Monte Carlo simulation of inclined incidence of fast electrons to solids

In the present work inclined incidence of accelerated electrons to solids 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 incidence 30 degree, 45 degree, and 60 degree at two beam energies emdash 25 and 50 keV emdash together with the energy and angular distributions of the backscattered electrons. The results show strong asymmetry of the exposure distributions. Their peaks are significantly lower, wider, and 40 endash 100 nm shifted, and their shapes are different in comparison with those for normal incidence of electrons. The ratio between the maximum values of exposure distributions due to the forward scattered and the backscattered electrons decreases with decreasing angle of incidence. These peculiarities of exposure distributions may lead to enhanced proximity effects and cause deviation from required pattern shapes. Therefore, if inclined incidence of accelerated electrons to any surface occurs during electron beam lithography, it has to be taken into account. copyright 1996 American Vacuum Society