Development of diagnostic tools for the EUV spectral range

摘要

The successful implementation of EUV lithography systems strongly relies both on the efficiency of the employed optical components and the precise control of the relevant source parameters. Utilizing a laser-based plasma source for the generation of 13nm radiation, metrology for comprehensive characterization of EUV radiation and the related optics is developed at Laser-Laboratorium Gottingen. A soft X-ray plasma is produced with the help of a Nd:YAG laser which is focussed into a pulsed xenon or oxygen gas jet. The alternate use of these two target gases accomplishes either a very intense broadband emission (Xe), or a less intense narrow-band line emission (O_2) at the wavelength of 13nm. Additional filtering with the help of Mo/Si mirrors yields quasi-monochromatic 13nm radiation, as needed for testing of optical components, especially reflectometry. The performance of the EUV source is monitored with respect to source diameter, emission characteristics, and 13nm conversion efficiency by the help of different diagnostic tools, including EUV sensitive pin-hole cameras, photo-diodes and an EUV spectrometer. Moreover, first wavefront measurements of EUV radiation are performed with the help of a Hartmann wavefront analyzer, which was sensibilized for 13nm radiation.