wherein the membrane separation means is provided with a nanofiltration membrane which selectively removes multivalent ions having a valence of two or more. 
     
     
         3 . The apparatus for treating an etching solution according to  claim 1 , wherein the membrane separation means is provided with a nanofiltration membrane which removes multivalent ions having a valence of two or more, alkali metal ions having a valence of one, and hydroxide ions. 
     
     
         4 . The apparatus for treating an etching solution according to  claim 2 , wherein the nanofiltration membrane is resistant to an alkali solution, is resistant to a temperature up to 70° C., and has a molecular weight cut off of 150 to 2000. 
     
     
         5 . The apparatus for treating an etching solution according to  claim 2 , wherein the membrane separation means is provided with an ultrafiltration membrane which is installed upstream of the nanofiltration membrane. 
     
     
         6 . The apparatus for treating an etching solution according to  claim 1 , wherein said apparatus further comprises concentration measuring means which measures the alkali concentration and the organic substance concentration in the permeated solution supplied from the membrane separation means;
 alkalinity adding means which adds an alkalinity to the permeated solution depending on the alkali concentration in the permeated solution measured with the concentration measuring means; and   organic substance adding means which adds an organic substance to the permeated solution depending on the organic substance concentration in the permeated solution measured with the concentration measuring means.   
     
     
         7 . The apparatus for treating an etching solution according to  claim 6 , wherein said apparatus further comprises dilution water adding means which adds dilution water to the permeated solution depending on the alkali concentration and/or the organic substance concentration. 
     
     
         8 . The apparatus for treating an etching solution according to  claim 6 , wherein the electric conductivity, or the electric conductivity and Na ion concentration of the etching solution supplied from the etching bath or the permeated solution of the membrane separation means are measured, and then the alkalinity adding means or the organic substance adding means is controlled based upon the results of the measurement. 
     
     
         9 . The apparatus for treating an etching solution according to  claim 6 , wherein said apparatus further comprises signal output means which outputs membrane exchange signals based on the electric conductivities of the membrane separation means before and after transport or the alkali concentration of the permeated solution. 
     
     
         10 . The apparatus for treating an etching solution according to  claim 1 , wherein said apparatus further comprises at least one temperature adjusting means selected of the group consisting of solution temperature adjusting means for adjusting a solution temperature (T 1 ) of the etching solution supplied to the membrane separation means and solution temperature adjusting means for adjusting a solution temperature (T 2 ) of the permeated solution of the membrane separation means. 
     
     
         11 . The apparatus for treating an etching solution according to  claim 10 , wherein said apparatus further comprises a heat exchange unit which performs heat exchange between a solution returning from the membrane separation means to the etching bath and a solution flowing out of the etching bath for the membrane separation means. 
     
     
         12 . A method for treating an etching solution using the apparatus for treating an etching solution according to  claim 1 .