Analysis of semiconductor copper plating bath chemistry using in process mass spectrometry

Abstract

An in-process mass spectrometry (IPMS) system is disclosed that uses an internal standard to determine the concentration of an analyte in a sample. The internal standard has a different molecular composition than the analyte but is sufficiently similar chemically and physically to the analyte such that it behaves substantially the same as the analyte during an ionization process in the mass spectrometer.

1 . A method of quantifying the concentration of an analyte in a solution; comprising 
 providing a sample of the solution containing the analyte;    mixing the sample with a solution of an internal standard solution, the internal standard having a different molecular composition than the analyte;    ionizing a portion of the mixture; and    introducing the ions into a mass spectrometer for determination of the concentration of the analyte in the sample, wherein the internal standard is sufficiently similar chemically and physically to the analyte such that it behaves substantially the same as the analyte during the ionization act.    
   
   
       2 . The method of  claim 1 , wherein the mixing the sample with the internal standard act comprises mixing a predetermined volume of the sample with a predetermined volume of the solution of the internal standard having a predetermined concentration, and wherein the determination of the concentration of the analyte in the sample depends upon the predetermined volumes and the predetermined concentration of the internal standard.  
   
   
       3 . The method of  claim 2 , further comprising: 
 diluting the mixture with a predetermined volume of diluent; wherein the determination of the concentration of the analyte in the sample also depends upon the predetermined volume of diluent.    
   
   
       4 . The method of  claim 1 , wherein the solution containing the analyte is a process solution for electroplating copper on semiconductor wafers.  
   
   
       5 . The method of  claim 4 , wherein the analyte is bis (3-sulfopropyl) disulfide (SPS) and wherein the internal standard is bis (2-sulfoethyl) disulfide (SES).  
   
   
       6 . The method of  claim 5 , further comprising: 
 based upon the determination of the concentration of SPS in the electroplating bath, adjusting the concentration of SPS to achieve a desired concentration.