Expansion of the electrons in an EUV-induced plasma in argon

There is an increasing global demand for more computational power and memory capacity. To achieve further miniaturization of semiconductors, the next logical step is to use lithography machines based on Extreme Ultra- Violet (EUV) radiation at 13.5nm (92 eV). The topic of this contribution is the physical processes, which occur in a low pressure gas such as Ar and H2 (0.1{10 Pa) due to absorption of EUV photons and the creation of EUV induced plasma. The long term impact of such a plasma on the lithography machine is of main interest for the industry. The electron density is measured with microwave cavity resonance spectroscopy (MCRS). In MCRS measurements the resonant frequency of a specic mode in a cavity is determined, this frequency depends on the electron density in the cavity. In principle, this is an averaged density of the entire cavity. However, by combining several resonant modes, we can obtain information on the spatial distribution of the electron density. In this contribution we show that we can obtain information about the expansion of an EUV-induced plasma in argon by combining the TM010 and TM110 mode.