Programmable physical action during integrated circuit wafer cleanup

Abstract

Wafer cleaning systems ( 10, 25 ) utilizing both chemical and physical action to clean integrated circuit wafers ( 14, 24 ) is disclosed. Chemical cleaning action is provided by liquid retained within a tank ( 2, 22 ), sized either to hold a single wafer ( 24 ) or a batch of wafers ( 14 ) held within a carrier ( 12 ). Physical action is provided in the wafer cleaning system either by way of inert gas bubbling through a baffle ( 5 ) or by way of ultrasonic energy applied by transducers ( 28 ) located in the tank ( 2, 22 ). The systems ( 10, 25 ) have a programmable controller ( 20, 30 ) for initiating the physical cleaning action after insertion of the wafers ( 14, 24 ) into the chemical bath, and for ceasing the physical action prior to removal of the wafers ( 14, 24 ). After a waiting time after the ceasing of the physical action, to calm the chemical bath and to permit any retained bubbles to escape to the atmosphere, the wafers ( 14, 24 ) may then be removed from the chemical bath, with reduced risk of staining and particle release. A recirculating pump ( 35 ) and filter ( 33 ) system may also be incorporated to clean the chemical bath; during such time as wafers are not present in the chemical bath, the programmable controller ( 20, 30 ) may initiate the physical action to assist in cleaning of the tank ( 2, 22 ).

I claim:  
     
         1 . A method of cleaning an integrated circuit wafer during its manufacture, comprising the steps of: 
 immersing at least one partially fabricated integrated circuit wafer into a chemical bath;    causing a physical action to occur within the chemical bath to assist in the cleaning;    ceasing the physical action; and    then removing the at least one wafer from the chemical bath.    
     
     
         2 . The method of  claim 1 , further comprising: 
 after the ceasing step, waiting for a selected time prior to the removing step.    
     
     
         3 . The method of  claim 1 , further comprising: 
 repeating the steps of causing a physical action and ceasing the physical action before removing the at least one wafer from the chemical bath.    
     
     
         4 . The method of  claim 1 , wherein the step of causing the physical action comprises: 
 bubbling an inert gas into the chemical bath.    
     
     
         5 . The method of  claim 1 , wherein the step of causing the physical action comprises: 
 applying electrical energy to an ultrasonic transducer disposed within the chemical bath.    
     
     
         6 . The method of  claim 5 , wherein the step of causing the physical action further comprises: 
 bubbling an inert gas into the chemical bath.    
     
     
         7 . The method of  claim 1 , further comprising: 
 after the removing step, again causing the physical action while no wafer is disposed within the chemical bath.    
     
     
         8 . The method of  claim 7 , wherein the chemical bath is held within a tank; and further comprising: 
 during the step of causing the physical action while no wafer is disposed within the chemical bath, filtering the chemical bath to remove particles therefrom.    
     
     
         9 . The method of  claim 8 , further comprising: 
 monitoring the particle concentration in the chemical bath; and    ceasing the physical action responsive to the monitored particle concentration being below a threshold.    
     
     
         10 . The method of  claim 7 , further comprising: 
 ceasing the physical action; and    then repeating the immersing, causing, ceasing, and removing steps.    
     
     
         11 . The method of  claim 1 , wherein the immersing step immerses a single wafer into the chemical bath.  
     
     
         12 . The method of  claim 1 , wherein the immersing step immerses a plurality of wafers and a carrier holding the plurality of wafers into the chemical bath.  
     
     
         13 . A wafer cleaning apparatus, comprising: 
 a tank for holding a chemical bath liquid and at least one integrated circuit wafer to be cleaned by the liquid;    means, located within the tank, for producing a physical action within the liquid to assist in the cleaning of the at least one wafer; and    a programmable controller, coupled to the producing means, and programmed to control the producing means to activate the physical action for a selected duration, so that the physical action ceases while the at least one wafer is present in the liquid.    
     
     
         14 . The wafer cleaning apparatus of  claim 13 , wherein the producing means comprises: 
 an inlet coupled to the tank for receiving an inert gas;    a baffle, disposed within the tank and coupled to the inlet, for dispersing the inert gas into the liquid as bubbles.    
     
     
         15 . The wafer cleaning apparatus of  claim 14 , wherein the producing means further comprises: 
 a valve disposed in the inlet, for controlling the flow of the inert gas;    wherein the programmable controller is coupled to the valve.    
     
     
         16 . The wafer cleaning apparatus of  claim 13 , wherein the producing means comprises: 
 at least one ultrasonic transducer disposed within the tank;    wherein the programmable controller is coupled to the at least one ultrasonic transducer, to control the application of electrical energy thereto.    
     
     
         17 . The wafer cleaning apparatus of  claim 13 , wherein the programmable controller is also programmed to control the producing means to activate the physical action for a selected duration while no wafer is present in the liquid.  
     
     
         18 . The wafer cleaning apparatus of  claim 17 , further comprising: 
 a recirculating pump, having an input for receiving liquid from the tank, and having an output coupled to the tank, for recirculating liquid; and    a filter, disposed in series with the pump, for cleaning the recirculating liquid.    
     
     
         19 . The wafer cleaning apparatus of  claim 18 , further comprising: 
 a particle monitor, for measuring particulate concentration in the recirculating liquid.