Electron scattering and transmission through SCALPEL masks

Electron scattering in thin solid films used for the fabrication of masks f or electron projection lithography, e.g., SCALPEL(R), is investigated. We h ave developed an analytical model to calculate electron transmission throug h the mask membrane and image contrast due to different scattering properti es of the patterned area and the membrane. The model utilizes cross section s for electron elastic and inelastic scattering on an atom with exponential ly screened Coulomb potential of the nucleus derived in the first Born appr oximation. The variety and controversy of theoretical and empirical adjustm ents of the screening parameter are briefly analyzed and attributed to the misinterpretation of experimental data ignoring the effects mostly, due to plural scattering of electrons and dense packing of atoms in thin solid fil ms. This model frees us from the computational limitations of Monte Carlo s imulations and proves to be effective for the straightforward characterizat ion of various alternative materials for SCALPEL mask membrane and scattere r. The model includes the appropriate effects of the projection optics and back-focal plane aperture. (C) 1998 American Vacuum Society.