Influence of secondary electrons in proximal probe lithography

This article describes the limitations of proximal probe lithography due to electrons that are mirrored by the electric field between the tip and the surface. The incident beam generates two kinds of electrons at the sample surface: primary electrons which are elastically backscattered and secondary electrons which are produced in the resist/substrate system. The electric field confines the electrons emanating from the surface. The electron trajectories are bent in such a way that the electrons impinge on the sample surface in the vicinity of their origin. These reflected electrons contribute to the exposure of the resist and therefore, limit the resolution. For hexadecanethiol monolayers on gold substrates, we have measured the energy distribution of the mirrored electrons and the secondary electron yield as a function of the primary energy. With near edge x-ray absorption fine structure spectroscopy, we have investigated the relevance of low energy electrons in the exposure of hexadecanethiol films. Simulations of secondary electron trajectories can explain the occurrence of triple line structures observed in field emission proximal probe lithography. (C) 1997 American Vacuum Society.