Electron Generation in Tin-oxo Cage Extreme Ultraviolet Photoresists

Extreme Ultraviolet Lithography photoresists undergo chemical reactions initiated by ionizing radiation. Understanding the decay pathways in the photoresist following photoionization requires knowledge about the states and species that are generated during the ultrafast primary and secondary ionization processes while the energy of the photons (92 eV) is ultimately converted to heat and chemical reaction products. Here we use Total Electron Yield spectroscopy to investigate the electron generation following excitation of the resist with photons in the energy range from 5 to 150 eV. We estimate that each EUV photon gives rise to 3 - 4 electrons. Changes in the material during irradiation lead to changes in the yield of electrons, which is qualitatively explained by considering changes in the absorption spectrum and density that are due to chemical change.