Etching method and apparatus for semiconductor wafers

Abstract

A method for etching semiconductor wafers in an etching apparatus including an etching bath filled with an etchant and capable of setting liquid temperature and process sequence, comprises selecting a predetermined etching program suitable for etching of the semiconductor wafer, counting the number of the semiconductor wafers to be charged in the etching bath before the etching, calculating a temperature drop of the etchant based on the counted number, setting the liquid temperature of the etchant to an initial temperature B obtained by adding the temperature drop of the etchant to a predetermined etching temperature A, charging the semiconductor wafers in the etching bath at a predetermined timing to etch the semiconductor wafers, and setting the liquid temperature at the predetermined etching temperature A, immediately before or after the liquid temperature reaches the initial temperature B.

1 - 8 . (canceled)  
   
   
       9 . An apparatus for etching semiconductor wafers, comprising: 
 an etching bath in which an etchant is filled;    a counter which counts the number of silicon wafers to be charged in the etching bath before charging the wafers into the etching bath;    a computer which calculates a temperature drop of the etchant at a time of charging the semiconductor wafers based on the number of wafers, and set an initial temperature B of the etchant at the time of charging the semiconductor wafers to be higher than a predetermined etching temperature A by the temperature drop;    a first heater disposed on at least a part of an outer wall of the etching bath; and    a temperature adjustment unit which controls heating of the first heater to control a temperature of the etchant at the initial temperature B or the predetermined etching temperature A.    
   
   
       10 . The apparatus according to  claim 9 , further comprising a transfer system in which the semiconductor wafers are mounted on a holder to be charged into the etching bath, and the holder is transferred to the etching bath.  
   
   
       11 . The apparatus according to  claim 10 , wherein the transfer system charges the semiconductor wafers mounted on the holder into the etching bath, after the temperature of the etchant reaches the initial temperature B.  
   
   
       12 . The apparatus according to  claim 10 , wherein the computer calculates the initial temperature B including a thermal capacity of the holder.  
   
   
       13 . The apparatus according to  claim 9 , wherein the temperature adjustment unit controls the predetermined etching temperature A at not higher than a boiling point of the etchant.  
   
   
       14 . The apparatus according to  claim 9 , further comprising a concentration monitor which monitors a concentration of the etchant.  
   
   
       15 . The apparatus according to  claim 14 , further comprising a pure water replenishing unit which replenishes pure water to keep the concentration of the etchant constant, when the concentration of the etchant is higher than a desired concentration.  
   
   
       16 . The apparatus according to  claim 9 , further comprising a wafer preheating unit which preheats the semiconductor wafers before charging the semiconductor wafers into the etching bath, so that a difference between the initial temperature B and the predetermined etching temperature A is minimized.  
   
   
       17 . The apparatus according to  claim 9 , wherein the etching bath is configured to keep H 3 PO 4  as the etchant.  
   
   
       18 . The apparatus according to  claim 9 , wherein the etching bath includes an inner bath in which the etchant is filled for the wafers to be charged, and an outer bath which is disposed along an outside upper end of the inner bath to receive an overflow of the etchant, and the first heater is disposed over an outer surface of the inner bath.  
   
   
       19 . The apparatus according to  claim 9 , further comprising a circulation system including an outlet pipe from the etching bath, a filter, a pump, and a supply pipe to the etching bath to circulate the etchant filled in the etching bath.  
   
   
       20 . The apparatus according to  claim 19 , wherein the circulation system includes a second heater controlled by the temperature adjustment unit to heat the etchant.