Chloride in acidic copper baths

Importance of the Topic

The control of chloride concentration in acidic copper plating baths is critical for the semiconductor industry. Trace chloride accelerates deposition and prevents anode polarization, while excessive levels compromise deposit quality and lead to defects. Reliable monitoring ensures optimal plating speed and high-quality copper layers.

Objectives and Overview of the Study

This application note demonstrates a fully automated titration method to determine chloride content in acid copper baths. The approach aims to simplify sample handling, reduce errors, and deliver reproducible results compared to alternative techniques such as ion chromatography.

Used Methodology and Instrumentation

• Sample Processor: 814 USB Sample Processor for automated dosing, rinsing, and sample handling.
• Titrator: 905 Titrando potentiometric titrator, compatible with OMNIS or tiamo software, enabling dynamic and endpoint titration modes.
• Electrode: iAg Titrode with Ag2S coating for selective silver detection and stable endpoint determination.
• Procedure: To a measured volume of copper bath, add 5 mL nitric acid, dilute with deionized water to cover the electrode, then titrate with standardized silver nitrate until the equivalence point.

Main Results and Discussion

The automated titration yielded a chloride concentration of 49.17 mg/L with high precision (RSD 0.31%, n = 10). Titration curves exhibited sharp inflection points and consistent endpoints, confirming method robustness for routine analysis.

Benefits and Practical Applications

• Fully automated workflow eliminates manual dilution and handling, lowering operator effort and risk of errors.
• Potentiometric titration hardware is cost-effective compared to chromatographic systems.
• Excellent reproducibility and compliance with GMP/GLP and 21 CFR Part 11 when paired with OMNIS or tiamo software.

Future Trends and Potential Applications

Ongoing advances in titration automation, sensor technology, and software integration will further streamline process control in plating baths. Future developments may include in-line monitoring, multicomponent titrations, miniaturized electrode systems, and AI-driven data evaluation to enhance throughput and predictive maintenance.

Conclusion

Potentiometric titration using an automated sample processor and a sulfide-coated silver electrode provides a fast, precise, and cost-effective technique for chloride determination in acid copper plating baths. The method boosts laboratory productivity and ensures consistent plating quality.