National Physical Laboratory

METAMC: Metrology for Airborne Molecular Contaminants


Technological progress in several high-tech industries is enabled, if not driven, by the ability to operate at an ever smaller scale. This introduces new challenges, also in the metrological realm. Airborne molecular contamination (AMC) is chemical contamination in the form of vapours or aerosols that has adverse effects on products, processes or instruments. Examples of possible adverse effects include the corrosion of metal surfaces on the wafer, and the formation of contamination layers on surfaces like optics and wafers after reaction/condensation. Industrial sectors for which the control of AMC is crucial include the semiconductor-, nanotechnology-, photovoltaic- and high brightness and organic LED industries.

Recent progress in quantitative molecular spectroscopy has brought the detection limits of typical contaminants to a level that meets the industrial need for AMC measurements. In particular, laser-based techniques have reached such technical maturity that their use in the industrial environment has become realistic. The easy adsorbance of the common AMCs, combined with their very low concentration make sampling, as well as transportation and generation of calibration gases, presents a challenge. Validation of methods for sampling, measurement, and generation of calibration gases will be necessary.

Beyond the state of the art

This project will assess the practical potential of state-of-the art optical spectroscopic techniques for traceable AMC monitoring in clean room environments and evaluate whether advanced optical techniques would be applicable in the future for detecting even smaller AMC quantities. The main objectives are to:

  • Investigate the principal and practical usability) of photoacoustic spectroscopy, cavity ring-down spectroscopy and cavity-enhanced absorption spectroscopy for AMC online detection with a time resolution and sensitivity better than 5 min and 1 nmol mol-1
  • Develop an advanced spectroscopic system (Noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy, NICE-OHMS) for improved sensitivity and report on options both for extending the method to more complex molecules and alternative optical techniques such as femtosecond combs or FTIR, for trace gas detection of multiple components
  • Improve the applicability of gas chromatography to AMC monitoring by using a technique based on a negative temperature gradient
  • Develop dynamic generation methods for generating reference standards for several key AMCs in manufacturing environments (e.g. NH3, HCl and HCHO) at trace amount fractions.
  • Develop suitable sampling techniques for practical AMC monitoring


  • Inform industry to assist decision making, leading to fewer product failures and less downtime of facilities
  • Increase the competitiveness of the European Industry. Benefits are not limited to the semiconductor industry; other industries that will benefit include aerospace, pharmaceuticals, medical devices, food, and healthcare
  • Develop ultra-sensitive and portable AMC monitoring equipment
  • Develop new material generation methods (portable and miniaturised) that can provide low amount of substance fractions required for reliable and traceable AMC equipment calibrations at appropriate facilities

Contact us

For further information on this research, please contact us:

METAMC project website
Customer enquiry tel: +44 20 8943 8715

Last Updated: 23 Dec 2014
Created: 10 Dec 2014


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