Mask charging phenomena during electron beam exposure in the EPL system

We solve the charge continuity equation and obtain the saturated charge density distribution and the electric potential distribution in and around the mask material. We obtain the accumulated charge distribution by Monte Carlo simulation of electron trajectories after electron beam irradiation. Because of secondary electron emission, all surfaces of the structure are charged positively, especially those of the line region. Electrons which cannot escape from the surface are stored inside the mask material, and those parts are charged negatively. The potential distribution can be obtained by solving the Poisson equation with three-dimensional boundary conditions.