Endpoint compensation in electroprocessing

Abstract

Method for process control of electro-processes is provided. In one embodiment, the method includes processing a conductive layer formed on a wafer using a target endpoint, detecting breakthrough of the conductive layer to expose portions of an underlying layer, and adjusting the target endpoint in response to the detected breakthrough. In another embodiment, the target endpoint is adjusted relative to an amount of underlying layer exposed through the conductive layer.

1 . A method for producing a desired profile on a wafer by electro-processing, comprising: 
 electro-processing a conductive layer formed on the wafer;    detecting breakthrough of the conductive layer to expose portions of an underlying layer; and    adjusting a target endpoint of the electro-processing process in response to the detected breakthrough.    
     
     
         2 . The method of  claim 1 , wherein the step of electro-processing further comprises: 
 determining a pre-processing profile of the wafer;    providing a target profile; and    determining a difference between the pre-processing profile and the target profile.    
     
     
         3 . The method of  claim 1 , wherein the step of electro-processing further comprises: 
 determining an amount of charge removed from the wafer; and    terminating the electro-processing process when the desired profile is substantially achieved according to the determined amount of charge removed.    
     
     
         4 . The method of  claim 3 , wherein the step of determining the amount of charge removed from the wafer further comprises: 
 determining an amount of charge removed from the wafer by each of a plurality of electrodes biased relative to the wafer; and    terminating the electro-processing process at electrodes when the desired profile is substantially achieved according to the determined amount of charge removed for the respective electrode.    
     
     
         5 . The method of  claim 1 , wherein the step of detecting breakthrough of the conductive layer further comprises: 
 sensing a discontinuity in a metric of electro-processing.    
     
     
         6 . The method of  claim 5 , wherein the metric of electro-processing is current passing between an electrode biased relative to the wafer.  
     
     
         7 . The method of  claim 5 , wherein the metric of electro-processing is voltage measured between an electrode and the water.  
     
     
         8 . The method of  claim 1 , wherein step of adjusting the target endpoint further comprises: 
 updating a target endpoint in response to an amount of the underlying layer exposed through the conductive layer.    
     
     
         9 . The method of  claim 8 , wherein step of updating the target endpoint further comprises: 
 comparing an sensed current to a projected current of a non-breakthrough electro-processing condition.    
     
     
         10 . The method of  claim 8 , wherein step of updating is iteratively performed until the endpoint is reached.  
     
     
         11 . The method of  claim 1 , wherein the step of electro-processing further comprises: 
 determining, for the wafer, a removal profile in order to obtain the desired profile;    establishing a current path between the wafer and an electrolyte solution;    contacting the wafer to a processing pad;    applying a bias between to the wafer and at least a first electrode; and    electro-processing the wafer under the influence of the bias to selectively change a thickness of a conductive material of the wafer.    
     
     
         12 . The method of  claim 11 , wherein the step of processing further comprises: 
 applying at least a second bias between the wafer and at least a second electrode, the second bias being different from the first bias; and    determining an amount of charge removed from the wafer by each electrode.    
     
     
         13 . The method of  claim 1 , wherein terminating the electro-processing comprises terminating the first and second biases when a target amount of charge is removed for each respective electrode.  
     
     
         14 . The method of  claim 1 , wherein determining the amount of charge removed from the wafer by each electrode comprises integrating, with respect to time, a respective current provided to each electrode.  
     
     
         15 . A method for removing a desired amount of material from a wafer by electropolishing, comprising: 
 determining, for the wafer, a target charge required to achieve a desired removal profile;    electropolishing the wafer to selectively remove different amounts of conductive material from the wafer according to the desired removal profile;    determining an amount of charge removed from a plurality of locations on the wafer;    detecting breakthrough of the conductive material;    adjusting the target charge required in response to the breakthrough of the conductive material; and    terminating the electropolishing when the desired removal profile is substantially achieved.    
     
     
         16 . The method of  claim 15 , wherein determining the desired removal profile comprises: 
 determining a pre-processing profile of the wafer;    providing a target profile; and    determining a difference between the pre-processing profile and the target profile.    
     
     
         17 . The method of  claim 15 , wherein determining the amount of charge removed and determining the thickness of material removed are performed periodically.  
     
     
         18 . The method of  claim 15 , where in step of detecting further comprises: 
 sensing a discontinuity of current passing between the wafer and the electrode.    
     
     
         19 . The method of  claim 15 , where in step of detecting further comprises: 
 sensing a discontinuity of voltage measured between the wafer and the electrode.    
     
     
         20 . The method of  claim 15 , where in step of adjusting further comprises: 
 updating the target charge in response to a charge in area of an underlying layer exposed through the conductive material.    
     
     
         21 . The method of  claim 20 , where in step of updating further comprises: 
 determining the exposed area from a sensed current.    
     
     
         22 . The method of  claim 21 , where a relationship between the exposed area the sensed current is proportional.  
     
     
         23 . The method of  claim 21 , where a relationship between the exposed area the sensed current is empirically determined.  
     
     
         24 . The method of  claim 21 , where a relationship between the exposed area the sensed current is stored in a database.  
     
     
         25 . The method of  claim 21 , where a relationship between the exposed area the sensed current is calculated.  
     
     
         26 . The method of  claim 15 , wherein determining the amount of charge removed from the plurality of locations comprises determining, for each zone, a total amount of charge removed from the wafer as a result of the bias for that zone.  
     
     
         27 . A method for producing a desired profile on a wafer by electro-processing, comprising: 
 determining a target endpoint for a plurality of zones on a wafer;    processing a conductive layer of the wafer; and    adjusting the target endpoint for each zone in-situ.    
     
     
         28 . The method of  claim 27 , wherein the step of adjusting further comprises: 
 detecting breakthrough of the conductive layer.    
     
     
         29 . The method of  claim 27 , wherein the step of adjusting further comprises: 
 determining an amount of an underlying layer exposed through the conductive layer.    
     
     
         30 . The method of  claim 29 , wherein the amount of an underlying layer exposed through the conductive layer corresponds to a sensed current.