Determination of Trace Impurities in Electronic Grade Arsine by GC-ICP-QQQ

Significance of the Topic

Arsine (AsH3) is a crucial precursor gas for III-V compound semiconductors such as GaAs, AlGaAs, and InGaAsN. Trace impurities of hydride dopants (e.g., GeH4, SiH4, PH3, H2S) can introduce energy levels in the semiconductor band gap, degrading carrier mobility, increasing leakage currents, and altering optical properties. Sub-ppb detection of these contaminants is essential to maintain device performance and yield in microelectronics and optoelectronics.

Objectives and Study Overview

This application note describes the development of a streamlined analytical method using gas chromatography coupled to triple quadrupole ICP-MS (GC-ICP-QQQ) to quantify multiple hydride impurities in electronic grade arsine at sub-ppb levels. The goal was to achieve low detection limits for SiH4, PH3, H2S, and GeH4 in a single injection using a multi-tune acquisition program.

Methodology and Instrumentation

• Sample and Standard Preparation: A 10 ppm hydride standard was dynamically diluted to 24 ppb. Qualitative retention time standards for H2Se, SbH3, and SnH4 were generated via hydride generation with sodium borohydride.
• GC Separation: Agilent 7890B with a single 100 m × 0.53 mm × 5 µm DB-1 column, Ar carrier at 20 psig, isothermal 30 °C oven, and 60 µL injection. A high-flow Deans switch vents the arsine matrix to protect the ICP torch.
• ICP-QQQ Detection: Agilent 8900 with ORS4 collision/reaction cell. MS/MS mode provides double mass filtering. Cell gases (H2, O2) and no-gas modes were evaluated to remove interferences via kinetic energy discrimination or reactive mass shifts.
• Multi-Tune Acquisition: A time-programmed method automatically switches cell gases and measurement modes during the run to optimize signal for each analyte.

Main Results and Discussion

Silane, phosphine, hydrogen sulfide, and germane were separated and quantified with single-digit ppb to sub-ppb detection limits. Optimal conditions included H2 cell gas for SiH4 on-mass at m/z 28, and O2 cell gas for P and S reaction products at m/z 47 and 48. Germane achieved a 0.01 ppb DL on-mass at m/z 74. Additional analytes (H2Se, SbH3, SnH4) were resolved using a low-sulfur column; their DLs were estimated at ~1 ppb.

Benefits and Practical Applications

• A single-column, single-injection method reduces analysis complexity and cycle time.
• Sub-ppb quantitation enables rigorous quality control of process gases in semiconductor manufacturing.
• Improved detection of trace dopants supports higher device yields and consistent performance.

Future Trends and Opportunities

• Expanding the method to cover additional hydride gases and isotopic variants.
• Integration with on-line sampling and real-time process monitoring systems.
• Advancements in CRC chemistries and instrument design for enhanced sensitivity and lower backgrounds.

Conclusion

The developed GC-ICP-QQQ multi-tune workflow enables sensitive, interference-free measurement of key hydride impurities in electronic-grade arsine at sub-ppb levels using a single GC system and injection. This robust approach enhances process control in III-V semiconductor fabrication.

References

• Geiger W.M., McElmurry B., Anguiano J., Kelinske M. Determination of Trace Impurities in Electronic Grade Arsine by GC-ICP-QQQ. Agilent Technologies Application Note, 2020.
• Feng J., Clement R., Raynor M. Characterization of High-Purity Arsine and GaAs Epilayers. J. Cryst. Growth. 310(23):4780–4785, 2008.
• Geiger W.M., Soffey E. GC-ICP-QQQ Achieves Sub-ppb Detection Limits for Hydride Gas Contaminants. Agilent 8800 ICP-QQQ Application Handbook, 4th ed., 2020.
• Meyer C.J., Geiger W.M. Specialty Gas Analysis: A Practical Guidebook. Wiley-VCH, 1997.
• Wells G., Prest H., Russ C.W. Signal, Noise, and Detection Limits in Mass Spectrometry. Agilent Publication 5990-7651EN.