MONTE-CARLO SIMULATION OF INCLINED INCIDENCE OF FAST ELECTRONS TO SOLIDS

In the present work inclined incidence of accelerated electrons to sol ids is simulated using Monte Carlo technique. Spatial distributions of absorbed electron energy density in a 125 nm poly(methylmethacrylate) resist layer on bulk Si substrate are obtained for angles of incidenc e 30 degrees, 45 degrees, and 60 degrees at two beam energies-25 and 5 0 keV-together with the energy and angular distributions of the backsc attered electrons. The results show strong asymmetry of the exposure d istributions. Their peaks are significantly lower, wider, and 40-100 n m shifted, and their shapes are different in comparison with those for normal incidence of electrons. The ratio between the maximum values o f exposure distributions due to the forward scattered and the backscat tered electrons decreases with decreasing angle of incidence. These pe culiarities of exposure distributions may lead to enhanced proximity e ffects and cause deviation from required pattern shapes. Therefore, if inclined incidence of accelerated electrons to any surface occurs dur ing electron beam lithography, it has to be taken into account. (C) 19 96 American Vacuum Society.