Outgassing rate measurements made traceable for the semiconductor industry

Outgassing of materials that are exposed to vacuum or are installed in vacuum systems limits the lowest achievable pressure or prevents processes in a vacuum due to chemical or physical effects. With EUV lithography for wafer illumination outgassing rate measurements have become very important for industry. Mirrors reflecting the soft EUV-light for illumination are very sensitive to impurities of water and hydrocarbon molecules.
In the past, outgassing rate measurements were performed using different methods and the results were neither comparable nor traceable to the SI. This made it difficult for the semiconductor industry to set a value for limits of outgassing rates of different materials and establish standards for outgassing rate measurements.
To improve this situation, several steps have been taken to ensure comparability and traceability of outgassing rate measurements. The first step was to establish a primary standard for partial pressure and outgassing rate measurements. The second step was to standardise traceable outgassing rate measurements by ISO TS 20177 and to characterise quadrupole mass spectrometers for outgassing rate measurements by ISO TS 20175. The third and final step was to develop reference outgassing samples for water vapor and dodecane by which outgassing rate measurement systems can be compared or validated. Dodecane is considered as a representative molecule for other hydrocarbons.
This poster will highlight the different steps towards comparability and traceability of outgassing rate measurements.