Measurement Study on Materials’ Partial Outgassing Rate for EUVL Vacuum System Based on Single Quadrupole Mass Spectrometer

In the prediction of vacuum performance of the ultraviolet lithography (EUVL) tool, making the right material choices for various parts of vacuum system means the difference between success and failure for the project as a whole. To meet the outgassing budget of the vacuum minienvironment in the material designing, outgassing behavior is an important evaluation criterion, including total outgassing rate, outgassing species and partial outgassing rate of water (H₂O) and hydrocarbons (C_xH_y), for a certain amount of which will either absorb EUV light or contaminate optical mirrors. In order to have a comprehensive measurement, equipment containing single sample chamber, a pumping system, a purging channel and a detecting set was established. In consideration of the cost reduction, test error lessening and practical engineering requirement, the orifice throughput method together with only one quadrupole mass spectrometer (QMS) was employed. Afterwards, the nitrogenous equivalent value of total and partial outgassing rates could be acquired, following the effective pumping rate and the partial pressure were calibrated at first through introducing nitrogen. With the purpose of verifying the correctness of the new principle and having a wise judgement, carbon fiber reinforced polymer (CFRP) laminates and glass ceramics (GC) were selected as detection objects, because they were the potential option to serve the circuit board. An outgassing experiment of different time was conducted on them using the above device to obtain their gas mass spectrums, partial and total outgassing rates. The results revealed that CFRP let out a lot of water and hydrocarbons and a mass of hydrocarbons were still released even after 10 h pumping in spite of that hydrocarbons’ partial outgassing rate droped quicker than that of water. Besides, its total outgassing rate was beyond of the experiential threshold value. On the contrary, no hydrocarbon was given off after a period as short as 1 h pumping for GC sample, along with its total outgassing rate below the experiential threshold value. As a consequence, GC material is more suitable for EUVL vacuum system than CFRP in terms of the vacuum characteristic merely. However, from the view of materials’ thermal property which is important in the circuit board level test, GC has a lower thermal conductivity than CFRP, and thus the proper material is still under investigation. It is proposed that, for the researcher, more material properties of mechanical, thermal, optical, electrical, magnetic, chemical and so on should also be taken into account in addition to the vacuum character, when putting one material into practical environmental use.