Direct photo-etching of poly (methyl methacrylate) using focused extreme ultraviolet radiation from a table-top laser-induced plasma source

摘要

In order to perform material interaction studies with intense extreme ultraviolet (EUV) radiation, a Schwarzschild mirror objective coated with Mo/Si multilayers was adapted to a compact laser-based EUV plasma source (pulse energy 3 mJ atλ= 13.5 nm, plasma diameter ～300 μm). By 10x demagnified imaging of the plasma a pulse energy density of ～75 mJ/cm~2 at a pulse length of 6 ns can be achieved in the image plane of the objective. As demonstrated for poly(methyl methacrylate) (PMMA), photoetching of polymer surfaces is possible at this EUV fluence level. This paper presents first results, including a systematic determination of PMMA etching rates under EUV irradiation. Furthermore, the contribution of out-of-band radiation to the surface etching of PMMA was investigated by conducting a diffraction experiment for spectral discrimination from higher wavelength radiation. Imaging of a pinhole positioned behind the plasma accomplished the generation of an EUV spot of 1 μm diameter, which was employed for direct writing of surface structures in PMMA.