Trace oxygen and moisture in bulk UHP gases, measured to ppb

Q: Does ASTG offer fixed or portable trace gas monitoring?

Both. The GPMS is a fixed system for continuous fab-wide monitoring; ASTG analytical carts provide mobile, self-contained measurement to ppb for commissioning, spot-checks and validation.

In a semiconductor fab, the bulk gases feeding your tools are only as good as their last measurement. Trace oxygen and moisture in ultra-high-purity (UHP) nitrogen, argon, hydrogen or helium oxidise surfaces, shift process chemistry and erode yield. By the time a wafer reveals the damage, the gas that caused it has long since passed through. Effective monitoring catches the impurity in the line, not the defect on the wafer.

ASTG measures trace oxygen and moisture across your bulk UHP gases to the part-per-billion (ppb) level, continuously, and reports straight into your facility monitoring system. A drift then shows up as a rising number well before it becomes a process excursion.

Request a trace O₂ and moisture assessment for your fab

What we measure

Each analyser uses cavity ring-down spectroscopy (CRDS), a long-path optical technique well suited to resolving impurities at trace levels. Every spectrometer runs on an onboard PLC that reports to your facility monitoring system (FMS).

Bulk gas	Measured impurity	Technique
Nitrogen (N₂)	Trace oxygen and moisture, ppb level	Cavity ring-down spectroscopy
Argon (Ar)	Trace oxygen and moisture, ppb level	Cavity ring-down spectroscopy
Hydrogen (H₂)	Trace oxygen and moisture, ppb level	Cavity ring-down spectroscopy
Helium (He)	Trace oxygen and moisture, ppb level	Cavity ring-down spectroscopy
Oxygen (O₂)	Trace moisture, ppb level	Cavity ring-down spectroscopy
Carbon dioxide (CO₂)	Trace moisture, ppb level	Cavity ring-down spectroscopy

The systems

ASTG Gas Purity Monitoring System (GPMS) for trace oxygen and moisture in bulk UHP gases

Gas Purity Monitoring System (GPMS). A fixed analytical system for continuous, fab-wide monitoring. It uses a series of cavity ring-down spectrometers, each reporting through an onboard PLC to your FMS, and comes in one, three, five and six-gas configurations (1G, 3G, 5G and 6G) to match the gases you run.

Analytical carts. Mobile, self-contained systems such as the PCAS-200 and PCAS-500, for continuous trace O₂ and moisture measurement to the part-per-billion level. They suit commissioning, spot-checks and validation where a fixed point is not installed.

Continuous Quality Control (CQC). Real-time, automated monitoring that alarms on any excursion and keeps an auditable record of gas quality across the process.

Why the margin matters

Detecting an impurity at the specification limit is not the same as proving you sit beneath it. The value of a monitoring programme lies in the margin between what the instrument can resolve and the limit it is measured against. The further the detection limit sits below the limit, the earlier a drift becomes visible and the more defensible every pass becomes. We explain this in our guide to detection limits versus compliance limits.

Frequently asked questions

Which gases can ASTG monitor for trace oxygen and moisture?
Trace oxygen and moisture in bulk nitrogen, argon, hydrogen and helium, and trace moisture in oxygen and carbon dioxide, all to the part-per-billion level.

What technique does the GPMS use?
A series of cavity ring-down spectrometers (CRDS), each on an onboard PLC that reports to your facility monitoring system. Configurations cover one to six gases.

Does ASTG offer fixed or portable trace gas monitoring?
Both. The GPMS is a fixed system for continuous, fab-wide monitoring. ASTG analytical carts provide mobile, self-contained measurement to ppb for commissioning, spot-checks and validation.

Download the application note (PDF) · Download the GPMS data sheet (PDF)