Method of monitoring trace constituents in plating baths
First Claim
1. A method for monitoring the minor constituents present in a solution used in a plating process wherein said minor constituents affect plating deposit properties, said method comprising the steps of:
- (a) applying a selected dc potential to a working electrode which has been subjected to pretreatment and is positioned with said solution containing said minor constituents;
(b) superimposing a constant ac signal on said dc potential applied to said working electrode, said ac signal having a peak to peak potential and a frequency and producing an ac current;
(c) varying said dc potential at a chosen sweep rate over a chosen range; and
(d) measuring said ac current at one or more phase angles with respect to said constant ac signal between said working electrode and a counter electrode positioned within said solution as said dc potential is varied over said range, said measurement of ac current in relation to varying dc potential being expressed as an ac current spectra wherein the improvement comprises varying in combination each parameter comprising said peak to peak potential of said ac signal, said frequency of said ac signal, said sweep rate of said dc potential, said range of dc potential, said one or more phase angles, and said pretreatment of said working electrode, to determine the specific value of each said parameter which, when taken in combination with the remaining said parameters, provides maximum spectra detail in said ac current spectra to determine and monitor said minor constituents in said solution which affect said plating deposit properties.
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Accused Products
Abstract
A method for monitoring the minor constituents present in a plating bath solution which affect plating deposit properties. The method involves applying a predetermined dc potential to a working electrode positioned within the plating bath solution. A constant ac signal is superimposed on the dc potential. The dc potential is varied at a predetermined rate over a predetermined range, which includes potentials which plate and strip the plating deposit. The ac current of the applied ac signal is measured between the working electrode and a counter electrode positioned within the plating bath solution as the dc potential is varied over the predetermined range. The measurement of the ac current in relation to varying dc potential is expressed as an ac current spectra or fingerprint. By optimizing all ac and dc measurement variables, spectra are obtained which contain fine structure and which enable the monitoring of minor plating bath constituents which affect plating deposit properties.
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Citations
21 Claims
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1. A method for monitoring the minor constituents present in a solution used in a plating process wherein said minor constituents affect plating deposit properties, said method comprising the steps of:
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(a) applying a selected dc potential to a working electrode which has been subjected to pretreatment and is positioned with said solution containing said minor constituents; (b) superimposing a constant ac signal on said dc potential applied to said working electrode, said ac signal having a peak to peak potential and a frequency and producing an ac current; (c) varying said dc potential at a chosen sweep rate over a chosen range; and (d) measuring said ac current at one or more phase angles with respect to said constant ac signal between said working electrode and a counter electrode positioned within said solution as said dc potential is varied over said range, said measurement of ac current in relation to varying dc potential being expressed as an ac current spectra wherein the improvement comprises varying in combination each parameter comprising said peak to peak potential of said ac signal, said frequency of said ac signal, said sweep rate of said dc potential, said range of dc potential, said one or more phase angles, and said pretreatment of said working electrode, to determine the specific value of each said parameter which, when taken in combination with the remaining said parameters, provides maximum spectra detail in said ac current spectra to determine and monitor said minor constituents in said solution which affect said plating deposit properties. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. In a cyclic voltammetric stripping method for monitoring the presence of minor constituents in a metal plating bath solution wherein:
- (a) a dc potential is applied to a pretreated working electrode immersed in said plating bath solution and said dc potential is cycled at a constant sweep rate over a chosen range so that a small amount of said metal is alternately deposited on the surface of said working electrode by electrodeposition and stripped off by anodic dissolution;
(b) a constant ac signal is superimposed on said dc potential applied to working electrode, said ac signal having a chosen peak to peak potential and a chosen frequency and producing an ac current;
(c) measuring said ac current at one or more phase angles with respect to said constant ac signal between said working electrdoe and a counter electrode positioned within said plating bath solution as said dc potential is cycled, said measurement of said ac current in relation to said cycled dc potential being expressed as an ac current spectra of said plating bath solution wherein the improvement comprises varying in combination each parameter comprising said peak to peak potential of said ac signal said frequency of said ac signal, said sweep rate of said dc potential, said range of said dc potential, said one or more phase angles, and said pretreatment of said working electrode to determine the specific value of each said parameter which, when taken in combination with the remaining said parameters, provides maximum spectra detail in said ac current spectra to determine and monitor said minor constituents present in said plating bath solution. - View Dependent Claims (21)
- (a) a dc potential is applied to a pretreated working electrode immersed in said plating bath solution and said dc potential is cycled at a constant sweep rate over a chosen range so that a small amount of said metal is alternately deposited on the surface of said working electrode by electrodeposition and stripped off by anodic dissolution;
Specification