Eci Technology, Inc.

Michael James Perpich

Peter Bratin

Michael Pavlov

Alex Kogan

Gene Chalyt

Eugene Shalyt

Suppressor and anti-suppressor additives in an acid copper sulfate plating bath are analyzed by the cyclic voltammetric stripping (CVS) method without cleaning or rinsing the cell between the two analyses. The suppressor analysis is performed first and the suppressor concentration in the resulting measurement solution is adjusted to a predetermined value corresponding to full suppression. This fully-suppressed solution is then used as the background electrolyte for the anti-suppressor analysis. This integrated analysis approach provides results comparable to those obtained with cell cleaning and rinsing between the analyses but significantly reduces the analysis time, consumption of expensive chemicals, and quantity of hazardous waste generated.

Efficient analysis of organic additives in an acid copper plating bath

The concentration of citrate complexing agent in an electroless cobalt or nickel plating bath is determined by titrating a sample of the electroless plating bath containing a small concentration of free fluoride ion with a standard lanthanum nitrate solution. During the titration, Laion first reacts preferentially with the citrate complexing agent and then with fluoride ion, which reduces the free fluoride ion concentration. The endpoint for the titration is indicated by a substantial decrease in the free fluoride ion concentration, which is detected via a fluoride ion specific electrode (ISE). The method can be used for analysis of other complexing agents.

Measurement of complexing agent concentration in an electroless plating bath

Relative concentrations of active suppressor additive species and suppressor breakdown contaminants in an acid copper electroplating bath are determined by cyclic voltammetric stripping (CVS) dilution titration analysis using two negative electrode potential limits. The analysis results for the more negative potential limit provide a measure of the suppressor additive concentration alone since the suppressor breakdowvn contaminants are not effective at suppressing the copper deposition rate at the more negative potentials. The analysis results for the less negative potential limit provide a measure of the combined concentrations of the suppressor additive and the suppressor breakdown contaminants. Comparison of the results for the two analyses yields a measure of the concentration of the suppressor breakdown contaminants relative to the suppressor additive concentration.

Detection of suppressor breakdown contaminants in a plating bath

In the present invention, the test reference electrode used for voltammetric analysis of a plating bath is calibrated relative to the zero-current point between metal plating and stripping at a rotating platinum disk electrode in the plating bath supporting electrolyte. This calibration is readily performed during the normal course of cyclic voltammetric stripping (CVS) or cyclic pulse voltammetric stripping (CPVS) plating bath analysis the need for additional instrumentation or removal of the test reference electrode from the analysis equipment. Automatic calibration of the reference electrode enabled by the present invention, saves labor, time and expense, and minimizes errors in the plating bath analysis.

Voltammetric reference electrode calibration

The concentration of a reducing agent in an electroless bath for plating a first metal is determined from the effect of the reducing agent on the electrodeposition rate of a second metal. For electroless cobalt and nickel baths, a sample of the electroless plating bath is added to an acid copper plating solution and the copper electrodeposition rate is measured by cyclic voltammetric stripping (CVS) analysis. Separate analyses for hypophosphite and dimethylamineborane in baths employing both reducing agents are attained via selective decomposition of the dimethylamineborane in acidic solution.

Measurement of the concentration of a reducing agent in an electroless plating bath

The concentration of chloride ion in an acid copper electroplating bath is determined from the effect that chloride exerts on the copper electrodeposition rate in the presence of organic additives. A cyclic voltammetric stripping (CVS) rate parameter is measured, before and after standard addition of a plating bath sample, in an acid copper electrodeposition solution containing little or no chloride and at least one organic additive. Cross contamination and waste disposal issues associated with the reagents and reaction products involved in chloride titration analyses are avoided. The method may also be applied to analysis of other halides (bromide and iodide) and other solutions.

Voltammetric measurement of halide ion concentration

Acid copper electroplating baths used to form ultra-fine circuitry features on semiconductor chips contain suppressor, anti-suppressor and leveler additives that must be closely controlled in order to obtain acceptable copper deposits. Cyclic voltammetric stripping (CVS) methods are available to measure the concentrations of the suppressor and anti-suppressor based on the effects of these additives on the copper electrodeposition rate. The present invention is a method that also uses measurements of the copper electrodeposition rate to determine the concentration of the leveler additive. The other two additives are included in the measurement solution at concentrations determined to provide the optimum compromise between minimal interference, high sensitivity and good reproducibility for the leveler analysis. In this case, measurement precision is greatly improved compared to that provided by inclusion of the interfering additives in the measurement solution at their concentrations in the bath sample at the time of the analysis, which would be the standard analytical procedure.

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Hackensack, NJ, United States of America

Michael James Perpich