Dependence of the electron irradiation induced decomposition of cadmium chloride thin films on the beam energy dissipation profile

Abstract

The influence of primary beam energy and film thickness on decomposition by uniform electron irradiation of vacuum deposited thin films of cadmium chloride on silicon substrates has been studied for primary beam energies from 1 to 5 keV. Remaining film thickness versus dose measurements, obtained by ellipsometry, are compared to a theoretically derived model. This model is based on a steady state solution of the continuity equation for beam generated excess carriers within the thin film with a carrier generating function proportional to the Gaussian approximation for the rate of energy dissipation versus depth function. The proportionality constant is equal to the energy of formation of an electron–hole pair. The variation of the rate of energy dissipation with depth is derived from Monte Carlo calculations. The principle of scaling is shown to apply when energy loss is normalized with respect to the primary beam energy and depth with respect to the Bethe range. An energy-independent, universal thickness-versus-dose curve is proposed in view of the application of this material as an electron beam resist.