On the link between electron shadowing and charging damage

Charging and topography evolution simulations during plasma etching of high aspect ratio line-and-space patterns reveal that electron shadowing of the sidewalls critically affects charging damage. Decreasing the degree of electron shadowing by using thinner masks decreases the potentials of the etched features with a concomitant reduction in catastrophic tunneling currents through underlying thin gate oxides. Simultaneously, the potential distribution in the trench changes, significantly perturbing the local ion dynamics which, in turn, cause the notching effect to worsen. Since the latter can be reduced independently by selecting an appropriate etch chemistry, the use of thinner (hard) masks is predicted to be advantageous for the prevention of gate oxide failure.