Electron density in Extreme Ultra-Violet generated plasmas

The electron density in an Extreme Ultra-Violet generated plasma In order to meet the demand of increasing computer speed and memory capacity, industries are striving to reduce the size of computer chips. This miniaturization can be achieved by reducing the wavelength in lithography machines to Extreme Ultra-Violet (EUV, 92 eV). The low-pressure (around 1 Pa) transparent background gas (e.g. H2 and He) in the lithography machine is partially ionized by the absorption of EUV photons. The study of these low-density (1E15 m-3) pulsed plasmas is interesting and experimentally challenging. In this research the electron density is studied in an EUV-generated plasma in argon. The electron density is measured with microwave cavity resonance spectroscopy (MCRS). In MCRS measurements the resonance frequency in a cavity is determined, this frequency depends on the electron density in the cavity. The first results show a detection limit of 1E14 m-3 and a time-resolution of 16 ns. The electron density is measured as a function of argon pressure and EUV intensity.