Influence of the mask-scattered electrons in the cell-projection lithography

The influence of the mask-scattered electron on the pattern exposed at the wafer surface is simulated in the cell-projection lithography optical syste m. In order to obtain accurate distributions in the intensity and its direc tion of the scattered electron from the cell mask, the so called direct sim ulation of the elastic and inelastic scattering events of electron trajecto ries is performed in the mask material. In this treatment, the mask-scatter ed electrons are produced not only by the multiple scattering of the primar y electrons, but also by the cascade multiplication of electrons in the mas k. In the present simulation model all the electron trajectories above and below the cell mask are traced considering the cell-projection lithography optical system. In the present study we will discuss the thickness necessar y for the cell mask to work as the stencil mask in the projection lithograp hy system, and the transmittance of the mask-scattered electrons and the co ntrast of the exposure pattern at the wafer surface is obtained. (C) 1999 A merican Vacuum Society. [S0734-211X(99)10506-7].