Extreme UV secondary electron yield measurements of Ru, Sn, and Hf oxide thin films

Abstract. Background: The secondary electron yield (SEY) of materials is important for topics as nanoparticle photoresists and extreme ultraviolet (EUV) optics contamination. Aim: Experimentally measure SEY and secondary electron energy distributions for Ru, Sn, and Hf oxide. Approach: The SEY and energy distribution resulting from 65 to 112 eV EUV radiation are measured for thin-film oxides or films with native oxide. Results: The total SEY can be explained by EUV absorption in the topmost nanometer of (native) oxide of the investigated materials. Conclusions: Although the relative SEY of Ru and Sn is well-explained by the difference in EUV absorption properties, the SEY of HfO2 is almost a factor 2 higher than expected. Based on the energy distribution of secondary electrons, this may be related to a lower barrier for secondary electron emission.