Semiconductor wafer washing system and method of supplying chemicals to the washing tanks of the system

Abstract

A semiconductor wafer washing system can execute a method in which the washing solution is quickly changed over and over again without the need to alter the structure of the system. The wafer washing system includes a washing solution supply section in which a plurality of chemicals are stored separately, and from which selected ones of the chemicals can be supplied in a predetermined ratio into a washing tank. A circulation section includes circulation piping connected to the washing tank for circulating the washing solution to and from the tank. A discharge section selectively discharges residual chemicals or washing solution from the washing solution supply section, the washing tank and the circulation section. A controller controls the flow of chemicals and washing solution in the washing solution supply section, the circulation section and the discharge section, respectively.

1 . A method of producing semiconductor wafer washing solution during the manufacturing of semiconductor devices, said method comprising: 
 storing chemicals, capable of constituting different forms of washing solution, separately in respective chemical storage tanks;    providing a washing tank having a main part, and a supplementary part extending around and partitioned from said main part;    supplying chemicals from respective ones of the chemical storage tanks into the main part of the washing tank in a predetermined ratio to produce an original washing solution in the washing tank and until a portion of the washing solution overflows the main part of the washing tank into the supplementary part;    circulating the washing solution that has flown into the supplementary part of the washing tank back into the main part of the washing tank to facilitate the mixing of the chemicals constituting the washing solution;    subsequently submerging semiconductor wafers into the washing solution in the main part of the washing tank to thereby wash the wafers; and    draining washing solution circulating from the supplementary part of the washing tank back to the main part of the washing tank.    
   
   
       2 . The method as defined in  claim 1 , wherein said supplying of the chemicals into the main part of the washing tank comprises measuring the flow rates of the chemicals, respectively, as the chemicals flow from the chemical storage tanks towards the main part of the washing tank, and regulating the flow of the chemicals based on the measured flow rates.  
   
   
       3 . The method as defined in  claim 1 , wherein said supplying of the chemicals into the main part comprises supplying the chemicals into a mixing tank whereby the chemicals are mixed together, measuring the level of the mixture of chemicals in the mixing tank, and supplying the mixture of chemicals from the mixing tank into the main part of the washing tank once the chemicals supplied into the mixing tank rise to a predetermined level in the washing tank.  
   
   
       4 . The method as defined in  claim 3 , wherein said supplying of the mixture of chemicals from the mixing tank into the main part of the washing tank comprises introducing purge gas into the mixing tank to pressurize the interior thereof.  
   
   
       5 . The method as defined in  claim 4 , and further comprising cutting off the flow of the mixture of chemicals from the mixing tank to the washing tank, and positioning the end of a discharge guide pipe at a predetermined position in the top portion of the mixing tank, and while the flow of the mixture of chemicals from the mixing tank to the washing tank is cut off, opening the discharge guide pipe to a drain when the level of the chemicals in the tank exceeds said predetermined level, whereby pressure in the mixing tank created by the purge gas discharges an excess of the mixture of chemicals from the mixing tank through the discharge guide pipe and to the drain.  
   
   
       6 . The method as defined in  claim 3 , and further comprising cutting off the flow of the mixture of chemicals from the mixing tank to the washing tank, and positioning the end of a discharge guide pipe at a predetermined position in the bottom portion of the mixing tank, and while the flow of the mixture of chemicals from the mixing tank to the washing tank is cut off, opening the discharge pipe to a drain.  
   
   
       7 . The method as defined in  claim 1 , and further comprising filtering the washing solution circulating from the supplementary part of the washing tank towards the main part of the washing tank to remove impurities from the washing solution, and effecting a heat exchange with the washing solution circulating from the supplementary part of the washing tank towards the main part of the washing tank to maintain the washing solution at a constant temperature while the wafers are being washed.  
   
   
       8 . The method as defined in  claim 7 , wherein said circulating of the washing solution from the supplementary part of the washing tank back to the main part of the washing tank comprises measuring the pressure of the washing solution flowing from the supplementary part of the washing tank, and based on the measured pressure, regulating the pressure of the washing solution that is flowing from the supplementary part of the washing tank back to the main part of the washing tank, and wherein said draining of the washing solution circulating from the supplementary part of the washing tank back to the main part of the washing tank is carried out when the pressure of the washing solution flowing from the supplementary part of the washing tank exceeds a predetermined pressure.  
   
   
       9 . The method as defined in  claim 1 , and further comprising drawing the original washing solution from the washing tank into a washing solution storage tank after the wafers have been washed, and subsequently supplying chemicals from respective ones of the chemical storage tanks into the main part of the washing tank in a ratio different from said predetermined ratio to produce a new form of washing solution in the washing tank.  
   
   
       10 . The method as defined in  claim 9 , and further comprising, after the original washing solution has been drawn into the washing solution storage tank and before the chemicals constituting the new form of washing solution have been supplied into the washing tank, supplying a cleaning washing solution into the washing tank, circulating the cleaning washing solution between the main and supplementary parts of the washing tank to thereby clean the washing tank, and then draining the cleaning washing solution.  
   
   
       11 . The method as defined in  claim 9 , and further comprising drawing said new form of the washing solution from said washing tank into another washing solution storage tank, supplying chemicals from respective ones of the chemical storage tanks into the main part of the washing tank in said predetermined ratio to produce a cleaning washing solution in the washing tank having the same characteristics as the original washing solution that is stored in the washing solution storage tank, circulating the cleaning washing solution between the main and supplementary parts of the washing tank to thereby clean the washing tank, subsequently draining the cleaning washing solution, and, after the washing tank is cleaned, drawing the original washing solution from the washing solution storage tank back into the washing tank.  
   
   
       12 . The method as defined in  claim 9 , and further comprising drawing said new form of the washing solution from said washing tank into another washing solution storage tank, subsequently supplying the original washing solution from the washing solution storage tank back into the washing tank to produce a cleaning washing solution in the washing tank, circulating the cleaning washing solution between the main and supplementary parts of the washing tank to thereby clean the washing tank, subsequently draining the cleaning washing solution, and after the washing tank is cleaned supplying chemicals from respective ones of the chemical storage tanks into the main part of the washing tank in said predetermined ratio to produce a second batch of washing solution in the washing tank having the same characteristics as the original washing solution.  
   
   
       13 . The method as defined in  claim 1 , and further comprising temporarily storing the washing solution drained in the course of its circulating from the supplementary part of the washing tank back to the main part of the washing tank, diluting the temporarily stored washing solution, and then discharging the diluted washing solution.