One-point recalibration method for reducing error in concentration measurements for an electrolytic solution

Abstract

The present invention relates to a method for mathematically re-calibrating and adjusting an initial concentration analysis model that suffers from electrochemical measurement errors caused by surface state changes in the working/counter/reference electrode after extended usage. Specifically, such recalibration method reimburses long-term drift in the electrochemical measurements based on a single point testing.

1 . A method of analyzing concentration of a component of interest in an electrolytic solution, said method comprising: 
 (a) establishing an initial model for determining concentration as a function of a measurable parameter;    (b) providing a standard electrolytic solution that contains the component of interest at a known concentration;    (c) calculating the theoretical value for the measurable parameter from the function;    (d) measuring the actual parameter of the solution;    (e) determining an adjustment factor based on the theoretical and actual parameters; and    (f) constructing a revised model that calculates the concentration as a function of the parameter as adjusted by the adjustment factor.    
   
   
       2 . The method of  claim 1 , further comprising repeating steps (b)-(f) to revise the model.  
   
   
       3 . The method of  claim 2 , wherein said repeating is conducted on a periodical or threshold basis.  
   
   
       4 . The method of  claim 1 , wherein said electrolytic solution comprises electrochemical deposition solution containing one or more metal components.  
   
   
       5 . The method of  claim 4 , wherein said metal components are selected from the group consisting of aluminum, silver, gold, iridium, palladium, tantalum, titanium, chromium, cobalt, tungsten, tin, and lead.  
   
   
       6 . The method of  claim 1 , wherein the adjustment factor is determined as the difference between the theoretical calculated value of the parameter and the measured actual parameter value, and wherein the adjustment factor is added to the measurable parameter in constructing the revised model.  
   
   
       7 . The method of  claim 1 , wherein said electrolytic solution contains organic and inorganic components.  
   
   
       8 . The method of  claim 1 , wherein said electrolytic solution comprises copper electrochemical deposition solution.  
   
   
       9 . The method of  claim 8 , wherein said copper electrochemical deposition solution contains copper sulfate, chloride and sulfuric acid.  
   
   
       10 . The method of  claim 9 , wherein said copper electrochemical deposition solution further comprises one or more organic additives selected from the group consisting of suppressors, accelerators, and levelers.  
   
   
       11 . The method of  claim 1 , wherein the component of interest is sulfuric acid.  
   
   
       12 . The method of  claim 1 , wherein the component of interest is copper.  
   
   
       13 . The method of  claim 1 , wherein the measurable parameter is obtained by immersing first and second electrodes in the electrolytic solution, applying a cyclic electrical potential between the first and second electrodes, and analyzing current response of the electrolytic solution.  
   
   
       14 . The method of  claim 13 , wherein the current response of the electrolytic solution contains one or more current peaks, and wherein said measurable parameter is the integrated area of one of said current peaks.  
   
   
       15 . The method of  claim 1 , as conducted in an electrochemical deposition process.  
   
   
       16 . A method of operating an electrochemical deposition process including an electrochemical deposition bath containing electrolytic solution, said method comprising: 
 analyzing concentration of a component of interest in the electrolytic solution, comprising: 
 (a) establishing an initial model for determining concentration as a function of a measurable parameter;  
 (b) providing a standard electrolytic solution that contains the component of interest at a known concentration;  
 (c) calculating the theoretical value for the measurable parameter from the function;  
 (d) measuring the actual parameter of the solution;  
 (e) determining an adjustment factor based on the theoretical and actual parameters; and  
 (f) constructing a revised model that calculates the concentration as a function of an adjusted parameter, wherein the adjusted parameter is equal to the measurable parameter plus the adjustment factor, and wherein the adjustment factor is determined as the difference between the theoretical parameter value and the actual parameter value; and  
   adjusting composition of the bath in accordance with the revised model.    
   
   
       17 . The method of  claim 16 , wherein the electrochemical deposition process comprises a copper electrochemical deposition process.  
   
   
       18 . The method of  claim 16 , wherein the component of interest is selected from the group consisting of sulfuric acid and copper.  
   
   
       19 . The method of  claim 16 , wherein the electrochemical deposition process comprises an electrochemical deposition process for depositing a material selected from the group consisting of aluminum, silver, gold, iridium, palladium, tantalum, titanium, chromium, cobalt, tungsten, and alloys and amalgams containing one or more of the foregoing.  
   
   
       20 . The method of  claim 16 , wherein said adjusting composition of the bath in accordance with the revised model, comprises addition of one or more components to the bath to maintain composition of the bath in an effective state for electrochemical deposition operation.