Eci Technology, Inc.

Peter Bratin

Michael Pavlov

Eugene Shalyt

Alex Kogan

Michael James Perpich

Gene Chalyt

D Morgan Tench

Vladimir Dozortsev

Guang Liang

Julia Tyutina

Semyon Aleynik

Isaak Tsimberg

Victor Ososkov

The thickness of a palladium coating on copper (or another substrate) is measured by passing a cathodic current through a predetermined area of the coating in contact with an electrolytic solution and measuring the potential as a function of time. Protons from the electrolytic solution are electrochemically reduced to palladium hydride at cathodic potentials less negative than required for evolution of hydrogen. As formation of the PdHbeta-phase throughout the Pd coating is completed, the cathodic potential increases rapidly to a cathodic potential plateau corresponding to evolution of hydrogen gas on the PdHsurface. This step in the cathodic potential provides an endpoint time for the measurement. The absolute thickness of the Pd coating is calculated from the integrated cathodic charge passed up to the endpoint time and the predetermined area of the coating in contact with the electrolytic solution.

Palladium coating thickness measurement

Silicon ions in an alkaline etchant solution are analyzed by acidifying a sample of the etchant solution, adding fluoride ions in excess of the concentration required to react with all of the silicon ions, and using a fluoride ion specific electrode (FISE) to detect free fluoride ions in the resulting test solution. Good sensitivity and precision are provided by using a relatively acidic test solution and only a slight excess of fluoride ions, and limiting the analysis range to the maximum expected silicon concentration in the etchant solution.

Etchant product analysis in alkaline etchant solutions

An auxiliary leveler additive that cannot be analyzed by conventional CVS methods for acid copper plating baths is analyzed by cyclic voltammetry at a platinum rotating disk electrode from its effect on the anodic current at very positive potentials.

Analysis of an auxiliary leveler additive in an acid copper plating bath

The chloride concentration in an acid copper plating bath is determined from the chloride oxidation current measured under controlled hydrodynamic conditions at a noble metal electrode using specific voltammetric parameters. The measurement is made directly on the undiluted plating bath so that the chloride measurement is fast and no waste stream is generated.

Chloride analysis in acid copper plating baths

A simple titration method involving a single copper ion titrant detected by a copper ion specific electrode provides the concentrations of both copper ions and bath complexing agent (ethylene diamine, for example) in alkaline copper electroplating baths of the type used to deposit or thicken copper seed layers on silicon wafers. Standard addition of an excess of a strong complexing agent (EDTA, for example) and back-titration with the copper ion titrant yields the bath copper ion concentration, and continued titration to a second endpoint, preferably after addition of hydroxide to adjust the pH of the analysis solution, yields the total concentration of bath complexing agent. Based on these analyzes, the concentration of free bath complexing agent may be calculated. The method also provides direct determination of the free bath complexing agent concentration via standard addition of excess bath complexing agent to a sample of the plating bath and titration with the copper ion titrant.

Analysis of copper ion and complexing agent in copper plating baths

Low concentrations of silicon in an etchant solution are analyzed by adding a predetermined concentration of fluoride ions to a test solution comprising a predetermined volume of the etchant solution, and measuring the concentration of fluoride ions in the test solution. Reaction with silicon ions in the test solution reduces the concentration of fluoride ions, which are present in stoichiometric excess, so that the silicon concentration of the etchant solution can be calculated from the difference between the predetermined and measured concentrations of fluoride ions in the test solution. The method is especially suited for analysis of silicon nitride etchants comprising a high concentration of phosphoric acid.

Analysis of silicon concentration in phosphoric acid etchant solutions

The stability of an electroless plating bath for depositing a metal (e.g., nickel) is determined by titrating a sample of the plating bath with a titrant comprising ions of a catalytic metal (e.g., palladium) and detecting hydrogen released at the titration endpoint. The quantity of titrant required to attain the endpoint provides a measure of the stability of the electroless plating bath.

Method and apparatus for determining the stability of an electroless plating bath

An additive breakdown product in an acid copper plating bath sample is detected by performing a voltammetric analysis for the leveler additive in two measurement solutions comprising different volume fractions of the copper plating bath sample in a background electrolyte. When the plating bath sample contains a substantial concentration of the additive breakdown product, the analyses for the first and second measurement solutions indicate different concentrations for the leveler additive in the plating bath sample. A comparison of the leveler additive concentrations indicated by the two analyses provides a measure of the concentration of the additive breakdown product.

Detection of additive breakdown products in acid copper plating baths

The 3-mercaptopropylsulfonic acid (MPSA) breakdown product of the bis(sodiumsulfopropyl)disulfide (SPS) additive used in acid copper plating baths accelerates copper electrodeposition and can be detected by cyclic voltammetric stripping (CVS) analysis. In the presence of oxygen, MPSA decomposes rapidly in acid copper sulfate baths so that the CVS stripping peak area (A) decreases on successive cycles. The slope of a plot of Avs. CVS cycle number (or time) or logarithm of the CVS cycle number (or time) provides a measure of the initial MPSA concentration.

Detection of an unstable additive breakdown product in a plating bath

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.

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Flushing, NY, United States of America

Peter Bratin