A study of EUV resist outgassing characteristics using a novel outgas analysis system

We have designed a novel outgas analysis system to help gain a better understanding of EUV resist outgassing characteristics. In this paper, we will discuss the performance results of this outgas analysis system which incorporates a stand-alone discharge produced plasma extreme ultra violet (EUV) source of comparatively high power output and various outgas evaluation methods such as quadropole mass spectrometry (QMS), gas chromatography - mass spectrometry (GC-MS), quartz crystal microbalance (QCM) and 'witness mirror'. In this analysis system, the GC-MS evaluation set-up is quite unique from the commonly available outgassing systems with the utilization of the 'cold-trap sampling technique'. In this sampling technique; a 'trap box' is used with an cryostat-based internal cooling system used to lower the trap-box temperature to increase the efficiency of the trapping of outgas elements released from the resist wafer fragment during exposure. After exposure, the trap-box is then transferred to a heating chamber where the outgas elements that have adhered is heated and released to a thermal desorption tube for GC-MS analysis. After successive experiments using a polymer resist, we have succeeded in proving the improved efficiency of outgas trapping through the cold-trap method. Compared to the amount of trapped outgas at room temperature, a considerable amount of resist outgas was measured with the trap-box cooled at very low temperatures. With the QMS analysis results, it was also observed that the low molecular-type resist released lesser outgassing elements compared to the polymer resist. This work is partially supported by the New Energy and Industrial Technology Development Organization (NEDO).