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

There are two major critical issues to be solved in the technology of the electron beam projection lithography. One of them is the Coulomb interaction among electrons in the shaped beam. The other is the influence of the scattered electrons, which are produced at the mask. It is known that the scattered electrons hardly expose the wafer surface directly. However, the scattered electrons may exert the Coulomb interaction on the shaped beam along their trajectories to the wafer. In order to estimate their influences quantitatively, it is necessary to know the electron scattering behavior at the mask precisely. In the present study we propose a new simulation model, which expresses the electron scattering phenomena in the mask material, and we estimate the effect of the Coulomb interaction effect between the scattered electrons and electrons in the shaped beam.