Measuring down to 10ppt
US-based Extraction Systems has introduced Vantara, which it claims is the first continuous air sampling system to give lithographers the power to detect and measure molecular contaminants at less than 10 parts per trillion (ppt).
The company says this new capability is essential to "understanding and ultimately preventing optics contamination in 193nm and 157nm lithography". According to Extraction Systems: "Extremely low concentrations of certain organic contaminants can degrade 193nm optics performance and lifetimes. Collaborative research between Extraction and leading research organisations has shown that these contaminants show up on deep UV optical elements as damaging films, which cause transmission loss, illumination non-uniformity, light scattering and ultimately diminish exposure tool productivity, image quality and optics lifetime". Vantara is said to provide an accurate and convenient means for collecting ultra-low levels of condensable-organic species from molecular weight C6 to C30. The system incorporates a sampling device and analytical method to separate, quantify and identify individual organic components at a detection limit of less than 10 ppt, or approximately 0.001 micrograms/m3, "representing a one hundred fold improvement over conventional sampling methods". In addition, the systems ability to continuously collect air samples, provides lithographers with a cumulative view of contamination exposure history. In comparison, says the company, conventional methods incorporate periodic, short-term sampling, resulting in a limited snapshot view of contamination exposure history. Extraction Systems says the sampling device can be easily installed and replenished, negating the need and costs to bring in specialised analytical experts to manage air-sampling programmes on-site.