Sub-ppb detection limits for hydride gas contaminants using GC-ICP-QQQ

Importance of the Topic

In both petrochemical and semiconductor industries, ultratrace hydride gases such as phosphine, arsine, hydrogen sulfide and carbonyl sulfide can deactivate catalysts, alter polymer quality and impair device performance. Reliable sub-ppb quantification of these contaminants is essential to predict catalyst lifetime, prevent production downtime and ensure semiconductor yield and reliability.

Objectives and Overview of the Study

The study introduces a high-sensitivity gas chromatography–triple quadrupole ICP-MS (GC-ICP-QQQ) method using the Agilent 8800 to achieve sub-ppb detection limits for key hydride gases. The main goals were:

• Determine detection limits for individual hydrides (PH3, GeH4, AsH3) under ideal conditions.
• Evaluate multielement analysis performance with oxygen mass-shift MS/MS mode.
• Compare the new method against conventional GC-ICP-MS (Agilent 7900) to assess sensitivity gains.

Methodology and Instrumentation

A 100 m × 0.53 mm × 5 µm DB-1 capillary column on an Agilent 7890 GC was interfaced to the 8800 ICP-QQQ. Key GC parameters included isothermal operation at ambient temperature, 20 psig inlet, 4 psig outlet, helium carrier with argon makeup and a 400 µL sample loop. The 8800 ICP-QQQ employs two quadrupoles (Q1 and Q2) flanking an ORS3 collision/reaction cell. In MS/MS mass-shift mode, O2 converts P+, S+, Ge+ and As+ into their oxide ions (PO+, SO+, GeO+, AsO+) for interference removal. H2 cell gas mode was used for on-mass measurement of Si+ at m/z 28 by reacting away CO+ and N2+ interferences.

Main Results and Discussion

Sub-ppb detection limits were achieved for all target analytes:

• Phosphine (PH3): 8.7 ppt (S/N method) and 19 ppt (replicate standard deviation).
• Germane (GeH4): 3.9 ppt (S/N).
• Arsine (AsH3): 1.3 ppt (S/N).
• Hydrogen sulfide (H2S) and carbonyl sulfide (COS): ~0.11 ppb (S/N) and 0.12–0.21 ppb (replicate SD).
• Silane (SiH4): ~0.20 ppb (S/N) and 0.14 ppb (replicate SD).

The 8800 ICP-QQQ method delivered 5–10× lower detection limits for P, S, PH3 and COS compared to conventional GC-ICP-MS on the Agilent 7900, while achieving single-digit ppt performance for Ge and As.

Benefits and Practical Applications of the Method

• Interference-free quantification at ultratrace levels enables precise monitoring of high-purity feedstocks and precursor gases.
• Tightened detection limits support increasingly stringent industry specifications and quality assurance protocols.
• Enhanced selectivity of MS/MS modes minimizes matrix effects, simplifying data interpretation in complex gas matrices.

Future Trends and Applications

• Adoption of alternative column chemistries, such as porous polymers, to reduce background signals and improve silane determination.
• Extension to other trace hydrides and volatile impurities in semiconductor and petrochemical processes.
• Integration into automated, on-line process control systems for real-time contamination monitoring.

Conclusion

The GC-ICP-QQQ approach with the Agilent 8800 ICP-QQQ demonstrates superior sensitivity and selectivity for hydride gas contaminants, achieving sub-ppb detection limits that surpass conventional quadrupole ICP-MS. This capability enhances quality control, process optimization and risk mitigation in both petrochemical production and semiconductor manufacturing.