Basic Performance of the Agilent 7700s ICP-MS for the Analysis of Semiconductor Samples

Importance of the Topic

ICP-MS is a cornerstone technique in semiconductor manufacturing, where monitoring ultra-trace contaminant levels in high-purity chemicals is critical for device performance and yield. The ability to achieve low detection limits, robust interference removal, and stable operation under varying sample matrices makes the Agilent 7700s ICP-MS a vital tool for quality control and process optimization.

Objectives and Study Overview

• Compare the sensitivity and background equivalent concentrations (BECs) of the 7700s with its predecessor models (7500cs and 7500s).
• Evaluate interference removal using the new ORS3 collision-reaction cell in He, H₂, and optional NH₃ modes.
• Assess long-term signal stability in acid matrices and volatile organic solvents.
• Demonstrate routine cool plasma operation for problematic elements.

Used Instrumentation

• Agilent 7700s ICP-MS fitted with a PFA nebulizer, platinum interface cones, and high-transmission ion lens.
• Third-generation ORS3 collision-reaction cell capable of He collision, H₂ reaction, and optional NH₃ modes.
• Frequency-matching RF generator for rapid impedance adjustments in organic matrices.
• Organic solvent torch options with 1.0 mm and 1.5 mm injectors for variable volatility.

Methodology

Measurements were performed on calibration standards and spikes in 1% HNO₃, undiluted isopropyl alcohol (IPA), and concentrated HCl. Detection limits (DLs) and BECs were determined for over 40 elements, including those measured in cool plasma. Long-term stability tests over 9 hours in acid and 4 hours in IPA recorded signal drift and relative standard deviation. Interference removal efficiency was assessed via collision-induced dissociation (CID) and kinetic energy discrimination (KED) in the ORS3 cell.

Main Results and Discussion

• Sensitivity of the 7700s is ~40% higher than the 7500cs, with random background noise reduced by half.
• Detection limits and BECs in 1% HNO₃ dropped significantly for alkali, alkaline earth, transition, and heavy elements; many analytes reached sub-ppt levels.
• He mode with KED effectively removed helium-based polyatomic interferences; H₂ reaction mode delivered the lowest DLs for Fe, Se, and Si (direct measurement of mass 28).
• Optional NH₃ mode enabled vanadium analysis in undiluted 20% HCl with a DL of ~2.3 ppt despite strong ClO interferences.
• Long-term stability: signal drift within ±5% and %RSD below 3% over 9 hours in acid and below 5% RSD over 4 hours in IPA.
• Cool plasma operation demonstrated robust performance for elements prone to oxide and argide interferences, maintaining stability under automated mode switching.

Contributions and Practical Applications

• Reduced cleanroom footprint and service demands lower operational costs and simplify installation in controlled environments.
• Comprehensive gas-mode flexibility supports multi-element workflows across diverse semiconductor process chemicals.
• Enhanced interference removal expands direct analysis capabilities, including high-purity acids and organic solvents critical to wafer cleaning and etching steps.

Future Trends and Possibilities for Use

• Integration of additional reactive gases and advanced cell designs may further lower detection thresholds for emerging contaminants.
• Automation and inline sampling could enable real-time process monitoring and tighter control of ultrapure chemical production.
• Extension of cool plasma techniques to broader industrial and environmental matrices where matrix suppression is beneficial.

Conclusion

The Agilent 7700s ICP-MS delivers substantial advancements in sensitivity, interference removal, and stability compared to previous models. Its compact design, flexible ORS3 cell, and robust RF generator facilitate reliable trace analysis in semiconductor chemicals, ensuring stringent quality standards and streamlined laboratory operation.

Reference

Junichi Takahashi; Agilent Technologies Application Note – "Basic Performance of the Agilent 7700s ICP-MS for the Analysis of Semiconductor Samples"; Agilent Technologies; 2010.