Direct Analysis of Trace Metallic Impurities in High Purity Hydrochloric Acid by 7700s/7900 ICP-MS

Significance of the Topic

Hydrochloric acid is essential in semiconductor cleaning to remove metallic contaminants from silicon wafers. Monitoring trace impurities in high purity HCl ensures process reliability and prevents device failures. Direct determination of metals at ultralow levels in concentrated HCl addresses challenges of contamination and spectral interferences.

Study Objectives and Overview

This work demonstrates the analytical performance and robustness of the Agilent 7700s 7900 ICP MS equipped with an Octopole Reaction System for direct quantification of trace metals in undiluted 20 percent HCl. By eliminating dilution steps, the method reduces contamination risk and streamlines sample preparation.

Used Methodology and Instrumentation

An Agilent 7700s ICP MS with ORS and optional third cell gas line was used. The ORS supports helium collision, hydrogen reaction and ammonia reactive modes. Key components included platinum sampling and skimmer cones, a PFA nebulizer and a quartz torch. High purity HCl TAMAPURE AA100 at 20 percent was analyzed directly. Calibration standards at 10 20 50 and 100 ppt were prepared in acid blank.

Main Results and Discussion

Detection limits and background equivalent concentrations were determined for 42 elements in a single automated run sequence of cool plasma, no gas and gas modes, within six minutes per sample. Detection limits ranged from 0.01 ppt for thorium and uranium to several ppt for elements like arsenic and germanium. Element specific approaches included

• Chromium analysis by cool plasma combined with helium mode to suppress ClOH plus interference and achieve low background levels
• Potassium determination using ammonia cell gas with cool plasma to remove ArCl interference and reach 0.4 ppt detection limit
• Germanium quantification in high energy helium mode leveraging collision induced dissociation for chloride dimer ions
• Arsenic measurement at mass 75 using high energy helium collision mode to dissociate ArCl plus interferences directly
• Vanadium analysis by ammonia reaction cell under hot plasma to eliminate ClO interference and improve sensitivity

Contributions and Practical Applications of the Method

The robust anti corrosion design of the 7700s 7900 ICP MS allows direct handling of concentrated HCl without sample dilution. The ORS enhances removal of polyatomic interferences and provides flexibility with up to three gas lines. This approach delivers lower detection limits, reduces sample handling errors and ensures reliable monitoring in semiconductor QA QC and high purity chemical industries.

Future Trends and Potential Applications

Continued development of reaction cell technologies and high energy collision modes is expected to extend interference removal to additional matrices and elements. The flexibility of multiple gas lines could enable novel reactive gases for targeted interference suppression. Online process monitoring and integration with automated sample introduction may further improve throughput and data quality in industrial analytics.

Conclusion

The Agilent 7700s 7900 ICP MS with Octopole Reaction System and enhanced cool plasma capability achieves direct trace metal analysis in concentrated HCl with ultralow detection limits. By combining collision and reaction cell modes, the method overcomes chloride based interferences and simplifies workflow. This represents a significant advancement for high purity acid analysis in semiconductor and related fields.

Reference

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