Non-thermal surface modification of solids induced by EUV laser pulses

Abstract

Summary form only given. We report results of experiments connected with surface modification of organic and inorganic materials with an intense EUV laser beam. The samples were irradiated by laser beam from a discharge-plasma EUV source (with wavelength 46.9 nm) based on a high-current capillary discharge driver. A detailed description of our driver CAPEX can be found in the early published paper [1]. The laser beam is focused with a spherical (R=2100 mm) Si/Sc multilayer-coated mirror on polymethylmethacrylate (PMMA), gold-covered-PMMA and gallium arsenide (GaAs) samples. For analysis of laser beam footprints an atomic-force microscope (AFM) was used. It turned out that the energy of focused EUV laser beam is sufficient for ablation not only easily ablative material PMMA but also thin layer of gold (thickness ∼40 nm) and GaAs by single shot, even if the focus is significantly influenced by astigmatism (astigmatic difference ∼16 mm). Non-thermal desorption/ablation regimes [2] were observed in all materials. Surface of PMMA and GaAs samples was irradiated by single shot and five shots through a small Au grid (step 12.5 × 12.5 µm, windows 7.5 × 7.5 µm) closely attached to this surface. Analysis of the exposed regions by AFM show that diffraction pattern in single window of grid in desorption region of footprints on GaAs sample was observed similarly as in earlier experiments with PMMA [3]. On the other hand, in ablation region of footprints, where crater was several time dipper than in desorption region, no diffraction pattern is observed.