Electroplating bath control

Abstract

Disclosed is a method of analyzing organic components in an electroplating bath. Also disclosed is a method of controlling electroplating baths by monitoring the components of the plating bath in real-time.

What is claimed is:  
     
         1 . A method for determining the level of components in an electroplating bath comprising the steps of: 
 a) obtaining a plurality of solutions wherein each solution has known and different concentrations of an analyte, but where the quantity of the analyte in each solution differs from the quantity in the other solutions;    b) providing an apparatus having a first chamber and a second chamber, the first chamber being separated from the second chamber by a liquid-impermeable, gas-permeable membrane;    c) introducing each solution individually into the first chamber and carrying out a predetermined sequence of steps including: 
 i) reducing the pressure in the second chamber relative to the first chamber to produce a gas stream;  
 ii) directing at least a portion of the gas stream to a mass spectrometer;  
 iii) measuring a characteristic mass/charge peak for the analyte;  
   d) for each solution, correlating the quantity of analyte with the measurement of the characteristic mass/charge peak;    e) introducing a bath having an unknown quantity of the analyte into the first chamber;    f) performing the predetermined sequence of steps; and    g) choosing from the correlation in step d) a quantity of the analyte which corresponds to the recorded characteristic mass/charge peak measurement for the analyte.    
     
     
         2 . The method of  claim 1  wherein the analyte is selected from brightener, accelerator, suppressor, leveler or mixtures thereof.  
     
     
         3 . The method of  claim 1  wherein the electroplating bath is selected from copper, nickel, chromiurn, zinc, tin, gold, silver, and their alloys.  
     
     
         4 . The method of  claim 3  wherein the copper electroplating bath comprises a source of copper ions and an electrolyte.  
     
     
         5 . The method of  claim 4  wherein the electrolyte is acidic.  
     
     
         6 . The method of  claim 1  wherein the first chamber further comprises a working electrode, an auxiliary electrode and a reference electrode.  
     
     
         7 . The method of  claim 6  wherein a reducing potential is applied to the working electrode in step c) prior to step i).  
     
     
         8 . The method of  claim 1  wherein the membrane comprises an inert, non-conductive material.  
     
     
         9 . The method of  claim 1  wherein the pressure in the second chamber is reduced by application of a vacuum.  
     
     
         10 . An electroplating system comprising an electroplating tank suitable for containing an electroplating bath, the tank having an outlet for directing a portion of an electroplating bath to an apparatus for determining the level of components in the electroplating bath, the apparatus comprising: a first chamber separated from a second chamber by a liquid-impermeable, gas-permeable membrane; a means for reducing the pressure in the second chamber relative to the first chamber to produce a gas stream; and a means for directing at least a portion of the gas stream to a mass spectrometer.  
     
     
         11 . The electroplating system of  claim 10  wherein the first chamber further comprises a working electrode, an auxiliary electrode and a reference electrode.  
     
     
         12 . The electroplating system of  claim 11  further comprising a power source for controlling an electrochemical potential of the working electrode.  
     
     
         13 . The electroplating system of  claim 10  wherein the membrane comprises an inert, non-conductive material.  
     
     
         14 . The electroplating system of  claim 10  further comprising a vacuum source.  
     
     
         15 . The electroplating system of  claim 11  further comprising a controlling means for adding organic components to the electroplating bath.  
     
     
         16 . The electroplating system of  claim 15  wherein the controlling means is connected to the mass spectrometer.  
     
     
         17 . The electroplating system of  claim 15  wherein the organic components are selected from brighteners, accelerators, suppressors, levelers or mixtures thereof.  
     
     
         18 . The electroplating system of  claim 10  wherein the working electrode comprises a noble metal or the base metal of the electroplating bath.  
     
     
         19 . A method for electrolytically depositing metal on a substrate comprising the steps of: a) contacting the substrate with an electroplating bath comprising a source of metal ions, and electrolyte and one or more organic additives; b) subjecting the electroplating bath to sufficient current density for a period of time sufficient to deposit a desired thickness of metal on the substrate; and c) monitoring the one or more organic additives by i) obtaining a plurality of solutions wherein each solution has known and different concentrations of an organic additive, but where the quantity of the organic additive in each solution differs from the quantity in the other solutions; ii) providing an apparatus having a first chamber and a second chamber, the first chamber being separated from the second chamber by a liquid-impermeable, gas-permeable membrane; iii) introducing each solution individually into the first chamber and carrying out a predetermined sequence of steps including: aa) reducing the pressure in the second chamber relative to the first chamber to produce a gas stream; bb) directing at least a portion of the gas stream to a mass spectrometer; cc) measuring a characteristic mass/charge peak for the organic additive; iv) for each solution, correlating the quantity of organic additive with the measurement of the characteristic mass/charge peak; v) introducing a portion of the electroplating bath having an unknown quantity of the organic additive into the first chamber; vi) performing the predetermined sequence of steps; and vii) choosing from the correlation in step iv) a quantity of the organic additive which corresponds to the recorded characteristic mass/charge peak measurement for the organic additive.