An improved electron scattering simulation at the mask in a projection lithography system

A simulation model is presented, which can be used to express the electron energy loss spectrum and the small angular scattering of electrons at the m ask in the electron beam projection lithography optical system. The simulat ion model of electron trajectories in the mask material is described. It is shown that the calculated electron energy loss spectrum and the angular sc attering distribution agree well with the experimental results. Using this simulation, we obtain the data of the energy, the position, the scattering angle and the scattering azimuthal angle for each transmitted electron thro ugh the mask. As the application of the data, the following two results are obtained: (1) The longitudinal Coulomb interaction effect among scattered electrons generated at the mask and the image forming electrons are calcula ted and the defocusing characteristics in a typical cell-projection optical system are obtained. (2) The electron displacement characteristics at the wafer plane are obtained considering the scattering at the mask in the scat tering with angular limitation projection electron lithography (SCALPEL) pr oof of concept system by neglecting the Coulomb interaction effect among el ectrons.