Determination of fixed electron‐beam‐induced positive oxide charge

Abstract

Contrary to previous beliefs, electron‐beam‐induced positive charges in insulators persist where created for at least several weeks without discernible movement. Formerly, coating with a thin metal overlay was thought to allow the charge to leak away. Coating with a conductor is shown to shield electric fields from affecting the imaging probe, but to remove no charge from the specimen. A new technique is introduced for the evaluation of the properties of electron‐beam‐induced positive charges in metal‐oxide‐semiconductor (MOS) capacitors. MOS structures were subjected to partial area exposure in a scanning electron microscope. These exposures resulted in the creation of areas of localized positive charge within the oxide, which was observed as steps in the capacitance‐voltage data. A systematic study was performed. It related the exposed area to the step height and the amount of induced charge to the voltage shift of the step. A model describing the observed phenomenon is presented, followed by a comparison of theoretical and experimental results. The progress of the charge over time was studied by performing capacitance‐voltage analysis 30 min after electron beam exposure and up to 4 weeks later.

Localization of Multiple DNA Sequences on Nanopatterns

“…In this study, we demonstrate site-specific immobilization of multiple DNA sequences on nanopatterns created by advanced lithographic tools. It is known that surface charging occurs following the electron beam exposure of an insulator. − Recently Chi et al . have shown that the positive charge generated at the top surface of a SiO 2 insulating layer by the electron beam exposure can be used to immobilize negatively charged DNA molecules at the nanoscale.…”