Energy dependence of proximity parameters investigated by fitting before measurement tests

Abstract

Some years ago a method for fast and accurate experimental evaluation of the proximity parameters α, β, η was suggested [S. V. Dubonos et al., Microelectron. Eng. 21, 293 (1993)]. The method, called the fitting before measurement procedure, is used for regular measurements of β and η in a wide energy range for different bulk substrates (Si, SiO2, mica, ZrO2, Al2O3, InAs, GaAs) and of α as function of resist thickness and energy. An empirical relation from the fitting procedure allows one to extrapolate the β and η values to other substrates and energies. It is demonstrated that a resist of micron thickness can remarkably reduce the resolution of e-beam lithography. It is important that the reducing could not be improved by accurate focusing of the beam but could be overcome only by using a higher accelerating voltage. A phenomenological relation helps to predict resolution as function of resist thickness and electron energy.