THE INFLUENCE OF THE SUBSTRATE ON PROXIMITY EFFECT AND EXPOSURE DOSE FOR THE INORGANIC RESIST LIF(ALF3)

The critical exposure dose of the inorganic electron beam resist LiF(A lF3) is an increasing function of resist thickness. The thickness of t he substrate also has an influence, even when backscattering is neglig ible. A simple model is presented in order to predict the critical dos e for given resist and substrate thickness. This model is based on str ess relaxation during exposure within the highly tensile-strained resi st film. Finally, an unusual proximity effect, which occurs predominan tly in dense line gratings, is discussed in the context of the same mo del.